JP2010272635A - Chemical mechanical polishing method - Google Patents

Abstract

Disclosed is a chemical mechanical polishing method that has a high polishing rate, suppresses the occurrence of dishing, and has excellent flatness.
A polishing process for polishing the same conductive film on the same surface plate using a polishing liquid is performed twice or more, and is performed immediately before and between the first polishing process and the last polishing process. A chemical mechanical polishing method comprising a cooling step of cooling the platen so as to be -5 ° C to -80 ° C with respect to the temperature of the platen immediately after completion of the polishing step.
[Selection figure] None

Description

  The present invention relates to a method for polishing a substrate having a conductor film used when performing chemical mechanical planarization in a semiconductor device manufacturing process.

In the development of semiconductor devices typified by semiconductor integrated circuits (hereinafter sometimes referred to as “LSI”), in order to increase the integration and speed of semiconductor devices, wiring miniaturization and lamination methods are studied. Has been.
For this purpose, various techniques such as chemical mechanical polishing (hereinafter sometimes referred to as “CMP”) are employed. CMP is used for polishing an interlayer insulating film (such as SiO 2) and a metal thin film used for wiring to smooth the substrate, or to remove an excess metal thin film at the time of wiring formation (for example, Patent Documents). 1).

A general method of CMP is as follows.
A polishing pad is affixed on a circular polishing platen (platen), and the surface of the polishing pad is immersed in a polishing liquid. The surface of the substrate (wafer) is pressed against the polishing pad, and both the polishing platen and the substrate are rotated with a predetermined pressure (polishing pressure) applied from the back surface.
In CMP, the surface of a substrate is flattened by mechanical friction generated by the above operation.

  Conventionally, tungsten and aluminum have been widely used in interconnect structures as wiring metals. However, LSIs using copper, which has lower wiring resistance than these metals, have been developed with the aim of achieving higher performance. As a method for wiring this copper, a damascene method is known (for example, see Patent Document 2). Further, a dual damascene method in which a contact hole and a wiring groove are simultaneously formed in an interlayer insulating film and a metal is embedded in both has been widely used. As a target material for copper wiring, a high-purity copper target of five nines or more is shipped.

  However, in recent years, in order to miniaturize the wiring in accordance with the demand for higher density, improvements in the conductivity and electronic characteristics of the copper wiring are required. On the other hand, the use of a copper alloy obtained by adding a third component to high-purity copper has begun to be studied.

  There is also a need for high-speed metal polishing means that can increase productivity without contaminating these high-definition and high-purity materials. In particular, since copper is a soft metal, when polishing copper or copper alloys, only the center is polished deeper, resulting in dish-like depressions (dishing), or the surface of multiple wiring metal surfaces is a dish. A phenomenon (erosion) that forms a concave-shaped recess and a polishing flaw (scratch) are likely to occur, and an increasingly accurate polishing technique is required.

  In recent years, wafers have become larger in order to improve productivity. Currently, wafers with a diameter of 200 mm or more are widely used, and manufacture of wafers with a diameter of 300 mm or more has started. As the size of the wafer increases, the difference in polishing rate between the central portion and the peripheral portion of the wafer tends to increase, and there is a strong demand for uniform polishing within the wafer surface.

On the other hand, as a chemical polishing method in which mechanical polishing means is not applied to copper and a copper alloy, a chemical polishing method based only on a dissolving action is disclosed (for example, see Patent Document 3).
However, in the chemical polishing method, since polishing is performed only by a chemical dissolution action, problems such as dishing of recesses, that is, dishing, are likely to occur compared to CMP in which the metal film of the protrusions is selectively chemically and mechanically polished. Flatness has become an issue.

In addition, when copper wiring is used in LSI manufacturing, a diffusion prevention layer called a barrier layer is generally provided between the wiring portion and the insulating layer in order to prevent copper ions from diffusing into the insulating material. The barrier layer is formed of a barrier material such as TaN, TaSiN, Ta, TiN, Ti, Nb, W, WN, Co, Zr, ZrN, Ru, CuTa alloy, MnSi _X O _Y , and MnO _X. Two or more layers are provided.
Since these barrier materials have a conductive property, the barrier material on the insulating layer must be completely removed in order to prevent an error such as a leakage current. For this removal processing, a method similar to that for polishing the bulk of the metal wiring material can be applied. This is what is called barrier CMP.

  Further, in the bulk polishing of copper, dishing is likely to occur particularly in a wide metal wiring portion. Therefore, it is desirable that the amount of polishing and removal can be adjusted between the wiring portion and the barrier portion in order to be finally flattened. For this reason, it is desired that the polishing liquid for barrier polishing has an optimal polishing selectivity of copper / barrier metal. Further, since the wiring pitch and the wiring density are different in each level of the wiring layer, it is further desirable that the polishing selectivity can be adjusted as appropriate.

  The metal polishing composition (metal polishing liquid) used for CMP generally contains solid abrasive grains (for example, alumina, silica) and an oxidizing agent (for example, hydrogen peroxide, peroxodisulfate). It is considered that the basic mechanism of CMP using such a metal polishing liquid is that polishing is performed by oxidizing the metal surface with an oxidizing agent and removing the oxide film with abrasive grains (for example, non-polishing). (See Patent Document 1).

