HK1148110B - Etching agent, etching method and liquid for preparing etching agent - Google Patents
Etching agent, etching method and liquid for preparing etching agent Download PDFInfo
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- HK1148110B HK1148110B HK11102026.1A HK11102026A HK1148110B HK 1148110 B HK1148110 B HK 1148110B HK 11102026 A HK11102026 A HK 11102026A HK 1148110 B HK1148110 B HK 1148110B
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Description
Technical Field
The present invention relates to processing of a semiconductor substrate on which a titanium (Ti) based metal film is formed, particularly processing of a semiconductor substrate on which a copper (Cu) wiring is formed, and mainly relates to an etchant and an etching method for a Ti based metal film such as a Ti film or a titanium-Tungsten (TiW) alloy film. The present invention relates to processing of a semiconductor substrate on which a metal bump or a metal wiring having a lower ionization tendency than tungsten is formed, particularly processing of a semiconductor substrate on which a tungsten (W) based metal film is formed, and mainly relates to an etchant and an etching method for a W based metal film such as a W film or a TiW alloy film.
Background
Conventionally, as an etching solution for a Ti-based metal film such as a Ti film or a TiW alloy film, for example, a hydrogen peroxide etching solution, an acidic etching solution such as a hydrofluoric acid-hydrogen peroxide mixed solution or a phosphoric acid-hydrogen peroxide mixed solution, and the like are known.
However, when the hydrogen peroxide solution contains a metal such as copper, silver, or gold, the decomposition of hydrogen peroxide is promoted, and there are problems that the life of the etching solution is shortened, it is difficult to control the hydrogen peroxide concentration in the etching solution, and the etching rate is lowered.
In addition, with, for example, a hydrofluoric acid-hydrogen peroxide mixed solution, there are problems such as a slow etching rate, a large corrosion of the underlying metal or the metal on the substrate, and the like; with the phosphoric acid-hydrogen peroxide mixture, there are problems such as generation of etching residues, corrosion of underlying metal or metal on the substrate being large, and the like.
In such a situation, as a method for etching a Ti-based metal film such as a Ti film or a TiW alloy film without generating an etching residue, a method for etching a Ti-based film on a semiconductor substrate using a solution containing hydrogen peroxide and a chelating agent has been proposed (patent document 1).
However, some types of underlying metals or metals on a semiconductor substrate have problems such as deterioration of etching selectivity due to corrosion of other metals, shortening of the life of an etching solution due to acceleration of decomposition of hydrogen peroxide, and reduction of etching rate.
In addition, in order to etch Ti and TiW alloys without discoloring the solder, an etching solution containing hydrogen peroxide, a phosphonic acid-based compound, and the like, for example, is disclosed (patent document 2). However, only nitrogen-containing phosphonic acids are disclosed as phosphonic acid-based compounds, and such phosphonic acid-based compounds have, for example, the following problems: the solution is strongly colored and contains many metal impurities when used in an etchant for a semiconductor substrate, and therefore, when added to a hydrogen peroxide-containing solution, the stability is concerned.
Under such a situation, it has been desired to develop an etching method for improving the etching selectivity of a Ti-based metal film in the processing of a semiconductor substrate having a Cu wiring and a semiconductor substrate useful for forming a solder bump not containing lead (Pb), and an etching solution for selectively etching the Ti-based metal film.
On the other hand, conventionally, a coating film using a metal having a low tendency to be plasmatized with gold or silver has not only physical properties such as good electrical conductivity and good thermocompression bonding properties but also chemical properties such as oxidation resistance and chemical resistance, and therefore, it is suitably used for bump formation, wiring formation, and the like on a semiconductor substrate (for example, patent document 3 and the like).
In addition, as an etching solution for etching tungsten (W) and/or a titanium-Tungsten (TiW) alloy in the presence of such a metal having excellent conductivity, for example, an etching solution having the following characteristics is known from other points of view: the etching solution contains at least hydrogen peroxide water and an alkali component, and has a pH of 7 or less (for example, patent document 4). However, such an etching solution has a problem that side etching of W, TiW alloy or the like cannot be sufficiently suppressed in the current situation where precision of wiring or the like is required.
Patent document 1: japanese laid-open patent publication No. 2002-155382
Patent document 2: japanese patent laid-open publication No. 2003-328159
Patent document 3: japanese laid-open patent publication No. 2007-100130
Patent document 4: japanese laid-open patent publication No. 2004-31791
Disclosure of Invention
In view of the above circumstances, an object of the present invention is to provide a method for etching a Ti-based metal film on a semiconductor substrate (particularly, a method for selectively etching a Ti-based metal film on a semiconductor substrate having a Cu wiring) and an etching solution used for the method.
The present inventors have also found that when the etchant for a Ti-based metal film on a semiconductor substrate on which a Cu wiring of the present invention has been formed is used as an etchant for forming a metal bump having a lower ionization tendency than that of tungsten or a W-based metal film on a semiconductor substrate on which a metal wiring or a metal bump having a lower ionization tendency than that of tungsten, the metal bump or the W-based metal film immediately below the metal wiring is etched, that is, side-etched, because of contact corrosion (Galvanic corrosion ) of dissimilar metals between tungsten and metals having a lower ionization tendency than that of tungsten (metals having a lower ionization tendency than that of gold and silver). Therefore, the present inventors have repeatedly developed an etchant for Ti-based metal films and developed an etchant capable of suppressing contact corrosion (galvanic corrosion) of dissimilar metals, and thus have provided an etchant that is applicable to a semiconductor substrate on which a W-based metal film is provided, on which metal bumps or metal wirings having a low tendency to form a plasma of gold or silver are formed.
The present invention relates to an etchant for a semiconductor substrate, which comprises a solution containing (A) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, and (C) an alkaline compound, and (D-1) a copper corrosion inhibitor and/or 0.01 to 3 wt% of (D-2) 2 or more anionic species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group.
The present invention also relates to an etching method for selectively etching a Ti-based metal film on a semiconductor substrate using the etchant for a semiconductor substrate.
Further, the present invention relates to an etching method for etching a W-based metal film on a semiconductor substrate using the etchant for a semiconductor substrate.
Further, the present invention relates to an etchant preparation solution for a semiconductor substrate, which comprises a solution containing (B) a phosphonic acid-based chelating agent having a hydroxyl group and (C) an alkali compound, and (D-1) a copper etching inhibitor and/or (D-2) 2 or more types of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group.
In the etchant of the present invention, by selectively etching a Ti-based metal film on a semiconductor substrate, particularly a Ti-based metal film on a substrate having a Cu wiring formed on an upper portion thereof, using an etchant for a semiconductor substrate comprising a solution containing (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) an inorganic base among alkaline compounds, (C-1) and (D-1) a copper anticorrosive agent, the following effects can be exhibited as compared with the conventional method: for example, corrosion of the underlying metal or the metal on the substrate is suppressed, the elution amount of the metal into the etchant is reduced, the life of the etchant is increased, and the etching selectivity of the Ti-based metal film is increased, thereby enabling etching without any residue.
In addition, when a Ti-based metal film on a semiconductor substrate, particularly a Ti-based metal film on a substrate having Cu wiring is selectively etched, the following effects can be exhibited by using a substance obtained by mixing the etchant preparation liquid for a semiconductor substrate of the present invention with hydrogen peroxide at the time of use: for example, the degradation of the etchant performance due to the decomposition of hydrogen peroxide can be further suppressed, the instability of hydrogen peroxide due to the coexistence with an alkali can be avoided, and the etching rate of the Ti-based metal film can be appropriately adjusted based on the mixing ratio of the etchant preparation liquid and hydrogen peroxide.
In the etchant of the present invention, by using a semiconductor substrate etchant comprising a solution containing (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) an alkaline compound, and 0.01 to 3 wt% of (D-2) 2 or more types of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group, for example, a W-based metal film on a semiconductor substrate to which metal bumps or wires having a lower ionization tendency than tungsten (low ionization tendency metal) of gold, silver, palladium, tin, or an alloy thereof are applied is etched, whereby effects such as suppression of dissimilar metal contact corrosion (galvanic corrosion) between the W-based metal and the metal having a lower ionization tendency than tungsten, and suppression of side etching due to the corrosion can be exerted.
Detailed Description
In the present invention, the Ti-based metal film is a film of a Ti-based metal formed on a substrate using a Ti alloy such as Ti or TiW (hereinafter, may be simply referred to as "Ti-based film").
In the present invention, the W-based metal film refers to a film of a W-based metal formed on a substrate using a W alloy such as W or TiW alloy (hereinafter, may be simply referred to as "W-based film").
The hydrogen peroxide (a) in the etchant of the present invention is used for oxidizing a Ti film, a W film, a TiW alloy film, or the like, and facilitates a dissolution reaction of an alkaline compound (alkali compound) such as an inorganic base or an organic amine.
In the etchant of the present invention, the concentration of hydrogen peroxide (a) used in the etchant for a Ti-based metal film on a semiconductor substrate on which a copper wiring is formed (hereinafter, may be simply referred to as the etchant of the present invention <1 >) is usually 10 to 35% by weight, preferably 15 to 30% by weight, more preferably 15 to 26% by weight, and further preferably 20 to 26% by weight, based on the concentration in the etchant.
In the etchant of the present invention, the concentration of hydrogen peroxide (a) used in the etchant for a W-based metal film on a semiconductor substrate on which a metal bump or a metal wiring having a lower ionization tendency than tungsten is formed (hereinafter, may be simply referred to as the etchant of <2> of the present invention) is usually 10 to 35 wt%, preferably 15 to 35 wt%, more preferably 20 to 35 wt%, and still more preferably 24 to 32 wt%, based on the concentration in the etchant.
The hydrogen peroxide (a) may be used as it is, for example, a commercially available hydrogen peroxide diluted to an appropriate concentration with distilled water, purified water, ion-exchanged water, ultrapure water, or the like.
The use of (B) the phosphonic acid-based chelating agent having a hydroxyl group in the etchant of the present invention has the following effects: which prevents hydrogen peroxide from decomposing to maintain oxidizing power, and which coordinates with hydrogen peroxide to form a water-soluble complex on Ti or W to dissolve the Ti film, the W film, or the TiW alloy film.
Examples of the phosphonic acid chelating agent (B) having a hydroxyl group include alkane polyphosphonic acids having a hydroxyl group such as 1-hydroxyethylidene-1, 1 '-diphosphonic acid (HEDPO), 1-hydroxypropylidene-1, 1' -diphosphonic acid, and 1-hydroxybutylidene-1, 1 '-diphosphonic acid, and 1-hydroxyethylidene-1, 1' -diphosphonic acid (HEDPO) is particularly preferable. These phosphonic acid-based chelating agents exhibit the effect of suppressing the generation of etching residues and undissolved matter on the etched substrate, etc., because the solubility of the chelate compound is good in the presence of hydrogen peroxide, Ti-based or W-based metal oxide, and Cu.
