CN1333444C - Copper chemical mechanical polishing solutions using sulfonated amphiprotic agents - Google Patents

Abstract

A family of slurries useful in modifying exposed surfaces of wafers for semiconductor fabrication are provided along with methods of modifying exposed surfaces of wafers for semiconductor fabrication utilizing such a family of working slurries, and semiconductor wafers. The slurries of the invention are a solution of initial components, the components comprising: a sulfonated zwitterion selected from 2-(N-Morpholino)ethanesulfonic acid, (3-[N-Morpholino])propanesulfonic acid, 2-[(2-Amino-2-oxoethyl)amino]ethanesulfonic acid, Piperazine-N, N'-bis(2-ethanesulfonic acid), 3-(N-Morpholino)-2-hydroxypropanesulfonic acid, N ,N-Bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 3-(N-Morpholino)propanesulfonic acid, N-(2-Hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid), N-Tris(hydroxymethyl)methyl-2 aminoethanesulfonic acid, 3-[N ,N-Bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, 3-[N -Tris(hydroxymethy I)methylamino)- 2-hydroxypropanesulfonic acid, N-(2-hydroxyethyl)piperazine-N'-(2-hydroxypropanesulfonic acid), Piperazine-N ,N'-bis(2-hydroxypropanesulfonic acid), N-(2-Hydroxyethyl)piperazine-N'-(3-propanesulfonic acid), N-Tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, 3-[( 1,1 -Dimethy 1- 2-hydroxyethyl)amino]-2-hydroxypropanesulfonic, acid, 2-(N- Cyclohexylamino)ethanesulfonic acid, 3-(Cyclohexylamino)-2-hydroxy-I-propanesulfonic acid, 2-Amino-2-methyl-I-propanol, 3-(Cyclohexylamino)-1-propanesulfonic acid, an oxidizing agent; optionally, a passivating agent; optionally a chelating agent, optionally abrasive particles, optionally a surfactant, optionally a secondary buffering agent and water. The method of the invention comprises the steps of: a] providing a wafer comprising a first material having a surface etched to form a pattern and a second material deposited over the surface of the first material; b] contacting the second material of the wafer with abrasive in the presence of the working slurry.

Description

Copper Chemical Mechanical Polishing Solution Using Sulfonated Amphoteric Reagents

Related application reference

This application claims priority to prior US Application 60/425,690, filed November 12,2002.

Background of the invention

field of invention

The present invention relates to improved slurry compositions, methods for chemical mechanical polishing or planarization of semiconductor wafers, and semiconductor wafers produced according to the above methods.

Description of prior art

In the manufacture of integrated circuits, semiconductor wafers used for semiconductor fabrication typically undergo a myriad of processing steps, including deposition, patterning, and etching steps. These specific steps of manufacturing semiconductor wafers are as Tonshoff et al., "Abrasive Machining of Silicon" (grinding processing of silicon), published in Annals of the International Institution for Production Engineering Research, (Volume 39/2/1990), pages 621-635 middle. During each manufacturing step, it is often necessary or desirable to modify or refine the exposed surface of the wafer so that the wafer can be used in a subsequent assembly or manufacturing step. In traditional semiconductor device assembly schemes, silicon wafers undergo multiple processing steps to deposit uniform layers of two or more separate materials that together form a single layer of a multilayer structure. In this process, usually a uniform layer of the first material is applied to the wafer itself, or to an existing layer of an intermediate formed by any means commonly used in the art, a pattern is etched on the layer, and then the pattern Fill with the second material. Alternatively, patterns of approximately uniform thickness of the first material can be deposited through a mask on the wafer or on preassembled layers in the wafer, and can then be completed by filling adjacent areas of these patterns with the second material. processing of this layer. After the deposition step, the material or layer deposited on the wafer surface typically requires further processing before undergoing additional deposition or subsequent processing steps. After completion, the outer surface is substantially completely flat, parallel to the bottom surface of the silicon wafer. A specific example of such a process is a damascene process.

In the damascene process, a pattern is etched in an oxide dielectric layer such as _SiO2 . An optional adhesion layer and/or barrier layer is then deposited on the oxide surface. Typical barrier layers may include: tantalum, tantalum nitride, titanium nitride or titanium, or tungsten. Next, a metal (such as copper) is deposited over or on top of the adhesion layer and/or barrier layer. The copper metal layer is then refined, thinned or polished by removing the copper metal and the tack and/or barrier layer areas on the underlying dielectric surface. Typically, enough surface metal is removed so that the exposed outer surface of the wafer is composed of metal and oxide dielectric material. Viewed from above the exposed surface of the wafer, it can be seen that the copper metal corresponds to the etched pattern and the barrier layer or dielectric material is adjacent to the flat surface of the copper metal. The copper (or other metal) and oxide dielectric materials on the wafer's modified surface have inherently different hardnesses that are prone to controlled corrosion. Methods for improving semiconductor surfaces combine physical and chemical processes. This process is known as chemical mechanical planarization (CMP). The abrasive CMP process used to improve wafers made by the damascene process must be able to improve both the metal (such as copper) and the barrier or dielectric material without creating defects in the surface of either material. The grinding process must result in a planar exposed outer surface on a wafer with exposed areas of metal and exposed areas of dielectric material.

Chemical mechanical polishing (or planarization) (CMP) is an area in semiconductor processing that is undergoing rapid change. CMP can provide complete (millimeter size) and localized (micron to nanometer size) planarization on the wafer surface. This planarization improves the coverage of dielectric materials and metals (such as copper) on the wafer and increases the latitude of lithography, etching and deposition processes. Many equipment companies have advanced CMP technology through advances in CMP engineering, while chemical companies have focused on consumables such as slurries and pads. For example, conventional CMP methods for modifying or refining the exposed surface of a wafer use a technique of polishing the wafer surface with a slurry having a large amount of loose abrasive particles dispersed in an aqueous medium. Typically, the slurry is applied to a polishing pad against which the wafer surface is rotated to remove desired material from the wafer surface. The slurry may also typically contain chemicals that react with the wafer surface to increase the rate of metal removal.

