JP6232243B2 - Semiconductor wetting agent and polishing composition - Google Patents

Description

  The present invention relates to a wetting agent for semiconductors and a polishing composition, and more particularly to a wetting agent for semiconductors and a polishing composition used for final polishing of a silicon wafer.

  Semiconductor devices using a silicon wafer as a substrate are widely used in information communication devices such as personal computers and mobile phones, and digital home appliances such as digital cameras and televisions. As semiconductor chips have been highly integrated and increased in capacity in recent years, the processing accuracy of semiconductor devices has been continually miniaturized. Wafers prior to device formation have defects such as smoothness and scratches. The so-called intactness requirement that does not exist is becoming increasingly severe.

As a wafer smoothing technique, a polishing process called CMP (Chemical Mechanical Polishing) is often used. In the smoothing treatment by CMP, a polishing composition containing fine abrasive grains and a basic compound is used. While supplying this polishing composition to the surface of the polishing pad, the surface is polished by relatively moving the polishing pad in pressure contact with the wafer as the object to be polished. At this time, since the mechanical polishing by the abrasive grains and the chemical polishing by the basic compound proceed simultaneously, the wafer surface can be smoothed over a wide range with high accuracy.
Generally, in wafer polishing by CMP, high-precision smoothing is realized by performing polishing in 3 to 4 stages. In primary polishing and secondary polishing performed in the first stage and the second stage, since the main purpose is to smooth the surface, the polishing rate tends to be regarded as important. On the other hand, in the final polishing in the third stage or the fourth stage, the haze and COP (Crystal Originated Particles) of the wafer surface are suppressed, and further, agglomerated abrasive grains, polishing pad debris, and polishing are removed. Emphasis is also placed on the prevention of contamination caused by the adhesion of so-called particles such as silicon powder.

  As a polishing composition used for the above-mentioned finish polishing, it is known that a method of adding a water-soluble polymer compound to the polishing composition is effective. Patent Document 1 discloses a polishing composition containing a water-soluble polymer compound having a molecular weight of 100,000 or more and a water-modified salt. Patent Document 2 describes a polishing composition containing a water-soluble polymer compound, and indicates that a cellulose derivative or polyvinyl alcohol can be used as the water-soluble polymer compound.

Japanese Patent Laid-Open No. 2-158684 JP 11-116942 A

However, in the invention described in Patent Document 1, the water-soluble polymer compound used is not sufficiently adsorbed to the wafer surface, and the haze and COP of the wafer surface after finish polishing are not satisfactory. Further, water-soluble salts added for the purpose of improving the polishing properties are also not preferable from the viewpoint of dispersibility of the silica abrasive grains. If the dispersibility of the silica abrasive grains is insufficient, the surface roughness of the wafer surface after finish polishing tends to increase, and problems such as scratches tend to occur.
Similarly, the cellulose derivative or polyvinyl alcohol described in Patent Document 2 is not sufficiently adsorbable on the wafer surface. In addition, in the Example of Patent Document 2, an experimental example using hydroxyethyl cellulose as a specific water-soluble polymer compound is disclosed, but since it is a compound derived from a natural product, there is a problem in that quality variation is large. There was also.

  The present invention has been made in view of such circumstances, and provides a wetting agent for semiconductor and a polishing composition effective in smoothing the wafer surface with high accuracy and effective in suppressing COP in surface polishing of a silicon wafer. It is an object to do.

  As a result of intensive studies to solve the above problems, the present inventors use a semiconductor wetting agent containing a water-soluble polymer obtained by acetalization reaction between polyvinyl alcohol and an aldehyde compound having 1 to 7 carbon atoms. Thus, the inventors have found that there is an effect in smoothing the wafer surface after polishing and suppressing COP, and have completed the present invention.

