JP6797796B2 - Wetting agent for polishing and polishing liquid composition - Google Patents

Description

Cross-reference to related applications This application is a related application of Japanese Patent Application No. 2015-132376, which was filed on July 1, 2015, and claims priority based on this Japanese application. All contents described in this Japanese application shall be incorporated herein by reference.
The present invention relates to a wetting agent for polishing and a polishing liquid composition, and more particularly to a wetting agent for semiconductor polishing and a semiconductor polishing liquid composition used for finish polishing of a silicon wafer and the like.

Semiconductor devices using silicon wafers as substrates are widely used in information and communication equipment such as personal computers and mobile phones, and digital home appliances such as digital cameras and televisions. With the recent increase in the integration and capacity of semiconductor chips, the processing accuracy of semiconductor devices is steadily becoming finer, and wafers before device formation are subject to defects such as smoothness and scratches. The demand for so-called intactness that does not exist is becoming more and more stringent.

As a wafer smoothing technique, a polishing process called CMP (Chemical Mechanical Polishing: Chemical Mechanical Polishing) is often used. In the smoothing treatment by CMP, a polishing liquid composition containing fine abrasive grains and a basic compound is used. While supplying this polishing liquid composition to the surface of the polishing pad, the surface is polished by relatively moving the pressure-welded polishing pad and the wafer to be polished. At this time, the surface of the wafer can be smoothed with high accuracy over a wide range by simultaneously performing mechanical polishing with abrasive grains and chemical polishing with a basic compound.
Generally, in wafer polishing by CMP, high-precision smoothing is realized by performing 3 to 4 steps of polishing. In the primary and secondary polishing performed in the first and second stages, the polishing speed tends to be emphasized because the main purpose is rough polishing of the rough wafer surface after being sliced from the silicon ingot. There is. On the other hand, in the final polishing of the third stage or the fourth stage, not only the polishing speed but also the intactness of the wafer surface and a high degree of smoothness are required.

Parameters of intactness and smoothness include various surface defects such as haze, LPD (Light Point Defect), and scratch scratches. If various surface defects are present on the surface of the wafer manufactured by the above CMP process, pattern defects, insulation withstand voltage defects, ion implantation defects, and other deterioration of device characteristics are caused in the subsequent device forming process, which causes a decrease in yield. Therefore, it is necessary to manufacture a wafer having as few surface defects as possible.
In order to obtain a wafer with few surface defects, a method of adding a water-soluble polymer compound to the polishing liquid composition is generally adopted. The water-soluble polymer compound functions as a wetting agent, exerts a stress relaxation effect by adsorbing to the surface of abrasive grains and wafers, and reduces damage to the wafer by abrasive grains and foreign substances. Further, it can be expected to have an effect of imparting hydrophilicity to the wafer surface and preventing adhesion of abrasive grains and foreign substances. As a result, it enables a high degree of smoothing of the wafer surface as compared with the case where the water-soluble polymer compound is not added.
Under such circumstances, a polishing liquid composition containing a water-soluble polymer compound has been proposed. Patent Document 1 discloses a polishing liquid composition containing hydroxyethyl cellulose (HEC) as a water-soluble polymer. Further, Patent Document 2 describes a polishing liquid composition containing a water-soluble polymer compound having a molecular weight of 100,000 or more, a water-soluble salt, and the like. Patent Document 3 discloses a polishing liquid composition containing various water-soluble polymers having a weight average molecular weight of 1,000,000 or less and a molecular weight distribution of less than 5.0.

Japanese Unexamined Patent Publication No. 2004-128089 Japanese Unexamined Patent Publication No. 2-158648 International Publication No. 2014/0344425

However, since HEC described in Patent Document 1 is a polymer derived from a natural product, there is a problem that control of the chemical structure is restricted and the quality varies widely. In addition, natural cellulose, which is a raw material of HEC, contains water-insoluble matter derived from cellulose, and the water-insoluble matter itself and silica particles aggregated by the water-insoluble matter as nuclei are formed after polishing. It could increase the number of surface defects.
Further, although Patent Document 2 describes various synthetic water-soluble polymer compounds, there is no description regarding the difference in effect based on the difference in structural units and the molecular weight distribution, and the type and conditions of use of the object to be polished. In some cases, sufficient polishing performance may not be obtained.
Patent Document 3 describes that the molecular weight distribution of the water-soluble polymer correlates with the reduction of LPD. However, due to the above-mentioned improvement in semiconductor device accuracy and the like, the adsorptivity to the surface of the object to be polished such as a wafer Further improvements were required for surface smoothness and the like.

The present invention has been made in view of such circumstances. That is, it is a wetting agent for polishing containing a synthetic water-soluble polymer useful for surface polishing of silicon wafers and the like, and has excellent adsorption power and wettability to the surface of the object to be polished and the dispersion stability of abrasive grains. It is an object of the present invention to provide a polishing wetting agent and a polishing liquid composition which do not adversely affect the above.

As a result of diligent studies to solve the above problems, the present inventors have obtained a polishing liquid composition containing a water-soluble polymer having a low dispersity in which the main chain portion is composed of only carbon-carbon bonds, on the surface of the wafer after polishing. We have found that it is effective in smoothing and suppressing LPD, and have completed the present invention.

The present invention is as follows.
[1] Water-soluble having a main chain portion composed of repeating units consisting only of carbon-carbon bonds and having a dispersity (PDI) of 2.0 or less represented by a weight average molecular weight (Mw) / number average molecular weight (Mn). Wetting agent for polishing containing a sex polymer.
[2] When the water-soluble polymer is prepared into an aqueous solution having a concentration of 10% by mass and a pH of 10, the hydrolysis rate of the water-soluble polymer after 1 month under the condition of 60 ° C. is 5.0% or less. , The polishing wetting agent according to the above [1].
[3] The polishing wetting agent according to the above [1] or [2], wherein the weight average molecular weight (Mw) of the water-soluble polymer is in the range of 10,000 or more and 1,000,000 or less.
[4] The polishing according to any one of [1] to [3] above, wherein the water-soluble polymer contains 10 mol% or more and 100 mol% or less of structural units derived from a monomer having a nitrogen atom in the molecule. Wetting agent.
[5] The monomer having a nitrogen atom in the molecule comprises N- (meth) acryloylmorpholine, N-alkyl (meth) acrylamide compound, (di) alkylaminoalkylamide compound, and N-vinyllactam compound. The polishing wetting agent according to the above [4], which is 1 or 2 or more selected from the group.
[6] The polishing wetting agent according to the above [4], wherein the monomer having a nitrogen atom in the molecule is N- (meth) acryloyl morpholine.
[7] A polishing liquid composition containing the polishing wetting agent, water, abrasive grains and an alkaline compound according to any one of the above [1] to [6].
[8] The polishing liquid composition according to the above [7], which is used for finish polishing of a silicon wafer.
[9] Water-soluble having a main chain portion composed of repeating units consisting only of carbon-carbon bonds and having a dispersity (PDI) of 2.0 or less represented by a weight average molecular weight (Mw) / number average molecular weight (Mn). The process of polishing a silicon wafer in the presence of a sex polymer,
A method for producing a polished product of a silicon wafer.