The concentration of the phosphonic acid-based chelating agent having a hydroxyl group (B) in the etchant of <1> in the present invention is usually 0.1 to 3% by weight, preferably 0.2 to 2% by weight, more preferably 0.3 to 1% by weight, and still more preferably 0.4 to 0.8% by weight, based on the concentration in the etchant.
The concentration of the phosphonic acid-based chelating agent having a hydroxyl group (B) in the etchant of <2> in the present invention is usually 0.1 to 3 wt%, preferably 0.1 to 2 wt%, more preferably 0.15 to 1 wt%, and still more preferably 0.2 to 0.6 wt%, based on the concentration in the etchant.
The phosphonic acid chelating agent (B) having a hydroxyl group may be any one of those commercially available.
The basic compound (C) in the etchant of the present invention means a basic compound selected from the group consisting of (C-1) inorganic bases and (C-2) organic amines, and in the etchant of the present invention <1>, the basic compound is required to be an inorganic base. The inorganic base is used for dissolving an oxide such as a Ti film, a W film, or a TiW alloy film, which is oxidized by hydrogen oxide, while maintaining the pH of the solution in a predetermined range. Specific examples of the inorganic base (c-1) as the etchant of <1> in the present invention include ammonia, and alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, among which alkali metal hydroxides are preferable, and potassium hydroxide is more preferable.
On the other hand, specific examples of the inorganic base (c-1) as the etchant of <2> in the present invention include ammonia, and alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, among which alkali metal hydroxides are preferable, and sodium hydroxide is more preferable.
The organic amine (c-2) in the etchant of the present invention is used only in the etchant of the present invention <2>, and is used for dissolving an oxide such as a W film or a TiW alloy film, which is oxidized by oxidation and oxidation, while maintaining the pH of the solution in a predetermined range, in the same manner as the inorganic base (c-1). Specific examples of the organic amine include tetramethylammonium hydroxide (TMAH) and choline hydroxide, and among them, tetramethylammonium hydroxide (TMAN) is preferable.
In the etchant of <2> of the present invention, the basic compound may be at least 1 or more basic compounds selected from the group consisting of the inorganic base (c-1) and the organic amine (c-2), and among them, at least 1 or more basic compounds selected from the group consisting of sodium hydroxide and tetramethylammonium hydroxide (TMAH) are preferable, and among them, it is more preferable to use either one of sodium hydroxide or tetramethylammonium hydroxide (TMAH) alone. Sodium hydroxide and tetramethylammonium hydroxide (TMAH) are preferred because they generate ions having a small molar electrical conductivity (large hydration radius), such as sodium ions and quaternary ammonium ions, in an aqueous solution, and contact with a metal having a lower ionization tendency than tungsten (metal having a low ionization tendency), thereby suppressing transfer of electrons to hydrogen ions on the surface of the metal and further easily suppressing dissolution of tungsten (galvanic corrosion).
The concentration of the inorganic base (c-1) used in the etchant of the present invention varies depending on the kind of the inorganic base used, (B) the phosphonic acid-based chelating agent having a hydroxyl group, and the copper anticorrosive (D-1) described later, and the amount of the inorganic base added, and is usually 0.2 to 12% by weight, preferably 0.5 to 10% by weight, and more preferably 0.8 to 4% by weight, based on the concentration in the etchant.
In the etchant of <2> of the present invention, the concentration of the (c-1) inorganic base used differs depending on the kind of the inorganic base used, (B) the kind and the amount of the (D-2) phosphonic acid chelating agent having a hydroxyl group and 2 or more types of anion species having no oxidizing power other than the phosphonic acid chelating agent having a hydroxyl group, and the pH of the solution, and is usually 0.1 to 5% by weight, preferably 0.2 to 4% by weight, and more preferably 0.2 to 2% by weight, based on the concentration in the etchant.
The (D-1) copper anticorrosive agent of the etchant of <1> of the present invention is preferably used in the etchant of <1> of the present invention, and examples of the copper anticorrosive agent include epihalohydrin-modified polyamide, benzotriazole compound, hydroxycarboxylic acid, nitrogen-containing cyclic compound, and the like, which are generally used in this field.
Examples of the epihalohydrin-modified polyamide used as the copper anticorrosive agent (D-1) include those obtained by substituting a part or all of hydrogen atoms of an — NH-group present in the main chain of a polycondensate obtained by reacting a diaminoalkylamine with a dicarboxylic acid by using either one or both of a group represented by the following general formula [1] and a glycidyl group.
(wherein X represents a halogen atom.)
Examples of the polycondensate include those having a repeating unit represented by the general formula [2 ].
{ formula [2]In, R1Represents an alkylene group having 1 to 6 carbon atoms, an arylene group or a compound represented by the general formula [ 3]]A group shown, R3And R4Each independently represents an alkylene group having 1 to 6 carbon atoms. }
(formula [ 3]]In, R2Represents an alkylene group having 1 to 6 carbon atoms. )
Specific examples of the epihalohydrin-modified polyamide exemplified as the copper anticorrosive (D-1) include those composed of either one or both of the repeating unit represented by the general formula [4] and the repeating unit represented by the general formula [5], and those composed of a combination of these and the repeating unit represented by the general formula [2 ].
(in the formula, R1、R3、R4And X is the same as above. )
(in the formula, R1、R3、R4And X is the same as above. )
Further, since the repeating unit represented by the above general formula [4] may be converted into a structure of the repeating unit represented by the general formula [6] by, for example, heat treatment or the like, the description thereof includes the case where the repeating unit represented by the general formula [6] is mixed even when only the repeating unit represented by the general formula [4] is described.
(in the formula, R1、R3、R4And X is the same as above. )
In the general formulae [1] and [4], examples of the halogen atom represented by X include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like, and among them, a chlorine atom is preferable.
In the general formula [2]]And [4]]～[5]In (1) as R1、R3And R4The alkylene group having 1 to 6 carbon atoms may be any of linear, branched or cyclic, and usually includes alkylene groups having 1 to 6 carbon atoms, and specifically includes linear alkylene groups such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene and hexamethylene; branched alkylene groups such as propylene, methylmethylene, dimethylmethylene, ethylmethylene, methylethylene, methyltetramethylene and ethyltetramethylene; for example, a cyclic alkylene group such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, etc., and among them, a tetramethylene group is preferable.
As R1The arylene group generally includes arylene groups having 6 to 10 carbon atoms, and examples thereof include phenylene and naphthylene.
In the general formula [3]In (1) as R2The alkylene group having 1 to 6 carbon atoms may be any of linear, branched or cyclic, and usually includes alkylene groups having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms), and specifically includes linear alkylene groups such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene and hexamethylene; for example propylene, methylmethylene, bisBranched alkylene groups such as a methylmethylene group, an ethylmethylene group, a methylethylene group, a methyltetramethylene group, and an ethyltetramethylene group; for example, a cyclic alkylene group such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group, and among them, an alkylene group having 1 to 3 carbon atoms such as a methylene group, an ethylene group, a trimethylene group, a propylene group, or a dimethylmethylene group is preferable.
The epihalohydrin-modified polyamide exemplified as the copper anticorrosive (D-1) may be commercially available, or may be appropriately synthesized by a conventional method, and for example, a polymer polyamide having a repeating unit obtained by reacting a corresponding dicarboxylic acid or a derivative thereof with a diaminoalkylamine or a derivative thereof with epihalohydrin such as epichlorohydrin may be produced.
Examples of commercially available products of the epihalohydrin-modified polyamide include the following commercially available products as an aqueous solution containing the epihalohydrin-modified polyamide: euramine P-5500 (trade name, manufactured by Mitsui chemical Co., Ltd.) (an aqueous solution containing 12.5 wt% of an epihalohydrin-modified polyamide having a molecular weight of 4,000 to 5,000), Euramine P-5600 (trade name, manufactured by Mitsui chemical Co., Ltd.) (an aqueous solution containing 30.0 wt% of an epihalohydrin-modified polyamide having a molecular weight of 2,000 to 3,000), WS-4020 (trade name, manufactured by Star light PMC Co., Ltd.) (an aqueous solution containing 25 wt% of an epihalohydrin-modified polyamide having a molecular weight of 400,000 to 600,000), and the like.
The molecular weight of the epihalohydrin-modified polyamide used as the copper anticorrosive (D-1) is usually about 2,000 to 1,000,000, preferably 2,000 to 800,000, and more preferably 3,000 to 600,000.
As the benzotriazole compound (D-1) as the copper anticorrosive agent in the etchant of <1> of the present invention, benzotriazole and its derivatives are exemplified. Examples of the benzotriazole derivative include those having, for example, a carboxyl group on the benzotriazole ring; an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, a propyl group, etc.; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.; specific examples of the substituent include 4-carboxybenzotriazole, 5-methylbenzotriazole and 5-chlorobenzotriazole.
Examples of the hydroxycarboxylic acid as the (D-1) copper anticorrosive agent in the etchant of <1> of the present invention include, for example, a hydroxycarboxylic acid such as citric acid and isocitric acid; for example, hydroxycarboxylic acids such as glycolic acid, lactic acid, glyceric acid, tartronic acid, malic acid, tartaric acid, mevalonic acid and pantoic acid.
Examples of the nitrogenous cyclic compound which is exemplified as the (D-1) copper anticorrosive agent in the etchant of <1> of the present invention include nucleic acid bases, and specifically, purine derivatives such as adenine, guanine, 2-aminopurine and guanosine; pyrimidine derivatives such as cytosine, thymine, uracil, 6-methyluracil, and 5-ethyluracil; carboxylic acids containing a heterocycle such as quinaldine; amino acids such as cysteamine hydrochloride; bipyridine, and the like. These copper corrosion inhibitors may be used in a mixture of 2 or more thereof as appropriate.
Among these copper corrosion inhibitors (D-1), preferred are, for example, epihalohydrin-modified polyamide, Benzotriazole (BTA), citric acid, adenine and the like.
The concentration of the copper anticorrosive agent (D-1) used in the etchant of <1> of the present invention is not particularly limited as long as it is a concentration equal to or higher than that of the copper anticorrosive agent, and specifically, the concentration of the copper anticorrosive agent is usually 0.05 to 5% by weight, preferably 0.05 to 2% by weight, and more preferably 0.08 to 1.5% by weight.
The etchant of <2> of the present invention is used for an etchant for a W-based metal film on a semiconductor substrate on which a metal bump or a metal wiring having a lower ionization tendency than tungsten is formed, wherein 0.01 to 3 wt% of 2 or more types of anion species having no oxidizing power other than (D-2) phosphonic acid-based chelating agents having a hydroxyl group are contained in the etchant of the present invention. The anionic species means an anionic species derived from a compound capable of dissociating into a cation and an anion in an aqueous solution, and more specifically, it means an anion generated when an inorganic acid or an organic acid is dissociated in an aqueous solution, that is, an anionic species derived from an inorganic acid or an organic acid. In addition, the anion species described herein do not include hydroxide ions generated from at least 1 or more basic compounds selected from (C) (C-1) inorganic bases and (C-2) organic amines.