Newer alternatives to CMP slurries use abrasive pads to flatten the semiconductor surface, eliminating the need for the aforementioned slurries containing polishing particles. An alternative CMP process is reported in World Patent WO 97/11484, published March 27, 1997. The abrasive pad has a textured abrasive surface comprising abrasive particles dispersed in a binder. During polishing, the abrasive pad contacts the surface of the semiconductor wafer, usually in the presence of a working slurry without additional abrasive particles. The aqueous slurry is applied to the wafer surface to chemically improve or increase the efficiency of removal of material from the wafer surface by the movement of the abrasive body.

The slurries suitable for the above process and the above slurries or abrasive pads are usually aqueous solutions of various additives, including metal complexing agents, oxidizing agents, passivators, surfactants, wetting agents, buffers, viscosity modifiers or A blend of these additives. Additives may also include reagents that react with a second material, such as a metal or metal alloy conductor on the wafer surface, such as oxidizing, reducing, passivating or complexing agents. Examples of these working slurries can be found in US Patent Application Serial No. 09/091,932, filed June 24, 1998.

Variables that can affect wafer CMP processing include choice of contact pressure between the wafer surface and abrasive body, polishing pad composition, use of low-grade polishing pads, shape of grooves in the polishing pad, type of slurry media, and contact pressure between the wafer surface and abrasive body. The relative speed and relative motion, as well as the flow rate of the slurry medium. These variables are interdependent and are selected based on the individual metal surfaces to be polished.

The CMP process improves the deposited metal layer until the barrier layer or oxide dielectric material is exposed on the outer surface of the wafer, which is rarely a problem because the metal pattern on the wafer surface is sub-micron. The removal rate of the deposited metal should be relatively fast to minimize the need for additional expensive CMP tools, and the metal must be completely removed from areas not etched. Metal remaining in the etched area must be confined to discrete areas where it is continuous to ensure proper conductivity. Therefore, the CMP process must be uniform, controlled, and reproducible on submicron to nanoscale dimensions.

In the above CMP process, dishing performance, scratches or defects, and metal removal rate are the measures of CMP performance. These performance measures may depend on the use of the working slurry and machining process described above. Dishing is a measure of the amount of metal, such as copper, that has been removed from the connection blocks or traces below the surface of the semi-finished wafer, consisting of copper and barrier or dielectric top layers after removal of the surface copper or copper plated barrier layer. height difference between. Removal rate refers to the amount of material removed per unit time. A preferred removal rate is greater than at least about 1000 Angstroms/minute. Lower removal rates, such as hundreds of angstroms per minute or less, are disadvantageous because they result in an increase in the overall manufacturing cost (price of ownership) of the wafer.

In order to reduce the possibility of dishing and increase the metal removal rate of semiconductor devices, it is important that the components in the slurry have very narrow concentration ranges and pH values. The pH of the slurry used in polishing semiconductor devices depends on the composition of the surface layer to be polished. In most cases it is necessary to have the slurry at the proper pH to form an oxide layer surface at a rate relative to the removal of metal oxide by mechanical grinding. For example, when polishing dielectric materials such as _SiO2 , the pH of the slurry is usually greater than 10, which facilitates the formation of silanol bonds:

SiO ₂ +2H ₂ O→Si(OH) ₄ (aqueous solution) pH＜9

Si(OH) ₄ (aqueous solution)+OH ^- →SiO(OH) ₃ +H ₂ O pH＞9

SiO(OH) ₃ →Multinuclear substance pH＞10.5

2Si(OH) ₄ (aqueous solution)→(HO) ₃ Si-O-Si(OH) ₃ +H ₂ O

The pH of the _SiO2 polishing slurry must be greater than 10 to ensure the rapid formation of silicon dioxide after mechanically polishing the surface.

For copper polishing slurries, US Patent 6,117,783 shows the importance of a pH of about 6.0 to form cuprous(I) oxide, _Cu2O . Cuprous oxide can only be formed in near neutral to slightly alkaline media. In low pH slurries, protective oxides may not form on the copper surface, increasing the propensity for aggressive attack of the oxidizing agent on the copper metal. In high pH slurries, the removed copper can precipitate out of solution, forming unwanted particulate matter that adheres to the wafer surface. Therefore, the prepared copper polishing slurry must have a narrow pH range to ensure high yield after CMP.

Another important aspect is to adjust the zeta potential of the slurry by controlling the pH. The zeta potential is a measure of the electrostatic potential of the interaction between the charge double layer ions of the anions and the cations surrounding the inorganic polishing particles in the slurry. The zeta potential depends on the properties of the polishing body (such as Al ₂ O ₃ , CeO ₂ , SiO _{2 ,} etc.) and the pH of the slurry. Slurries with an unfavorable zeta potential are generally unstable, with the result that particles settle out of the slurry or agglomerates. This is very detrimental to performance during CMP polishing.

Another measure of zeta potential is the isoelectric point (IEP) of the polishing particle. The IEP is the pH at which the zeta potential value is zero. The chemical composition and properties of particles have a significant impact on IEP. Some selected IEP values are 3.8 to 9.4 for alumina particles and a narrower range of 1.5 to 3.7 for silica.

Certain metal oxides, such as TiO, have an IEP value of 9.5, while pure tungsten is about 1. Some wide range of IEP values is a major obstacle for technicians to control the zeta potential of particles that may end up attaching to the wafer surface. Additionally, the zeta potential between the polishing particles and the wafer can cause the particles to be attracted and attached to the wafer surface, resulting in the need for a post-CMP cleaning step to remove the attached particles.

Therefore, it is critical to keep the zeta potential within the specified range by controlling the slurry pH during CMP to keep it constant.

It would be desirable to improve chemical mechanical planarization processes by providing working slurries suitable for improving the exposed surfaces of semi-finished wafers for semiconductor manufacturing, and methods for improving the exposed surfaces of semi-finished wafers for semiconductor manufacturing using such working slurries, Improved, sustained metal removal rates are preferred. It is desirable to provide a more stable working slurry than commercially available slurries. Furthermore, it is desired to provide a working slurry suitable for the above method, so that the fabricated metal-containing structured wafer has better planarization effect and fewer defects.