The water-soluble polymer contained in the polishing wetting agent of the present invention has a sufficiently narrow molecular weight distribution. Therefore, a polishing wetting agent made of a polymer having a desirable molecular weight can be obtained from the viewpoints of adsorption / desorption to the surface of an object to be polished such as a wafer and dispersion stability of abrasive grains in the polishing liquid composition. This makes it possible to improve the smoothness of the wafer surface after polishing and further enhance the ability to suppress surface defects such as LPD. Further, since the dispersibility of silica is also good, scratches and surface roughness due to aggregated silica abrasive grains are small, and a wafer surface having excellent scratch resistance can be obtained.

Hereinafter, typical and non-limiting specific examples of the present disclosure will be described in detail. This detailed description is intended to provide those skilled in the art with details for carrying out the preferred examples of the present invention and is not intended to limit the scope of the present disclosure. In addition, the additional features and inventions disclosed below can be used separately or together with other features and inventions to provide a further improved abrasive wetting and polishing solution composition.

In addition, the combination of features and processes disclosed in the following detailed description is not essential for implementing the present disclosure in the widest range, and is particularly for explaining typical specific examples of the present disclosure. It is to be described. In addition, the various features of the above and below representative examples, as well as the various features of those described in the independent and dependent claims, are described herein in providing additional and useful embodiments of the present disclosure. It does not have to be combined according to the specific examples given or in the order listed.

All features described herein and / or claims are, separately, as a limitation to the disclosure at the time of filing and the specific matters claimed, apart from the composition of the features described in the examples and / or claims. And it is intended to be disclosed independently of each other. In addition, all numerical ranges and statements relating to groups or groups are made with the intention of disclosing their intermediate composition as a limitation to the disclosure at the time of filing and the specific matters claimed.

Hereinafter, the present invention will be described in detail. In addition, in this specification, "(meth) acrylic" means acrylic and methacrylic, and "(meth) acrylate" means acrylate and methacrylate. Moreover, "(meth) acryloyl group" means an acryloyl group and a methacryloyl group.

<Water-soluble polymer>
The polishing wetting agent of the present invention is composed of repeating units in which the main chain portion is composed of only carbon-carbon bonds, and has a dispersity (PDI) represented by weight average molecular weight (Mw) / number average molecular weight (Mn) of 2. Includes water-soluble polymers of .0 or less. Here, "the main chain portion consists of only carbon-carbon bonds" means that those containing carbon-oxygen bonds, carbon-nitrogen bonds, etc. in the main chain itself, such as polyether, polyester, and polyamide, are excluded. Used in. Therefore, for example, the type of bond derived from the substituent of the polymerizable functional group of the constituent monomer, such as the carbon-hydrogen bond derived from the acryloyl group or the pendant group introduced when the acrylic monomer is polymerized, is considered. do not do. Further, a polishing wetting agent containing a water-soluble polymer having a carbon-carbon unsaturated bond in the main chain portion is included in the scope of the present invention.

A water-soluble polymer in which the main chain portion is composed of a repeating unit consisting only of carbon-carbon bonds can be obtained, for example, by polymerizing a vinyl-based monomer.
The vinyl-based monomer is not particularly limited, and specifically, specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. (Meta) Acrylic Acid Alkyl Ester Compound; Unsaturated Acids such as (Meta) Acrylic Acid, Crotonic Acid, Maleic Acid, Itaconic Acid and Fumaric Acid and Their Salts; Unsaturated Acid Anhydrous such as Maleic Anhydrous; 2-acrylamide Sulfonic acid group-containing monomers such as -2-methylpropanesulfonic acid and salts thereof; (meth) acrylamide; N- (meth) acryloylmorpholine; methyl (meth) acrylamide, ethyl (meth) acrylamide, n-propyl (meth) ) N-alkyl (meth) acrylamide compounds such as acrylamide, isopropyl (meth) acrylamide, n-butyl (meth) acrylamide and 2-ethylhexyl (meth) acrylamide; methylaminopropyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide , Ethylaminopropyl (meth) acrylamide and (di) alkylaminoalkylamide compounds such as diethylaminopropyl (meth) acrylamide; methylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate and (Di) Alkylaminoalkyl (meth) acrylate compounds such as diethylaminoethyl (meth) acrylate; N-vinyllactam compounds such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam; aromatics such as styrene, vinyltoluene and vinylxylene Group vinyl compounds; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-hexyl vinyl ether, 2-ethylhexyl vinyl ether, n-octyl vinyl ether, n-nonyl vinyl ether. And alkyl vinyl ethers having an alkyl group having 1 to 10 carbon atoms such as n-decylvinyl ether; vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate. , Vinyl ester compounds such as vinyl piperate and vinyl versaticate; α-olefins such as ethylene, propylene and butylene are exemplified. One or more of them can be used.
Among the above, N- (meth) acryloyl morpholine and N-alkyl (meth) acrylamide compounds are excellent in that they have appropriate adsorptivity to wafers and abrasive grains and are excellent in hydrolysis resistance under alkaline conditions. , (Di) Alkylaminoalkylamide compound, N-vinyllactam compound and other monomers having a nitrogen atom in the molecule are preferable, and N- (meth) acrylate morpholine is particularly preferable.