Specific examples of the anion species derived from an inorganic acid include a sulfate ion, a sulfite ion, a chloride ion, a phosphate ion, a phosphite ion, and a hypophosphite ion, and among them, a sulfate ion, a chloride ion, and a phosphate ion are preferable.
Specific examples of the anionic species derived from an organic acid include carbonate ions; monocarboxylic acid ions such as acetate ions; a hydroxytricarboxylic acid ion such as a citric acid ion and an isocitric acid ion; examples of the hydroxyl carboxylic acid ion include glycolic acid ion, lactic acid ion, glycerate ion, tartronate ion, malic acid ion, tartaric acid ion, mevalonate ion, and pantoate ion, among which carbonate ion, acetate ion, citrate ion, and malic acid ion are preferable, and among them, citrate ion and malic acid ion are more preferable.
The concentration of 2 or more types of anion species having no oxidizing power other than (D-2) the phosphonic acid-based chelating agent having a hydroxyl group is required to be 0.01 to 3 wt%, preferably 0.02 to 1 wt%, more preferably 0.03 to 0.5 wt%, and particularly preferably 0.03 to 0.3 wt%, based on the concentration in the etchant of the present invention <2 >. In particular, the intended effect of the present invention can be more reliably obtained by suppressing the use concentration of the anion species to 0.3 wt% or less.
(D-2) the action of 2 or more types of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group is as follows: first, the pH of a solution (aqueous solution) of the etchant of <2> of the present invention is maintained at a constant value, i.e., functions as a buffer; the second is an action capable of suppressing galvanic corrosion, which is one of the effects intended by the present invention. In order to exert such a buffering action and a galvanic corrosion inhibition action, the total weight% of the anion species in the aqueous solution of the etchant of <2> of the present invention is important, and if too small, the anion species does not exert a buffering action; on the other hand, if too much, galvanic corrosion is promoted on the contrary, and as briefly mentioned above, the anionic species is used at a concentration of at least 0.01 to 3% by weight.
Among 2 or more types of anion species having no oxidizing power other than (D-2) phosphonic acid-based chelating agents having a hydroxyl group in an amount of 0.01 to 3 wt%, a combination of 0.0001 to 0.5 wt% of at least 1 or more types of anion species derived from an inorganic acid selected from the group consisting of sulfate ions, sulfite ions, chloride ions, phosphate ions, phosphite ions and hypophosphite ions and 0.0099 to 2.5 wt% of at least 1 or more types of anion species derived from an organic acid selected from the group consisting of citrate ions and malate ions can be suitably used; 0.0001 to 0.5% by weight of any 1 kind of organic acid-derived anion species selected from carbonate ions, acetate ions, citrate ions, or malate ions, and 0.0099 to 2.5% by weight of an organic acid-derived anion species selected from citrate ions or malate ions, other than the organic acid-derived anion species selected as described above; 0.0001 to 0.5 wt% of at least 1 or more kinds of anion species derived from an inorganic acid selected from a sulfate ion, a sulfite ion and a chloride ion, and 0.0099 to 2.5 wt% of at least 1 or more kinds of anion species derived from an inorganic acid selected from a phosphate ion, a phosphite ion and a hypophosphite ion, and the like.
In the etchant of <2> of the present invention, by using a combination of at least 1 kind of anion species having an action of suppressing dissimilar metal contact corrosion (galvanic corrosion) and further at least 1 kind of anion species functioning as a buffer as 2 or more different kinds of anion species, the action of suppressing dissimilar metal contact corrosion (galvanic corrosion), which is one of the effects of the present invention, can be more reliably exerted. Further, as the anion species having an action of suppressing the dissimilar metal contact corrosion (galvanic corrosion), at least 1 or more kinds of anion species derived from an inorganic acid selected from a sulfate ion, a sulfite ion, a chloride ion, a phosphate ion, a phosphite ion and a hypophosphite ion, and at least 1 or more kinds of anion species derived from an organic acid selected from a carbonate ion, an acetate ion, a citrate ion and a malate ion can be preferably mentioned, and as the anion species functioning as a buffer, at least 1 or more kinds of anion species derived from an inorganic acid selected from a phosphate ion, a phosphite ion and a hypophosphite ion, and at least 1 or more kinds of anion species derived from an organic acid selected from a citrate ion and a malate ion can be preferably mentioned. Preferable examples of the anion species that can be used for any purpose include phosphate ion, phosphite ion, hypophosphite ion, citrate ion, and malate ion.
The amount of the anion species which exerts the effect of suppressing the dissimilar metal contact corrosion (galvanic corrosion) needs to be small, and the specific concentration to be used is usually 0.0001 to 0.5% by weight, preferably 0.001 to 0.2% by weight, and more preferably 0.002 to 0.2% by weight, based on the concentration in the etchant of the <2> of the present invention. If the amount exceeds 0.5 wt%, the electrolyte concentration in the etchant becomes too high, and an environment in which electron transfer is likely to occur is created, and contact corrosion (galvanic corrosion) of dissimilar metals is promoted, which is not preferable. Such anion species exert an effect of dispersing an electrical influence over a wide range while maintaining an electric double layer formed on the surface of the W-based metal film by hydroxide ions.
On the other hand, the specific concentration of the anion species serving as a buffer is usually 0.0099 to 2.5 wt%, preferably 0.019 to 0.8 wt%, more preferably 0.028 to 0.3 wt%, and further preferably 0.028 to 0.1 wt%, based on the concentration in the etchant of <2> of the present invention. The total value of the anion species functioning as a buffer and the anion species functioning to suppress contact corrosion (galvanic corrosion) of dissimilar metals is the use concentration of 2 or more anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group. As described briefly above, when the concentration of the anion species for suppressing the dissimilar metal contact corrosion (galvanic corrosion) is set to 0.002 to 0.2 wt% and the concentration of the anion species for buffering is reduced to 0.028 to 0.1 wt%, the dissimilar metal contact corrosion (galvanic corrosion) can be more reliably suppressed while the buffering effect is ensured.
The form of supplying the 2 or more types of anion species having no oxidizing power other than the (D-2) phosphonic acid-based chelating agent having a hydroxyl group is not particularly limited as long as the anion species is dissociated in an aqueous solution to form the anion species, and the anion species may be supplied in the form of, for example, an inorganic acid or an organic acid such as sulfuric acid, sulfurous acid, hydrochloric acid, phosphoric acid, carbonic acid, acetic acid, citric acid, or malic acid, or in the form of a salt of an inorganic acid or an organic acid such as sodium sulfate, sodium sulfite, sodium chloride, sodium phosphate, sodium hydrogen phosphate, sodium carbonate, sodium hydrogen carbonate, sodium acetate, sodium citrate, or sodium malate; in the etchant of <2> of the present invention, the kind of the cationic species in the etchant may become important in some cases, and therefore, when the supply is performed in the form of a salt, the supply is preferably performed in the form of a sodium salt or a quaternary ammonium salt.
Citric acid, malic acid, and the like as "copper anticorrosive agents" to be added to the etchant of <1> of the present invention are contained in the etchant of <2> of the present invention in a concentration range in which they can be used as "copper anticorrosive agents" in the case of "2 or more kinds of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group" and "buffer" in the case of "2 or more kinds of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group". Therefore, in the etchant of <1> and <2> of the present invention, citric acid, malic acid, and the like may act as "copper anticorrosive agent" and as "2 or more anionic species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group" depending on the amount of the added citric acid, malic acid, and the like. The addition of these citric acid, malic acid, etc. for both of these purposes is not excluded. That is, in the etchant of <1> of the present invention, a hydroxycarboxylic acid such as a hydroxycarboxylic acid or a citric acid may be used in combination with the "copper etching inhibitor" in the "2 or more types of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group", but it is preferable to set the total use concentration of the "copper etching inhibitor" and the hydroxycarboxylic acid in the above-mentioned concentration range of the "copper etching inhibitor". On the other hand, in the etchant of <2> of the present invention, "copper etching inhibitor" may be used in combination with "2 or more kinds of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group", but it is desirable that "a compound which is dissociated in an aqueous solution to generate the anion species" is not used as the copper etching inhibitor as described later, and in the case of using the copper etching inhibitor, the concentration is set so that the total weight% of the anion species falls within the above range.
As described above, the etchant of <1> of the present invention is an etchant for semiconductor substrates comprising a solution containing at least (A) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C-1) an inorganic base and (D-1) a copper etching inhibitor, while the etchant of <2> of the present invention is an etchant for semiconductor substrates comprising a solution containing (A) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) at least 1 or more alkali compounds selected from (C-1) inorganic bases and (C-2) organic amines, and 0.01 to 3 wt% of (D-2) 2 or more anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group.
The etchant of <1> of the present invention comprises at least (A) hydrogen peroxide, (B) a phosphonic acid chelating agent having a hydroxyl group, (c-1) an inorganic base, and (D-1) a copper anticorrosive agent, and the pH of the solution is adjusted to be maintained in a range of usually 7 to 10, preferably 8 to 9.5, and more preferably 8.5 to 9.2.
If the pH of the solution is too high, problems such as a decrease in stability of hydrogen peroxide and an increase in corrosion of peripheral metals (Al, etc.) and semiconductor substrates (Si, etc.) may occur; when the pH is too low, problems such as a decrease in the Ti etching rate, a decrease in the ability of chelating agent to form a complex, a deterioration in the balance between the Ti and W etching rates of the TiW alloy, the generation of an etching residue, and an increase in side etching occur, and therefore, it is preferable to adjust and maintain the pH in the above range.
If necessary, for the purpose of maintaining the solution of the present invention in the above pH range, a pH adjuster generally used in this field may be used. In addition to the inorganic base, a pH adjuster may also be used as needed, for example, for the purpose of improving the stability of the solution.
Examples of the pH adjuster include boric acid, nitric acid, hydrochloric acid, sulfuric acid, and hydrofluoric acid. These pH adjusting agents may be used in a mixture of 2 or more kinds as appropriate. The concentration of the pH adjuster is usually 0.05 to 4 wt%, preferably 0.2 to 3 wt%, and more preferably 1 to 2 wt% based on the concentration of the etchant of the present invention <1 >.
The etchant of <2> of the present invention comprises at least (A) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) at least 1 or more basic compounds selected from (C-1) inorganic bases and (C-2) organic amines, and 0.01 to 3 wt% of 2 or more anionic species having no oxidizing power other than (D-2) phosphonic acid-based chelating agents having a hydroxyl group, and the pH of the solution is adjusted to be maintained in a range of usually 6 to 10, preferably 6 to 9, and more preferably 7 to 8.5.
