JP2010153576A - Grinding material for semiconductor integrated circuit, grinding method, and manufacturing method for semiconductor integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that because cerium oxide abrasive gains achieve low grinding speed in grinding a silicon nitride film, silicon oxide abrasive grains are often used to achieve the same grinding speed in grinding the silicon nitride film and a silicon dioxide film and when the cerium oxide abrasive gains used for grinding the silicon dioxide film remain on a surface to be ground, the cerium oxide abrasive grains aggregate together with the silicon oxide abrasive grains to form coarse particles which damage the surface to be ground or destabilize the grinding speed. <P>SOLUTION: A grinding material is used for chemically and mechanically grinding a surface to be ground in manufacturing a semiconductor integrated circuit. The grinding material contains cerium oxide abrasive grains, an acid with a molecular weight of 600 or less, and water, and shows pH of 2 or higher and less than 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing technique used in a manufacturing process of a semiconductor integrated circuit device. More specifically, a polishing agent suitable for planarizing a surface to be polished including a silicon nitride film used in a semiconductor integrated circuit device, and a surface to be polished including a silicon nitride film used in the manufacturing process of the semiconductor integrated circuit device. Relates to the polishing technology.

  In recent years, along with the higher integration and higher functionality of semiconductor integrated circuit devices, development of microfabrication technology for miniaturization and higher density has been demanded. In particular, the importance of a planarization technique by chemical mechanical polishing (hereinafter referred to as CMP) is increasing.

  For example, as semiconductor integrated circuit devices become finer and the number of wiring layers increases, surface irregularities (steps) on each film in the manufacturing process tend to increase, but this step exceeds the depth of focus of photolithography and is sufficient. CMP is an indispensable technique for preventing the problem that a high resolution cannot be obtained. Specifically, the CMP includes planarization of an inter-film insulating film (ILD film: Inter-Level Dielectrics), shallow trench isolation (STI), tungsten plug formation, and a multi-layer consisting of copper and a low dielectric constant film. It is used in the film wiring formation process. Recently, a silicon nitride film is sometimes used as an electrode protective film due to changes in the STI manufacturing method, and CMP is also employed for planarizing a surface to be polished having a silicon nitride film (Non-Patent Document 1). reference).

  In the manufacturing process of a semiconductor integrated circuit device, when a surface to be polished including a silicon nitride film is planarized, a silicon dioxide film is generally formed on the silicon nitride film to be polished, and silicon dioxide is obtained. The film is once planarized with cerium oxide abrasive. Thereafter, the ratio between the polishing rate of the silicon nitride film and the polishing rate of the silicon dioxide film (hereinafter, (A polishing rate) / (B polishing rate) is also referred to as “a polishing rate ratio of A and B”) is approximately the same. Thus, the surface to be polished can be flattened when the silicon nitride film is exposed.

  However, in general, a polishing agent containing cerium oxide abrasive grains does not have a high polishing rate for a silicon nitride film, so that it is difficult to polish a silicon nitride film simultaneously with the polishing of a silicon oxide film (see Patent Document 1). Therefore, in order to make the polishing rate of the silicon nitride film and the silicon dioxide film comparable, a desired polishing rate ratio is often realized by a polishing agent containing silicon oxide abrasive grains (Patent Documents 2 and 3). reference).

  When polishing by the method as described above, if the cerium oxide abrasive grains used at the time of polishing the silicon dioxide film remain on the surface to be polished, the cerium oxide abrasive grains aggregate with the silicon oxide abrasive grains to become coarse particles, The occurrence of problems such as scratches on the surface to be polished and unstable polishing rate may be considered.

International Patent Publication No. 2004-010487 JP 2006-120728 A JP 2007-335847 A 2007 Proceedings chemical mechanical polish for ULSI multilevel interconnection conference P165-170

  The present invention solves the above problems and is a chemical mechanical polishing abrasive for polishing a surface to be polished in the manufacture of a semiconductor integrated circuit device, comprising a silicon oxide film surface and a silicon nitride film surface. It is an object of the present invention to provide an abrasive suitable for polishing a surface to be polished including: Another object of the present invention is to provide a method for polishing a surface to be polished, which includes the surface of a silicon dioxide film and the surface of a silicon nitride film, using the above-described abrasive. Furthermore, an object of the present invention is to provide a method for manufacturing a semiconductor integrated circuit device, which includes a step of polishing a surface to be polished by the above polishing method.