The water-soluble polymer of the present invention preferably has a structural unit derived from the above-mentioned monomer having a nitrogen atom in the molecule in a range of 10 mol% or more and 100 mol% or less with respect to all the structural units of the water-soluble polymer. , 30 mol% or more and 100 mol% or less, more preferably 50 mol% or more and 100 mol% or less, and even more preferably 70 mol% or more and 100 mol% or less. When the structural unit derived from the monomer having a nitrogen atom in the molecule is in the range of 10 mol% or more and 100 mol% or less, the adsorptivity to the above-mentioned wafer and abrasive grains is appropriately maintained without deteriorating the solubility in water. It is preferable because it can be imparted to.

In the present invention, since a water-soluble polymer in which the main chain portion is composed of a repeating unit consisting only of carbon-carbon bonds is used, a wettable agent for polishing having excellent stability can be obtained. On the other hand, a water-soluble polymer having a carbon-oxygen bond or a carbon-nitrogen bond in the main chain portion may cause main chain cleavage due to alkaline hydrolysis or autoxidation, etc., and polishing conditions and storage conditions In some cases, the performance as a wetting agent may not be exhibited stably.

Further, the polishing liquid composition is generally prepared under the condition that an alkaline compound is blended, and is stored and used. Therefore, as the water-soluble polymer contained in the wetting agent for polishing, one having good alkali hydrolysis resistance is preferable.
In the evaluation of the alkali hydrolysis, for example, the water-soluble polymer is prepared in an aqueous solution having a concentration of 10% by mass and a pH of 10, and allowed to stand at 60 ° C. for 1 month to produce the water-soluble polymer by hydrolysis. The amount of the compound derived from the side chain of the monomer unit constituting the water-soluble polymer is determined by GC (for example, gas chromatography GC-2014, manufactured by Shimadzu Corporation, or a gas capable of ensuring the same degree of accuracy and accuracy as the device concerned. After the measurement with a chromatography device), it can be evaluated by the hydrolysis rate obtained by calculating the percentage with respect to the theoretical amount. In the present invention, the hydrolysis rate of the water-soluble polymer is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less.

The weight average molecular weight (Mw) of the water-soluble polymer of the present invention is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 30,000 to 800,000, and even more preferably. Is in the range of 50,000 to 600,000. A weight average molecular weight (Mw) of 10,000 or more is preferable in terms of good wettability to a wafer or the like, and a weight average molecular weight (Mw) of 1,000,000 or less is preferable in terms of dispersibility stability of abrasive grains. preferable.
In the present invention, the weight average molecular weight (Mw) was obtained as a polymethylmethacrylate conversion value measured by gel permeation chromatography (GPC). Further, the number average molecular weight (Mn) is also obtained by the same method.

The magnitude of the molecular weight of the water-soluble polymer in the polishing liquid composition affects the adsorption / desorption rate to the object to be polished such as a wafer. Generally, it is considered that the adsorption / desorption rate for a wafer or the like is higher as the molecular weight is lower. Therefore, in the polishing process in which the polishing liquid composition is always supplied, the lower the molecular weight of the water-soluble polymer, the faster it is adsorbed on the wafer or the like to hinder the polishing, resulting in a decrease in the polishing rate (decrease in productivity). On the other hand, in the cleaning step after polishing, the surface of the wafer or the like is quickly desorbed from the surface, so that the hydrophilicity of the surface of the wafer or the like is lowered and the wettability is lowered. In this case, particles or the like may eventually adhere to the exposed wafer surface or the like, leading to deterioration of surface defects.
On the other hand, if the molecular weight of the water-soluble polymer is too high, the dispersibility of abrasive grains such as silica contained in the polishing liquid composition may be deteriorated, causing aggregation of abrasive grains. In this case, the number of surface defects on the wafer may be increased due to scratches caused by the agglomerated abrasive grains and adhesion of the agglomerated abrasive grains themselves. Further, since the viscosity of the aqueous solution of the water-soluble polymer is increased, the filterability thereof is deteriorated, and there is a possibility that the productivity at the time of producing the polishing liquid composition is lowered.

Therefore, it is preferable that the water-soluble polymer has a suitable molecular weight depending on the intended use and does not contain a low molecular weight substance or a high molecular weight substance that is significantly different from the target molecular weight region. That is, it is preferable that the molecular weight distribution of the water-soluble polymer is narrow, and in the present invention, the dispersity (PDI) represented by the value obtained by dividing the weight average molecular weight (Mw) of the water-soluble polymer by the number average molecular weight (Mn). ) Is 2.0 or less. The PDI is preferably 1.8 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. The lower limit of PDI is usually 1.0.
When the PDI is 2.0 or less, it is possible to ensure good adsorption in the polishing process, wettability to the surface of the object to be polished after polishing, and good abrasive grain dispersion stability in a well-balanced manner. Become. Therefore, when used in the wafer polishing process, the entire wafer can be polished uniformly and evenly. In addition, since it does not contain a polymer with a remarkably high molecular weight, it exhibits good abrasive grain dispersibility, and scratches and surface roughness due to agglomerated abrasive abrasive grains, and surface contamination in which the abrasive grain agglomerates themselves adhere to the wafer surface as particles. Etc. are suppressed. As a result, further improvement in surface smoothness and scratch resistance is expected in the finish polishing of the wafer surface.

<Manufacturing method of water-soluble polymer>
The method for producing the water-soluble polymer in the present invention is not particularly limited, and a known polymerization method can be adopted, but the living radical is easy to control the molecular weight distribution and easily obtain a polymer having a small PDI. The polymerization method and the living anion polymerization method are preferable, and the living radical polymerization is more preferable in that the range of applicable monomers is wide.
As the living radical polymerization used in the present invention, any process such as a batch process, a semi-batch process, a dry continuous polymerization process, or a continuous stirring tank type process (CSTR) may be adopted. In addition, the polymerization type can be applied to various aspects such as bulk polymerization using no solvent, solvent-based solution polymerization, aqueous emulsion polymerization, miniemulsion polymerization or suspension polymerization.
There are no particular restrictions on the type of living radical polymerization method: atom transfer radical polymerization method (ATRP method), reversible addition-cleavage chain transfer polymerization method (RAFT method), nitroxy radical method (NMP method), organic tellurium compounds. Various polymerization methods such as a polymerization method using (TERP method), a polymerization method using an organic antimony compound (SBRP method), a polymerization method using an organic bismuth compound (BIRP method), and an iodine transfer polymerization method can be adopted. Among these, the RAFT method and the NMP method are preferable because there is no risk of wafer contamination due to mixing of a metal or a metalloid compound.