If the pH of the solution is too high, problems such as a decrease in stability of hydrogen peroxide and an increase in corrosion of peripheral metals (Al, etc.) and semiconductor substrates (Si, etc.) may occur; when the pH is too low, for example, the etching rate of W decreases, the ability of the phosphonic acid-based chelating agent having a hydroxyl group to form a complex decreases, the balance between the etching rates of Ti and W of the TiW alloy deteriorates, etching residue occurs, and side etching increases, and therefore, it is preferable to adjust and maintain the pH in the above range.
In the etchant of <2> of the present invention, since the total weight% of the anion species in the solution is important, it is preferable to adjust and maintain the pH in the above range in which the concentration of (C) at least 1 or more basic compounds selected from (C-1) inorganic bases and (C-2) organic amines and (D-2) 2 or more anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group is in the range of 0.01 to 3 wt%. That is, in the etchant of <2> of the present invention, since the concentration range of the anion species is important, it is preferable not to use a compound or the like which is dissociated in an aqueous solution to generate the anion species, other than 2 or more anion species having no oxidizing power other than (D-2) the phosphonic acid-based chelating agent having a hydroxyl group.
The etchant of the present invention can be prepared by mixing and dissolving in water (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group and (C) an alkaline compound, and (D-1) a copper corrosion inhibitor and/or 0.01 to 3 wt% of 2 or more anionic species having no oxidizing power other than (D-2) a phosphonic acid-based chelating agent having a hydroxyl group, so that these components have the above-mentioned concentrations. The components may be added to water in the order of preference, or may be dissolved in water after all the components are added. The etchant of the present invention thus prepared is preferably subjected to a filtration treatment or the like before use. The water used here may be distilled water, purified water, ion-exchanged water, ultrapure water or the like which has been purified by distillation, ion-exchange treatment or the like.
In the etchant of <1> of the present invention, (A) hydrogen peroxide, (B) a phosphonic acid chelating agent having a hydroxyl group, (c-1) an inorganic base and (D-1) a copper etching inhibitor are used, and in addition, reagents generally used in a known etching method can be used.
Examples of such a reagent include nonionic surfactants used for the purpose of reducing the surface tension of a solution to improve wettability with a semiconductor surface, anionic surfactants, cationic surfactants, amphoteric surfactants, and the like, and among them, nonionic surfactants such as NCW1002 (polyoxyethylene/polyoxypropylene alkyl ether, manufactured by wako pure chemical industries, ltd.) are particularly preferable. These surfactants can be used in the concentration range generally used in this field, and are usually 0.001 to 1% by weight, preferably 0.01 to 0.5% by weight, based on the concentration in the etchant of the present invention <1 >.
On the other hand, in the etchant of <2> of the present invention, a surfactant or the like may be used in addition to (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) at least 1 or more basic compounds selected from (C-1) inorganic bases and (C-2) organic amines, and 0.01 to 3 wt% of 2 or more anionic species having no oxidizing power other than (D-2) phosphonic acid-based chelating agents having a hydroxyl group, but as described briefly above, the etchant preferably does not contain other components that affect the wt% because the total weight% of the anionic species in the solution is important.
In the etchant of <2> of the present invention, as the surfactant to be used as needed, for example, a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and the like are used for the purpose of reducing the surface tension of the solution to improve the wettability with the semiconductor surface, and among these surfactants, it is preferable to use a compound which does not dissociate in an aqueous solution and does not generate an anionic species, which is needless to say. The amount of these surfactants used is usually 0.001 to 1% by weight, preferably 0.01 to 0.5% by weight, based on the concentration in the etchant of <2> of the present invention.
As described above, the etchant of the present invention is prepared by using, as its main components, (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group and (C) an alkaline compound, and (D-1) a copper anticorrosive agent and/or 0.01 to 3 wt% of 2 or more types of anion species having no oxidizing power other than (D-2) a phosphonic acid-based chelating agent having a hydroxyl group, and can be supplied in various forms such as a 1-liquid system, a 2-liquid system, and the like. In the case of using the etchant, the etchant can be used as it is in the case of a 1-liquid system, or in the case of a 2-liquid system or other multi-liquid system, the entire solutions can be mixed appropriately before use to prepare a solution containing all the components as described above, and the solution can be used.
Among these, a multi-liquid system of 2 or more liquids is preferable because of problems such as safety during transportation or storage, and stability of the solution, and a 2-liquid system is particularly preferable from the viewpoint of stability-simplicity, and specifically, a 2-liquid system composed of (1) a solution containing hydrogen peroxide and (2) an etchant preparation liquid (hereinafter, sometimes simply referred to as "etchant preparation liquid of the present invention") is preferable from the viewpoint of, for example, suppressing deterioration in performance of the etchant due to decomposition of hydrogen peroxide and avoiding instability of hydrogen peroxide due to coexistence with an alkaline compound (alkali compound), wherein the etchant preparation liquid is composed of a solution containing a phosphonic acid-based chelating agent having a hydroxyl group, an alkali compound, and 2 or more types of anion species having no oxidizing power other than the copper anticorrosive agent and/or the phosphonic acid-based chelating agent having a hydroxyl group.
In the multi-liquid system such as the 2-liquid system described above, the concentration of each component in each solution to be used may be appropriately selected so as to be contained in each solution, so that the concentration in a solution containing all the components prepared by appropriately mixing all the solutions, that is, the final concentration may be in the above-described concentration range. That is, for example, in the case where the etchant of the <1> of the present invention is a 2-liquid system, a solution (first liquid) containing 10 to 50% by weight (preferably 15 to 30% by weight, more preferably 15 to 26% by weight, and even more preferably 20 to 26% by weight) of hydrogen peroxide and an etchant preparation liquid (second liquid) composed of a solution containing 0.1 to 3% by weight (preferably 0.2 to 2% by weight, more preferably 0.3 to 1% by weight, and even more preferably 0.4 to 0.8% by weight) of a phosphonic acid-based chelating agent having a hydroxyl group, 0.2 to 12% by weight (preferably 0.5 to 10% by weight, and even more preferably 0.8 to 4% by weight) of an inorganic base, and 0.05 to 5% by weight (preferably 0.05 to 2% by weight, and even more preferably 0.08 to 1.5% by weight) of a copper anticorrosive agent may be prepared so that the first liquid and the second liquid are in a ratio of usually 1: 9 to 98: 2 (preferably 4: 6 to 9: 1), More preferably 6: 4 to 8: 2) (weight ratio) [ solution 1: solution 2) the concentrations in the solution containing all the components prepared by mixing them as appropriate, that is, the final concentrations were as follows: the hydrogen peroxide is usually 10 to 35 wt%, preferably 15 to 30 wt%, more preferably 15 to 26 wt%, further preferably 20 to 26 wt%, the phosphonic acid-based chelating agent having a hydroxyl group is usually 0.1 to 3 wt%, preferably 0.2 to 2 wt%, more preferably 0.3 to 1 wt%, further preferably 0.4 to 0.8 wt%, the inorganic base is usually 0.2 to 12 wt%, preferably 0.5 to 10 wt%, more preferably 0.8 to 4 wt%, and the copper anticorrosive agent is usually 0.05 to 5 wt%, preferably 0.05 to 2 wt%, more preferably 0.08 to 1.5 wt%.
When the etchant of the <2> of the present invention is a 2-liquid type, a solution (first liquid) containing 10 to 35 wt% (preferably 20 to 35 wt%, more preferably 24 to 35 wt%, and further preferably 30 to 35 wt%) of hydrogen peroxide, a phosphonic acid-based chelating agent containing 0.1 to 30 wt% (preferably 0.1 to 20 wt%, more preferably 0.15 to 10 wt%, and further preferably 0.2 to 6 wt%) of a hydroxyl group, at least 1 or more alkali compounds selected from inorganic bases and organic amines, and 0.01 to 6 wt% (preferably 0.02 to 2 wt%, more preferably 0.03 to 1 wt%), may be prepared separately, More preferably 0.03 to 0.6 wt.%) of an etchant preparation liquid (liquid 2) composed of a solution of 2 or more types of anion species having no oxidizing power other than a phosphonic acid-based chelating agent having a hydroxyl group, wherein the ratio (weight ratio) of the liquid 1 to the liquid 2 is usually 30: 70 to 99: 1 (preferably 60: 40 to 95: 5, more preferably 80: 20 to 95: 5) [ liquid 1: solution 2) the concentrations in the solution containing all the components prepared by mixing them as appropriate, that is, the final concentrations were as follows: hydrogen peroxide is usually 10 to 35 wt%, preferably 15 to 35 wt%, more preferably 20 to 35 wt%, further preferably 24 to 32 wt%, the phosphonic acid-based chelating agent having a hydroxyl group is usually 0.1 to 3 wt%, preferably 0.1 to 2 wt%, more preferably 0.15 to 1 wt%, further preferably 0.2 to 0.6 wt%, and at least 1 or more alkaline compounds selected from inorganic bases and organic amines are usually 0.1 to 5 wt%, preferably 0.2 to 4 wt%, more preferably 0.2 to 2 wt%, and the amount of 2 or more types of anionic species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group is usually 0.01 to 3 wt%, preferably 0.02 to 1 wt%, more preferably 0.03 to 0.5 wt%, and still more preferably 0.03 to 0.3 wt%.
Similarly, in the 2-liquid system, the pH of each solution is not particularly limited, and the pH of each solution may be adjusted so that the pH, that is, the final pH of a solution containing all the components, which is prepared by appropriately mixing all the solutions, is within the above pH range. In other words, in the case of the 2-liquid system described above, for example, in the etchant of the <1> of the present invention, the pH of each solution may be adjusted so that the final pH after mixing the 2 liquids is usually 7 to 10, preferably 8 to 9.5, more preferably 8.5 to 9.2; in the etchant of <2> of the present invention, the pH of each solution may be adjusted so that the final pH after mixing the solutions 2 is usually 6 to 10, preferably 6 to 9, and more preferably 7 to 8.5.
In the etching method using the etchant of <1> of the present invention, the substrate can be treated with the etchant of the present invention by bringing the etchant comprising a solution containing at least (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (c-1) an inorganic base, and (D-1) a copper etching inhibitor into contact with the Ti-based metal film on the semiconductor substrate.
The etching method using the etchant of <2> of the present invention can be carried out by bringing an etchant comprising a solution containing at least (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) at least 1 or more basic compounds selected from (C-1) inorganic bases and (C-2) organic amines, and 0.01 to 3 wt% of at least 2 or more anion species having no oxidizing power other than (D-2) phosphonic acid-based chelating agents having a hydroxyl group into contact with a W-based metal film on a semiconductor substrate, or the like.
That is, the etching method of the present invention may be carried out according to an etching method, a spray etching method, or the like, which is a known etching method, in addition to etching of a substrate using the etchant of the present invention as described above.