  The present invention is a chemical mechanical polishing abrasive for polishing a surface to be polished in the manufacture of a semiconductor integrated circuit device, wherein the abrasive comprises cerium oxide abrasive grains, an acid having a molecular weight of 600 or less, and water. And a polishing agent characterized by containing a pH in the range of 2 or more and less than 4.

  Further, the present invention is a method for polishing a surface to be polished, in which a polishing agent is supplied to a polishing pad, the surface to be polished of a semiconductor integrated circuit device is brought into contact with the polishing pad, and polishing is performed by relative movement between the two. There is provided a polishing method in which the surface to be polished is a surface to be polished including the surface of a silicon dioxide film and the surface of a silicon nitride film, and the polishing agent is used as the polishing agent.

  Furthermore, the present invention provides a method for manufacturing a semiconductor integrated circuit device, comprising a step of polishing a surface to be polished by the above polishing method.

  According to the present invention, when a surface to be polished is polished in the manufacture of a semiconductor integrated circuit device, an appropriate polishing rate ratio can be obtained between the silicon nitride film and the silicon oxide film, and thereby the surface to be polished is highly flat. Can be realized.

  The abrasive of the present invention is a chemical mechanical polishing abrasive for polishing a surface to be polished of a semiconductor integrated circuit device (hereinafter also simply referred to as a semiconductor device), and the surface to be polished is covered with a silicon nitride film. Including a polishing surface, the abrasive contains cerium oxide abrasive grains, an acid having a molecular weight of 600 or less, and water, and the pH of the abrasive is in the range of 2 or more and less than 4.

  When the polishing agent of the present invention is used, when the surface to be polished of the semiconductor device is a surface to be polished including the surface of the silicon dioxide film and the surface of the silicon nitride film, the polishing rate ratio between the silicon dioxide film and the silicon nitride film is Control becomes easy. Two or more silicon nitride films may be included in one semiconductor device. In the present invention, the “surface to be polished” means an intermediate surface that appears in the process of manufacturing a semiconductor device.

  This state is illustrated in FIGS. 1, 2, and 3, and will be described below with reference to the drawings. 1, 2 and 3 are schematic cross-sectional views of a semiconductor device in which a silicon nitride film 2, a silicon dioxide film 3, a silicon nitride film 4 and a silicon dioxide film 5 are laminated on a substrate 1. FIG.

  In FIG. 1, the silicon dioxide film 5 is flattened while suppressing dishing with a semiconductor abrasive that contains cerium oxide abrasive grains as described in Patent Document 1 and can polish the silicon dioxide film at high speed. As will be described later, when the silicon dioxide film is polished with a polishing agent containing cerium oxide abrasive grains, the pressure applied during polishing of the convex portions of the silicon dioxide film in FIG. When the silicon dioxide film is flattened as in 2 and the silicon nitride film 4 is exposed, the silicon dioxide film is no longer polished and polishing can be completed.

  In the polishing agent of the present invention, the ratio between the polishing rate (Vsn) of the silicon nitride film 4 and the polishing rate (Vso) of the silicon dioxide film 5 (that is, the polishing rate ratio Vsn / Vso) can be made close to 1. Therefore, when the silicon nitride film 4 and the silicon dioxide film 5 are polished with the polishing agent of the present invention from the time when the silicon nitride film 4 is exposed as shown in FIG. 2, the silicon dioxide film 3 immediately below the silicon nitride film 4 can also be polished. As shown in FIG. 3, a semiconductor device in which the silicon nitride films 2 and 4 and the silicon dioxide films 3 and 5 are all highly planarized can be formed.

  The polishing rate ratio Vsn / Vso of the polishing agent containing the conventional cerium oxide abrasive was 0.1 or less in the patterned wafer. When the silicon nitride film is completely removed, the allowable amount of the silicon dioxide film is about 20 nm. In general, a silicon nitride film is often formed to have a thickness of about 10 nm. When this silicon nitride film is polished at a rate of about 10 nm / min, the polishing rate of the silicon oxide film must be reduced to about 30 nm / min. The amount of dishing is not about the allowable amount of 20 nm. From these points, in the pattern (silicon nitride film: 50 μm / silicon oxide film: 50 μm) on the 864 STI pattern wafer defined by Sematech, the polishing rate ratio Vsn / Vso is preferably 0.3 or more.