For example, when the surface of a wafer is contaminated with a metal in surface polishing of a silicon wafer or the like, the metal reacts with silicon or a silicon oxide film to cause uplift, depression, pit formation, dendritic foreign matter formation, etc. on the wafer. As a result of causing an abnormality in flatness of the transistor, there is a risk of impairing the wiring pattern of the transistor. In addition, the insulation resistance of the silicon oxide film (insulating film) of the transistor may be deteriorated to induce electrical destruction of the transistor, or the excess charge in the silicon oxide film may become a single unit and cause the transistor to malfunction. ..
Therefore, it is preferable to prevent metal from being mixed into the water-soluble polymer contained in the polishing wetting agent. In the present invention, the metal that prevents mixing into the water-soluble polymer includes not only metals such as alkali metals, alkaline earth metals, transition metals and other metals, but also metalloids such as Te. And. Examples of the alkali metal include Na, K and the like. Examples of the alkaline earth metal include Ca and the like. Examples of the transition metal include Ni, Cu, Fe, Cr, Zn, Ti, W, Co and the like. Examples of the other metal include Al and the like. In the present invention, the content of each of the above metals (including semimetals) with respect to the water-soluble polymer is preferably 100 ppm or less.

In the RAFT method, controlled polymerization proceeds via a reversible chain transfer reaction in the presence of a specific chain transfer agent (RAFT agent) and a general free radical polymerization initiator, and the molecular weight of the polymer is generally high. Can be adjusted by the charging ratio of the monomer and the RAFT agent.
In the present invention, various known RAFT agents such as dithioester compounds, xanthate compounds, dithiocarbamate compounds and trithiocarbonate compounds can be used.

The ratio of the RAFT agent used is appropriately adjusted depending on the type of monomer used and the RAFT agent, etc., but is 0.01 mass based on the total mass of all the monomers constituting the entire water-soluble polymer. It is preferably used at a ratio of% or more and 5.0% by mass or less, more preferably 0.05% by mass or more and 3.0% by mass or less, and 0.1% by mass or more and 2.0% by mass or less. More preferred.

As the polymerization initiator used in the polymerization by the RAFT method, known radical polymerization initiators such as azo compounds, organic peroxides and persulfates can be used, but they are easy to handle for safety and are used during radical polymerization. An azo compound is preferable because side reactions are unlikely to occur.
Specific examples of the above azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-2, 4-Dimethylvaleronitrile), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-) Carbonitrile), 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2'-azobis (N-butyl-2-methylpropionamide) and the like.
Only one kind of the radical polymerization initiator may be used, or two or more kinds thereof may be used in combination.

The ratio of the radical polymerization initiator used is not particularly limited, but it should be used in a ratio of 0.01% by mass or more and 1.0% by mass or less based on the total mass of all the monomers constituting the entire water-soluble polymer. Is preferable, a ratio of 0.01% by mass or more and 0.3% by mass or less is more preferable, and a ratio of 0.01% by mass or more and 0.1% by mass or less is further preferable.

The reaction temperature during the polymerization reaction by the RAFT method is preferably 40 ° C. or higher and 100 ° C. or lower, more preferably 45 ° C. or higher and 90 ° C. or lower, and further preferably 50 ° C. or higher and 80 ° C. or lower. If the reaction temperature is less than 40 ° C., the reaction rate may be significantly slowed down. On the other hand, if the reaction temperature is higher than 100 ° C., the initiators and solvents that can be used are limited, and side reactions such as radical chain transfer are likely to occur, so that the PDI of the polymer may increase.

In the NMP method, a specific alkoxyamine compound or the like having nitroxide is used as a living radical polymerization initiator, and the polymerization proceeds via the nitroxide radical derived from this. In the present invention, the type of nitroxide radical used is not particularly limited.
According to the NMP method, assuming that no side reaction occurs, the molar ratio of the living radical polymerization initiator to the vinyl-based monomer used is the degree of polymerization of the polymer obtained as it is. In the present invention, it is preferable to react 1 mol of the living radical polymerization initiator with about 60 mol or more and 6,000 mol or less of the vinyl-based monomer, and more preferably about 150 mol or more and 5,000 mol or less. Particularly preferably, it is about 300 mol or more and 4,000 mol or less.

The reaction temperature of the living radical polymerization initiator in the NMP method and the vinyl-based monomer used is preferably 50 ° C. or higher and 140 ° C. or lower, more preferably 60 ° C. or higher and 130 ° C. or lower, and further preferably 70 ° C. or lower. It is 120 ° C. or higher, and particularly preferably 80 ° C. or higher and 120 ° C. or lower. If the reaction temperature is less than 50 ° C., the reaction rate may be significantly slowed down. On the other hand, if the reaction temperature is higher than 140 ° C., side reactions such as radical chain transfer are likely to occur, so that the PDI of the polymer may increase.

In the present invention, the polymerization of the water-soluble polymer may be carried out in the presence of a chain transfer agent, if necessary, regardless of the polymerization method.
Known chain transfer agents can be used, and specifically, ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 1-hexanethiol, 2-hexane. Thiol, 2-methylheptane-2-thiol, 2-butylbutane-1-thiol, 1,1-dimethyl-1-pentanethiol, 1-octanethiol, 2-octanethiol, 1-decanethiol, 3-decanethiol, 1-Undecane thiol, 1-Dodecane thiol, 2-Dodecane thiol, 1-Tridecane thiol, 1-Tetradecane thiol, 3-Methyl-3-undecane thiol, 5-Ethyl-5-Decan thiol, tert-Tetradecane thiol, 1 -In addition to alkylthiol compounds having an alkyl group having 2 to 20 carbon atoms such as hexadecanethiol, 1-heptadecanethiol and 1-octadecanethiol, mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol and the like can be mentioned. One or more of the above can be used.