In the etching method of the present invention, the etchant preparation liquid of the present invention (that is, the etchant preparation liquid composed of a solution containing a phosphonic acid-based chelating agent having a hydroxyl group, an alkali compound, and 2 or more kinds of anion species having no oxidizing power other than the copper etching inhibitor and/or the phosphonic acid-based chelating agent having a hydroxyl group) may be used after the etchant preparation liquid and the hydrogen peroxide-containing solution are appropriately mixed at the time of use to prepare a solution (etchant) containing all the components.
Specific examples of the etching method known per se include (1) a method of immersing a semiconductor substrate on which a Ti-based metal film or a W-based metal film is formed in an etchant, (2) a method of stirring the solution by mechanical means in a state where the semiconductor substrate on which the Ti-based metal film or the W-based metal film is formed is immersed in an etchant, (3) a method of stirring the solution by vibration such as ultrasonic waves in a state where the semiconductor substrate on which the Ti-based metal film or the W-based metal film is formed is immersed in an etchant, and (4) a method of spraying an etchant onto a semiconductor substrate on which the Ti-based metal film or the W-based metal film is formed.
In the method of the present invention, when etching is performed as described above, the semiconductor substrate on which the Ti-based metal film or the W-based metal film is formed may be oscillated as necessary.
In the method of the present invention, the etching method is not particularly limited, and for example, a batch method, a single-sheet method (e.g., a Yeye method), or the like can be used.
Examples of the semiconductor substrate having a Ti-based metal film formed thereon to which the etchant and the etching method of <1> of the present invention are applied include a substrate having a Cu wiring formed on the semiconductor substrate having a Ti-based metal film formed thereon.
Examples of the metal constituting the Pb-free solder In the step of using the etchant of <1> of the present invention include Sn alloys containing tin (Sn) as a main component, for example, alloys of Sn and 1 or more metals selected from silver (Ag), bismuth (Bi), indium (In), copper (Cu), nickel (Ni), zinc (Zn), aluminum (Al), antimony (Sb), gold (Au), and the like. Specific examples of the Pb-free solder include Sn-Ag based, Sn-Ag-Bi-In based, Sn-Ag-Bi based, Sn-Cu-Ag based, Sn-Ag-Bi-Cu based, Sn-Cu-Ni based, Sn-Zn-Bi based, Sn-Zn-Al based, Sn-Zn-In based, Sn-Bi-In based, Sn-Sb based, Sn-In based, Sn-Au based, etc., among which Sn-Cu based, Sn-Ag based, Sn-Cu-Ag based, etc. are preferable, and Sn-Cu is more preferable.
The etchant and the etching method of <1> of the present invention are suitably used in a process for producing a substrate having a Pb-free solder bump on a semiconductor substrate according to the present invention (that is, a semiconductor substrate having a Ti-based metal film formed thereon, particularly, a semiconductor substrate having a Cu wiring on the Ti-based film).
As a method for forming a Pb-free solder bump, a method generally used in this field can be used, and for example, the following treatment can be performed: the semiconductor substrate of the present invention (i.e., the semiconductor substrate having the Ti-based metal film formed thereon) is patterned by coating a resist or the like as necessary, then, 1 or more metal films selected from metals constituting the Pb-free solder are laminated, and thereafter, the metals constituting the Pb-free solder are subjected to plating treatment and further treated by a conventional method in the art such as heating.
In the case of using a substrate in which a Cu wiring is further formed on the Ti-based metal film, for example, a Ni film, a Cr film, or the like may be formed on the Cu wiring in order to improve the bondability between the Cu wiring and the Sn alloy constituting the Pb-free solder bump.
On the other hand, examples of the semiconductor substrate having a W-based metal film formed thereon to which the etchant and the etching method of <2> of the present invention are applied include a substrate having a metal bump or a metal wiring having a lower ionization tendency than tungsten provided on the semiconductor substrate having a W-based metal film formed thereon.
Examples of the metal constituting the metal bump or metal wiring having a lower ionization tendency than tungsten in the step using the etchant of <2> of the present invention include gold (Au), silver (Ag), palladium (Pd), tin (Sn), or an alloy thereof; or an alloy containing these metals as main components, since these metals have a lower ionization tendency than tungsten, they constitute metal bumps or metal wirings which cause contact corrosion (galvanic corrosion) of dissimilar metals. Among these metal bumps and metal wires, gold (Au) bumps and gold (Au) wires are preferable.
The method for forming the metal bump or the metal wiring may be a method generally carried out in this field, and specifically, for example, a circuit may be formed on a semiconductor substrate used in the present invention, that is, a semiconductor substrate on which a W-based metal film is formed, by using a resist or the like, and then, may be subjected to a treatment such as gold plating or chemical vapor deposition.
In the case of using a substrate having a gold bump formed on the W-based metal film, for example, a conductor/bonding site such as a nickel (Ni), palladium (Pd), or copper (Cu) film may be present between the W-based metal film and the bump in order to improve the bonding property between the W-based metal film and the bump.
Examples of the semiconductor substrate used in the present invention include silicon materials such as silicon, amorphous silicon, polysilicon, a silicon oxide film, and a silicon nitride film; a semiconductor substrate made of a compound semiconductor such as gallium-arsenic, gallium-phosphorus, indium-phosphorus, or the like. Among them, the etchant and the etching method of the present invention are suitably used for a semiconductor substrate made of a silicon-based material.
In etching using an etchant for a Ti-based metal film on a semiconductor substrate on which copper wiring is formed, that is, the etchant of <1> of the present invention, when the temperature is increased, etching can be completed in a shorter time than at normal temperature, but when the treatment temperature is high, decomposition of hydrogen peroxide becomes severe, and the life of the etchant becomes short. The temperature during etching has a lower limit of usually not less than room temperature, preferably not less than 20 ℃, and more preferably not less than 25 ℃, and an upper limit of usually not more than 60 ℃, preferably not more than 50 ℃, and more preferably not more than 40 ℃. That is, the temperature of the etching solution of the present invention may be brought into contact with the substrate after the temperature is in the above-described temperature range.
In the etching using the etchant for a W-based metal film on a semiconductor substrate on which a metal bump or a metal wiring having a lower ionization tendency than tungsten is formed, that is, the etchant of <2> of the present invention, the etching can be completed in a shorter time than that at normal temperature by heating, and moreover, the difference in etching rate between a portion etched by the etchant and a portion etched in parallel by dissimilar metal contact corrosion (galvanic corrosion) is relatively small, the treatment time for the etchant to come into contact with the metal is shortened, the side etching is suppressed, and therefore, it is preferable to set the treatment temperature higher than room temperature. Specifically, the etchant may be brought into contact with the substrate after the treatment temperature is set to a temperature range of, for example, 10 to 70 ℃, preferably 20 to 60 ℃, and more preferably 30 to 60 ℃.
The etching treatment time is not limited because the surface state and shape of the object to be treated are not constant, but in actual use, it is usually 1 minute to 1 hour, preferably 1 minute to 30 minutes, and more preferably 1 minute to 15 minutes.
When the etching agent for a Ti-based metal film on a semiconductor substrate on which a copper wiring is formed of the present invention, that is, the etching agent of <1> of the present invention is used to perform etching treatment on a semiconductor substrate on which a Ti-based metal film is formed, the Ti-based film can be selectively etched. In particular, when the etchant is used for a substrate having a Cu wiring on the Ti-based film, the etching selectivity of Ti with respect to Cu can be improved. Further, by suppressing the amount of Cu dissolved, excessive side etching does not occur, and decomposition of hydrogen peroxide by Cu can be suppressed, so that the life of the etchant can be increased and the process margin can be increased.
The etchant for a Ti-based metal film on a semiconductor substrate having a copper wiring formed thereon according to the present invention, that is, the etchant of <1> according to the present invention can be suitably used in a solder bump forming step containing no Pb.
When the etchant for a W-based metal film on a semiconductor substrate on which a W-based metal film is formed is etched using the etchant for a W-based metal film on a semiconductor substrate on which a metal bump or a metal wiring having a lower ionization tendency than tungsten of the present invention, that is, the etchant of the present invention <2>, not only the W-based metal film can be etched quickly, but also the etching of the W-based metal film directly under the metal bump or the metal wiring, that is, the side etching due to dissimilar metal contact corrosion (galvanic corrosion) between the metal bump or the metal wiring having a lower ionization tendency than tungsten, and tungsten can be suppressed.
In the case where sodium hydroxide or tetramethylammonium hydroxide is used as (C) at least 1 or more basic compounds selected from (C-1) inorganic bases and (C-2) organic amines, particularly in the etchant for a W-based metal film on a semiconductor substrate on which metal bumps or metal wirings having a lower ionization tendency than tungsten are formed, the presence of a small amount of a specific anionic species such as sulfate ion or citrate ion suppresses electron transfer, which is one of causes of dissimilar metal contact corrosion (galvanic corrosion), and the presence of a cationic species such as sodium ion or quaternary ammonium ion generated from these substances can diffuse the electrical influence to a wide range while maintaining the electric double layer, thereby having advantages such as the capability of suppressing dissimilar metal contact corrosion (galvanic corrosion).
Further, when the etchant preparation liquid of the present invention is used, it is used as an etchant by being appropriately mixed with a solution containing hydrogen peroxide at the time of use, and therefore, for example, reduction in the performance of the etchant due to decomposition of hydrogen peroxide can be suppressed, instability of hydrogen peroxide due to coexistence with an alkaline compound (alkali compound) can be avoided, and there are advantages in that the etching rate of a Ti-based metal film or a W-based metal film can be appropriately adjusted by mixing hydrogen peroxide with the etchant preparation liquid at an arbitrary ratio.
In the etchant of <1> of the present invention, when alkali hydroxide and ammonia (particularly, alkali hydroxide) are used for pH adjustment of the etchant preparation liquid, effects such as an improvement in the selectivity of Ti/Cu, an increase in the dissolution rate of Ti, and high productivity can be expected in the case of etching a Ti-based metal film with an etchant obtained by mixing the alkali hydroxide with a solution containing hydrogen peroxide, as compared with the case of pH adjustment using an organic base such as tetramethylammonium hydroxide.
The present invention will be described in more detail below by way of examples and comparative examples, but the present invention is not limited to these examples and comparative examples.
Examples
Example 1
(1) Preparation of etchant of the invention <1>
An etchant consisting of the following composition was prepared.
24.5% by weight of hydrogen peroxide
Phosphonic acid chelating agent (HEDPO) 0.5% by weight
Copper anticorrosive agent (benzotriazole) 0.1% by weight
Inorganic base (potassium hydroxide) 2.0% by weight
72.9% by weight of water
pH 9.0
Additionally, HEDPO ═ 1-hydroxyethylidene-1, 1' -diphosphonic acid
(2) Etching of
The Ti plate and the Cu plate, whose surface areas and weights were measured in advance, were immersed in the etchant of the above (1) at room temperature for 10 minutes to perform etching treatment.