  When a silicon dioxide film is polished with a polishing agent containing cerium oxide abrasive grains, there is a property that the polishing rate increases rapidly due to an increase in pressure. On the other hand, the polishing rate of the silicon nitride film increases in proportion to the pressure increase. Stress concentrates at the convex portions of the patterned wafer, and a strong polishing pressure is applied locally. For this reason, the silicon dioxide film has a sharply increased polishing rate and is likely to be locally polished at the convex portion of the patterned wafer as compared with the silicon nitride film. For these reasons, it is preferable that Vsn / Vso in the patterned wafer is sufficiently large so that the silicon nitride film can be sufficiently polished even if a local pressure increase occurs. Vsn / Vso is preferably 0.5 or more, more preferably 0.8 or more, and further preferably 1.0 or more.

<Cerium oxide>
In the present invention, cerium oxide is used as the abrasive grains in the abrasive. As the cerium oxide abrasive grains in the present invention, a cerium oxide powder obtained by adding an alkali to a cerium (IV) ammonium nitrate aqueous solution to produce a cerium hydroxide gel, filtering, washing and firing can be preferably used. In addition, cerium oxide abrasive grains obtained by pulverizing and firing high-purity cerium carbonate, and further pulverizing and classifying can be preferably used, but are not particularly limited thereto.

  The average particle diameter (diameter) of the cerium oxide abrasive grains is 0.01 to 0.5 μm, particularly 0.02 to 0.3 μm, more preferably 0.05 to 0.2 μm from the viewpoint of polishing characteristics and dispersion stability. preferable. If the average particle size is too large, there is a possibility that polishing scratches such as scratches are likely to occur on the surface of the semiconductor substrate. If the average particle size is too small, the polishing rate may be low. Moreover, since the ratio of the surface area per unit volume is large, it is easily influenced by the surface state. Depending on conditions such as pH and additive concentration, aggregation may easily occur. When aggregation occurs, scratches such as scratches are likely to occur on the surface of the semiconductor substrate. The average particle diameter is a numerical value measured by a laser diffraction scattering method.

  The blending amount of cerium oxide is preferably 0.1 to 5% by mass, more preferably 0.15 to 3% by mass, based on the total mass of the abrasive, It is particularly preferable to contain 2 to 1.5% by mass.

(acid)
The abrasive of the present invention contains an acid having a molecular weight of 600 or less. As the acid having a molecular weight of 600 or less, an inorganic acid or an organic acid can be used. The acid having a molecular weight of 600 or less is preferably at least one acid selected from the group consisting of carboxylic acid, nitric acid and sulfonic acid. More preferably, the carboxylic acid is at least one carboxylic acid selected from the group consisting of oxalic acid, acetic acid, formic acid and citric acid. More preferably, the acid having a molecular weight of 600 or less contains at least one acid selected from the group consisting of carboxylic acids and sulfonic acids and nitric acid. The molecular weight of the acid is more preferably 500 or less, and particularly preferably an acid having a molecular weight of 300 or less. Hereinafter, an acid having a molecular weight of 600 or less is simply referred to as an acid. The acid is used in such an amount that the abrasive is in the pH range described below. Further, the low pH due to the use of an excessive amount of acid can be adjusted to the pH range described below with a pH adjuster described below.

(water)
Although there is no restriction | limiting in particular about the water of this invention, From the influence with respect to another agent, the mixing of an impurity, the influence on pH etc., pure water, ultrapure water, ion-exchange water etc. can be used preferably.

(PH)
The pH range of the abrasive of the present invention is pH 2 or more and less than 4 in consideration of the polishing characteristics and dispersion stability of the abrasive. When the pH is less than 2, the dispersibility may be lowered. When the pH is more than 4, the polishing rate of the silicon oxide film (Vso) is large, and the polishing rate (Vsn) of the silicon nitride film is small. (Vsn / Vso) cannot be obtained. When the pH is less than 2.5, it is necessary to add a strong acid. For this reason, a pH range of 2.5 to less than 4 is preferable because many types of acids can be used, and a range of 3.0 to less than 4 is more preferable. The abrasive pH of the present invention can be adjusted by the type and amount of acid used. In some cases, it may be further adjusted using a pH adjusting agent.