Among the chain transfer agents, alkylthiol compounds having an alkyl group having 2 to 20 carbon atoms are preferable, and those having an alkyl group having 4 to 20 carbon atoms are more preferable, and those having an alkyl group having 4 to 20 carbon atoms are more preferable, from the viewpoint of improving the adsorptivity to the wafer. Those having 6 to 20 alkyl groups are more preferable.
When a chain transfer agent is used, its preferred amount is 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total amount of the monomers.

In the present invention, a known polymerization solvent can be used in living radical polymerization. Specifically, aromatic compounds such as benzene, toluene, xylene and anisole; ester compounds such as methyl acetate, ethyl acetate, propyl acetate and butyl acetate; ketone compounds such as acetone and methyl ethyl ketone; dimethylformamide, acetonitrile, dimethylsulfoxide, Examples include alcohol and water. Further, it may be carried out in a form such as bulk polymerization without using a polymerization solvent.

<Wetting agent for polishing>
The polishing wetting agent of the present invention comprises the water-soluble polymer and water. It is preferable to use water having high purity so as not to impair the effect as a wetting agent. Specifically, it is preferable to use pure water or ultrapure water from which foreign substances have been removed by filtration after removing impurity ions with an ion exchange resin, or distilled water. In addition to this, the wetting agent may contain an organic solvent such as alcohol and ketones which are highly miscible with water.
The ratio of the water-soluble polymer in the polishing wetting agent is not particularly limited as long as it has a viscosity that is easy to handle as an aqueous solution, but is preferably in the range of 1% by mass or more and 50% by mass or less, and in the range of 3% by mass or more and 40% by mass or less. Is more preferable, and a range of 5% by mass or more and 30% by mass or less is further preferable.

Since the water-soluble polymer in the present invention has a sufficiently small PDI, it has high uniformity of adsorption force and adsorption rate with respect to abrasive grains such as silica and the surface of the object to be polished such as a wafer. Therefore, in the polishing liquid composition containing the water-soluble polymer of the present invention, the surface of the object to be polished can be polished uniformly and evenly. Further, since it does not contain a component having a remarkably high molecular weight, it is excellent in abrasive grain dispersibility, and scratches and surface contamination on the surface of the object to be polished due to abrasive aggregates are suppressed.

<Abrasive liquid composition>
The polishing liquid composition of the present invention comprises the above-mentioned polishing wetting agent, water, abrasive grains and an alkaline compound. The polishing liquid composition of the present invention is not particularly limited, but can be used for polishing a silicon wafer, particularly for finish polishing. The ratio of the polishing wetting agent in the polishing liquid composition is not particularly limited, but it is preferable that the polishing liquid composition has an appropriate viscosity for handling in CMP and for adsorbing on the wafer surface. The specific viscosity of the polishing liquid composition is preferably in the range of 0.1 mPa · s or more and 10 mPa · s or less, and more preferably in the range of 0.3 mPa · s or more and 8 mPa · s or less. It is more preferably in the range of 5 mPa · s or more and 5 mPa · s or less.
Further, the water-soluble polymer is preferably used in a range of 0.001% by mass or more and 10% by mass or less of the entire polishing liquid composition, and is in a range of 0.005% by mass or more and 5% by mass or less. Is more preferable.

Colloidal silica or the like can be used as the abrasive grains. When colloidal silica is used for the abrasive grains, its content in the polishing liquid composition is preferably 0.1% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. It is more preferably 3% by mass or more and 20% by mass or less. When the amount of colloidal silica used is 0.1% by mass or more, the polishing speed of mechanical polishing is good. Further, when it is 50% by mass or less, the dispersibility of the abrasive grains is maintained, and the smoothness of the wafer surface can be made good.

The average particle size of 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 nm or more and 500 nm or less, preferably in the range of 5 nm or more and 300 nm or less. The range of 5 nm or more and 200 nm or less is more preferable.

The alkaline compound is not particularly limited as long as it is a water-soluble alkaline 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, cesium hydroxide and the like. 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. Of these, ammonia or quaternary ammonium hydroxide salt is preferable from the viewpoint of less contamination of the semiconductor substrate.
The polishing liquid composition of the present invention is preferably adjusted to have a pH of 8 to 13 by adding the alkaline compound. It is more preferable to adjust the pH range to 8.5 or more and 12 or less.

In addition to the above, the polishing liquid composition may further contain an organic solvent, various chelating agents, a surfactant, an organic acid compound, an inorganic acid compound, an antiseptic and the like, if necessary.

(Production method for polished silicon wafers)
According to the present specification, a method for producing a polished product of a silicon wafer is also provided. In this production method, the main chain portion is composed of repeating units consisting only of carbon-carbon bonds, and the dispersity (PDI) represented by weight average molecular weight (Mw) / number average molecular weight (Mn) is 2.0 or less. A step of polishing a silicon wafer in the presence of a water-soluble polymer can be provided. As a form of protecting the wafer surface with the water-soluble polymer, in addition to being supplied as a wetting agent for semiconductors containing the water-soluble polymer and water, polishing containing the water-soluble polymer, water, abrasive grains and an alkali compound of the present disclosure. The form of supplying the composition for wafer to the wafer is included. As for the water-soluble polymer, the wetting agent for semiconductors, and the polishing liquid composition in the present production method, various embodiments already described can be applied as they are.

The polishing step of this production method may be performed as any polishing step of the wafer polishing process. That is, the polishing process in the first half of the polishing process, which is mainly for rough polishing and requires a high polishing rate, may be used, or the main purpose is finish polishing, and it is required to finish the wafer surface at a high level of scratch resistance and smoothness. It may be carried out as a polishing step in the latter half of the polishing process, a so-called finish polishing step.

Hereinafter, the present invention will be specifically described based on Examples. The present invention is not limited to these examples. In the following, "parts" and "%" mean parts by mass and% by mass unless otherwise specified.
The analysis method of the water-soluble polymer obtained in the production example and the evaluation method of the wetting agent for semiconductors or the polishing liquid composition in Examples and Comparative Examples are described below.