Summary of the invention

The present invention provides improved slurry compositions, and methods of chemical mechanical polishing or planarization of semiconductor wafers.

Specifically, the present invention provides (a) suitable slurries needed to improve the exposed surface of structured wafer semi-finished products in semiconductor manufacturing, (b) methods of using such working slurries to improve the exposed surface of structured wafer semi-finished products in semiconductor manufacturing, and (c) a semiconductor wafer produced as described above.

One aspect of the present invention provides a working slurry suitable for improving the surface of a wafer for manufacturing semiconductor devices, the slurry comprising the following components:

a. Sulfonated zwitterions,

b. Oxidizing agents,

c. A liquid carrier, preferably aqueous,

d. optional inorganic or organic polishing particles,

e. an optional chelating agent,

f. Optional secondary buffer,

g. Optional metal or metal oxide passivators,

h. Optional surfactants, viscosity modifiers, wetting agents, lubricants, soaps and the like, and

i. An optional blocker to enhance metal selectivity.

Another aspect of the present invention provides a method for improving the surface of a wafer for manufacturing a semiconductor device, comprising the steps of:

a) providing a wafer comprised of a first material having a surface etched in a pattern and a second material deposited on the surface of the first material,

b) using a slurry of the present invention in combination with a polishing pad that contacts a second material of the wafer, the slurry comprising a plurality of loose abrasive particles dispersed therein, and

c) relatively moving the wafer while the slurry and the polishing pad contact the exposed surface of the wafer until the wafer is flat and includes at least one exposed area of the first material and one exposed area of the second material.

Another embodiment of the invention is an article of manufacture comprising a metal surface produced from the slurry of the invention.

Detailed Description of the Invention

It has now been found that the addition of sulfonated zwitterions to conventional slurries increases copper removal rates and also provides a buffering effect on the slurries.

The present invention provides a working slurry for improving or refining the surface of a semi-finished structured wafer suitable for the manufacture of semiconductors. The present invention also provides methods for improving the surface of semiconductor semi-finished products using these working slurries.

The main feature of the CMP slurry of the present invention is that it includes sulfonated zwitterions and an oxidizing agent.

While not being bound by theory, it is believed that the sulfonated zwitterions can adjust the pH of the slurry to a desired range, thereby promoting surface copper oxide that is ground off the surface of the electronic device. In addition, the zwitterions of the present invention are characterized as having nitrogen and sulfonic acid moieties capable of forming copper complexes that minimize the tendency of copper to deposit on the backside of silicon devices.

The compositions of the present invention comprise a slurry, preferably an aqueous slurry, comprising the following components: sulfonated zwitterions, oxidizing agent, optional inorganic polishing particles, optional chelating agent, optional secondary Grade buffers, optional deactivators, optional surfactants, viscosity modifiers, wetting agents, lubricants, soaps and the like.

Use a liquid carrier to make a slurry. The liquid carrier may be aqueous or non-aqueous so long as the carrier is compatible with the environment in which it is used. Preferably the carrier is aqueous.

The pH of the slurry of the invention preferably varies from 2 to 11.

As discussed above, the sulfonated zwitterions of the present invention are particularly effective in various CMP slurries for effective removal of metal layers, barrier layers, and dielectric materials in electronic devices. In particular, the paste of the present invention is suitable for removing copper from damascene integrated circuits.

At least one soluble sulfonated zwitterion is generally included in the CMP slurry of the present invention. The sulfonated zwitterion is introduced as an alkyl acid or salt of R ₁ R ₂ -N-(CR ₃ R ₄ ) _x SO ₃ M,

Wherein _R1 and _R2 can be alkyl, aryl, hydroxide, hydrogen, heteroatom ring, aryl ring or alkyl ring structure, _R3 and _R4 can be halogen, alkyl, aryl, hydroxide compound, hydrogen, heteroatom ring, aryl ring or alkyl ring structure, x is 2 to 4, M can be hydrogen, alkali metal or alkaline earth metal, amine or ammonium ion. Preferred sulfonated zwitterions are: 2-(N-morpholino)ethanesulfonic acid, (3-[N-morpholino])propanesulfonic acid, 2-[(2-amino-2-oxyethyl) Amino]ethanesulfonic acid, piperazine-N,N'-bis(2-ethanesulfonic acid), 3-(N-morpholino)-2-hydroxypropanesulfonic acid, N,N-bis(2-hydroxyethyl Base)-2-aminoethanesulfonic acid, 3-(N-morpholino)propanesulfonic acid, N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid), N-tri( Hydroxymethyl)methyl-2-aminoethanesulfonic acid, 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, 3-[N-tri(hydroxymethyl) Methylamino]-2-hydroxypropanesulfonic acid, N-(2-hydroxyethyl)piperazine-N'-(2-hydroxypropanesulfonic acid), piperazine-N,N'-bis(2-hydroxypropanesulfonic acid) acid), N-(2-hydroxyethyl)piperazine-N′-(3-propanesulfonic acid), N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, 3-[(1, 1-Dimethyl-2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, 2-(N-cyclohexylamino)ethanesulfonic acid, 3-(cyclohexylamino)-2-hydroxy-1-propane Sulfonic acid, 2-amino-2-methyl-1-propanol, 3-(cyclohexylamino)-1-propanesulfonic acid.

The concentration range of sulfonated zwitterions is wide. The preferred concentration of the sulfonated zwitterion is about 0.01 to 100 g/L, more preferably 0.1 to about 100 g/L, more preferably about 5 to 75 g/L, more preferably about 10 to 50 g/L.

The zwitterion concentration is preferably maintained at a level that maintains the pH in a range that promotes copper oxidation and helps chelate the scavenged copper.