The present invention is as follows.
[1] A water-soluble polymer obtained by an acetalization reaction between polyvinyl alcohol and an aldehyde compound having 1 to 7 carbon atoms, wherein 70 to 99 mol% of vinyl alcohol structural units and acetalized structural units 1 to 1 are included in the molecule. A semiconductor wetting agent comprising a water-soluble polymer having 30 mol% [2] The semiconductor-use as described in [1] above, wherein the water-soluble polymer has a number average molecular weight of 1,000 to 200,000 Wetting agent.
[3] A polishing composition comprising the semiconductor wetting agent according to [1] or [2] 2, water, abrasive grains, and an alkali compound.
[4] The polishing composition according to [3], wherein the abrasive grains are colloidal silica.
[5] A composition for polishing a silicon wafer, comprising the polishing composition according to any one of [3] or [4].

  The wetting agent for semiconductors of the present invention has excellent adsorptivity to the wafer surface after polishing. For this reason, by using the polishing composition containing the semiconductor wetting agent, it is possible to increase the smoothness of the polished wafer surface and to suppress the COP because of excellent etching resistance. Furthermore, since the dispersibility of silica is also good, there are few scratches and surface roughness due to the agglomerated silica abrasive grains, and it is possible to obtain a wafer surface excellent in free of charge.

  The present invention will be described in detail below. In the present specification, “(meth) acryl” means acryl and methacryl, and “(meth) acrylate” means acrylate and methacrylate. The “(meth) acryloyl group” means an acryloyl group and a methacryloyl group.

〔式中、Ｙは、水素又は炭素数１〜６の直鎖又は分岐アルキル基であって、該アルキル基は官能基によって置換されていてもよい。〕 <Water-soluble polymer>
The wetting agent for semiconductors of the present invention is a water-soluble polymer obtained by acetalization reaction between polyvinyl alcohol and an aldehyde compound having 1 to 7 carbon atoms, and contains 70 to 99 mol% of vinyl alcohol structural units and acetalization in the molecule. And a water-soluble polymer having 1 to 30 mol% of the structural units.
Here, the said vinyl alcohol unit shows the structural unit represented by the following formula | equation (1). The acetalized structural unit mainly represents a structural unit represented by the following general formula (2).
[—CH ₂ CH (OH) —] (1)

[Wherein Y is hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a functional group. ]

The water-soluble polymer in the present invention has a vinyl alcohol structural unit represented by the formula (1) in a range of 70 to 99 mol%. A preferable range of the structural unit is 70 to 95 mol%, and a more preferable range is 75 to 90 mol%. The structural unit represented by the formula (1) is important in that the adsorptivity to the wafer is good and the solubility of the water-soluble polymer in water is ensured.
When the vinyl alcohol structural unit in the water-soluble polymer is less than 70 mol%, the solubility in water is not sufficient, and the effect of the wetting agent for semiconductors of the present invention may not be obtained. On the other hand, when it exceeds 99 mol%, the acetalized structural unit represented by the formula (2) is less than 1 mol%, and the adsorptivity to the wafer may be insufficient.

  In Formula (2), Y is hydrogen or a linear or branched alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a functional group. Y may be one of these, or two or more may be used in combination. Among the above, a linear or branched alkyl group having 3 to 6 carbon atoms is preferable in that the adsorptivity to the wafer is good.

In the water-soluble polymer, the acetalized structural unit needs to be in the range of 1 to 30 mol%. A preferable range of the structural unit is 5 to 30 mol%, and a more preferable range is 10 to 25 mol%. The acetalized structural unit is an important structural unit for imparting adsorptivity to a wafer.
If the acetalized structural unit is less than 1 mol%, the adsorptivity to the wafer may be insufficient, and if it exceeds 30 mol%, the solubility in water may be insufficient.

  The number average molecular weight of the water-soluble polymer is preferably in the range of 1,000 to 200,000, more preferably in the range of 1,500 to 100,000, still more preferably 2,000 to 50,000. Range. When the number average molecular weight is 1,000 or more, the wettability of the wafer tends to be good, and when it is 200,000 or less, the dispersibility of the abrasive grains can be ensured.