  The abrasive of the present invention can contain components other than the above components. Examples of other components include a dispersant, a silicon dioxide film protective agent, and a pH adjuster. A dispersing agent is contained in order to stably disperse cerium oxide abrasive grains in a dispersion medium such as pure water. A silicon dioxide film protective agent is for adsorb | sucking to the surface of a silicon dioxide film, and protecting the surface, Thereby, dishing is suppressed. The pH adjuster is for adjusting the pH of the dispersant as described above. The abrasive | polishing agent of this invention can contain 1 or more types of these components.

(Water-soluble polymer)
As the dispersant and the silicon dioxide film protective agent, a water-soluble polymer is preferable, and examples thereof include a water-soluble polymer that functions as a dispersant, a water-soluble polymer that functions as a silicon dioxide film protective agent, and a water-soluble polymer having both functions. Further, a water-soluble polymer having an action other than these can be used as the water-soluble polymer. The water-soluble polymer may have an acidic group, a salt group in which the acidic group is neutralized, a basic group, a salt group in which the basic group is neutralized, a hydroxyl group, and other characteristic groups. In the present invention, the water-soluble polymer refers to a polymer that dissolves 1% by mass or more with respect to pure water and has a weight average molecular weight (Mw) exceeding 600.

  The water-soluble polymer needs to be in a state of being completely dissolved in the abrasive liquid at the concentration contained in the abrasive of the present invention. For this reason, it is preferable that the water-soluble polymer has a solubility capable of dissolving 5% by mass or more in pure water. The weight average molecular weight (Mw) of the water-soluble polymer is not limited as long as the molecular weight is in a range exceeding 600 and having water solubility, but is preferably 1,000 or more, and in the range of 2,000 to 250,000. More preferably. Particularly preferred water-soluble polymers have a weight average molecular weight (Mw) in the range of 3,000 to 20,000. When the weight average molecular weight (Mw) is less than 2,000, the effect as a dispersant or a silicon dioxide film protective agent as described later may not be sufficient. If it exceeds 250,000, even if it is water-soluble, it may adversely affect physical properties such as fluidity of the abrasive. The most preferred water-soluble polymer is a water-soluble polymer having a weight average molecular weight (Mw) of 4,000 to 10,000.

  In the present invention, the water-soluble polymer acts as a dispersant or a silicon dioxide film protective agent as described above. The blending ratio of the water-soluble polymer having an action as a dispersant or a silicon dioxide film protective agent is in the range of 0.01 to 2% by mass with respect to the total amount of the abrasive, and the dispersibility, the polishing rate, and the uniformity of the abrasive slurry. It is preferable to set appropriately considering the properties, polymerization average molecular weight and the like. The water-soluble polymer in the abrasive is more preferably in the range of 0.015 to 1% by mass, and further preferably in the range of 0.02 to 0.5% by mass.

  Examples of water-soluble polymers having a dispersing action include water-soluble polymers having a carboxylic acid group such as polyacrylic acid and neutralized products thereof, and other water-soluble polymers such as polyvinyl pyrrolidone, polyethylene glycol, and polyoxyethylene alkyl ether. Can do. In particular, a water-soluble polymer having an ammonium carboxylate base is preferable. Specific examples include a polymer in which at least a part of the carboxylic acid group of polyacrylic acid is neutralized with an ammonium carboxylate group.

  When a water-soluble polymer having a dispersing action is used, the blending ratio is preferably 0.1 to 2.0% by mass with respect to the mass of the cerium oxide abrasive, and 0.3 to 1.5% by mass More preferably. When the content of the dispersant is lower than this range, the dispersibility of the cerium oxide abrasive grains, which are abrasive grains, tends to be insufficient. Moreover, when the content rate of a dispersing agent is higher than this range, the tendency which influences the flatness at the time of grinding | polishing and a grinding | polishing speed is seen.

  Examples of the water-soluble polymer having a silicon dioxide film protecting action include water-soluble polymers having a carboxylic acid group such as polyacrylic acid and neutralized products thereof, and water-soluble polymers such as polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, and polysaccharides. It is done. Examples of the polysaccharide include pullulan, cellulose, dextrin, hydroxyethyl cellulose, hydroxypropyl cellulose and the like. In particular, a polysaccharide having a weight average molecular weight (Mw) of 10,000 or more is preferable.