Suitable chemical oxidizing agents include: hydrogen peroxide, cupric chloride; ammonium, sodium and potassium persulfates; ferric chloride; potassium ferricyanide; nitric acid, potassium nitrate, ammonium molybdate, potassium iodate, hydroxylamine, Diethylhydroxylamine, OXONE (potassium hydrogen persulfate preparation), transition metal complexes such as ferricyanide, ammonium ferric EDTA, ammonium ferric citrate, ferric citrate, ammonium ferric oxalate, urea-hydrogen peroxide, sodium peroxide , benzyl peroxide, di-tert-butyl peroxide, peracetic acid, monopersulfuric acid, dipersulfuric acid, iodic acid and its salts, and mixtures thereof. The concentration of the oxidizing agent in the deionized water is about 0.01 to 50% by weight, preferably 0.02 to 40% by weight. When hydrogen peroxide is used as the oxidizing agent, the concentration (weight percent) in the aqueous solution is generally about 0.5 to 15%, preferably about 1.0 to 7.5%, most preferably about 1.0 to 5.0%.

The CMP slurry may also contain additives such as polishing particles (inorganic or organic abrasive particles), buffers, metal chelating agents, passivators, surfactants, viscosity modifiers, wetting agents, lubricants, soaps and the like thing.

Inorganic abrasive particles may also be included in the working slurry. These inorganic particles can increase the removal rate of metals and/or dielectric materials. Examples of these inorganic particles include: SiO ₂ , Al ₂ O ₃ , CeO ₂ , zirconia, calcium carbonate, garnet, silicates and titanium dioxide. The average particle size of these inorganic particles should be less than about 1000 angstroms, preferably less than about 500 angstroms, more preferably less than about 250 angstroms. The working slurry preferably contains less than 10% by weight, preferably less than 1% by weight, more preferably less than 0.5% by weight of inorganic particles. Although abrasive particles can be added to the CMP slurry, the CMP process using three-dimensional abrasive particles can be fixed into an abrasive polishing pad and a slurry that preferably does not contain abrasives.

A secondary buffer can be added to the working slurry to help control pH. As mentioned above, pH has a significant effect on the properties of the copper surface and the copper removal rate. Most preferred are buffers that are compatible with semiconductors, need to be cleaned after CMP, and minimize the potential for reactions of impurities such as alkali metals and alkaline earth metals in the slurry. Additionally, the most preferred buffers can be adjusted to a pH range from acidic to near neutral to basic. Monobasic, dibasic and polybasic acids can be used as buffers for complete or partial deprotonation reactions with bases such as ammonium hydroxide. The ammonium salts of these acids are preferred, but other alkali metal and alkaline earth metal salts of carboxylic acids may also be used. Representative examples include: salts of carboxylic acids, such as dicarboxylic acids, tricarboxylic acids and polycarboxylic acids. Preferred compounds include, for example, malonic acid, oxalic acid, citric acid, tartaric acid, succinic acid, malic acid, adipic acid, salts and mixtures thereof. Nitrogenous compounds that can act as buffers in pulp include: aspartic acid, glutamic acid, histidine, lysine, arginine, ornithine, cysteine, tyrosine and carnosine , bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane, tris(hydroxymethyl)aminomethane, N-(2-acetamido)-2-iminodiacetic acid, 1,3-bis [Tris(hydroxymethyl)methylamino]propane, triethanolamine, N-tris(hydroxymethyl)methylglycine, N,N-bis(2-hydroxyethyl)glycine and glycine. Ammonium hydrogen phosphate may also be used in the slurry of the present invention.

The use of chelating or complexing agents in the CMP slurries of the present invention enhances the removal of copper from the wafer surface. By adding a complexing agent that can combine with copper, the solubility of copper metal or copper oxide dissolved in water can be increased, and the oxidation and dissolution of copper can be strengthened.

In the working stock according to the invention, the concentration of the complexing agent is always about 0.01 to 50% by weight. Preferred complexing agent acids or salts during copper leveling are: citric acid, oxalic acid, iminodiacetic acid, 2-aminoethylphosphonic acid, aminotris(methylenephosphonic acid), 1-hydroxyiminodiacetic acid, Ethyl-1,1-di-phosphonic acid and diethylenetri-aminepenta(methylenephosphonic acid). The concentration of chelating agent in the slurry is from 0.01 to about 50% by weight, preferably from 0.5 to about 10% by weight, most preferably from 1 to about 10% by weight.

Corrosion inhibitors or passivators for copper are well known. Copper is known to passivate cuprous oxide to some extent, especially at neutral or slightly alkaline pH. Addition of a passivating agent to the working slurry can protect areas of the copper surface that have not contacted the abrasive body from premature, excessive removal by the oxidant, or control the concentration of the oxidant that reacts with the exposed surface of the metal. The most widely used copper inhibitors are tolyltriazole, mercaptobenzothiazole and benzotriazole and their derivatives, known as pyrrole derivatives. The amount and type of passivating agent will depend in part on the desired planarization criteria (removal rate, surface finish and degree of planarization). The preferred concentration (weight percent) in the working slurry is about 0.025 to 0.20%, preferably about 0.050 to 0.15%, more preferably about 0.050 to 0.10%.

Surfactants may also be included in the slurry of the present invention at a concentration of about 0.1 to 15% by volume. Examples of surfactants include polyethylene glycol, polypropylene glycol, polyoxyethylene ether, glycerin, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oil Alkenyl ethers and mixtures thereof.

The slurries of the present invention may also contain viscosity modifiers to achieve the desired viscosity of about 5 to 25 centipoise. Examples of viscosity modifiers include Polyox ^™ available from Union Carbide and Carpool ^™ available from BF Goodrich. Those skilled in the art can understand that surfactants, viscosity modifiers and other known additives can be added to the working slurry according to the needs of specific applications.

Inhibitors may also be included in the slurries of the present invention to inhibit the ability of the system to polish at least partial regions of one or more layers in a multilayer substrate. The preferred concentration (weight percent) in the working slurry is about 0.025 to 20%, preferably about 0.10 to 10%, more preferably about 0.50 to 5%.

Suitable inhibitors are adsorbed on the first metal layer, the second layer and/or one or more additional layers of the multilayer substrate and at least partially inhibit the removal of these layers by the slurry of the present invention. Preferably the blocking agent at least partially inhibits the removal of the second layer by the slurry.