(3) Results
An appropriate amount of the etchant obtained in (2) above after etching was diluted with a 0.1mol/L nitric acid solution, and the amounts of Ti and Cu dissolved were measured using an inductively coupled plasma emission spectrometer (trade name "SPS 3000ICP emission spectrometer", manufactured by SII NanoTechnology corporation). The amount of the obtained metal was estimated as the amount of the dissolved metal per unit area, and the dissolution rate (nm/min) was calculated. The results are shown in Table 1 together with the dissolution rate ratio of Ti/Cu.
Examples 2 to 5
(1) Preparation of etchant of the invention <1>
The preparation was carried out in the same manner as in example 1, except that the components in the etchant were used in the predetermined amounts shown in table 1 below.
(2) Etching of
The procedure was carried out in the same manner as in example 1.
(3) Results
The amounts of metals on the surfaces of the Cu plate and the Ti plate etched were measured in the same manner as in example 1. The results are shown together in Table 1. In table 1, the water content of each etching solution is omitted.
[ Table 1]
| Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | |
| H2O2 | 24.5％ | 25％ | 24.5％ | 24.5％ | 25％ |
| Phosphonic acid (HEDPO) | 0.5％ | 0.5％ | 0.5％ | 0.5％ | 0.5％ |
| Inorganic base | KOH 2％ | KOH 3.8％ | KOH 2.1％ | KOH 2.2％ | NH3 1.5％ |
| Copper corrosion inhibitor | BTA 0.1％ | EPA 1％ | 0.1 percent of adenine | 0.1 percent of citric acid | EPA 1％ |
| pH | 9 | 9 | 9 | 9 | 9 |
| Ti dissolution rate (nm/min) | 48 | 35 | 45 | 48 | 103 |
| Cu dissolution rate (nm/min) | 0.05 | 0.05 | 0.22 | 0.34 | 2 |
| Ratio of Ti/Cu dissolution rate | 960 | 694 | 205 | 141 | 51 |
The respective resins are benzotriazole and epichlorohydrin modified polyamide resin EPA
Comparative examples 1 to 4
(1) Preparation of etchant
The preparation was carried out in the same manner as in example 1, except that the components of the etchant were used in the predetermined amounts shown in table 2 below.
(2) Etching of
The procedure was carried out in the same manner as in example 1.
(3) Results
The amounts of metals on the surfaces of the Cu plate and the Ti plate etched were measured in the same manner as in example 1. The results are shown together in Table 2.
[ Table 2]
| Comparative example 1 | Comparative example 2 | Comparative example 3 | Comparative example 4 | |
| H2O2 | 17.5％ | 16.9％ | 17.5％ | 24.5％ |
| Chelating agents | EDTA 1％ | HEDPO 0.5％ | DEPPO 0.5％ | HEDPO 0.5％ |
| Alkali | NH3 1.9％ | NH3 1,3％ | KOH 1.5％ | TMAH 2.5％ |
| Copper corrosion inhibitor | - | - | - | BTA 0.1％ |
| pH | 9.1 | 9.3 | 9 | 9 |
| Ti dissolution rate (nm/min) | 59 | 16 | 10 | 2.0 |
| Cu dissolution rate (nm/min) | 5.2 | 0.9 | 0.7 | 0 |
| Ratio of Ti/Cu dissolution rate | 11 | 18 | 14 | - |
The corresponding salts EDTA, DEPPO, diethylenetriamine pentamethylene phosphonic acid, TMAH, tetramethylammonium hydroxide
From the results of examples 1 to 5, it is understood that Ti can be effectively etched without substantially etching Cu by using the etchant of <1> of the present invention.
On the other hand, it is clear from the results of comparative examples 1 to 3 that when an etchant containing no copper etching inhibitor is used, Cu is easily etched, and Ti cannot be efficiently etched.
Further, from the results of example 1 and comparative example 4, it is understood that in the case of using organic amine (TMAH) as the base, Cu is not etched at all and Ti is hardly etched, whereas in the case of using inorganic base (KOH) in the etchant of <1> of the present invention as the base, Ti can be selectively etched, that is, Ti can be effectively etched without etching Cu almost.
Further, from the results of examples 2 and 5, it is understood that in the case of using potassium hydroxide as the base, the Ti/Cu dissolution rate ratio is improved, that is, Ti can be selectively etched, as compared with the case of using ammonia.
Example 6
(1) Preparation of etchant of the invention <1>
An etchant consisting of the following composition was prepared.
24.5% by weight of hydrogen peroxide
Phosphonic acid-based chelating agent (60% HEDPO solution) 0.8% by weight
[ HEDPO content: about 0.5 wt.%
Copper anticorrosive agent (benzotriazole) 0.1% by weight
Inorganic base (potassium hydroxide) 2.0% by weight
72.6% by weight of water
pH 9.0
Additionally, HEDPO: the trade name is "DEQEST 2010" (manufactured by SOLUTIA JAPAN, Inc.).
(2) Etching of
The Ti plate and the Cu plate were immersed in the etchant of (1) for 30 minutes, 60 minutes, and 90 minutes, respectively, at room temperature, and then subjected to etching treatment.
(3) Results
The hydrogen peroxide concentration in the etchant before and after etching was measured by redox titration, and the decomposition rate of hydrogen peroxide before and after etching was estimated by the following equation. The results are shown in Table 3.
Hydrogen peroxide decomposition rate (%) (hydrogen peroxide concentration before etching-hydrogen peroxide concentration after etching) × 100/(hydrogen peroxide concentration before etching)
Comparative example 5
(1) Preparation of etchant
An etchant consisting of the following composition was prepared.
24.5% by weight of hydrogen peroxide
2.0% by weight of a nitrogen (N) -containing phosphonic acid chelating agent
(25% DEPPO heptasodium salt aqueous solution) [ DEPPO content: 0.5 wt.%
Copper anticorrosive agent (benzotriazole) 0.1% by weight
Inorganic base (potassium hydroxide) 1.7% by weight
Water 71.7% by weight
pH 9.0
In addition, DEPPO: the product name is "DEQEST 2066" (manufactured by SOLUTIA JAPAN, Inc.).
(2) Etching of
The same etching treatment as in example 6 was performed.
(3) Results
The hydrogen peroxide concentration was measured in the same manner as in example 6. The results are shown together in Table 3.
[ Table 3]
From the results in table 3, it is understood that the decomposition rate of hydrogen peroxide is high and the life of the etchant is shortened when the nitrogen (N) -containing phosphonic acid-based chelating agent is used, whereas the decomposition rate of hydrogen peroxide is low and the life of the etchant is lengthened when the phosphonic acid-based chelating agent (HEDPO) of the present invention is used.
Example 7
(1) Preparation of etchant of the invention <1>
An etchant consisting of the same composition as in example 2 described in table 1 was prepared.
(2) Etching of
The Ti plate and the Cu plate were immersed in the etchant of (1) above at 40 ℃ for 10 minutes, 20 minutes, and 30 minutes, respectively, to perform etching treatment.
(3) Results
The hydrogen peroxide concentration in the etchant before and after etching was measured by redox titration, and the decomposition rate of hydrogen peroxide before and after etching was estimated by the following equation. The results are shown in Table 4.
Hydrogen peroxide decomposition rate (%) (hydrogen peroxide concentration before etching-hydrogen peroxide concentration after etching) × 100/(hydrogen peroxide concentration before etching)
Example 8
(1) Preparation of etchant of the invention <1>
An etchant consisting of the following composition was prepared.
25.0% by weight of hydrogen peroxide
Phosphonic acid chelating agent (HEDPO) 0.5% by weight
Copper corrosion inhibitor (EPA) 1.0 wt%
Inorganic base (ammonia) 0.9% by weight
72.6% by weight of water
pH 8.5
(2) Etching of
Etching treatment was performed in the same manner as in example 7.
(3) Results
The hydrogen peroxide concentration was measured in the same manner as in example 7. The results are shown in Table 4.
[ Table 4]
It is known that the stability of hydrogen peroxide is lowered when the pH is high, but from the results in Table 4, it is known that the life of the etchant is short because the decomposition rate of hydrogen peroxide is high even though the pH is low in the case of using ammonia as the inorganic base (example 8, pH8.5) compared with the case of using potassium hydroxide (example 7, pH 9.0). As is clear from the above description, the inorganic base used in the present invention is preferably an alkali metal hydroxide such as potassium hydroxide.
Reference example 1 and examples 9 to 14
(1) Preparation of etchant
An etchant having the following composition was prepared (the detailed composition is shown in table 5).
28.0% by weight of hydrogen peroxide
Phosphonic acid-based chelating agent (HEDPO) 0.34% by weight
Basic Compound (sodium hydroxide) 0.58% by weight
Citric acid (buffer) 0.07% by weight
0.0 to 0.2% by weight of sodium sulfate
Balance of water
pH 7.8
Additionally, HEDPO ═ 1-hydroxyethylidene-1, 1' -diphosphonic acid
(2) Etching of
A silicon wafer having a gold (Au) bump on a titanium-Tungsten (TiW) alloy film was immersed in each of the etchants of the reference example and the examples of (1) above at room temperature, and the time when the TiW alloy film on the wafer surface was in a vanished state was defined as the time when etching was terminated. After the etching was completed, the wafer was cleaned with pure water and immersed in a gold Etchant (trade name "Au-Etchant", manufactured by wako pure chemical industries, ltd.) to dissolve the gold bumps.
(3) Results
The length of the upper surface side of the TiW alloy film remaining in a rectangular shape on the wafer obtained in (2) above and masked with the gold bump was observed and measured by a scanning electron microscope (trade name "S-4800", manufactured by Hitachi High Technologies). The side etching was compared by calculating the relative length (%) of the length of the sides of the TiW alloy films remaining in a rectangular shape after etching in each example, with the length of the sides of the TiW alloy films when the etchant containing no sodium sulfate (reference example 1) was taken as 100. The results are shown in Table 5.
[ Table 5]
| Reference example 1 | Example 9 | Example 10 | Example 11 | Example 12 | Example 13 | Example 14 | |
| H2O2 | 28.0％ | 28.0％ | 28.0％ | 28.0％ | 28.0％ | 28.0％ | 28.0％ |
| Phosphonic acid (HEDPO) | 0.34％ | 0.34％ | 0.34％ | 0.34％ | 0.34％ | 0.34％ | 0.34％ |
| Basic compound | NaOH 0.58％ | NaOH 0.58％ | NaOH 0.58％ | NaOH 0.58％ | NaOH 0.58％ | NaOH 0.58％ | NaOH 0.58％ |
| Citric acid (anion 1) | 0.07％ | 0.07％ | 0.07％ | 0.07％ | 0.07％ | 0.07％ | 0.07％ |
| Sodium sulfate (anion 2) | 0％ | 0.001％ | 0.005％ | 0.01％ | 0.02％ | 0.1％ | 0.2％ |
| Side length of relative convex point | 100 | 101 | 103 | 107 | 111 | 109 | 107 |
| pH | 7.8 | 7.8 | 7.8 | 7.8 | 7.8 | 7.8 | 7.8 |
Comparative example 6
(1) Preparation of etchant
An etchant consisting of the following composition was prepared.