A polishing agent containing peroxodisulfate has a feature that a high polishing rate can be obtained, but has a problem that dishing and erosion are likely to proceed. As one means for solving the dishing, benzotriazoles are used as an anticorrosive agent that suppresses polishing of a metal film (see, for example, Patent Document 4).
According to these methods, a protective film is formed on the metal film of the semiconductor substrate, and the convex film is removed by the abrasive grains, but the metal film is left in the concave part to obtain a desired conductor pattern. Occurrence of dishing is suppressed by the protective film of the recess, and high flatness is obtained.

  However, even with metal polishing liquids that use these anticorrosive agents that provide high flatness, the occurrence of erosion due to corrosion of the barrier film cannot be suppressed, and further improvements regarding flatness required for device manufacturing are required. It was.

US Pat. No. 4,944,836 JP-A-2-278822 JP 49-122432 A JP-A-2005-116987

Journal of Electrochemical Society, 1991, 138, 11, 3460-3464 Journal of Electrochemical Society, 2000, 147, 10, 3907-3913

  The problem to be solved by the present invention is to provide a chemical mechanical polishing method capable of polishing with a high polishing rate and with suppressed dishing.

  As a result of intensive studies on the problems related to the chemical mechanical polishing described above, the present inventors have found that the problems can be solved by controlling the temperature of the surface plate in the following multistage polishing, and have completed the present invention. The present invention is as follows.

<1> Two or more polishing steps for polishing the same conductive film using the polishing liquid on the same platen, and performed immediately before and between the first polishing step and the last polishing step. A chemical mechanical polishing method comprising a cooling step of cooling a platen so that the temperature of the platen is −5 ° C. to −80 ° C. immediately after the polishing step is finished.

<2> Chemical mechanical polishing for cooling the platen so that the cooling step is −15 ° C. to −60 ° C. with respect to the temperature of the platen immediately after completion of the polishing step performed immediately before the cooling step. Method.
<3> When the polishing pressure in the n-th polishing step is P _n and the polishing pressure in the (n + 1) -th polishing step is P _{n + 1} , P _n and P _{n + 1} are different polishing pressures <1 > Or <2> The chemical mechanical polishing method.

<4> The chemical mechanical polishing method according to <3>, wherein the relationship between P _n and P _{n + 1} is P _n > P _{n + 1} .
<5> The chemical mechanical polishing method according to any one of <1> to <4>, wherein the cooling method in the cooling step is a method of cooling by applying an aqueous solvent on a surface plate.

<6> The chemical mechanical polishing method according to <5>, wherein the aqueous solvent is water.
<7> The chemical mechanical polishing method according to any one of <1> to <6>, wherein the same conductor film is a conductor film made of copper or a copper alloy.

In the polishing process, polishing is performed by applying a polishing pressure, so that the temperature of the surface plate, the pad, and the substrate rises due to friction between the pad on the surface plate and the substrate. In the case of polishing copper or copper alloy, chemical polishing, that is, etching progresses due to this temperature rise. When this etching progresses excessively, dishing or the like occurs to cause a step, and the flatness of the substrate deteriorates. In order to suppress dishing, polishing has been performed with a lower polishing pressure, and a polishing solution has been studied to suppress chemical etching due to physical polishing progress and heat generation. However, polishing at a low polishing pressure takes a long polishing time, and thus tends to cause a decrease in productivity. By adopting the polishing method of the present invention, it becomes possible to have a good step performance that could not be achieved so far, regardless of the polishing liquid, without reducing the throughput.
In the present invention, in particular, a method for polishing a substrate having a conductor layer (wiring) made of copper metal, copper alloy or the like as a raw material more quickly and with excellent flatness is realized.

At the initial stage of polishing (this polishing stage is hereinafter referred to as “polishing step (1)”), that is, at a stage where a high polishing rate is required without affecting the step (dishing) characteristics, the polishing progresses. By increasing the polishing temperature, a high polishing rate by chemical etching can be obtained. However, if polishing is continued under this condition, the final stage of polishing (this polishing stage is hereinafter referred to as “polishing step (2)”). The present invention has focused on the fact that steps (dishing) are likely to occur.
Therefore, the polishing is divided into a plurality of steps, and in the polishing step (1), high-efficiency polishing due to high temperature due to friction is performed without particularly controlling the temperature, and then the polishing is stopped and the surface plate is cooled. Later, the chemical etching in the polishing step (2), which is the next stage polishing step, is suppressed and polishing at a low temperature can solve the above problem, more specifically, at the end of the polishing step (1) The problem of the present invention is solved by cooling the platen so that the temperature of the platen in the cooling step at the start of the polishing step (2) is 5 ° C. or more and 80 ° C. or less, preferably 15 ° C. or more and 60 ° C. or less. I found out that
Compared to the conventional method in which polishing is performed from start to finish without controlling the temperature of the surface plate in polishing, the use of the polishing method of the present invention eliminates the reduction in throughput and suppresses the occurrence of dishing. Polishing became possible.

  After the polishing process (1) is completed, the surface plate cooling process is provided, and then the polishing process (2) is performed, so that dishing can be suppressed from both physical polishing and chemical etching. It is considered that both high throughput and low dishing, which could not be achieved so far, could be achieved by the polishing method regardless of the polishing liquid.

ADVANTAGE OF THE INVENTION According to this invention, the chemical mechanical polishing method which can implement | achieve grinding | polishing with high grinding | polishing speed | rate and suppressing generation | occurrence | production of dishing can be provided.
As a result, a substrate having a conductor film (wiring) made of copper metal, copper alloy, or the like as a raw material can be more quickly obtained. In addition, since a polishing method excellent in flatness can be provided, for example, according to the method of the present invention, it is expected that the productivity of LSI is increased.