The term "at least partially inhibited" as used herein means that the system has a polishing selectivity of first metal layer:second layer of at least about 5:1, preferably at least about 10:1, preferably at least about 30:1, more preferably at least It is about 50:1, most preferably at least about 100:1. The inhibitor can be any suitable cationically charged nitrogen-containing compound selected from the group consisting of amines, imines, amides, imides, polymers thereof and mixtures thereof. Suitable inhibitors also include, for example, cationically charged nitrogen-containing compounds selected from the group consisting of amines, imines, amides, imides, polymers thereof and mixtures thereof, characterized in that the inhibitor is not a sulfur-containing compound or an azole compound. Cationic charge as used herein means that a portion (eg >1%) of the inhibitor is protonated at the operating pH of the system of the invention. Preferred inhibitors may also have an opposite charge to the charged surface of the unpolished metal layer.

The slurry of the present invention may also contain a wetting agent, which can help the slurry evenly cover the surface of the wafer. Wetting agents may be cationic, anionic, nonionic, amphoteric, fully or partially fluorinated or mixtures thereof.

The slurry may be used at about 10°C to 70°C, more preferably at about 15°C to 60°C, most preferably at about 20°C to 50°C.

Another aspect of the present invention provides a method for improving the surface of a wafer for manufacturing a semiconductor device, comprising the steps of:

(a) providing a wafer comprised of a first material having a surface etched in a pattern and a second material deposited on the surface of the first material;

(b) contacting the second material of the wafer with the slurry of the present invention and the polishing pad, the slurry including a plurality of loose abrasive particles dispersed therein;

(c) relatively moving the wafer while the slurry and the polishing pad contact the exposed surface of the wafer until the wafer is flat and includes at least one exposed area of the first material and one exposed area of the second material.

The method preferably improves the semi-finished surface of the patterned wafer. The first material is usually a dielectric material with an applied intermediate material or an adhesive/barrier layer. Some suitable intermediate materials or tack/barrier layers include tantalum, titanium, tantalum nitride, titanium nitride. Other suitable intermediate materials or adhesion/barrier layers include metals, nitrides and suicides. The shape of the first material includes patterned regions, recessed regions and channels, and other structures capable of forming semiconductor devices. The second material is usually a conductive material selected from titanium, silver, aluminium, tungsten, copper or alloys thereof. The present invention is particularly useful for modifying the surface of conductive materials whose electrical resistance is typically less than about 0.1 ohm-cm. In general, preferred dielectric materials have a dielectric constant of less than about 5.

In this regard, the working slurry containing sulfonated zwitterions and inorganic particles is as described above.

Movement between the wafer and polishing pad occurs at a pressure in the range of about 0.1 to 25 psig, preferably about 0.2 to 15 psig, and most preferably about 1 to 6 psig. The wafer and polishing pad can be rotated and/or moved against each other in a linear fashion, circular fashion, helical fashion, uneven fashion, elliptical fashion or in any fashion. The wafer holder or pedestal may also oscillate or vibrate, such as by transmitting ultrasonic vibrations through the holder or pedestal. For example, the polishing pad and/or wafer rotate relative to each other and move linearly along the relative centers of the wafer and polishing pad. The rotation or rotational speed between the wafer and polishing pad can be from 1 to 10,000 rpm. The preferred rotational speed of the polishing pad is at least 10 to 1000 rpm, more preferably 10 to 250 rpm, most preferably 10 to 60 rpm. The preferred rotational speed of the wafer is 2 to 1000 rpm, more preferably 5 to 500 rpm, more preferably 10 to 100 rpm.

The CMP slurry of the present invention may be used without inorganic polishing particles mixed in an aqueous medium. On the contrary, a fixed three-dimensional polishing pad with many abrasive particles dispersed in at least a part of its thickness range can be used to remove some particles during the planarization process and expose more abrasive particles that can achieve the planarization function. Preferred abrasive polishing pads include a plurality of abrasive particles immobilized and dispersed in a binder.

In a stationary abrasive polishing process, contact and motion is maintained between the stationary abrasive pad and the wafer until the exposed surface of the wafer is flattened and includes at least one exposed area of second or conductive material and at least one first Or the exposed area of the dielectric material, and the exposed area of the conductive material and the exposed area of the dielectric material are in the same plane. The dielectric material may be overlaid with one or more intermediate materials, such as adhesive or barrier layers. After removal of excess conductive material, the exposed surface of the dielectric material is typically substantially free of intervening material. Alternatively, the clear metal layer may only expose the surface of the intermediate material. Continuous improvement then exposes dielectric and metal layers on the wafer surface.

The abrasive pads used with the slurries of the present invention may be circular, such as in the form of abrasive discs. The outer edge of the circular grinding disc is preferably smooth, or notched. The abrasive body can also be elliptical or of any polygonal shape, such as triangular, square, rectangular and the like. Alternatively, fixed abrasive pads may be in the form of brushes, belts or rollers, commonly referred to in the CMP polishing industry as abrasive tape rolls. During the manufacturing process, abrasive tape rolls can be marked. The abrasive body may be perforated to leave the abrasive coating and/or backing open to allow the passage of slurry media before, during or after use.

The interface pressure (ie, contact pressure) between the abrasive body and the wafer surface is generally less than about 30 psig, preferably less than about 15 psig, more preferably less than about 6 psig. Also, two or more processing conditions can be used in the planarization process. For example, the interfacial pressure in the first processing stage is higher than in the second processing step. The rotational and translational speeds of the wafer and/or polishing pad can also be varied during planarization.

The recessed portion of the pad acts as a channel to help spread the working slurry across the wafer surface. The recess also acts as a channel to help remove worn abrasive metal particles and other debris from the wafer-body interface. The recessed portion also prevents what is known in the art as "stiction", the tendency for abrasive bodies to adhere or become fixed on the wafer surface.

Methods of producing a uniform wear rate on a polishing target surface and/or polishing pad surface are discussed in US Patent Nos. 5,177,908; 5,234,867; 5,297,364; 5,486,129; 5,230,184; These methods are suitable for use in the present invention. Continuous belt or sheet material feed rolls and slurries are used in varying wafer planarization processes, and belts or rolls of textured three-dimensional abrasive composites can also be used with the working slurries of the present invention.