<Method for producing water-soluble polymer>
The water-soluble polymer in the present invention can be obtained, for example, by reacting a part of the hydroxyl groups of polyvinyl alcohols with an aldehyde compound in a solvent and acetalizing.
In general, acetalization is performed by dehydration condensation of polyvinyl alcohol and an aldehyde compound in the presence of an acid catalyst such as hydrochloric acid, and a conventionally known method can be used. For example, an aqueous solution containing 1 to 30% by mass of polyvinyl alcohol is prepared, and the reaction is allowed to proceed for 20 minutes to 6 hours by contacting an acid catalyst and an aldehyde compound in a temperature range of about −5 to 60 ° C. Thereafter, the temperature is raised by 10 to 50 ° C. as necessary, and the reaction is completed by further aging reaction for 30 minutes to 5 hours, and preferably a method of obtaining acetalized polyvinyl alcohol by cooling.

Examples of the aldehyde compound include formaldehyde and linear or branched alkyl aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, t-butyraldehyde, and hexyl aldehyde; and alicyclic rings such as cyclohexanecarbaldehyde and benzaldehyde. Formula or aromatic aldehydes may be mentioned. These may be used alone or in combination of two or more. Further, except for formaldehyde, one or more hydrogen atoms may be substituted with halogen or the like. Of these, linear or branched alkyl aldehydes are preferred from the viewpoint of high solubility in water and easy acetalization reaction. Among them, n-propyl aldehyde, n-butyraldehyde, n-pentyl aldehyde are preferable. It is more preferable that
As the aldehyde compound, in addition to the above, an aldehyde compound having 8 or more carbon atoms such as 2-ethylhexylaldehyde, nonylaldehyde, decylaldehyde and the like may be used.

  A commercially available polyvinyl alcohol may be used, or by saponifying a polyvinyl ester obtained by solution polymerization of vinyl esters such as vinyl formate, vinyl acetate and vinyl propionate in the presence of a polymerization initiator or the like. It can also be obtained. The vinyl esters are preferably vinyl acetate from the viewpoint of polymerization stability. In the present invention, polyvinyl alcohol may be either completely saponified or partially saponified, but in the case of partial saponification, the saponification rate is preferably 70 mol% or more, more preferably 80 mol% or more, More preferably, it is 90 mol% or more.

<Wetting agent for semiconductors>
The semiconductor wetting agent of the present invention comprises the water-soluble polymer and water. It is preferable to use high-purity water so as not to impair the effect as a wetting agent. Specifically, it is preferable to use pure water, ultrapure water, or distilled water from which foreign ions are removed by filtration after removing impurity ions with an ion exchange resin. In addition to this, the wetting agent may contain an organic solvent such as alcohol and ketone having high miscibility with water.
Although the ratio of the water-soluble polymer in the wetting agent for semiconductor is not particularly limited as long as it is a viscosity that can be easily handled as an aqueous solution, the range is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, The range of 30% by mass is more preferable.

The water-soluble polymer in the present invention is excellent in adsorptivity to the wafer surface and the like, and particularly exhibits high adsorptivity to the wafer surface in a state where the oxide film is completely removed. For this reason, when the semiconductor wetting agent of the present invention is used in the wafer surface treatment process, the smoothness of the polished wafer surface can be improved, and contamination caused by COP and particle adhesion can be reduced. The following mechanism is assumed as a reason why these effects can be obtained.
Regarding the smoothness of the wafer surface, the water-soluble polymer in the semiconductor wetting agent is adsorbed on the wafer surface, so that the friction between the wafer surface and the abrasive grains is reduced in the mechanical polishing of CMP. For this reason, it is considered that the minute unevenness formed on the wafer surface by mechanical polishing is reduced and the smoothness is improved.