The polishing method of the present invention has two or more polishing steps for polishing the same conductor film on the same surface plate using a polishing liquid, and between the first polishing step and the last polishing step, It is a chemical mechanical polishing method having a cooling step of cooling the platen so as to be −5 ° C. to −80 ° C. with respect to the temperature of the platen immediately after completion of the polishing step performed immediately before, Preferably, by cooling to −15 ° C. to −60 ° C., the polishing rate of the substrate having the conductor film is maintained at a high level, while the wiring recess is prevented from being scraped and the occurrence of dishing is suppressed. In this method, polishing with excellent flatness is achieved.
Hereinafter, this chemical mechanical polishing method (hereinafter, simply referred to as “polishing method”) will be described in detail.

<Polishing process>
(Polishing equipment)
First, an apparatus capable of carrying out the polishing method of the present invention will be described.
As a polishing apparatus applicable to the present invention, a holder for holding a substrate to be polished (semiconductor substrate or the like) having a surface to be polished and a motor or the like having a polishing pad attached (a motor capable of changing the number of rotations) are attached. ) A general polishing apparatus provided with a surface plate can be used. For example, FREX300 (manufactured by Ebara Corporation) can be used.

(Polishing pad)
The polishing pad used in the polishing method of the present invention is not particularly limited, and may be a non-foamed structure pad or a foamed structure pad. The former uses a hard synthetic resin bulk material like a plastic plate for a pad. The latter is further divided into three types: an independent foam (dry foam system), a continuous foam (wet foam system), and a two-layer composite (laminate system). The effect of this is expressed. The foaming may be uniform or non-uniform.

  The polishing pad may further contain abrasive grains (for example, ceria, silica, alumina, resin, etc.) used for polishing. In addition, the hardness may be either soft or hard, and either may be used. In the laminated system, it is preferable to use a different hardness for each layer. The material is preferably non-woven fabric, artificial leather, polyamide, polyurethane, polyester, polycarbonate or the like. In addition, the surface contacting the polishing surface may be subjected to processing such as lattice grooves / holes / concentric grooves / helical grooves. However, in this case, in the cooling step, it may be preferable from the standpoint of scratching or the like to cool the substrate separately from the surface plate.

  In the present invention, the end of the polishing step means when the supply of the polishing liquid to the surface plate of the polishing machine is stopped.

The temperature of the surface plate immediately after completion of the polishing step performed immediately before the cooling step is preferably 30 ° C. or higher and 85 ° C. or lower, and more preferably 40 ° C. or higher and 75 ° C. or lower.
This temperature range is preferable because a large polishing rate can be obtained.

  The temperature of the surface plate in the present invention is usually measured using a thermometer attached to the polishing apparatus. In the EREX300 (manufactured by Ebara Seisakusho), a laser-type thermometer is attached.

  The temperature of the conductor film, which is an object to be polished placed on the surface plate, is preferably 40 ° C. or more and 80 ° C. or less immediately after the polishing step performed immediately before the cooling step, and after the cooling step is completed. The temperature of the conductor film immediately before starting the polishing step to be performed is preferably 20 ° C. or higher and 45 ° C. or lower. When the conductor film is in this temperature range, the effect of the present invention is further great.

(Polishing pressure)
The polishing pressure for polishing the conductor film is not particularly limited, but polishing is preferably performed in the range of 7 hpa to 400 hpa, more preferably in the range of 7 hpa to 350 hpa, and still more preferably in the range of 35 hpa to 280 hpa. . Polishing at a value exceeding these ranges is difficult to apply in consideration of the stability of the polishing rate derived from the polishing liquid and the stable operation of the apparatus.

The polishing method of the present invention is characterized by polishing two or more times. When the polishing pressure in the n-th polishing is P _n and the polishing pressure in the (n + 1) -th polishing is P _{n + 1} , P and _n, that the P n _{+ 1} different, it is possible to reduce the level difference preferred.
In particular, the _{P n,} the relationship between P _{n + 1} and that it _{is P n> P} n _{+ 1} is, it is possible to reduce the more stepped preferred.
The (n + 1) -th polishing pressure is preferably set to 2/3 or less of the n-th polishing pressure, and the (n + 1) -th polishing pressure is preferably set to 2.0 psi or less.

  In the polishing method of the present invention, the temperature of the platen is changed and the substrate is polished by two or more polishing steps, but the polishing pressure can be changed in accordance with the timing of the number of polishings for changing the temperature of the platen. Since a level | step difference can be made smaller, it is preferable.

(Rotation speed of surface plate)
In the polishing method of the present invention, polishing is preferably performed at a rotation speed of the surface plate of 10 to 200 rpm, more preferably 25 to 180 rpm.

(Polishing liquid supply method)
In the present invention, while the target film is being polished, the polishing liquid is continuously supplied to the polishing pad on the surface plate by a pump or the like.
The supply amount of the polishing liquid onto the surface plate is preferably controlled in the range of 50 ml / min to 400 ml / min, more preferably in the range of 100 ml / min to 250 ml / min.
The polishing liquid that can be used in the present invention will be described in detail below.

<Surface plate cooling process>
(Temperature of the surface plate after polishing)
In the polishing method of the present invention, the same conductive film is polished twice or more on the same surface plate by changing the temperature of the surface plate, but the surface plate immediately after finishing the polishing step performed immediately before the cooling step For this temperature, a cooling step for cooling the platen is provided so as to be −5 ° C. to −80 ° C. with respect to the temperature of the platen immediately before starting the polishing step immediately after the cooling step. It is more preferable to cool the platen so that it becomes −15 ° C. to −60 ° C. with respect to the temperature of the platen immediately before starting the polishing step immediately after the cooling step.
The effect of this invention can be exhibited as it is in the range of this cooling temperature.