The amount of the working slurry of the invention applied to the wafer surface is preferably sufficient to aid in the removal of metal or metal oxide from the surface. In most cases there is sufficient working slurry of the invention. It will also be appreciated that certain planarization applications may require a second slurry other than the slurry of the present invention on the planarized interface. This second slurry can be the same as the first slurry, or it can be different. The flow rate of the dispersed working slurry is generally about 10 to 1000 ml/min, preferably 10 to 500 ml/min, more preferably about 25 to 250 ml/min.

The surface finish of the wafers can be evaluated by known methods. A preferred method is to measure the Rt value of the wafer surface, which provides a measure of "roughness" and indicates scratches or other surface defects. The wafer surface is preferably modified to have an Rt value of no greater than about 1000 Angstroms, more preferably no greater than about 100 Angstroms, and more preferably no greater than about 50 Angstroms.

Many processing steps may be required for a single semiconductor wafer. Therefore, a higher metal layer removal rate is required. Using the described CMP slurries, removal rates are typically at least 1000 Angstroms. Min, preferably at least 2000 Angstroms/min, more preferably at least 3000 Angstroms/min, most preferably at least 4000 Angstroms/min. The metal removal rate varies depending on the type of CMP tool and wafer processing surface. Although higher removal rates are generally required, the removal rates are preferably not so high as to compromise the surface finish and/or wafer surface morphology or make control of the planarization process difficult.

The invention is further illustrated by the following non-limiting examples.

Example 1

This example demonstrates the ability of sulfonated zwitterions to facilitate the removal of copper from semiconductor wafers. Copper wafers were polished using slurry PL-7102 commercially available from Fujimi. The wafer was spun at 80 rpm (or 0.62 m/s pad-wafer relative velocity) with a wafer pressure of 3 psi (or 20684 Pa). The polishing pad is a Rodel IC-1000 XY-Groove. The slurry flow rate at the center of the pad was 80 ml/min. The following removal rates (in nm/min) were obtained:

slurry Removal rate (nm/min)   Blank (no additives) 363.5   +15 g/L of piperazine-N,N'-bis(2-ethanesulfonic acid) 440.5   +15 g/L of N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) 534.0   +50 g/L of 3-[N-morpholino])propanesulfonic acid 567.6   +50 g/L of 2-(N-morpholino)ethanesulfonic acid 541.3   +50 g/L of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid 520.9

The copper removal rate was increased due to the sulfonated zwitterions.

Example 2

This example demonstrates the effect of sulfonated zwitterions on maintaining pH during exposure to oxidizing solutions.

Cut the pure copper foil into test pieces approximately 4 cm by 4 cm. The copper was cathodically cleaned in a solution containing 50 g/L NaOH at 60°C and 4.0 volts for 30 seconds. The copper foils were then rinsed in distilled water, followed by immersion in 5% sulfuric acid for 5 seconds. Rinse the copper again with distilled water.

Compositions were prepared according to the table below. The "blank" solution contained only 2% hydrogen peroxide and the pH was adjusted to 6.00. Various sulfonated zwitterions were tested for their ability to maintain pH over 5 hours.

combination Initial pH 5 hours pH@(ΔpH-5 hours) Voltage (for SCE) Appearance of copper foil Blank (2%H ₂ O ₂ ) 6.00 5.62(-0.38) +0.3350 Shiny + 25 g/L of 2-(N-morpholino)ethanesulfonic acid, sodium salt 6.03 5.98(-0.05) +0.3150 Dull + 50 g/L of 2-(N-morpholino)ethanesulfonic acid, sodium salt 6.04 5.98(-0.06) +0.3100 Dull + 25 g/L of 2-(N-morpholino)ethanesulfonic acid 6.04 6.01(-0.03) +0.3100 Dull + 50 g/L of 2-(N-morpholino)ethanesulfonic acid 6.03 5.99(-0.04) +0.3100 Dull + 50 g/L of N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) 6.01 5.94(-0.05) +0.3550 Dull +50 g/L of piperazine-N,N'-bis(2-ethanesulfonic acid) 6.01 5.86(-0.15) +0.3300 Dull + 50 g/L of 3-[N-(morpholino)]internalsulfonic acid 6.01 5.93(-0.08) +0.3150 Dull

It was found that the solution containing only _H2O2 resulted in a pH change of _-0.38 , while the solution containing the sulfonated zwitterions kept the pH close to the original value.

Example 3

This example compares buffers described in the literature and the present invention.

Clean the copper foil as described in Example 2. Soak the cleaned copper foil in the following solutions for 24 hours and record the change in pH, foil weight and copper appearance.

combination Initial pH Initial Cu weight (g) Final pH (ΔpH-24 hours)   Final Cu weight (% weight change) Copper foil appearance Blank (2%H ₂ O ₂ ) 6.01 0.1697 4.17(-1.84) 0.1669 (-1.6%) slightly dull   + 50 g/L Potassium Citrate 6.00 0.1722 6.45(+0.45) dissolve to dissolve +50 g/l of potassium phosphate 6.01 0.1949 6.04(+0.03) 0.1975 (+1.3%) Green coating on Cu   +50 g/L of 3-[N-morpholino])propanesulfonic acid 6.01 0.2116 5.18(-0.83) 0.2111 (-0.24%) severely tarnished   +50 g/L of 2-(N-morpholino)ethanesulfonic acid 6.00 0.1771 5.79(-0.21) 0.1784 (+0.73%) severely tarnished +30 g/l of glycine 5.99 0.2237 6.21(+0.22) dissolve to dissolve

The "blank" composition exhibited a significant pH shift after 24 hours. A slightly dull copper sheen indicates some degree of oxidation. Compositions containing citrate as a buffer/chelator maintained the pH, but the very strong complexation of the copper by the citrate completely dissolved the copper foil, indicating that the buffer was aggressive. Compositions containing phosphate as the primary buffer also maintain pH, but form a dark green film on the copper surface, which is disadvantageous in CMP applications. Compositions containing sulfonated zwitterionic buffers brought the pH closer to the starting pH than the "blank" solution, forming the desired oxide or dull film without attacking live dissolved copper samples.

Example 4

This example demonstrates the use of OXONE (2KHSO ₅ ·KHSO ₄ ·K ₂ SO ₄ ) as an oxidant and the effect of a zwitterionic buffer.