In addition, as described above, in mechanical polishing, the polishing composition is supplied to the wafer surface and the polishing pad is pressed against the wafer surface and rotated to physically polish the wafer surface. Therefore, the polishing pad is pressed against a portion other than the COP on the wafer surface and polished in a direction perpendicular to the wafer surface. As the mechanical polishing proceeds, the COP gradually decreases, and the COP disappears when the wafer surface is polished beyond the depth. Therefore, it is considered that the mechanical polishing shows the effect of reducing the number of COPs and the size thereof.
On the other hand, in chemical polishing, the polishing composition enters the COP during polishing, and the basic compound corrodes or etches the inside of the COP. As described above, since the polishing is performed in the direction perpendicular to the inner wall of the COP, it is considered that the COP on the wafer surface increases with the progress of chemical polishing.
In the present invention, it is assumed that the water-soluble polymer adsorbed on the wafer surface has a function of suppressing chemical polishing more than mechanical polishing. It is presumed that this tendency becomes stronger as the water-soluble polymer adsorbability to the wafer becomes higher, and as a result, a wafer surface having high smoothness and low COP can be obtained.

  Furthermore, when the water-soluble polymer is adsorbed on the wafer surface, the surface is hydrophilized. Thereby, contamination due to adhesion of particles during polishing can also be prevented.

<Polishing composition>
The polishing composition of the present invention comprises the semiconductor wetting agent, water, abrasive grains, and an alkali compound. The ratio of the semiconductor wetting agent in the polishing composition is not particularly limited, but it is preferable that the polishing composition has an appropriate viscosity for handling in CMP and adsorbing to the wafer surface. The specific viscosity of the polishing composition is preferably in the range of 0.1 to 10 mPa · s, more preferably in the range of 0.3 to 8 mPa · s, and 0.5 to 5 mPa · s. More preferably, it is in the range.
Moreover, it is preferable to use the said water-soluble polymer so that it may become the range of 0.001-10 mass% of the whole composition for abrasive | polishing agents, and it is more preferable that it is the range of 0.005-5 mass%.

  Colloidal silica or the like can be used as the abrasive. When colloidal silica is used as the abrasive, the content in the polishing composition is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and 3 to 20% by mass. More preferably it is. If the usage-amount of colloidal silica is 0.1 mass% or more, the polishing rate of mechanical polishing will become favorable. Moreover, if it is 50 mass% or less, the dispersibility of an abrasive grain is hold | maintained and the smoothness of a wafer surface can be made favorable.

  The average particle size of the corridal silica is appropriately selected from the required polishing rate and the smoothness of the wafer surface after polishing, but is generally in the range of 2 to 500 nm, preferably in the range of 5 to 300 nm. A range of ˜200 nm is more preferable.

The alkali compound is not particularly limited as long as it is a water-soluble alkali compound, and alkali metal hydroxides, amines, ammonia, quaternary ammonium hydroxide salts, and the like can be used. Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, rubidium hydroxide and cesium hydroxide. Examples of amines include triethylamine, monoethanolamine, diethanolamine, triethanolamine, diisopropanolamine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylpentamine, and tetraethylpentamine. Examples of the quaternary ammonium hydroxide salt include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Among these, ammonia or a quaternary ammonium hydroxide salt is preferable from the viewpoint of less contamination of the semiconductor substrate.
The polishing composition of the present invention is preferably adjusted to have a pH of 8 to 13 by adding the alkali compound. More preferably, the pH range is adjusted to 8.5-12.

  In addition to the above, an organic solvent, various chelating agents, surfactants, and the like can be added to the abrasive composition as necessary.

Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited by these Examples. In the following, “parts” and “%” mean mass parts and mass% unless otherwise specified.
It describes below about the analysis method of the water-soluble polymer obtained by the manufacture example, and the evaluation method of the wetting agent for semiconductors or polishing composition in an Example and a comparative example.