  In the polishing method of the present invention, the surface plate cooling step for cooling the surface plate is performed after the supply of the polishing liquid is stopped. Although there is no restriction | limiting in particular in the method of cooling a surface plate to the said predetermined temperature, From the viewpoint of workability | operativity, the method of providing an aqueous solvent to a surface plate is preferable. The aqueous solvent is applied for cooling the platen, but the substrate disposed on the platen is also cooled at the same time.

The head that supports the surface plate and the conductor film is preferably cooled in a rotated state. If cooling is performed while the rotation is stopped, there is a concern that the uniform cooling of the surface plate will not be performed. In addition, the number of revolutions of the polishing machine during cooling and the pressing pressure of the conductor film can be arbitrarily selected. However, the higher the number of revolutions, the higher the pressing pressure, the slower the cooling rate, which affects the throughput of the entire polishing process. There are things to do.
For this reason, the number of rotations of the head that supports the surface plate and conductor film during cooling can be set to be the same as or lower than the number of rotations during polishing, but is arbitrarily set according to the specifications and purpose of the device. There are no particular restrictions. Also, the pressure of the conductor film during cooling is not particularly limited, and even if it is equal to the polishing pressure during the polishing process, or if the wafer does not slip out during rotation, the retainer ring pressure is only moderately applied, otherwise It may be in a state where no pressure is applied.
Here, in the rotary type or sliding type polishing machine, even if the rotation and sliding of the apparatus are continued during the surface plate cooling process, the polishing of the conductive film does not proceed in the state where the polishing liquid is not supplied.

  In order to suppress heat generation due to friction between the surface plate and the conductor film as much as possible during cooling, the conductor film can be separated from the surface plate. However, separating the conductor film from the surface plate slows down the cooling of the conductor film, and the conductor film remains heated at the start of polishing in the polishing process immediately after the cooling process, which may adversely affect the throughput. . Therefore, it is necessary to appropriately select a cooling method according to the purpose.

  The aqueous solvent in the cooling step is not particularly limited as long as it is aqueous and has an effect of cooling the surface plate. Water or an organic solvent compatible with water (water-soluble organic solvent such as methanol, ethanol, etc.) Alcohols), a mixture of water and a water-soluble organic solvent, and the like. The aqueous solvent may contain a surfactant. Considering the impact on polishing after changing the pressure, it is preferable to use water, water-soluble organic solvents and their mixtures, they are inexpensive, safe, and have no problem of waste liquid treatment From the viewpoint of the above, water is more preferable.

  When the above-mentioned aqueous solvent is applied, it is preferable to continuously apply the aqueous solvent for cooling until the target temperature is reached. The application rate of the aqueous solvent in this case can be arbitrarily selected according to the purpose, but is preferably controlled in the range of 10 ml / min to 10000 ml / min, and more preferably in the range of 100 ml / min to 8000 ml / min. . The application rate may be selected in consideration of the specifications of the polishing apparatus and the cooling efficiency, and is not limited to the above range.

  As a method of applying the cooling solvent described above, it is possible to apply a certain amount of cooling solvent from one nozzle in the same method as adding the polishing liquid, but as a method of increasing the cooling efficiency, Spraying in the form of a mist is also preferable. Specifically, it is preferable to use a method of spraying (spraying) a cooling solvent using an atomizer. This is because the entire platen can be uniformly cooled in a shorter time by the atomizer, and at the same time, the substrate can be instantaneously cooled.

When using an atomizer, it is preferable to simultaneously injecting a gas such as N ₂ or air. By using together, it becomes possible to cool a surface plate and a board | substrate further more rapidly. The pressure at which the water-soluble solvent is sprayed can be arbitrarily selected in view of the target temperature and throughput, but is preferably used in the range of 10 to 10000 hPa, and more preferably in the range of 100 to 5000 hpa. preferable. Depending on the specifications of the device, it can be used outside the above range depending on the purpose.

  The temperature measurement of the platen after cooling is performed in the same manner as the temperature measurement of the platen after completion of the polishing step, and is −5 ° C. or more with respect to the temperature of the platen immediately after completion of the polishing step performed immediately before the cooling step, The case where it is preferably −15 ° C. or higher may be set as the end of the cooling step.

<Polishing process immediately after completion of cooling process>
After completion of the platen cooling step, a polishing step as the next step is performed. Usually, the polishing step immediately after the end of the cooling step is performed under the same conditions as the polishing step performed immediately before the cooling step, which is the previous step.

(Conductor film)
Next, the conductor film to be polished in the polishing method of the present invention will be described.
The conductor film that is the object to be polished in the present invention is preferably a substrate (wafer) having wiring made of copper or a copper alloy. As the wiring metal material, a copper alloy containing silver is suitable among the copper alloys. The silver content contained in the copper alloy exhibits an excellent effect at 10% by mass or less, further 1% by mass or less, and the most excellent effect in the copper alloy in the range of 0.00001 to 0.1% by mass. Demonstrate.

In the DRAM device system, for example, the conductor film in the present invention preferably has a wiring with a half pitch, preferably 0.15 μm or less, more preferably 0.10 μm or less, and further preferably 0.08 μm or less.
On the other hand, the MPU device system preferably has a wiring of preferably 0.12 μm or less, more preferably 0.09 μm or less, and still more preferably 0.07 μm or less.
For the conductor film having such wiring, the polishing method used in the present invention exhibits particularly excellent effects.