The copper foil was cleaned as described in Example 2. Cleaned copper samples were soaked in the following compositions for 24 hours and the changes in pH, copper appearance and solution color were recorded.

combination Initial pH Initial Cu weight ΔpH, 5 hours Appearance after 5 hours Solution color after 5 hours OXONE (20g/L) 6.00 0.2010 3.94(-2.06) stained light blue → green/blue/pH increase +50 g/L of piperazine-N,N'-bis(2-ethanesulfonic acid) 6.01 0.1972 5.46(-0.55) Oxidized (passivated) surface transparent + 50 g/L of hydroxyethylpiperazine-N'-(2-ethanesulfonic acid) 6.02 0.2537 5.71(-0.32) Oxidized (passivated) surface transparent +25 g/L 2-(N-morpholino)ethanesulfonic acid 6.00 0.2008 5.75(-0.25) Oxidized (passivated) surface amber + 50 g/L of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid 6.01 0.2103 5.63(-0.38) dark brown surface transparent

The pH change in the composition containing only OXONE was approximately -2.06 units, while the composition containing the sulfonated zwitterionic buffer exhibited a pH change of less than -1.0. Copper foils immersed in OXONE-only solutions were stained and etched unevenly. The surface of copper foil immersed in OXONE solution containing sulfonated zwitterions was uniformly oxidized.

Example 5

This example demonstrates the use of hydroxylamine as an oxidizing agent and the effect of sulfonated zwitterionic buffers.

Clean the copper foil as described in Example 2. The clean copper foil was immersed in the following composition for 5 hours, and the change in pH and the change in color of the solution were recorded.

combination Initial pH Final pH (ΔpH-5 hours) Solution color after 5 hours Blank (0.50 mol/L NH ₂ OH) 6.01 5.64(-0.41) transparent +50 g/L of piperazine-N,N'-bis(2-ethanesulfonic acid) 5.99 5.96(-0.03) very light purple +50 g/L of hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) 6.00 5.95(-0.05) light blue/purple + 50 g/L of 3-[N-morpholino]) internal sulfonic acid 6.02 5.96(-0.06) light blue/purple + 50 g/L of 2-(N-morpholino)ethanesulfonic acid 5.98 6.01(+0.03) very light blue +30 g/l glycine 6.01 5.99(-0.02) Navy blue + 50 g/L of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid 6.01 5.92(-0.09) very light blue

Compositions containing only hydroxylamine exhibited a pH change of approximately -0.46 units, while compositions containing the sulfonated zwitterionic buffer exhibited a pH change of less than -0.10. Compositions containing only hydroxylamine were clear, indicating very little copper dissolved or dissolved into solution in the form of cuprous ions. Hydroxylamine compositions containing glycine are dark blue, indicating rapid dissolution of copper as copper ions. The hydroxylamine composition containing the sulfonated zwitterion was light in color, indicating dissolution of the copper ion after complexation (it was the chromophore of the copper-zwitterion complex that developed the color).

Example 6

This example demonstrates the use of hydroxylamine as an oxidizing agent and the effect of sulfonated zwitterionic buffers after prolonged exposure to copper.

Clean the copper foil as described in Example 2. Cleaned copper samples were immersed in the following compositions for 5 hours and the change in pH, the change in copper weight after exposure to the electrolyte, and the change in color of the solution were recorded.

combination Initial pH Initial Cu weight (g) Final pH (ΔpH-24 hours)   Final Cu weight (% weight change) The color of the solution at the end of the test Blank (0.50 mol/L NH ₂ OH) 6.01 0.2150 4.83(-1.18) 0.2026 (-5.76%) light blue + 50 g/L Potassium Citrate 6.01 0.2204 6.17(+0.16) 0.0128 (-94.1%) light blue +50 g/L potassium phosphate 6.00 0.2541 5.85(-0.15) 0.2448 (-3.7%) light blue +50 g/L of piperazine-N,N'-bis(2-ethanesulfonic acid) 5.99 0.2108 5.54(-0.45) 0.1760 (-16.5%) light blue +50 g/L of hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) 6.00 0.1851 5.31(-0.69) 0.1458 (-21.2%) light blue + 50 g/L of 2-(N-morpholino)ethanesulfonic acid 5.98 0.1981 5.69(-0.29) 0.1524 (-36.2%) green +30 g/L glycine 6.01 0.2082 5.89(-0.12) dissolve light blue +50 g/L of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid 6.01 0.2430 5.62(-0.39) 0.1960 (-19.3%) Navy blue

The "blank" composition containing only hydroxylamine exhibited a pH change of -1.18 units with a moderate weight loss of approximately 5.67%. The use of citrate and glycine maintains the pH of the solution, but attacks the copper foil, resulting in excess copper dissolution. Similarly, using a phosphate buffer maintained the pH during the test, but the copper foil surface was covered with an unwanted, green copper phosphate coating that was difficult to handle during CMP. The use of sulfonated zwitterionic buffers exhibited moderate amounts of copper dissolution, but their ability to maintain pH was superior to that of no buffer solution. The color of the sulfonated zwitterionic buffer solutions indicated some degree of copper complexation by these buffers.

Claims (32)