  The blending ratio of the water-soluble polymer having a protective action for the silicon dioxide film is within a range of 0.01 to 2% by mass with respect to the total amount of the polishing agent from the viewpoint of obtaining a sufficient effect of suppressing the polishing rate of the silicon dioxide film. It is preferable to set appropriately considering the speed, the uniformity of the abrasive slurry, the polymerization average molecular weight and the like. The blending ratio of the silicon dioxide film protective agent in the abrasive is more preferably in the range of 0.015 to 1% by mass, and still more preferably in the range of 0.02 to 0.5% by mass.

(Dispersant other than water-soluble polymer)
The abrasive of the present invention may contain a dispersant other than the water-soluble polymer. As the dispersant other than the water-soluble polymer, anionic, cationic, nonionic and amphoteric surfactants can be used. In the present invention, the term “surfactant” refers to a compound having a lower molecular surface activity than the water-soluble polymer. Examples of the dispersant include alkylbenzene sulfonate, tetraalkylammonium salt, polyoxyethylene alkyl ether and the like. When using a dispersant other than the water-soluble polymer, it is preferable to use it together with the water-soluble polymer.

  When using a dispersant other than the water-soluble polymer, the content is preferably 0.1 to 2.0% by mass with respect to the mass of the cerium oxide abrasive, and 0.3 to 1.5% by mass More preferably. When using together with the said water-soluble polymer, it is preferable that both total amount becomes this range. When the content of the dispersant is lower than this range, the dispersibility of the cerium oxide abrasive grains, which are abrasive grains, tends to be insufficient. Further, when the blending ratio of the dispersant is higher than this range, there is a tendency to affect the flatness and polishing rate during polishing.

(pH adjuster)
The abrasive of the present invention may contain a basic compound as a pH adjuster. By changing the kind of basic compound and the amount of addition, the pH of the acid can be further controlled, so that the polishing rate ratio (Vsn / Vso) between the silicon nitride film and the silicon dioxide film can be controlled.

  The basic compound includes at least one base selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, monoethanolamine, ethylethanolamine, diethanolamine, propylenediamine, and ammonia. Preferred examples of the compound are as follows. Among these, ammonia is particularly preferable because the polishing rate can be easily controlled.

  The abrasive of the present invention does not necessarily have to be supplied to the polishing process as a mixture of all the constituent polishing materials. When supplying to a grinding | polishing process, the abrasive material may be mixed and it may become the composition of an abrasive | polishing agent. For example, the present invention is divided into a liquid containing cerium oxide abrasive grains, water and a surfactant, and a liquid containing a water-soluble polymer, a pH adjuster, an acid and water, and the mixing ratio is appropriately selected during polishing. You may use after adjusting to pH of this. Moreover, it can also be divided into a liquid containing cerium oxide abrasive grains, a water-soluble polymer, a pH adjuster and water, and a liquid containing acid and water. Further, a liquid having a pH of 4 or more containing cerium oxide abrasive grains, water and a surfactant is mixed with an acid and a water-soluble polymer to produce an abrasive having a pH of 2 or more and less than 4. Also good. Furthermore, other division methods may be used.

  As described above, by mixing a plurality of liquids when supplying to the polishing process, various selection ratios of the abrasive can be selected, and the polishing rate ratio between the silicon oxide film and the silicon nitride film can be controlled. Can do. Therefore, this method is useful when it is necessary to optimize the polishing rate ratio depending on the structure of the semiconductor device.

  When polishing a semiconductor substrate using the polishing agent of the present invention, the polishing agent is supplied to the polishing pad, the surface to be polished of the semiconductor device and the polishing pad are brought into contact with each other, and silicon oxide is caused by relative movement between the two. The surface to be polished including the surface of the film and the surface of the silicon nitride film is polished.

  A general polishing apparatus can be used as the polishing apparatus. For example, FIG. 4 is a diagram showing an example of a polishing apparatus applicable to the polishing method of the present invention. While supplying the polishing agent 36 from the polishing agent supply pipe 35, the semiconductor device 31 is held on the polishing head 32, brought into contact with the polishing pad 34 affixed to the surface of the polishing surface plate 33, and the polishing head 32 and the polishing surface plate 33. This is a method of rotating and rotating relative to each other. However, the polishing apparatus of the present invention is not limited to this.

  The polishing head 32 may move linearly as well as rotate. The polishing surface plate 33 and the polishing pad 34 may be as large as or smaller than the semiconductor device 31. In that case, it is preferable that the entire surface of the semiconductor device can be polished by relatively moving the polishing head 32 and the polishing surface plate 33.