(Barrier metal material)
In the conductor film used in the present invention, a barrier layer for preventing copper diffusion may be provided between the copper wiring and the insulating film (including the interlayer insulating film). As the barrier metal material constituting the barrier layer, a low-resistance metal material such as TiN, TiW, Ta, TaN, W, or WN is preferable, and Ta or TaN is particularly preferable.

(Polishing liquid)
As described above, the polishing liquid used in the method of the present invention may be any known polishing liquid as long as it is for conductor film polishing, and exhibits the effects of the present invention regardless of the type of the polishing liquid. To do.
As the polishing liquid, preferably, (a) abrasive grains, (b) anticorrosive, (c) oxidizing agent, (d) pH adjusting agent, (e) surfactant, and (f) other chelating agent (g) ) Polishing liquid dissolved in water and / or an organic solvent compatible with water, and the like. JP 2009-54796 A, JP 2008-235714 A, JP 2007-73548 A, US The polishing liquid disclosed in Japanese Patent No. 6083840, US Pat. No. 6,767,696B2 and the like can be used.
Hereinafter, the above-described components used for the polishing liquid will be described.

(A) Abrasive grains The polishing liquid used in the present invention preferably contains abrasive grains. For example, silica (for example, precipitated silica, fumed silica, colloidal silica, synthetic silica), ceria, alumina, titania, Examples thereof include zirconia, germania, manganese oxide, and diamond, and inorganic abrasives such as silica, alumina, and manganese oxide are preferably used. Among these, alumina and silica are more preferable.

The average particle size (primary particle size) of the abrasive grains contained in the polishing liquid of the present invention is preferably in the range of 5 nm to 1000 nm, more preferably 10 nm to 800 nm. In order to achieve a sufficient polishing speed, particles of 20 nm or more are preferable. For the purpose of not generating excessive frictional heat during polishing, the particle size is preferably 700 nm or less.
In addition, the value measured by the BET specific surface area method is used for the average particle diameter (primary particle diameter) of an abrasive grain here.

  Moreover, as an abrasive grain, it is also possible to use an organic polymer particle together with the above-mentioned inorganic abrasive grain. When inorganic abrasive grains and organic polymer particles are used in combination as abrasive grains, the content ratio can be appropriately set according to the purpose. Further, as abrasive grains, colloidal silica surface-modified with aluminate ions or borate ions, colloidal silica with controlled surface potential, such as colloidal silica subjected to various surface treatments, or composite abrasives composed of a plurality of materials It is also possible to use grains according to the purpose.

Although the addition amount of the abrasive grains in the polishing liquid is appropriately selected according to the purpose, it can be generally used in the range of 0.01 to 80% by mass with respect to the total mass of the polishing liquid. Although the polishing rate increases as the amount of abrasive grains increases, the amount of abrasive grains added is preferably 0.1 to 70% by mass from the viewpoint of suppressing scratches and the like caused by the abrasive grains. More preferably, it is -60 mass%.
When a plurality of types of abrasive grains are used, the added amount represents the total amount.
The above-mentioned abrasive grains can be used in combination of two or more, and depending on the purpose, the abrasive grains of the same type and different sizes are used in combination, or different kinds of abrasive grains are mixed. It is also possible to use it.

(B) Anticorrosive agent It is preferable to add (b) anticorrosive agent to the polishing liquid used in the present invention.
In the semiconductor packaging process, polishing may be performed until the copper wiring portion adjacent to the polyimide film is exposed. In such a case, it is preferable to add an anticorrosive agent according to the metal.
As a preferable anticorrosive, a heteroaromatic ring compound can be mentioned as a compound which forms a passive film on the metal surface to be polished.

  Here, the “heteroaromatic ring compound” is a compound having a heterocycle containing one or more heteroatoms. A hetero atom means an atom other than a carbon atom and a hydrogen atom. A heterocycle means a cyclic compound having at least one heteroatom. A heteroatom means only those atoms that form part of a heterocyclic ring system, either external to the ring system, separated from the ring system by at least one non-conjugated single bond, Atoms that are part of a further substituent of are not meant.

  A hetero atom is preferably a nitrogen atom, a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom, and more preferably a nitrogen atom, a sulfur atom, an oxygen atom, and a selenium atom. And particularly preferably a nitrogen atom, a sulfur atom and an oxygen atom, and most preferably a nitrogen atom and a sulfur atom.

  The number of heterocyclic ring members of the heteroaromatic ring compound that can be used in the anticorrosive agent is not particularly limited, and may be a monocyclic compound or a polycyclic compound having a condensed ring. The number of members in the case of a single ring is preferably 3 to 8, more preferably 5 to 7, and particularly preferably 5 and 6. The number of rings in the case of having a condensed ring is preferably 2 to 4, more preferably 2 or 3.