<Molecular weight measurement>
Gel permeation chromatography (GPC) measurements were performed on the polymers obtained in each production example under the conditions described below, and the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polymethyl methacrylate were determined. Obtained. Moreover, the degree of dispersion (PDI = Mw / Mn) was calculated from the obtained value.
○ Measurement conditions Column: Tosoh TSKgel SuperHM-M x 3 Solvent: N, N-dimethylformamide (containing 10 mM LiBr)
Temperature: 40 ° C
Detector: RI
Flow velocity: 300 μL / min

<Quantification of contained metals>
Approximately 100 to 200 mg of the water-soluble polymer obtained in each production example is precisely weighed in a pressure vessel made of polytetrafluoroethylene (PTFE), and ultra-high-purity sulfuric acid and ultra-high-purity nitric acid are added to perform microwave decomposition. , The decomposition product was weighed in 50 ml. For the above solution, an ICP mass spectrometer (Agilent 7500cs, manufactured by Agilent) was used, and the blank test value performed at the same time was subtracted to determine the content of each metal (including a semimetal) with respect to the water-soluble polymer.

≪Synthesis of polymerization control agent (RAFT agent)≫
Manufacturing example 0
(Synthesis of 1,4-bis (n-dodecylsulfanylthiocarbonylsulfanylmethyl) benzene)
To a 500 ml eggplant-shaped flask, 1-dodecanethiol (42.2 g), a 20% KOH aqueous solution (63.8 g), and trioctylmethylammonium chloride (1.5 g) were added, cooled in an ice bath, and carbon disulfide (15. 9 g) and tetrahydrofuran (hereinafter also referred to as "THF") (38 ml) were added, and the mixture was stirred for 20 minutes. A THF solution (170 ml) of α, α-dichloro-p-xylene (16.6 g) was added dropwise over 30 minutes. After reacting at room temperature for 1 hour, the mixture was extracted from chloroform, washed with pure water, dried over anhydrous sodium sulfate, and concentrated on a rotary evaporator. The obtained crude product is purified by column chromatography and then recrystallized from ethyl acetate to form 1,4-bis (n-dodecylsulfanylthiocarbonylsulfanylmethyl) benzene represented by the formula (1) (hereinafter, "" RAFT agent-A ") was obtained in a yield of 80%. From 1H-NMR measurement, the peak of the target product was confirmed at 7.2 ppm, 4.6 ppm, and 3.4 ppm.

≪Manufacturing of water-soluble polymer≫
Production Example 1 (Production of Polymer A)
RAFT agent-A (5 g), 2,2'-azobis2-methylbutyronitrile (0.3 g), acryloylmorpholin (hereinafter referred to as "Acryloylmorpholin") synthesized in Production Example 0 in a 1 L flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube. (Also referred to as "ACMO") (214 g) and anisole (279 g) were charged, sufficiently degassed by nitrogen bubbling, and polymerization was started in a constant temperature bath at 60 ° C. After 4 hours, the reaction was stopped by cooling with a dry ice / methanol bath. The polymerization rate of ACMO at this point was determined from GC (gas chromatography) measurement and found to be about 87%. The above polymerization solution was reprecipitated and purified from methanol and vacuum dried to obtain a polymer A. The molecular weight of the obtained polymer A was Mn25500 and Mw30000 as measured by GPC (gel permeation chromatography), and the PDI was 1.18. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 2 (Production of Polymer B)
The same operation as in Production Example 1 was carried out except that the charged raw materials were changed as shown in Table 1, to obtain a polymer B. The molecular weight of the polymer B was Mn65000 and Mw80000 as measured by GPC, and the PDI was 1.23. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 3 (Production of Polymer C)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 1, and polymer C was obtained. The molecular weight of the polymer C was Mn292000 and Mw351000 as measured by GPC, and the PDI was 1.20. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 4 (Production of Polymer D)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 1, to obtain a polymer D. The molecular weight of the polymer D was Mn412000 and Mw500,000 as measured by GPC, and the PDI was 1.21. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 5 (Production of Polymer E)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 1, to obtain a polymer E. The molecular weight of the polymer E was Mn621000 and Mw796000 as measured by GPC, and the PDI was 1.28. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 6 (Production of Polymer F)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 1, to obtain a polymer F. The molecular weight of the polymer F was Mn2400,000 and Mw346,000 as measured by GPC, and the PDI was 1.44. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 7 (Production of Polymer G)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 1, to obtain a polymer G. The molecular weight of the polymer G was Mn205000 and Mw351000 as measured by GPC, and the PDI was 1.71. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 8 (Production of Polymer H)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 1, and the polymer H was obtained. The molecular weight of the polymer H was Mn191000 and Mw368000 as measured by GPC, and the PDI was 1.93. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 9 (Production of Polymer I)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 1, and polymer I was obtained. The molecular weight of the polymer I was Mn13300 and Mw19800 as measured by GPC, and the PDI was 1.49. The obtained polymer I was saponified under the following two conditions.