<Acetalization rate>
The acetalization rate of polyvinyl alcohol was calculated by the following method. That is, in the acetalization reaction, since 2 mol of hydroxyl group derived from vinyl alcohol reacts theoretically with 1 mol of aldehyde, when the amount of aldehyde used is X mol% (with respect to hydroxyl group) and the reaction rate of aldehyde is Y%, Can be represented by
Acetalization rate (mol%) = 2 × X × Y
The reaction rate of aldehyde was measured using GC (gas chromatography GC-2014, manufactured by Shimadzu Corporation).

<Number average molecular weight (Mn)>
About the polymer obtained by each manufacture example, it measured by polystyrene conversion using GPC (gel permeation chromatography HLC-8220, product made from Tosoh).

<Etching resistance (E.R.)>
After measuring the weight of the wafer cut to 3 × 6 cm with a glass cutter, it was immersed in a 3% hydrofluoric acid aqueous solution for 20 seconds to remove the oxide film on the wafer surface, and then washed with pure water for 10 seconds. This process was repeated until the wafer surface was completely water repellent. Next, an etching chemical solution was prepared by adding a semiconductor wetting agent to ammonia water having an ammonia: water weight ratio of 1:19 so that the concentration of the water-soluble polymer was 0.18 wt%. The wafer was completely immersed in an etching chemical solution and left to stand at 25 ° C. for 12 hours for etching. From the wafer weight change before and after etching, the etching rate (E.R.) was calculated according to the following formula.

<Wettability>
The oxide film on the wafer surface was removed by the same method as etching resistance, and then immersed in a 0.18 wt% water-soluble polymer solution for 5 minutes. After immersion, the surface of the wafer was pulled up using a tweezers so as to be perpendicular to the liquid level, and the water-repellent distance from the end of the wafer at the time when 10 seconds had passed was visually confirmed, and judged according to the following criteria.
○: Water repellent distance less than 5 mm △: Water repellent distance 5 to 10 mm
×: Water repellent distance> 10mm

<Wafer appearance>
The wafer surface after etching was performed by the same method as the etching resistance was visually confirmed, and judged according to the following criteria.
○: No roughening on the surface △: The surface is slightly rough ×: The surface is extremely rough

<Alkali resistance>
5.0 g of a water-soluble polymer was added to 40 g of an aqueous alkali solution adjusted to pH 10 by dissolving sodium hydroxide in water in a 50 cc screw bottle, and the mixture was covered well and mixed. The hydrolysis rate after standing at 50 ° C. for 1 month in an aluminum block heater was evaluated from GC, and judged from the following criteria.
○: Hydrolysis rate of water-soluble polymer is less than 1% Δ: Hydrolyzate of water-soluble polymer is 1% or more and less than 5% ×: Hydrolysis rate of water-soluble polymer is 5% or more

<Silica dispersibility>
In a 9 cc screw bottle, 0.5 g of a water-soluble polymer aqueous solution having a resin solid content of 20% was added to 5.0 g of colloidal silica (primary particle size: 30 to 50 nm) and mixed well. The particle size (A) of the silica after standing overnight was measured by a dynamic light scattering method (ELSZ-1000, manufactured by Otsuka Electronics Co., Ltd.), and from the particle size (B) of colloidal silica not added with a water-soluble polymer. The rate of change was calculated according to the following formula and judged according to the following criteria.
Rate of change (%) = {(A−B) / B} × 100
○: Change rate is less than 10% Δ: Change rate is 10% to less than 30% ×: Change rate is 30% or more