Specific examples of these heteroaromatic rings include the following. However, it is not limited to these.
For example, pyrrole ring, thiophene ring, furan ring, pyran ring, thiopyran ring, imidazole ring, pyrazole ring, thiazole ring, isothiazole ring, oxazole ring, isoxazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, pyrrolidine Ring, pyrazolidine ring, imidazolidine ring, isoxazolidine ring, isothiazolidine ring, piperidine ring, piperazine ring, morpholine ring, thiomorpholine ring, chroman ring, thiochroman ring, isochroman ring, isothiochroman ring, indoline ring, isoindoline ring , Pyridine ring, indolizine ring, indole ring, indazole ring, purine ring, quinolidine ring, isoquinoline ring, quinoline ring, naphthyridine ring, phthalazine ring, quinoxaline ring, quinazoline ring, cinnoline ring, pteridine ring, Lysine ring, perimidine ring, phenanthroline ring, carbazole ring, carboline ring, phenazine ring, anti-lysine ring, thiadiazole ring, oxadiazole ring, triazine ring, triazole ring, tetrazole ring, benzimidazole ring, benzoxazole ring, benzothiazole ring Benzothiadiazole ring, benzofuroxan ring, naphthimidazole ring, benzotriazole ring, tetraazaindene ring, and the like, more preferably triazole ring and tetrazole ring.

  The heteroaromatic ring compound may have a substituent, and preferably, for example, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an alkyl group (a linear, branched, or cyclic alkyl group). Yes, it may be a polycyclic alkyl group such as a bicycloalkyl group or an active methine group), an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group (regarding the position of substitution).

  In addition, two of the above-described substituents can jointly form a ring (aromatic or non-aromatic hydrocarbon ring or heteroaromatic ring), which are further combined to form a polycyclic fused ring. can do.

Specific examples of the anticorrosive agent having a heteroaromatic ring compound include, but are not limited to, the following.
That is, 1,2,3,4-tetrazole, 5-amino-1,2,3,4-tetrazole, 5-methyl-1,2,3,4-tetrazole, 1H-tetrazole-5-acetic acid, 1H- Tetrazole-5-succinic acid, 1,2,3-triazole, 4-amino-1,2,3-triazole, 4,5-diamino-1,2,3-triazole, 4-carboxy-1H-1,2, , 3-triazole, 4,5-dicarboxy-1H-1,2,3-triazole, 1H-1,2,3-triazole-4-acetic acid, 4-carboxy-5-carboxymethyl-1H-1,2 , 3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 3-carboxy-1,2,4-triazole 3,5-di Rubokishi-1,2,4-triazole, 1,2,4-triazole-3-acetic acid, 1H-benzotriazole, a 1H- benzotriazole-5-carboxylic acid. These anticorrosive agents can be used alone or in combination of two or more.

  As content of (b) anticorrosive agent in polishing liquid, as a total amount, it is 0.0001-1 in 1L of polishing liquid at the time of using for polishing (namely, polishing liquid after dilution when diluting with water or aqueous solution). A range of 0.0 mol is preferable, a range of 0.0005 to 0.5 mol is more preferable, and a range of 0.0005 to 0.05 mol is still more preferable.

(C) Oxidizing agent It is preferable to add (c) an oxidizing agent to the polishing liquid.
(C) Examples of the oxidizing agent include hydrogen peroxide, peroxide, nitrate, iodate, periodate, hypochlorite, chlorite, chlorate, perchlorate, Examples thereof include sulfates, dichromates, permanganates, ozone water, silver (II) salts, and iron (III) salts.
Examples of iron (III) salts include iron (III) in addition to inorganic iron (III) salts such as iron (III) nitrate, iron (III) chloride, iron (III) sulfate, and iron (III) bromide. Organic complex salts are preferably used.

  Among these oxidizing agents, hydrogen peroxide, iodate, hypochlorite, and persulfate are preferably used, and hydrogen peroxide, hypochlorite, and persulfate are more preferably used. It is done. Moreover, it is also possible to use these oxidizing agents in combination of two or more kinds as necessary, for example, in order to make the reaction time with the polyimide film as instantaneous as possible.

  (C) The amount of the oxidizing agent used can be in the range of 0.0001 mol to 20 mol per liter of the polishing liquid, preferably in the range of 0.001 to 15 mol, more preferably in the range of 0.001 to 10 mol. Is preferably used.

(D) pH adjuster The polishing liquid used in the present invention can be polished in any pH range from acidic to alkaline, and may be pH 1 or less or pH 14 or more exceeding the measurement limit of a pH meter. Is preferably 1 or more, and more preferably 1.0 or more.
In order to adjust the pH of the polishing liquid to a desired pH, it is preferable to add a pH adjusting agent. Examples of the pH adjuster include alkali, acid, and pH buffer. Below, an alkali, an acid, and a buffering agent are demonstrated.

Examples of the pH adjuster for adjusting the pH of the polishing liquid to the acidic side include inorganic acids and organic acids.
Examples of inorganic acids include sulfuric acid, nitric acid, boric acid, phosphoric acid and the like. Among these inorganic acids, sulfuric acid, nitric acid, and phosphoric acid are preferably used, and sulfuric acid, nitric acid, and phosphoric acid are more preferably used.
Examples of organic acids include amino acids, acetic acid, glycolic acid, diglycolic acid and the like, but are not limited to these, and any organic acid can be selected as needed.
It is also possible to use several kinds of acids in combination, or to use organic acids and inorganic acids in combination.

  Examples of pH adjusters for adjusting the pH of the polishing liquid to the alkaline side include ammonium ammonium, tetramethylammonium hydroxide (TMAH), and other organic ammonium hydroxides, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. Alkali metal hydroxide, carbonate, phosphate, borate, tetraborate, hydroxybenzoate, glycyl salt, N, N-dimethylglycine salt, leucine salt, norleucine salt, guanine salt, 3, Examples include 4-dihydroxyphenylalanine salt, alanine salt, aminobutyrate, 2-amino-2-methyl-1,3-propanediol salt, valine salt, proline salt, trishydroxyaminomethane salt, lysine salt, etc. is not.