1. A slurry that is used for leveling the wafer surface suitable for manufacturing semiconductor devices, the slurry comprising: a. Sulfonated zwitterions, b. Oxidizing agents, c. Liquid carrier, d. Optional inorganic polishing particles, e. an optional chelating agent, f. Optional secondary buffer, g. optional passivating agent, h. Optional surfactants, viscosity modifiers, wetting agents, lubricants or soaps, and i. Optional inhibitors. 2. The slurry according to claim 1, wherein the sulfonated zwitterionic reagent has the following structure: R ₁ R ₂ -N-(CR ₃ R ₄ ) _x SO ₃ M Wherein _R1 and _R2 are alkyl, hydroxyl, hydrogen, heteroatom ring, aromatic ring or cycloalkyl structure, _R3 and _R4 are halogen, alkyl, hydroxyl, hydrogen, heteroatom ring, aromatic ring or cycloalkane The base structure, x is 2 to 4, M is hydrogen, alkali metal or alkaline earth metal, amine or ammonium ion. 3. The slurry according to claim 1, wherein the sulfonated zwitterions are selected from the group consisting of: 2-(N-morpholino)ethanesulfonic acid, 2-[(2-amino-2-oxyethyl)amino ]ethanesulfonic acid, piperazine-N, N'-bis(2-ethanesulfonic acid), 3-(N-morpholino)-2-hydroxypropanesulfonic acid, N,N-bis(2-hydroxyethyl )-2-aminoethanesulfonic acid, 3-(N-morpholino)propanesulfonic acid, N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid), N-three (hydroxy Methyl)methyl-2-aminoethanesulfonic acid, 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, 3-[N-tri(hydroxymethyl)methyl Amino]-2-hydroxypropanesulfonic acid, N-(2-hydroxyethyl)piperazine-N'-(2-hydroxypropanesulfonic acid), piperazine-N,N'-bis(2-hydroxypropanesulfonic acid) ), N-(2-hydroxyethyl)piperazine-N'-(3-propanesulfonic acid), N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, 3-[(1,1 -Dimethyl-1,2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, 2-(N-cyclohexylamino)ethanesulfonic acid, 3-(cyclohexylamino)-2-hydroxy-1- propanesulfonic acid, 3-(cyclohexylamino)-1-propanesulfonic acid or mixtures thereof. 4. The slurry according to claim 1, characterized in that the concentration of sulfonated zwitterions is 0.1 to 100 g/l. 5. The slurry of claim 1, wherein the pH varies from 2 to 11. 6. The slurry according to claim 1, wherein the oxidant is selected from the group consisting of hydrogen peroxide, cupric chloride, ammonium persulfate, sodium persulfate and potassium persulfate, ferric chloride, potassium ferricyanide, nitric acid , potassium nitrate, ammonium molybdate, potassium iodate, hydroxylamine, diethylhydroxylamine, OXONE, ferric cyanide, ammonium ferric EDTA, ferric ammonium citrate, ferric citrate and ferric ammonium oxalate, urea-hydrogen peroxide, peroxide Sodium, benzyl peroxide, di-tert-butyl peroxide, peracetic acid, monopersulfuric acid, dipersulfuric acid, iodic acid and their salts, and mixtures thereof. 7. The slurry according to claim 1, characterized in that the concentration of the oxidizing agent is in the range of 0.5 to 15%. 8. The slurry according to claim 1, characterized in that it contains inorganic polishing particles. 9. The slurry according to claim 8, characterized in that the inorganic _{polishing particles are selected from SiO2, Al2O3 , CeO2 ,} zirconia, calcium carbonate, garnet, silicate or titania. 10. The slurry of claim 1, wherein no inorganic polishing particles are used in the slurry. 11. The slurry of claim 1, wherein the secondary buffer is 0.1 to 100 g/l. 12. The slurry of claim 1, wherein the secondary buffer is an ammonium salt of a mono-, di- or polybasic acid, an alkali metal or alkaline earth metal salt of a mono-, di- or tricarboxylic acid, a phosphonic acid, or a Zwitterions of nitrogen or mixtures thereof. 13. The slurry of claim 12, wherein the nitrogen-containing zwitterion is an amino acid. 14. The slurry according to claim 1, which contains a passivating agent, characterized in that the passivating agent is tolyltriazole, mercaptobenzothiazole or benzotriazole. 15. The slurry according to claim 14, characterized in that the concentration of passivating agent is in the range of 0.025 to 0.20%. 16. The slurry according to claim 1, characterized in that surfactants, viscosity modifiers, wetting agents, lubricants or soaps are used. 17. The slurry according to claim 1, characterized in that the temperature is from 10°C to 70°C. 18. The slurry of claim 1, wherein at least one inhibitor has a polishing selectivity of at least 5:1 for the first metal layer and the second metal layer, wherein the inhibitor is a cationically charged Nitrogen compounds. 19. The slurry of claim 1, wherein the liquid carrier is a non-aqueous solvent. 20. The slurry of claim 1 wherein the liquid carrier is water. 21. The slurry of claim 2, wherein the sulfonated zwitterions are introduced as ammonium or potassium salts or mixtures thereof. 22. The slurry of claim 1 wherein the ground metal is masked with a chelating agent. 23. The slurry of claim 1, wherein the chelating agent is selected from the group consisting of salts of citric acid, iminodiacetic acid, 2-aminoethylphosphonic acid, aminotris(methylenephosphonic acid)1 -Hydroxyethylidene-1,1-di-phosphonic acid, diethylenetri-aminepenta(methylenephosphonic acid) and glycine. 24. The slurry of claim 1, wherein the wetting agent is cationic, anionic, nonionic, amphoteric, fluorinated or mixtures thereof. 25. A method of improving the surface of a wafer suitable for the manufacture of semiconductor devices, comprising the steps of: a. providing a wafer comprising a first material having a surface etched in a pattern and a second material deposited on the surface of the first material; b. contacting the second material of the wafer to the polishing pad in the presence of the working slurry of claim 1; and c. Relatively moving the wafer or polishing pad while the second material contacts the polishing pad until the exposed surface of the wafer is flattened and includes at least one exposed area of the first material and one exposed area of the second material . 26. The method of claim 25, wherein the slurry contains inorganic polishing particles. 27. The method of claim 25, wherein the inorganic polishing particles are immobilized on the polishing pad. 28. The method of claim 25, wherein no inorganic polishing particles are used. 29. The method of claim 25, wherein the polishing pad comprises a polymer pad on which is applied a slurry comprising a plurality of loose abrasive particles dispersed therein, the slurry being formed by applying the polishing pad metal layer that contacts the wafer. 30. The method of claim 25, wherein the first material is a dielectric material and the second material is a conductive material. 31. The method of claim 25, wherein the wafer further includes a barrier layer covering the dielectric material. 32. The method of claim 30, wherein the conductive material is a conductive metal selected from the group consisting of: titanium, silver, aluminum, tungsten, tantalum, tantalum nitride, tungsten nitride, tantalum oxide, tungsten oxide, oxide Silicon, copper or their alloys.