  The polishing conditions of the polishing apparatus are not particularly limited, but the polishing rate can be improved by applying a load to the polishing head 32 and pressing it against the polishing pad 34. The polishing pressure at this time is preferably about 0.5 to 50 kPa, and is particularly preferably about 3 to 40 kPa from the viewpoint of preventing polishing defects such as uniformity in the semiconductor device of the polishing rate, flatness, and scratches. Further, the rotation speed of the polishing surface plate and the polishing head is preferably about 50 to 500 rpm, but is not limited thereto.

  As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous resin, non-porous resin or the like can be used. Further, in order to promote the supply of the abrasive to the surface of the polishing pad and collect a certain amount of the abrasive, grooves such as a lattice shape, a concentric circle shape, and a spiral shape may be formed.

As described above, according to the present invention, when the surface to be polished is polished in the manufacture of a semiconductor device, an appropriate polishing rate ratio can be obtained between the silicon nitride film and other materials.
Therefore, in manufacturing a semiconductor device using this polishing method, the cost can be reduced and the throughput can be improved.

  Examples of the present invention will be described below. In the examples, “%” means mass% unless otherwise specified. The characteristic value was evaluated by the following method.

(PH)
It measured by pH81-11 made by Yokogawa Electric Corporation.

(Average grain size of abrasive grains)
It calculated | required using the laser scattering diffraction apparatus (The Horiba make, brand name: LA-920).

(Polishing characteristics)
(1) Polishing conditions Polishing was performed with the following apparatus and conditions.
Polishing machine: Fully automatic CMP machine MIRRA (manufactured by APPLIED MATERIALS)
Abrasive supply rate: 200 ml / min Polishing pad: K-groove of two-film pad IC-1400 or K-groove of single-film pad IC-1000 (manufactured by Rodel)
Polishing pad conditioning: MEC100-PH3.5L (Mitsubishi Materials Corporation)
Number of rotations of polishing platen: 127 rpm (common to all examples)
Number of revolutions of polishing head: 123 rpm (common to all examples)
Polishing pressure: 20.7 kPa or 27.6 kPa.

(2) Object to be polished The following object to be polished was used. As an object to be polished, an 8-inch silicon wafer substrate (wafer substrate A) formed with a silicon nitride film by a CVD method and an 8-inch silicon wafer substrate (wafer substrate) formed with a silicon dioxide film by a thermal oxidation method. B) was used respectively. In addition, as an object to be patterned, an 864 STI pattern defined by Sematech was used and polished to a point where a silicon nitride film was exposed by a cerium oxide abrasive CES-333-2.5 manufactured by Asahi Glass Co., Ltd. ( Wafer substrate C) was used.

(3) Method for evaluating characteristics of abrasives Measurement of polishing rate: A film thickness meter UV-1280SE (manufactured by KLA-Tencor) was used.

  By mixing with stirring cerium oxide abrasive grains with an average particle diameter of 0.17 μm, ammonium polyacrylate with a weight average molecular weight (Mw) of 5,000 and nitric acid in deionized water, Abrasive A having a particle concentration of 0.25%, an ammonium polyacrylate concentration of 540 ppm, a nitric acid concentration of 240 ppm, and a pH of 4.8 was produced.

  In the same manner as abrasive A, an abrasive containing at least one of acid 1 and acid 2 listed in Table 1 and ammonium polyacrylate having a weight average molecular weight (Mw) of 5,000 was produced. Samples of Comparative Examples 1 to 4 were used. Table 1 shows the composition, pH, and polishing pressure of the abrasive, and Table 2 shows the evaluation results of the polishing characteristics when wafer substrates A and B are used.

  By mixing cerium oxide abrasive grains, ammonium polyacrylate having a weight average molecular weight (Mw) of 5,000 and oxalic acid in deionized water with stirring, the abrasive concentration is 0.25% with respect to the total mass of the liquid. An abrasive having an ammonium polyacrylate concentration of 320 ppm, an oxalic acid concentration of 273 ppm, and a pH of 3.5 was produced as Example 16.

  Next, an abrasive having an oxalic acid concentration of 379 ppm was produced in the same manner as in Example 16, and designated as Example 17.

  Table 1 shows the composition, pH, and polishing pressure of the abrasive, and Table 2 shows the evaluation results of the polishing characteristics when wafer substrates A and B are used.