It is also effective to add a pH buffering agent to the polishing liquid in order to minimize the pH fluctuation during polishing.
Examples of what may act as a pH buffer include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, trisodium phosphate, tripotassium phosphate, phosphoric acid Disodium, dipotassium phosphate, sodium borate, potassium borate, sodium tetraborate (borax), potassium tetraborate, sodium o-hydroxybenzoate (sodium salicylate), potassium o-hydroxybenzoate, 5- Sodium sulfo-2-hydroxybenzoate (sodium 5-sulfosalicylate), potassium 5-sulfo-2-hydroxybenzoate (potassium 5-sulfosalicylate), ammonium hydroxide, and also glycine, alanine, N-methylglycine Amino acids and amino acid derivatives, butyric acid, Organic acids such as cholic acid may also be used as buffering agents.

As mentioned above, although the specific example of the pH adjuster was mentioned, it cannot be overemphasized that it is not limited to the said specific example, as long as the pH of polishing liquid can be adjusted to a desired value.
The addition amount of the pH adjusting agent is not limited as long as the pH of the polishing liquid can be adjusted to a desired value.

(E) Surfactant The polishing liquid used in the present invention can also contain a surfactant. The surfactant is preferably selected from the group consisting of anionic (anionic), cationic (cationic), nonionic (nonionic), and amphoteric (betaine) surfactants. .

Examples of the anionic surfactant include carboxylic acid, sulfonic acid, sulfate ester, phosphate ester and salts thereof.
Examples of the nonionic surfactant include ether type, ether ester type, ester type, and nitrogen-containing type nonionic surfactants.

  Cationic surfactants include alkylamine salts (for example, coconut amine acetate, stearylamine acetate), quaternary ammonium salts (for example, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride, distearyl). Dimethylammonium chloride, alkylbenzyldimethylammonium chloride), alkylpyridinium salts (for example, cetylpyridinium chloride) and the like.

  Amphoteric surfactants include alkylbetaine types (for example, lauric betaine (lauryldimethylaminoacetic acid betaine, stearylbetaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine), amine oxide type (for example, lauryl). Dimethylamine oxide) and the like.

Among the above surfactants, an anionic surfactant and a nonionic surfactant are more preferable in an acidic to neutral pH range, and an anionic surfactant can be more preferably used.
Among the anionic surfactants, a surfactant having a sulfo group is more preferable, and a surfactant having both a phenyl group and a sulfo group is more preferable. Examples of the surfactant having a phenyl group and a sulfo group at the same time include alkylbenzene sulfonic acid, alkyl diphenyl ether disulfonic acid, and salts thereof, and among these, alkylbenzene sulfonic acid is particularly preferable.

As the nonionic surfactant, an ether type, an ether ester type, or an ester type is preferably used.
Examples of the salt include ammonium salts (for example, salts with ammonia and triethanolamine), alkali metal salts (for example, lithium salts, sodium salts, potassium salts), halogens, and the like.

  The addition amount in the case of using the surfactant is preferably 0.0001 g to 10 g, more preferably 0.0005 g to 5 g in 1 L of the polishing liquid when used for polishing as a total amount. It is especially preferable to set it as 0.0005g-3g.

(F) Chelating agent The polishing liquid used in the present invention may contain a chelating agent (that is, a hard water softening agent) as necessary in order to reduce adverse effects such as mixed polyvalent metal ions.
Chelating agents include general water softeners and related compounds that are calcium and magnesium precipitation inhibitors, such as nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N, N, N-trimethylenephosphonic acid. , Ethylenediamine-N, N, N ′, N′-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediamine disuccinic acid ( SS form), N- (2-carboxylateethyl) -L-aspartic acid, β-alanine diacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, N , N′-bis (2-hydroxyben Le) ethylenediamine -N, N'-diacetic acid, 1,2-dihydroxybenzene-4,6-disulfonic acid.

Two or more chelating agents may be used in combination as necessary.
The addition amount of the chelating agent may be an amount sufficient to sequester metal ions such as mixed polyvalent metal ions. For example, 0.0003 mol to 0.07 mol in 1 L of a polishing liquid used for polishing. Add so that it is in the range.

(G) Water and / or organic solvent compatible with water As the water that can be used in the polishing liquid used in the present invention, those generally used for semiconductor materials such as distilled water and ion-exchanged water can be used. is there.

  Examples of organic solvents that are compatible with water include ketone-based, ether-based, alcohol-based, glycol-based, glycol ether-based and amide-based solvents, such as acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, dimethylacetamide, N- Typical examples include methyl pyrrolidone, dimethyl sulfoxide, acetonitrile, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol, propylene glycol, ethoxyethanol and the like. Among these, methyl ethyl ketone, tetrahydrofuran, dioxane, N-methylpyrrolidone, methanol, ethanol, ethylene glycol and the like can be preferably used, and methyl ethyl ketone, dioxane, N-methylpyrrolidone, methanol and ethanol are preferable.

  The content of the organic solvent in the case of using the above organic solvent together with water, as a total amount, in 1 L of a polishing liquid when used for polishing (that is, a polishing liquid after dilution when diluted with water or an aqueous solution), The range of 1-900g is preferable, More preferably, it is the range of 2-800g, More preferably, it is the range of 5-700g.

  Hereinafter, the present invention will be described specifically by way of examples. The present invention is not limited by these examples.

