JPH06101455B2 - Wafer polishing protection sheet and method for polishing wafer surface using this sheet - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a protective sheet for polishing a semiconductor wafer and a method for polishing a wafer using the same, and more specifically, it relates to a semiconductor wafer having a pattern formed on its surface by etching or the like. The present invention relates to a wafer polishing protective sheet that is particularly preferably used when polishing the back surface, and a wafer polishing method using the same.

TECHNICAL BACKGROUND OF THE INVENTION AND PROBLEMS THEREOF A pattern is formed on the surface of a semiconductor wafer such as silicon or gallium arsenide by etching or lift-off method. Next, the wafer having the pattern formed on the front surface is usually subjected to polishing treatment by a grinder or the like on the back surface thereof in a state where the adhesive sheet is adhered to the front surface. The purpose of polishing the back surface of the wafer on which the pattern is formed is to remove this oxide film because an oxide film may be formed on the back surface of the wafer during the first etching step. The purpose is to control the thickness of the patterned wafer.

By the way, when applying a polishing treatment to the back surface of a wafer having a pattern formed on the front surface, the back surface of the wafer is washed with purified water in order to remove the polishing dust generated and to remove the heat generated during polishing. Backside polishing processing is performed. Therefore, when the back surface polishing process is performed on the wafer, the protective sheet attached to the front surface of the wafer to protect the pattern formed on the front surface of the wafer needs to have water resistance. In such protective sheets, solvent-type acrylic pressure-sensitive adhesives have been widely used as pressure-sensitive adhesives.

After the polishing process on the back surface of the wafer is completed in this way, the protective sheet is peeled off from the wafer surface, but at this time, an adhesive such as an acrylic adhesive may inevitably adhere to the surface of the wafer on which the pattern is formed. It was For this reason, it is necessary to remove the adhesive attached to the wafer surface.

Conventionally, the removal of the acrylic-based adhesive agent adhering to the wafer surface has been performed by cleaning the wafer surface with a chlorine-containing organic solvent such as trichlene and then with purified water. However, it has been pointed out that chlorine-containing solvents such as trichlene used for cleaning the wafer surface may have a harmful effect on the human body or cause a fire. There is. Further, as described above, since the wafer surface cleaning step includes two steps of cleaning with an organic solvent such as trichlene and then cleaning with purified water, there is a problem that it takes time and labor.

In order to solve such a problem, for example, JP-A-60-
JP-A-189938 discloses an adhesive film as a protective sheet for polishing a wafer, which is provided with a pressure-sensitive adhesive layer having a property of being cured by light irradiation to be three-dimensionally reticulated on the surface of a light-transmitting substrate. There is.

However, there is a problem that even if such an adhesive film is used, it is not possible to completely prevent the adhesion of the adhesive to the wafer surface.

On the other hand, Japanese Patent Application Laid-Open No. 60-219750 discloses a method of polishing the back surface of a wafer by covering the surface of the wafer on which a pattern is formed with a water-soluble resin film.

However, in such a method, the water-soluble resin film is usually formed by applying a polyvinyl alcohol aqueous solution onto the wafer surface and then drying it. However, since this polyvinyl alcohol aqueous solution contains a large amount of water,
There has been a problem that it takes a long time for heating when forming the coating film. Also, if water is used to cool the wafer surface during polishing, the water-soluble resin will elute, so water cannot be used, and cooling of organic solvent systems such as Freon (carbon tetrafluoride) is not possible. There was a problem that the agent had to be used.

Therefore, if it is possible to clean the wafer surface with purified water and remove the adhesive agent adhering to the wafer surface in place of a chlorine-containing organic solvent such as trichlene, there is no danger to the human body or the risk of fire. Moreover, a great effect that the wafer surface cleaning process can be completed in one process is obtained. However, as mentioned above, since the wafer backside polishing process is performed while washing the wafer backside with purified water, if a water-soluble adhesive that has been widely used as a water-soluble adhesive has been used as an adhesive for the protective sheet. In this case, the adhesive is dissolved during the above polishing process, the polishing dust of the wafer enters between the wafer surface and the protective sheet, and the pattern formed on the wafer surface is destroyed. Will occur.

An object of the present invention is to solve the problems associated with the above-mentioned conventional techniques all at once, and when the back surface of a wafer having a pattern formed on the front surface is subjected to polishing treatment, the wafer is attached to the front surface of the wafer. A protective sheet to be attached, which can be removed by washing with water without using an organic solvent such as trichlene after the polishing process and removing the pressure-sensitive adhesive, which may have a harmful effect on the human body. It is an object of the present invention to provide a pressure-sensitive adhesive sheet having no property and capable of removing the pressure-sensitive adhesive attached to the wafer surface in one step.

SUMMARY OF THE INVENTION A first wafer polishing protection sheet according to the present invention comprises, on one surface of a base material, (i) a partially crosslinked product of a hydrophilic polymer containing a carboxyl group in which at least a part of a carboxyl group is partially neutralized. And (ii) at least one surfactant selected from the group consisting of anionic surfactants and cationic surfactants, which is liquid at room temperature. .