  From the results of Table 2, in the polishing agents of Examples 1 to 17, the polishing rate ratio between the silicon nitride film and the silicon dioxide film (polishing rate ratio Vsn / Vso) exceeded 0.6 and showed a high value. On the other hand, in the polishing agents of Comparative Examples 1 to 3, the polishing rate ratio Vsn / Vso was 0.3 or less, and the polishing rate ratio was small.

  Next, in the same manner as this polishing agent A, a polishing agent containing at least one of acid 1 and acid 2 and polyacrylic acid ammonium salt described in Table 3 was produced. Samples of Examples 18 to 23 and Comparative Example 4 It was. Table 3 shows the composition, pH, and polishing pressure of the abrasive. Table 4 shows the results of the polishing rate and the polishing rate ratio of the silicon nitride film and the silicon dioxide film measured using the wafer substrate C based on the reference point set in advance on the silicon wafer substrate.

  From the results of Table 4, in the polishing agents of Examples 18 to 23, the polishing rate ratio between the silicon nitride film and the silicon dioxide film (polishing rate ratio Vsn / Vso) exceeded 0.3 and showed a high value. On the other hand, in the polishing agent of Comparative Example 4, the polishing rate ratio Vsn / Vso was a very low polishing rate ratio of 0.04. For this reason, it was found that when the abrasive of the present invention was used, high flatness was obtained by polishing the surface to be polished including the silicon nitride film surface and the silicon dioxide film surface.

  The present invention is used as a chemical mechanical polishing abrasive for polishing a surface to be polished of a semiconductor integrated circuit device having a silicon dioxide film and a silicon nitride film in the manufacture of a semiconductor integrated circuit device. It is possible.

Schematic cross-sectional view of the polishing process of a semiconductor device in which a silicon nitride film and a silicon oxide film are laminated Schematic cross-sectional view of the polishing process of a semiconductor device in which a silicon nitride film and a silicon oxide film are laminated Schematic cross-sectional view of the polishing process of a semiconductor device in which a silicon nitride film and a silicon oxide film are stacked The figure which shows an example of the grinding | polishing apparatus applicable to the grinding | polishing method of this invention

Explanation of symbols

1: Substrate 2: Silicon nitride film 3: Silicon dioxide film 4: Silicon nitride film 5: Silicon dioxide film 31: Semiconductor device 32: Polishing head 33: Polishing surface plate 34: Polishing pad 35: Polishing agent supply pipe 36: Polishing agent

Claims (10)

  A chemical mechanical polishing abrasive for polishing a surface to be polished in the manufacture of a semiconductor integrated circuit device, wherein the abrasive contains cerium oxide abrasive grains, an acid having a molecular weight of 600 or less, and water, and a pH Is in the range of 2 or more and less than 4.   The abrasive according to claim 1, wherein the acid having a molecular weight of 600 or less is at least one acid selected from the group consisting of carboxylic acid, nitric acid and sulfonic acid.   The polishing agent according to claim 2, wherein the carboxylic acid is at least one carboxylic acid selected from the group consisting of oxalic acid, acetic acid, formic acid and citric acid.   The abrasive according to any one of claims 1 to 3, wherein the abrasive further contains a water-soluble polymer having a weight average molecular weight of 2,000 to 250,000.   The abrasive according to claim 4, wherein the water-soluble polymer is a water-soluble polymer having at least one group selected from the group consisting of a carboxylic acid group and a carboxylic acid group.   The abrasive | polishing agent of Claim 4 or 5 which contains the said water-soluble polymer 0.01-2 mass% with respect to the total mass of the said abrasive | polishing agent.   The abrasive | polishing agent in any one of Claims 1-6 which contains the said cerium oxide abrasive grain 0.1-5 mass% with respect to the total mass of the said abrasive | polishing agent.   The abrasive | polishing agent in any one of Claims 1-7 in which the said semiconductor integrated circuit device has a silicon dioxide film and a silicon nitride film.   A polishing method for supplying a polishing agent to a polishing pad, bringing the polishing surface of a semiconductor integrated circuit device into contact with the polishing pad and polishing the surface by relative movement between the polishing pad and the polishing surface. A polishing method comprising a surface to be polished including a surface of a silicon film and a surface of a silicon nitride film, wherein the abrasive according to any one of claims 1 to 8 is used as the abrasive.   A method for manufacturing a semiconductor integrated circuit device, comprising a step of polishing a surface to be polished by the polishing method according to claim 9.

Images