The polishing apparatus used was a FREX300 manufactured by Ebara Corporation. The substrate to be polished and the polishing pad used for evaluation are as shown below.
Substrate: Copper wiring wafer (pattern wafer) with a diameter of 300 mm
(Mask pattern 754CMP (ATDF))
Polishing pad: IC1400-K Groove (Rodel)

(Examples 1-9, Comparative Examples 1-7)
For polishing the substrate, the following polishing solution was supplied onto the surface plate at a flow rate of 280 ml / min, and after the first stage polishing (polishing step (1)) was performed for 30 seconds, the supply of the polishing solution was stopped and fixed. The cooling process (surface plate cooling process) which cools a board and a board | substrate was performed. Thereafter, the cooling was stopped, and the second-stage polishing (polishing step (2)) was then carried out at a polishing liquid flow rate of 280 ml / min. The progress of the polishing was controlled by endpoint detection, and the polishing of the second stage was completed when the overpolish time was 10 seconds.

Polishing conditions for the first and second stages, cooling process conditions after the first stage polishing and before the second stage polishing, the temperature of the surface plate immediately after the completion of the first stage polishing and the surface plate immediately before the start of the second stage polishing Tables 1 to 3 show the temperature difference which is the difference from the temperature. The temperature was measured in real time with a thermometer attached to the polishing apparatus.
Unless otherwise specified, the rotational speeds of the platen and head in the first stage polishing and the second stage polishing are 70 rpm, respectively, and the rotational speeds of the platen and head in the cooling process are Each was performed at 70 rpm.

  The polishing liquid used was the polishing liquid 101 described in Example 1-1 of JP-A-2009-54796.

(Evaluation method Polishing speed)
Polishing rate calculation: Cu blanket wafer was polished for 60 seconds using the polishing liquid obtained, and the metal film thickness before and after polishing was calculated from the electrical resistance value for 49 equally spaced locations on the wafer surface. The average value of the values obtained by dividing by the polishing time was taken as the polishing rate.

(Evaluation method Dishing evaluation)
For the evaluation of dishing, the step of the line-and-space portion (line 100 μm, space 100 μm) was measured with a contact-type step meter Dektak V3201 (manufactured by Veeco) on the pattern wafer of the conductive film to be polished used for the evaluation.
Tables 1 to 3 show the evaluation results.

As is clear from Tables 1 to 3, Examples 1 to 9 using the polishing method of the present invention showed small dishing and good flatness. In particular, Examples 4 to 6 in which the polishing pressure at the second stage was reduced showed small dishing and further showed good flatness.
On the other hand, Comparative Examples 1 to 3 polished without providing a cooling step had large dishing and poor flatness.
Further, in Comparative Example 4 in which the cooling process was not provided between the first stage and the second stage, and cooling was performed during overpolishing after the second stage polishing, dishing was large. Although the surface plate and the conductor film could be cooled during overpolishing, it was considered that the polishing liquid was also diluted at the same time, the polishing rate was lowered, and copper residue was partially generated. Further, in Comparative Example 6 in which cooling was attempted during the second polishing step, dishing was slightly smaller than in Comparative Example 2 in which cooling was not performed at all, but dishing was performed in comparison with Examples 1 to 9 of the present invention. And scratches were observed. In Comparative Example 6, it is considered that the polishing liquid was blown off by performing the second stage polishing while blowing air. Further, in Comparative Example 7 in which the rotational speed was lowered, dishing deteriorated. From the results of Comparative Example 7, it can be seen that it is effective to provide the cooling step between the first-stage polishing and the second-stage polishing, not during the polishing.

(Example 10)
In Example 1, the polishing pressure was further changed in the over-polishing process, and three-stage polishing was performed in which the pressure was changed to three stages. Table 4 shows the conditions for each polishing step and the evaluation results.

  As shown in Table 4, the polishing process is divided into three stages, the temperature difference of the surface plate between immediately after the completion of the first stage polishing and immediately before the start of the second stage polishing is 5 ° C. or more, and immediately after the completion of the second stage polishing. The tenth embodiment in which the temperature difference between the surface plate and the immediately before the start of the third stage polishing is 5 ° C. or more and the polishing method of the present invention is adopted is a polishing method with less dishing and better flatness than the first embodiment. I understand that.

Claims (7)

  A polishing process in which the same conductive film is polished twice or more on the same surface plate using a polishing liquid, and the polishing process performed immediately before and between the first polishing process and the last polishing process. A chemical mechanical polishing method comprising a cooling step of cooling a platen so as to be -5 ° C to -80 ° C with respect to the temperature of the platen immediately after the completion.   A chemical mechanical polishing method for cooling a platen such that the cooling step is at -15 ° C to -60 ° C with respect to the temperature of the platen immediately after completion of the polishing step performed immediately before the cooling step. The polishing pressure at the n-th polishing step and P _n, (n + 1) th when the polishing pressure was set to P _{n + 1} in the polishing step, according to claim 1, wherein the P _n, and the P n _{+ 1} is different polishing pressures Item 3. The chemical mechanical polishing method according to Item 2. The chemical mechanical polishing method according to claim 3, wherein a relationship between P _n and P _{n + 1} is P _n > P _{n + 1} .   The chemical mechanical polishing method according to any one of claims 1 to 4, wherein the cooling method in the cooling step is a method of cooling by applying an aqueous solvent on a surface plate.   The chemical mechanical polishing method according to claim 5, wherein the aqueous solvent is water.   The chemical mechanical polishing method according to claim 1, wherein the same conductor film is a conductor film made of copper or a copper alloy.