28.0% by weight of hydrogen peroxide
Phosphonic acid-based chelating agent (HEDPO) 0.34% by weight
Inorganic base (sodium hydroxide) 0.58% by weight
Citric acid (buffer) 0.07% by weight
Sodium sulfate 1.0% by weight
70.0% by weight of water
pH 7.8
(2) Etching of
The procedure was carried out in the same manner as in reference example 1.
(3) Results
In the same manner as in reference example 1, when the length of the edge of the TiW alloy film in reference example 1 was taken as 100, the relative length (%) of the length of the edge of the TiW alloy film remaining in a rectangular shape was calculated, and the side etching was compared. The results are shown in Table 6.
[ Table 6]
| Comparative example 6 | |
| H2O2 | 28.0％ |
| Phosphonic acid (HEDPO) | 0.34％ |
| Basic compound | NaOH 0.58％ |
| Citric acid (anion 1) | 0.07％ |
| Sodium sulfate (anion 2) | 1.0％ |
| Side length of relative convex point | 64.5 |
| pH | 7.8 |
As is clear from the results in tables 5 and 6, by adding an appropriate amount of sodium sulfate that becomes sulfate ion in an aqueous solution to the etchant, side etching can be suppressed as compared with the etchant without the addition of the sodium sulfate (reference example 1). Further, since the side etching is promoted if sodium sulfate which becomes sulfate ion in an aqueous solution is used in excess, the weight% of the anion species in the solution is important for the etchant of <2> of the present invention.
Examples 15 to 21
(1) Preparation of etchant of the invention <2>
An etchant was prepared in the same manner as in example 9, except that a predetermined amount of sodium chloride or sodium hydrogen phosphate was used instead of sodium sulfate. The composition of anion 2 in this etchant is shown in tables 7 and 8.
(2) Etching of
The procedure was carried out in the same manner as in reference example 1.
(3) Results
In the same manner as in reference example 1, when the length of the edge of the TiW alloy film in reference example 1 was taken as 100, the relative length (%) of the length of the edge of the TiW alloy film remaining in a rectangular shape was calculated, and the side etching was compared. The results are shown in tables 7 and 8 together with the composition of anion 2 in the etchant.
[ Table 7]
| Example 15 | Example 16 | Example 17 | |
| Additive salt (anion 2) | 0.004% of sodium chloride | Sodium chloride 0.016% | 0.08 percent of sodium chloride |
| Side length of relative convex point | 105 | 106 | 101 |
| pH | 7.8 | 7.8 | 7.8 |
[ Table 8]
| Example 18 | Example 19 | Example 20 | Example 21 | |
| Additive salt (anion 2) | Sodium hydrogen phosphate 0.005% | Sodium hydrogen phosphate 0.02% | 0.1 percent of sodium hydrogen phosphate | 0.2 percent of sodium hydrogen phosphate |
| Side length of relative convex point | 109 | 112 | 112 | 107 |
| pH | 7.8 | 7.8 | 7.8 | 7.8 |
From the results in tables 7 and 8, it is understood that the side etching can be suppressed by adding an appropriate amount of sodium chloride which becomes chloride ion in an aqueous solution and sodium hydrogen phosphate which becomes phosphate ion in an aqueous solution, as in the case of sodium sulfate which becomes sulfate ion in an aqueous solution.
Examples 22 to 25 and comparative example 7
(1) Preparation of etchant
An etchant was prepared in the same manner as in example 9, except that a predetermined amount of a salt of an anion species derived from an inorganic acid or an organic acid which is specifically changed in an aqueous solution was used instead of sodium sulfate. The composition of anion 2 in this etchant is shown in table 9.
(2) Etching of
The procedure was carried out in the same manner as in reference example 1.
(3) Results
In the same manner as in reference example 1, when the length of the edge of the TiW alloy film in reference example 1 was taken as 100, the relative length (%) of the length of the edge of the TiW alloy film remaining in a rectangular shape was calculated, and the side etching was compared. The results are shown in table 9 together with the composition of anion 2 in the etchant.
[ Table 9]
| Example 22 | Example 23 | Example 24 | Example 25 | Comparative example 7 | |
| Additive salt (anion 2) | Sodium sulfite 0.014% | Sodium acetate 0.023% | Sodium carbonate 0.012% | 0.025 percent of sodium malate | 0.016 percent of sodium nitrate |
| Side length of relative convex point | 108 | 108 | 101 | 114 | 96 |
| pH | 7.8 | 7.8 | 7.8 | 7.8 | 7.8 |
From the results in table 9, it is understood that the side etching can be suppressed also by the anion species having a reducing power such as sulfite ion, acetate ion which is an anion species derived from an organic acid, and malate ion which is an anion species having a chelating ability in example 22. On the other hand, in the case of an anionic species having an oxidizing power which becomes nitrate ions in an aqueous solution, such as sodium nitrate, side etching cannot be suppressed.
Examples 26 to 27 and comparative example 8
(1) Preparation of etchant
In example 26, a predetermined amount of malic acid was used without using citric acid, and the weight% of sodium sulfate was changed; in example 27, a predetermined amount of malic acid was used without using citric acid, and a predetermined amount of a salt which becomes a specific anion species derived from an organic acid in an aqueous solution was used without using sodium sulfate; except for this, an etchant was prepared in the same manner as in example 9. An etchant was prepared in the same manner as in example 9, except that a predetermined amount of sodium citrate was used instead of sodium sulfate in comparative example 8. The respective compositions of these etchants are shown in table 10.
(2) Etching of
The procedure was carried out in the same manner as in reference example 1.
(3) Results
In the same manner as in reference example 1, when the length of the edge of the TiW alloy film in reference example 1 was taken as 100, the relative length (%) of the length of the edge of the TiW alloy film remaining in a rectangular shape was calculated, and the side etching was compared. The results are shown in table 10 together with the components in the etchant.
[ Table 10]
| Example 26 | Example 27 | Comparative example 8 | |
| H2O2 | 28.0％ | 28.0％ | 28.0％ |
| Phosphonic acid (HEDPO) | 0.34％ | 0.34％ | 0.34％ |
| Basic compound | NaOH 0.58％ | NaOH 0.58％ | NaOH 0.58％ |
| Anion 1 | Malic acid 0.05% | Malic acid 0.05% | Citric acid 0.07% |
| Anion 2 | 0.02 percent of sodium sulfate | Citric acid 2Na 0.033% | Citric acid 2Na 0.033% |
| Relative bump edge length | 107 | 112 | 99 |
| pH | 7.9 | 7.9 | 7.8 |
As is clear from the results in table 10, the effect of suppressing the side etching can be obtained by adding 2 or more different anion species in predetermined amounts to the etchant. It is also understood that one of the anion species may be an anion species other than citric acid.
Reference example 2 and example 28
(1) Preparation of etchant
An etchant was prepared in the same manner as in reference example 1, except that in reference example 2, instead of NaOH as an inorganic base, a predetermined amount of tetramethylammonium hydroxide (TMAH) as an organic amine was used as a basic compound; in example 28, an etchant was prepared in the same manner as in example 9, except that NaOH as an inorganic base was not used as the basic compound and a predetermined amount of tetramethylammonium hydroxide (TMAH) as an organic amine was used as the basic compound in the same manner as in reference example 2. The respective compositions of these etchants are shown in Table 11.
(2) Etching of
The procedure was carried out in the same manner as in reference example 1.
(3) Results
In the same manner as in reference example 1, when the length of the edge of the TiW alloy film in reference example 2 was taken as 100, the relative length (%) of the length of the edge of the TiW alloy film remaining in a rectangular shape was calculated, and the side etching was compared. The results are shown in table 11 together with the components in the etchant.
[ Table 11]
| Reference example 2 | Example 28 | |
| H2O2 | 28.0％ | 28.0％ |
| Phosphonic acid (HEDPO) | 0.34％ | 0.34％ |
| Basic compound | TMAH 1.3％ | TMAH 1.3％ |
| Anion 1 | Citric acid 0.07% | Citric acid 0.07% |
| Anion 2 | - | 0.02 percent of sodium sulfate |
| Side length of relative convex point | 100 | 104 |
| pH | 7.8 | 7.8 |
The corresponding TMAH is tetramethyl ammonium hydroxide
As is clear from the results in table 11, when the basic compound was replaced with NaOH, which is an inorganic base, and TMAH, which is an organic amine, the effect of suppressing the side etching was also exhibited.
Reference examples 3 to 5
(1) Preparation of etchant
An etchant composed of the composition shown in table 12 was prepared.
(2) Etching of
The procedure was carried out in the same manner as in reference example 1.
(3) Results
In the same manner as in reference example 1, when the length of the edge of the TiW alloy film in reference example 1 was taken as 100, the relative length (%) of the length of the edge of the TiW alloy film remaining in a rectangular shape was calculated, and the side etching was compared. The results are shown in table 12 together with the components in the etchant.
[ Table 12]
| Reference example 3 | Reference example 4 | Reference example 5 | |
| H2O2 | 24.5％ | 24.5％ | 24.5％ |
| Phosphonic acid (HEDPO) | 0.50％ | 0.50％ | 0.28％ |
| Basic compound | KOH 1.64％ | KOH 3.00％ | NH3 8.4％ |
| Anion 1 | 1.04 percent of citric acid | 0.05 percent of citric acid | Boric acid 0.7% |
| Side length of relative convex point | 0 | 0 | 0 |
| pH | 7.7 | 8.9 | 10.7 |
From the results in table 12, it is understood that when the alkali concentration in the etchant is high and 2 or more kinds of anion species are not used, the side etching cannot be suppressed, the entire TiW alloy film covered with the gold bump is scraped off, and the bump is peeled off.
In the etchant of <2> of the present invention, the predetermined amount of the anion species not involved in dissolution other than the hydroxide ion for dissolving the W-based metal film and the phosphonic acid-based chelating agent having a hydroxyl group is contained in the etchant, and the purpose is as follows: that is, due to the dissimilar metal battery effect caused by the contact between tungsten and a metal having a lower ionization tendency than tungsten (metal having a lower ionization tendency), the electric double layer formed by hydroxide ions on the surface of the W-based metal film is dispersed and not limited to the vicinity of the interface where tungsten, the metal having a lower ionization tendency than tungsten, and the etchant (electrolytic solution) are in contact with each other, thereby reducing the dissimilar metal contact corrosion. From the results of examples 9 to 28, it is found that the anion species contained in the etchant is preferably an anion species which has no oxidizing power and can stably exist in an aqueous solution, and the concentration of the anion species needs to be adjusted to a range where the electric double layer is dispersed at the metal contact interface and the electron transfer on the film surface is not strong. It is also expected that the smaller the transfer of electrons to and from the surface of the metal having a lower ionization tendency than tungsten, the smaller the side etching due to the dissimilar metal contact corrosion, the more likely the cation species contained in the basic compound is. Further, from the results of reference examples 3 to 5, it is understood that sodium ions having a lower molar conductivity than potassium ions as the cation species contained in the basic compound and quaternary ammonium ions of TMAH as the organic amine are less likely to cause electron transfer than potassium ions, and therefore side etching due to dissimilar metal contact corrosion is suppressed. The results also suggest that the concentration range is to be limited. From these results, it is understood that by using the etchant and the etching method of <2> of the present invention, side etching due to contact corrosion of dissimilar metals generated when a laminated film composed of a W-based metal film and a metal having a lower ionization tendency than tungsten is processed can be reduced or suppressed.