(Saponification of Polymer I; Production of Polymer I-1)
Polymer I (60 g) and methanol (110 g) were added to a 500 mL flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, and nitrogen was dissolved while bubbling. The water content of this solution was 1.5%. After raising the temperature of this solution to 60 ° C., an alkaline solution in which potassium hydroxide (1.15 g) was dissolved in methanol (30 g) was added in a batch to start the saponification reaction. The degree of saponification after the reaction for 2 hours was measured and found to be 98 mol%. The solvent was removed to obtain a saponified product of Polymer I (Polymer I-1). When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 10 (Saponification of Polymer I; Production of Polymer I-2)
Polymer I (60 g) and methanol (110 g) were added to a 500 mL flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, and nitrogen was dissolved while bubbling. A saponification reaction similar to that of polymer I-1 was carried out except that the water content of this solution was adjusted to 4.5% to obtain polymer I-2. The saponification degree of the polymer I-2 was measured and found to be 85 mol%. Moreover, when the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 11 (Production of Polymer J)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 2, and a polymer J was obtained. The molecular weight of the polymer J was Mn269000 and Mw355000 as measured by GPC, and the PDI was 1.32. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 12 (Production of Polymer K)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 2, and the polymer K was obtained. The molecular weight of the obtained polymer K was Mn270000 and Mw345000 as measured by GPC, and the PDI was 1.28. When the composition ratio of acryloyl morpholine and N, N-dimethylacrylamide was determined from 1H-NMR measurement, it was found that acryloyl morpholine / N and N-dimethylacrylamide = 51/49 wt%. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 13 (Production of Polymer L)
(Production of Polymer L) 2-Methyl-2- [N-tert-butyl-N- (1-diethylphosphono-2,2-dimethylpropyl) -N-oxyl) in a 1 L flask equipped with a stirrer and a thermometer. ] Propionic acid (hereinafter also referred to as "SG1-MAA") (0.2 g), acryloyl morpholine (75 g), acrylic acid (75 g) and anisole (350 g) are charged, sufficiently degassed by nitrogen bubbling, and kept at a constant temperature of 115 ° C. Polymerization was started in the tank. After 5 hours, the reaction was stopped by cooling with a dry ice / methanol bath. When the polymerization rate of each monomer at this time was determined from GC measurement, it was about 95% for acryloyl morpholine and about 88% for acrylic acid. The above polymerization solution was reprecipitated and purified from methanol and vacuum dried to obtain a polymer L. The molecular weight of the obtained polymer L was Mn245000 and Mw347000 as measured by GPC (in terms of polystyrene), and the PDI was 1.42. When the composition ratio of acryloyl morpholine and acrylic acid was determined from 1H-NMR measurement, it was found that acryloyl morpholine / acrylic acid = 52/48 wt%. Moreover, when the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 14 (Production of Polymer M)
The in-system atmosphere of a 1 L flask equipped with a stirrer and a thermometer was replaced with nitrogen, and toluene (143 g), 1,2-dimethoxyethane (2.9 g), and diisobutyl (2,6-di-t-butyl-4) were replaced. A toluene solution (42 ml) containing 33 mmol of −methylphenoxy) aluminum was added, and the mixture was cooled to −30 ° C. A cyclohexane solution (0.7 ml) containing 1 mmol of sec-butyllithium was added thereto, and the mixture was stirred for 20 minutes. While stirring the solution, N, N-dimethylacrylamide (318 g) was added dropwise at −30 ° C. over about 10 hours. The solution was initially colored yellow and faded 3 minutes after the completion of the dropping. The polymerization reaction was stopped by adding 50 ml of methanol 3 minutes after the completion of the dropping. When the polymerization rate of N, N-dimethylacrylamide at this time was determined from the GC measurement, it was 99% or more. The above polymerization solution was reprecipitated and purified from methanol and vacuum dried to obtain a polymer M. The molecular weight of the obtained polymer M was Mn309000 and Mw348000 as measured by GPC, and the PDI was 1.13. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 15 (Production of Polymer N)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 2, and a polymer N was obtained. The molecular weight of the polymer N was Mn682000 and Mw1190000 as measured by GPC, and the PDI was 1.74. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Production Example 16 (Production of Polymer O)
The same operation as in Production Example 1 was carried out except that the raw materials to be charged were changed as shown in Table 2, and polymer O was obtained. The molecular weight of the obtained polymer O was Mn4200 and Mw5100 as measured by GPC (gel permeation chromatography), and the PDI was 1.21. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Comparative Production Example 1 (Production of Polymer P)
Put 2,2'-azobis2-methylbutyronitrile (1.5 g), acryloyl morpholine (176 g) and anisole (320 g) in a 1 L flask equipped with a stirrer and a thermometer, degas sufficiently with nitrogen bubbling, and 60 Polymerization was started in a constant temperature bath at ° C. After 3 hours, the reaction was stopped by cooling with a dry ice / methanol bath. The polymerization rate of acryloyl morpholine at this point was determined from GC measurement and found to be about 73%. The above polymerization solution was reprecipitated and purified from methanol and vacuum dried to obtain a polymer P. The molecular weight of the obtained polymer P was Mn282000 and Mw786000 as measured by GPC, and the PDI was 2.79. When the contained metal content was measured by an ICP mass spectrometer, all the metal contents were 100 ppm or less.

Tables 1 and 2 show the contents and physical property values of the polymers obtained in Production Examples 1 to 16 and Comparative Production Example 1.

Details of the compounds shown in Tables 1 and 2 are as follows.
ACMO: Acryloylmorpholine DMAAm: N, N-dimethylacrylamide VAC: Vinyl acetate AA: NVP acrylate: N-vinylpyrrolidone RAFT agent-A: 1,4-bis (n-dodecylsulfanylthiocarbonylsulfanylmethyl) benzene SG1-MAA : 2-Methyl-2- [N-tert-butyl-N- (1-diethylphosphono-2,2-dimethylpropyl) -N-oxyl] propionic acid (nitroxide compound manufactured by Arkema)
sec-BuLi: sec-Butyllithium DME: 1,2-dimethoxyethane iBu2ALBHT: Diisobutyl (2,6-di-t-butyl-4-methylphenoxy) Aluminum ABN-E: 2,2'-azobis (2-methyl) Butylnitrile)

Example 1
Using the polymer A obtained in Production Example 1, the following evaluation was performed as a wetting agent for polishing and a polishing liquid composition. The results obtained are shown in Table 3.

○：１．５ｎｍ／ｍｉｎ未満
△：１．５ｎｍ／ｍｉｎ以上２．０ｎｍ／ｍｉｎ未満
×：２．０ｎｍ／ｍｉｎ以上<Etching resistance (ER)>
After measuring the mass of the wafer cut out to 3 × 6 cm with a glass cutter, the wafer 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 surface of the wafer became completely water repellent. Next, an etching chemical solution was prepared by adding a polishing wetting agent to ammonia water having a mass ratio of ammonia: water of 1:19 so that the concentration of the water-soluble polymer was 0.18%. The wafer was completely immersed in the etching chemical solution and allowed to stand at 25 ° C. for 12 hours for etching. The etching rate (ER) was calculated from the changes in wafer mass before and after etching according to the following equation.