≪Acetalization of polyvinyl alcohol≫
Production Example 1
A 3 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer, and various introduction tubes was prepared, and 100 parts of PVA105 (polyvinyl alcohol manufactured by Kuraray Co., Ltd., saponification degree 98 mol%, polymerization degree 500) and pure water 400 The temperature was raised to 90 ° C. and completely dissolved while rotating the stirring blade at 150 rpm. Next, after cooling the internal temperature to 60 ° C., 11.0 parts of 98% sulfuric acid was added while continuing stirring. Further, an aqueous solution obtained by diluting 6.6 parts of n-butyraldehyde (manufactured by Wako Pure Chemical Industries, Ltd.) with 100 parts of pure water was added dropwise over 30 minutes. After reacting at 60 ° C. for 4 hours, 7.7 parts of 25% aqueous ammonia was added to terminate the reaction. From the results of gas chromatography (GC), it was confirmed that all of the aldehyde used had disappeared. Then, it vacuum-dried at 80 degreeC overnight, and obtained the polymer 1 of white solid. The acetalization rate was 8.0 mol%.
After the polymer 1 was reacted with acetic anhydride at 110 ° C. in pyridine for acetylation, the molecular weight was measured by GPC. As a result, Mn = 41,000.

Production Example 2
A white solid polymer 2 was obtained in the same manner as in Production Example 1 except that the aldehyde used was changed to 25.8 parts of a 37% formaldehyde solution (Wako Pure Chemical Industries, Ltd.). From the results of GC, it was confirmed that all of the aldehyde used had disappeared. The acetalization rate was 28.0 mol%. Moreover, Mn of the polymer 2 was 34,000.

Production Example 3
A white solid polymer 3 was obtained in the same manner as in Production Example 1 except that the aldehyde used was changed to 12.5 parts of n-propyl aldehyde (manufactured by Wako Pure Chemical Industries, Ltd.). From the results of GC, it was confirmed that all of the aldehyde used had disappeared. The acetalization rate was 19.0 mol%. Further, the Mn of the polymer 3 was 38,000.

Production Example 4
A white solid polymer 4 was obtained in the same manner as in Production Example 1 except that the aldehyde used was changed to 5.7 parts of n-hexylaldehyde (Wako Pure Chemical Industries, Ltd.). From the results of GC, it was confirmed that all of the aldehyde used had disappeared. The acetalization rate was 5.0 mol%. Moreover, Mn of the polymer 4 was 43,000.

Production Example 5
A white solid polymer 5 was obtained in the same manner as in Production Example 1 except that the polyvinyl alcohol used was changed to PVA115 (manufactured by Kuraray Co., Ltd., saponification degree 98 mol%, polymerization degree 1500). From the results of GC, it was confirmed that all of the aldehyde used had disappeared. The acetalization rate was 8.0 mol%. Further, the Mn of the polymer 5 was 129,000.

Production Example 6
A white solid polymer 6 was obtained in the same manner as in Production Example 1 except that the amount of n-butyraldehyde used was changed to 0.7 parts. From the results of GC, it was confirmed that all of the aldehyde used had disappeared. The acetalization rate was 0.8 mol%. Moreover, Mn of the polymer 6 was 43,000.

Production Example 7
In Production Example 1, an acetalization reaction was performed by the same operation except that the amount of n-butyraldehyde used was changed to 31.1 parts. However, polymer 7 insolubilized in water during the reaction was deposited. As a result of measuring the aldehyde contained in the solvent by GC, it was confirmed that the total amount of the aldehyde used had disappeared. The acetalization rate was 38.0 mol%. The Mn of the polymer 7 was 35,000.

Production Example 8
In Production Example 1, an acetalization reaction was performed by the same operation except that the aldehyde used was changed to 8.7 parts of n-octylaldehyde (manufactured by Wako Pure Chemical Industries, Ltd.). However, the water solubility of the raw material aldehyde was poor, the progress of the reaction was not observed, and the polymer 8 was not obtained.

Example 1
Water was added so that the concentration of the water-soluble polymer 1 was 15% by mass to prepare a semiconductor wetting agent. About the obtained wetting agent for semiconductors, etching resistance, wettability, wafer appearance and alkali resistance were evaluated. The results obtained are shown in Table 1.
Also, 10.0 g of colloidal silica dispersion (primary particle system 30-50 nm, silica solid content 10%) adjusted to pH 10.0 by adding aqueous ammonia and 0.1 g of the above-mentioned wetting agent for semiconductor were added. A composition for an abrasive was obtained. The obtained abrasive composition was evaluated for silica dispersibility, and Table 1 shows the results.