The second wafer polishing protection sheet according to the present invention has, on one surface of a base material, (i) a partially crosslinked product of a carboxyl group-containing hydrophilic polymer in which at least a part of carboxyl groups is partially neutralized, (Ii) at least one selected from the group consisting of anionic surfactants and cationic surfactants
It is characterized in that a pressure-sensitive adhesive layer containing a seed-type liquid surfactant at room temperature and (iii) a nonionic surfactant is provided.

Furthermore, the first wafer surface polishing method according to the present invention comprises: (i) a partially crosslinked product of a carboxyl group-containing hydrophilic polymer in which at least a part of the carboxyl groups is partially neutralized on one surface of the substrate; (Ii) A wafer polishing protective sheet provided with a pressure-sensitive adhesive layer containing at least one surfactant selected from the group consisting of anionic surfactants and cationic surfactants, which is liquid at room temperature, It is characterized in that it is adhered to the surface of the wafer on which the pattern is formed, and then the back surface of the wafer is polished while supplying water to the back surface of the wafer, and then the protective sheet is peeled off from the back surface of the wafer.

Furthermore, the second method for polishing a wafer surface according to the present invention comprises: (i) a partially crosslinked product of a carboxyl group-containing aqueous polymer in which at least a part of the carboxyl groups is partially neutralized on one surface of the substrate; A pressure-sensitive adhesive layer containing at least one liquid surfactant at room temperature selected from the group consisting of (ii) anionic surfactants and cationic surfactants, and (iii) a nonionic surfactant. The wafer polishing protective sheet provided is attached to the wafer surface on which the pattern is formed, and then the wafer back surface is polished while water is supplied to the wafer back surface, and then the protection sheet is peeled from the wafer back surface. Is said.

DETAILED DESCRIPTION OF THE INVENTION The wafer polishing protective sheet according to the present invention and the wafer surface polishing method using the sheet will be specifically described below.

The wafer polishing protective sheet 1 according to the present invention comprises a base material 2 and a pressure-sensitive adhesive layer 3 applied to the surface thereof, as shown in the sectional view of FIG. In order to protect the pressure-sensitive adhesive layer 3, it is preferable to temporarily adhere a peelable sheet 4 to the upper surface of the pressure-sensitive adhesive 3 as shown in FIG.

The wafer polishing protection sheet according to the present invention may have any shape such as a tape shape and a label shape. As the base material 2,
Those having excellent water resistance and heat resistance are suitable, and synthetic resin films are particularly suitable.

Specific examples of the substrate 2 include polyethylene film, polypropylene film, polyvinyl chloride film, polyethylene terephthalate film, polybutylene terephthalate film, polybutene film, polybutadiene film, polyurethane film, polymethylpentene film, ethylene vinyl acetate film. Are used. Further, as the base material 2, a crosslinked polyolefin or an ethylene-methacrylic acid copolymer film can be used. Furthermore, for the purpose of adjusting the film hardness,
For example, a laminate of a polyethylene terephthalate film and a polybutadiene film may be used, or a foamed product of the above film may be used.

The thickness of such a base material 2 is preferably about 10 to 500 μm.

In the present invention, the pressure-sensitive adhesive layer 3 is formed on one surface of the base material as described above.
As the above, the pressure-sensitive adhesive layer 3 containing the following components is applied.

That is, the pressure-sensitive adhesive layer 3 used in the present invention comprises (i) a partially crosslinked product of a carboxyl group-containing hydrophilic polymer in which at least a part of carboxyl groups is partially neutralized, and (ii) an anionic surfactant and At least one surfactant selected from the group consisting of cationic surfactants, which is liquid at room temperature.

(I) The partially crosslinked product of the carboxyl group-containing hydrophilic polymer in which at least a part of the carboxyl group is partially neutralized is a carboxyl group-containing hydrophilic polymer that partially neutralizes at least a part of the carboxyl group and It can be obtained by partially crosslinking a group-containing hydrophilic polymer with a crosslinking agent. The carboxyl group-containing hydrophilic polymer includes a carboxyl group-containing monomer (A) and a vinyl monomer (B). The copolymer of is preferably used.

Specific examples of the monomer (A) containing a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, monoalkyl itaconic acid, monoalkyl maleic acid, monoalkyl fumaric acid. Acid or the like is used.

As the vinyl-based monomer (B), vinyl ester,
One or two kinds of acrylic acid ester, methacrylic acid ester, acrylic acid alkoxyalkyl ester, methacrylic acid alkoxyalkyl ester, ethylene, styrene, methyl vinyl ether, vinyl chloride, acrylonitrile, acrylic acid hydroxyalkyl ester, methacrylic acid hydroxyalkyl ester, etc. The above is used.