◯: Less than 1.5 nm / min Δ: 1.5 nm / min or more and less than 2.0 nm / min ×: 2.0 nm / min or more

<Wetness>
After removing the oxide film on the wafer surface by the same method as that for etching resistance, the wafer was immersed in a 0.18% water-soluble polymer solution for 5 minutes. After immersion, the surface of the wafer was pulled up so as to be perpendicular to the liquid surface using tweezers, and the water repellency distance from the end of the wafer at 10 seconds was visually confirmed and judged according to the following criteria.
⊚: Water repellent distance less than 3 mm ○: Water repellent distance 3 mm or more and less than 5 mm Δ: Water repellent distance 5 mm or more and less than 7 mm ▲: Water repellent distance 7 mm or more and less than 10 mm ×: Water repellent distance 10 mm or more

<Alkali resistance>
Sodium hydroxide was used as an alkaline agent to prepare a water-soluble polymer in an aqueous solution having a concentration of 10% by mass and a pH of 10. 45 g of the obtained aqueous solution was taken in a 50 cc screw bottle and allowed to stand at 60 ° C. for 1 month in an aluminum block heater. After measuring the amount of the compound derived from the side chain of the monomer unit constituting the water-soluble polymer produced by hydrolysis of the water-soluble polymer by GC (gas chromatography GC-2014, manufactured by Shimadzu Corporation). , The percentage with respect to the theoretical amount was calculated and used as the hydrolysis rate. The alkali resistance was determined according to the following criteria according to the calculated value of the hydrolysis rate.
◯: Hydrolysis rate of water-soluble polymer is less than 5% Δ: Hydrolysis rate of water-soluble polymer is 5% or more and less than 10% ×: Hydrolysis rate of water-soluble polymer is 10% or more

<Silica dispersibility>
To 5.0 g of colloidal silica (primary particle diameter: 30 to 50 nm), 0.5 g of a water-soluble polymer aqueous solution having a resin solid content of 20% was added to a 9 cc screw bottle and mixed well. The particle size (A) of silica after standing overnight was measured by a dynamic light scattering method (ELSZ-1000, manufactured by Otsuka Electronics Co., Ltd.), and the particle size (B) of colloidal silica to which no water-soluble polymer was added was measured. The rate of change was calculated according to the following formula and judged from the following criteria.
Rate of change (%) = {(AB) / B} x 100
◯: Change rate is less than 5% Δ: Change rate is 5% or more and less than 10% ▲: Change rate is 10% or more and less than 20% ×: Change rate is 20% or more

<Aqueous solution filterability>
0.5 kg of a 1.5% polymer aqueous solution was suction-filtered (500 hPa), and the time required for total filtration was measured and determined from the following criteria.
⊚: less than 3 min ○: 3 min or more and less than 5 min Δ: 5 min or more and less than 10 min ▲: 10 min or more and less than 20 min ×: 20 min or more

Examples 2 to 16 and Comparative Examples 1 to 3
Various evaluations were carried out by the same operation as in Example 1 except that the polishing wetting agent was changed as shown in Table 3. The results obtained are shown in Table 3.
In Comparative Example 2, a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (hereinafter, also referred to as “PEO-PPO-PEO”) was used as the water-soluble polymer. Further, in Comparative Example 3, hydroxyethyl cellulose (hereinafter, also referred to as “HEC”) was used.

Details of the water-soluble polymers shown in Table 3 are as follows.
PEO-PPO-PEO: Polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (Pluronic F127, manufactured by Sigma-Aldrich)
HEC: Hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 250,000)

Examples 1 to 16 are experimental examples using the polishing wetting agent specified in the present invention. Since the dispersity of the water-soluble polymer is sufficiently small and the content of high molecular weight components and low molecular weight components that adversely affect the polishing performance is small, all of the etching resistance, wettability and silica dispersibility, which are indicators of adsorption power. Shows good performance in a well-balanced manner. Among them, Examples 1 to 8, 12, 13, 15 and 16 using a water-soluble polymer containing a structural unit derived from N-acryloyl morpholine in the molecule are said to have particularly excellent adsorptive power. Shown.
On the other hand, in Comparative Example 1 in which the PDI value of the water-soluble polymer was high, the result that the silica dispersibility deteriorated was observed. Comparative Example 2 is an example in which a water-soluble polymer having a carbon-oxygen bond in the main chain portion is used, and there is concern about the stability of the polymer. In addition, in this case, the result was that the adsorption force to the object to be polished was also insufficient.

Since the water-soluble polymer contained in the wetting agent for polishing of the present invention has a sufficiently small PDI, it has high uniformity of adsorption force and adsorption rate to abrasive grains such as silica and the surface of the object to be polished such as a wafer. .. Therefore, in the polishing liquid composition containing the water-soluble polymer of the present invention, the surface of the object to be polished can be polished uniformly and evenly. Further, since it does not contain a component having a remarkably high molecular weight, it is excellent in abrasive grain dispersibility, and scratches and surface contamination on the surface of the object to be polished due to abrasive aggregates are suppressed.
From the above, the polishing liquid composition containing the polishing wetting agent of the present invention exhibits good polishing performance for various objects to be polished, and is therefore particularly useful as a finishing polishing liquid composition for silicon wafers as a semiconductor material. Is.

Claims (6)

The main chain portion is composed of repeating units consisting only of carbon-carbon bonds, and the dispersity (PDI) represented by weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.44 or less, and the weight average A polishing wetting agent containing a water-soluble polymer having a molecular weight (Mw) of 80,000 or more and 347,000 or less , and the repeating unit containing a structural unit derived from N- (meth) acryloylmorpholine. Claim that when the water-soluble polymer is prepared into an aqueous solution having a concentration of 10% by mass and a pH of 10, the hydrolysis rate of the water-soluble polymer after 1 month under the condition of 60 ° C. is 5.0% or less. The polishing wetting agent according to 1. The polishing wetting agent according to claim 1 or 2, wherein the water-soluble polymer contains 10 mol% or more and 100 mol% or less of structural units derived from N- (meth) acryloyl morpholine. A polishing liquid composition containing the polishing wetting agent, water, abrasive grains and an alkaline compound according to any one of claims 1 to 3. The polishing liquid composition according to claim 4, which is used for finish polishing of a silicon wafer. The main chain portion is composed of repeating units consisting only of carbon-carbon bonds, and the dispersity (PDI) represented by weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.44 or less, and the weight average. A step of polishing a silicon wafer in the presence of a water-soluble polymer having a molecular weight (Mw) of 80,000 or more and 347,000 or less and containing a structural unit derived from N- (meth) acryloylmorpholine.
A method for producing a polished product of a silicon wafer.