Examples 2-5 and Comparative Examples 1-3
A semiconductor wetting agent and abrasive composition were prepared in the same manner as in Example 1 except that the water-soluble polymer shown in Table 1 was used. However, in Comparative Example 2, since the polymer after the acetalization reaction was insoluble or hardly dissolved in water, evaluation as a wetting agent and an abrasive composition could not be performed. The evaluation results of each sample are shown in Table 1.

Comparative Example 4
Wetting agent for semiconductor and polishing in the same manner as in Example 1 except that a commercially available polyvinyl alcohol (trade name “Kuraray Poval PVA505”, saponification degree 73.5 mol%, polymerization degree 500) manufactured by Kuraray Co., Ltd. was used as the water-soluble polymer. An agent composition was prepared, and the evaluation results are shown in Table 1.

Comparative Example 5
About the evaluation result, a wetting agent for semiconductor and an abrasive composition were prepared in the same manner as in Example 1 except that commercially available hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd., Mw = 90,000) was used as the water-soluble polymer. It is shown in Table 1.

Comparative Example 6
About the evaluation result, we prepared a wetting agent for semiconductor and an abrasive composition in the same manner as in Example 1 except that a commercially available polyvinyl pyrrolidone (trade name “PVP K30” manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the water-soluble polymer. It is shown in Table 1.

Details of the water-soluble polymer shown in Table 1 are as follows.
PVA505: low saponified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name “Kuraray Poval”
PVA505 ”, saponification degree 73.5 mol%, polymerization degree 500)
HEC: hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 90,000)
PVP K30: Polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.)

Examples 1 to 5 are experimental examples using the water-soluble polymer defined in the present invention, and because the adsorptivity to the wafer is high, results excellent in etching resistance, wettability and appearance on the wafer are obtained. ing. Moreover, it was confirmed that the silica dispersibility is excellent in the case of an abrasive composition.
On the other hand, Comparative Example 1 in which the acetalized structural unit in the water-soluble polymer does not satisfy the lower limit defined in the present invention has insufficient adsorbability on the wafer surface, so that the etching resistance, wettability and wafer appearance are reduced. The result was inferior. In Comparative Example 2 in which the acetalized structural unit exceeds the upper limit, as described above, the solubility of the polymer after acetalization in water was insufficient.
Further, in Comparative Example 4 using polyvinyl alcohol having a low saponification rate, hydrolysis of a unit derived from vinyl acetate occurred, so that the alkali resistance was insufficient. Comparative Examples 5 and 6 using a water-soluble polymer having a structural unit different from that of the water-soluble polymer of the present invention were not satisfactory in terms of adsorptivity to the wafer surface and silica dispersibility.

  Since the wetting agent for semiconductors of the present invention is excellent in the adsorptivity to the wafer surface after polishing, by using a polishing composition containing the wetting agent for semiconductors, the smoothness of the wafer surface after polishing is improved, and , COP can be suppressed. Furthermore, since the dispersibility of silica is also good, it is particularly useful as a composition for final polishing of silicon wafers.

Claims (5)

  A water-soluble polymer obtained by acetalization reaction between polyvinyl alcohol and an aldehyde compound having 1 to 7 carbon atoms, wherein 70 to 99 mol% of vinyl alcohol structural units and 1 to 30 mol% of acetalized structural units are contained in the molecule. A semiconductor wetting agent comprising a water-soluble polymer.   The wetting agent for a semiconductor according to claim 1, wherein the water-soluble polymer has a number average molecular weight of 1,000 to 200,000.   A polishing composition comprising the semiconductor wetting agent according to claim 1, water, abrasive grains, and an alkali compound.   The polishing composition according to claim 3, wherein the abrasive grains are colloidal silica.   A composition for polishing a silicon wafer, comprising the polishing composition according to claim 3.