Industrial applicability
In the etchant of the present invention, when a Ti-based metal film on a semiconductor substrate (particularly, a Ti-based metal film on a substrate to which Cu wiring is applied) is selectively etched using an etchant for a semiconductor substrate comprising a solution containing (a) hydrogen peroxide, (B) a phosphonic acid-based chelating agent, (c-1) an inorganic base, and (D-1) a copper etching inhibitor, that is, the etchant of the present invention <1>, effects such as suppression of corrosion of an underlying metal or a metal on a substrate, reduction of the amount of metal eluted into the etchant, increase of the life of the etchant, and improvement of the etching selectivity of the Ti-based metal film, and etching without residue can be exhibited, compared with conventional methods.
In the etchant of the present invention, when a W-based metal film on a semiconductor substrate to which a metal bump or wiring having a lower ionization tendency than tungsten such as gold (Au), silver (Ag), palladium (Pd), tin (Sn) or an alloy thereof having a lower ionization tendency than that of tungsten is applied is etched by using an etchant for a semiconductor substrate comprising a solution containing (A) hydrogen peroxide, (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) an alkali compound, and 0.01 to 3 wt% of (D-2) 2 or more types of anion species having no oxidizing power other than the phosphonic acid-based chelating agent having a hydroxyl group, <2> of the present invention, the effects of suppressing dissimilar metal contact corrosion (galvanic corrosion) between the W-based metal and the metal having a lower ionization tendency than tungsten, and further suppressing side etching due to the corrosion can be exhibited.
Claims (23)
1. An etchant for a semiconductor substrate, which is used for forming a metal bump or a metal wiring having a lower ionization tendency than tungsten on a tungsten (W) based metal film, comprising a solution containing at least the following components (A), (B) and (C) and 0.01 to 3 wt% of (D-2):
(A) hydrogen peroxide;
(B) a phosphonic acid-based chelating agent having a hydroxyl group;
(C) a basic compound;
(D-2) 2 or more anionic species selected from the group consisting of anionic species derived from inorganic acids and anionic species derived from organic acids, wherein the anionic species derived from organic acids is selected from the group consisting of carbonate ions, monocarboxylic acid ions, hydroxytricarboxylic acid ions and hydroxycarboxylic acid ions.
2. The etchant according to claim 1, wherein the inorganic acid in (D-2) is selected from the group consisting of a sulfate ion, a sulfite ion, a chloride ion, a phosphate ion, a phosphite ion and a hypophosphite ion.
3. The etchant of claim 1, wherein the metal bump or metal wire having a lower ionization tendency than tungsten is formed of gold, silver, palladium, tin, or an alloy thereof.
4. The etchant according to claim 1, wherein the metal bump or metal wiring having a lower ionization tendency than tungsten is a metal bump, and a copper wiring is formed between the metal bump and the tungsten-based metal film.
5. The etchant according to claim 1, wherein the tungsten-based metal film is a titanium-Tungsten (TiW) alloy film.
6. The etchant according to claim 1, wherein the solution has a pH of 6 to 10.
7. The etchant according to claim 1, wherein the phosphonic acid chelating agent (B) having a hydroxyl group is at least 1 or more selected from the group consisting of 1-hydroxyethylidene-1, 1 ' -diphosphonic acid, 1-hydroxypropylidene-1, 1 ' -diphosphonic acid, and 1-hydroxybutylidene-1, 1 ' -diphosphonic acid.
8. The etchant according to claim 1, wherein the (C) basic compound is at least 1 or more selected from inorganic bases and organic amines.
9. The etchant according to claim 1, wherein the basic compound (C) is any one of sodium hydroxide or tetramethylammonium hydroxide.
10. The etchant according to claim 1, wherein the 0.01 to 3% by weight of (D-2) 2 or more anionic species selected from anionic species derived from inorganic acids and anionic species derived from organic acids selected from carbonate ions, monocarboxylic acid ions, hydroxytricarboxylic acid ions and hydroxycarboxylic acid ions is a combination of 0.0001 to 0.5% by weight of at least 1 or more anionic species derived from inorganic acids selected from sulfate ions, sulfite ions, chloride ions, phosphate ions, phosphite ions and hypophosphite ions and 0.0099 to 2.5% by weight of at least 1 or more anionic species derived from organic acids selected from citrate ions and malate ions.
11. The etchant according to claim 1, wherein the 0.01 to 3 wt% (D-2) of 2 or more anionic species selected from anionic species derived from inorganic acids and anionic species derived from organic acids selected from carbonate ions, monocarboxylic acid ions, hydroxytricarboxylic acid ions and hydroxycarboxylic acid ions is a combination of 0.0001 to 0.5 wt% of any 1 anionic species derived from inorganic acids selected from sulfate ions, sulfite ions, chloride ions and phosphate ions and 0.0099 to 2.5 wt% of any 1 anionic species derived from organic acids selected from citrate ions and malate ions.
12. The etchant according to claim 1, wherein the 0.01 to 3% by weight of (D-2) 2 or more anionic species selected from anionic species derived from inorganic acids and anionic species derived from organic acids selected from carbonate ions, monocarboxylic acid ions, hydroxytricarboxylate ions and hydroxycarboxylic acid ions is a combination of 0.0001 to 0.5% by weight of any 1 anionic species derived from organic acids selected from carbonate ions, acetate ions, citrate ions and malate ions and 0.0099 to 2.5% by weight of anionic species derived from organic acids selected from citrate ions and malate ions other than the above selected anionic species derived from organic acids.
13. The etchant according to claim 1, wherein the 0.01 to 3% by weight of (D-2) 2 or more anionic species selected from anionic species derived from inorganic acids and anionic species derived from organic acids selected from carbonate ions, monocarboxylic acid ions, hydroxytricarboxylic acid ions and hydroxycarboxylic acid ions is a combination of 0.0001 to 0.5% by weight of at least 1 or more anionic species derived from inorganic acids selected from sulfate ions, sulfite ions and chloride ions and 0.0099 to 2.5% by weight of at least 1 or more anionic species derived from inorganic acids selected from phosphate ions, phosphite ions and hypophosphite ions.
14. The etchant according to claim 1, wherein the etchant contains 10 to 35% by weight of (A) hydrogen peroxide, 0.1 to 3% by weight of (B) a phosphonic acid-based chelating agent having a hydroxyl group, (C) 0.1 to 5% by weight of a basic compound, and 0.01 to 3% by weight of (D-2) 2 or more anion species selected from an anion species derived from an inorganic acid and an anion species derived from an organic acid selected from a carbonate ion, a monocarboxylic acid ion, a hydroxytricarboxylic acid ion, and a hydroxycarboxylic acid ion.
15. The etchant according to claim 1, wherein the etchant is prepared from a solution containing hydrogen peroxide and an etchant preparation solution containing a phosphonic acid-based chelating agent having a hydroxyl group, an alkali compound, and 2 or more kinds of anion species selected from an anion species derived from an inorganic acid and an anion species derived from an organic acid selected from a carbonate ion, a monocarboxylic acid ion, a hydroxytricarboxylic acid ion, and a hydroxycarboxylic acid ion.
16. An etching method for etching a tungsten-based metal film on a semiconductor substrate using the etchant according to claim 1.
17. The etching method according to claim 16, wherein the etchant is prepared by mixing a solution containing hydrogen peroxide with an etchant preparation solution comprising a solution containing a phosphonic acid-based chelating agent having a hydroxyl group, an alkali compound, and 2 or more types of anion species selected from an anion species derived from an inorganic acid and an anion species derived from an organic acid selected from a carbonate ion, a monocarboxylic acid ion, a hydroxytricarboxylic acid ion, and a hydroxycarboxylic acid ion.
18. The etching method according to claim 17, wherein a mixing ratio of the solution containing hydrogen peroxide to the etchant preparation liquid is 30: 70 to 99: 1.
19. An etchant preparation for a semiconductor substrate, which comprises a tungsten (W) -based metal film and a metal bump or metal wiring formed on the metal film, wherein the etchant preparation comprises at least the following components (B), (C) and (D-2),
(B) a phosphonic acid-based chelating agent having a hydroxyl group;
(C) a basic compound;
(D-2) 2 or more anionic species selected from the group consisting of anionic species derived from inorganic acids and anionic species derived from organic acids, wherein the anionic species derived from organic acids is selected from the group consisting of carbonate ions, monocarboxylic acid ions, hydroxytricarboxylic acid ions and hydroxycarboxylic acid ions.
20. The etchant preparation of claim 19, wherein the etchant preparation is used to prepare an etchant by mixing with a solution containing hydrogen peroxide.
21. The etchant preparation of claim 20, wherein the mixture ratio of the hydrogen peroxide solution to the etchant preparation is 30: 70 to 99: 1.
22. The etchant preparation according to claim 20, wherein the etchant preparation is adjusted so that a final pH of the etchant preparation after mixing with the solution containing hydrogen peroxide is in a range of 6 to 10.
23. The etchant preparation of claim 20, wherein the etchant preparation is used for preparing an etchant, and final concentrations of components of the etchant preparation and a solution containing hydrogen peroxide are as follows: (A) 10 to 35% by weight of hydrogen peroxide, (B) 0.1 to 3% by weight of a phosphonic acid chelating agent having a hydroxyl group, (C) 0.1 to 5% by weight of a basic compound, and (D-2) 0.01 to 3% by weight of at least 2 anionic species selected from the group consisting of anionic species derived from inorganic acids and anionic species derived from organic acids selected from the group consisting of carbonate ions, monocarboxylic acid ions, hydroxytricarboxylic acid ions, and hydroxycarboxylic acid ions.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007329530 | 2007-12-21 | ||
| JP2007-329530 | 2007-12-21 | ||
| PCT/JP2008/073246 WO2009081884A1 (en) | 2007-12-21 | 2008-12-19 | Etching agent, etching method and liquid for preparing etching agent |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| HK1148110A1 HK1148110A1 (en) | 2011-08-26 |
| HK1148110B true HK1148110B (en) | 2013-11-01 |
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