In some cases, as the carboxyl group-containing hydrophilic polymer, the above-mentioned carboxyl group-containing monomer (A), vinyl monomer (B), N-methylol acrylamide, alkoxymethyl acrylamide, dimethyl Functional monomers such as aminoethyl methacrylate, diacetone acrylamide, N-butyl acrylamide, acrylamide, methacrylamide, phosphoric acid group-containing monomers, epoxy group-containing monomers such as glycidyl methacrylate, and (a small amount) It is also possible to use a copolymer with a polyfunctional monomer (C) such as divinylbenzene, diallyl phthalate, diallyl malate or triallyl isocyanurate.

The carboxyl group-containing hydrophilic polymer according to the present invention can be produced by a known polymerization method such as bulk polymerization, solution polymerization or emulsion polymerization.

Also, in some cases, the carboxyl group-containing hydrophilic polymer according to the present invention is a homopolymer of an unsaturated carboxylic acid ester, or a copolymer of an unsaturated carboxylic acid ester and a monomer not containing a carboxyl group. It can also be produced by saponification and introducing a carboxyl group into the polymer.

Such a carboxyl group-containing hydrophilic polymer preferably contains the carboxyl group-containing monomer (A) in an amount of 1 to 60 mol%. The glass transition temperature of the carboxyl group-containing hydrophilic polymer is preferably room temperature or lower.

As the cross-linking agent used for partially cross-linking the carboxyl group-containing hydrophilic polymer, a compound containing a glycidyl group in the molecule, for example, neopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, bisphenol A diglycidyl ether,
Bisphenol F diglycidyl ether, phthalic acid diglycidyl ester, dimer acid diglycidyl ether,
Epoxy cross-linking agents such as triglycidyl isocyanurate, diglycerol triglycidyl ether, sorbitol tetraglycidyl ether, compounds containing an isocyanate group in the molecule, for example, tridendiisocyanate, isocyanate cross-linking agents such as diphenylmethane diisocyanate, melamine, phenol and the like. A methylol-based crosslinking agent, a chelate-based crosslinking agent, an aziridine-based crosslinking agent, or the like is used.

In the present invention, by partially crosslinking the carboxyl group-containing hydrophilic polymer with a crosslinking agent, the peel strength of the resulting hydrophilic pressure-sensitive adhesive can be adjusted to an appropriate level. Therefore, if the amount used is too small, since the degree of crosslinking of the carboxyl group-containing hydrophilic polymer is low, peel strength is too strong, which is not preferable, and if too much, the carboxyl groups almost react, and the hydrophilicity of the hydrophilic polymer is high. Damaged and not preferable.

Further, in order to partially neutralize at least a part of the carboxyl groups of the carboxyl group-containing hydrophilic polymer according to the present invention, it is sufficient to react the carboxyl group-containing aqueous polymer with a base. As ammonia,
Alkali ammonium salts and primary amines such as monoethylamine and monoethanolamine, secondary amines such as diethylamine and diethanolamine, tertiary amines such as triethylamine and triethanolamine,
An organic amino compound having alkalinity such as an amino compound having a plurality of Ns in one molecule such as diamine and polyethyleneimine and a cyclic amino compound such as pyridine is used.

In addition, if the amount is small, sodium hydroxide, potassium hydroxide, sodium salts showing an alkalinity, potassium salts and the like can be used.

Furthermore, when a cationic surfactant is used, this cationic surfactant acts as a base and the carboxyl group-containing hydrophilic polymer can be neutralized by the cationic surfactant. Therefore, when a cationic surfactant is used as the surfactant, a base for neutralizing the carboxyl group-containing hydrophilic polymer is optionally used.

The room-temperature liquid surfactant used in the pressure-sensitive adhesive layer 3 according to the present invention is selected from the group consisting of anionic surfactants and cationic surfactants. As the agent, polyoxyethylene alkyl ether sulfuric acid ester and its salt, polyoxyethylene alkylphenyl ether sulfuric acid ester and its salt, polyoxyethylene alkyl ether phosphoric acid ester and its salt, polyoxyethylene alkylphenyl ether phosphoric acid Among the esters and salts thereof, those which are liquid at room temperature are used.

As the cationic surfactant, a cationic surfactant such as an ethylene oxide-addition type alkylamine or an ethylene oxide-addition type alkyldiamine, for example, an ethylene oxide-addition type alkyltrimethylenediamine or an ethylene oxide-addition type alkyl quaternary ammonium salt is used. Of these, those that are liquid at room temperature are used. The above-mentioned anionic surfactants or cationic surfactants can be used alone or in admixture of two or more.

Further, in the pressure-sensitive adhesive layer 3 according to the present invention, in addition to the anionic surfactant or the cationic surfactant as described above, a nonionic surfactant which is liquid at room temperature can be used together.

Depending on the amount used, this nonionic surfactant may bleed from the pressure-sensitive adhesive layer 3 and contaminate the wafer surface. If the wafer surface is contaminated, a large amount of water is required for washing. It is preferred to use an amount that does not. The amount used varies depending on the type of the nonionic surfactant, but for example, an amount of 30 parts by weight or less is suitable for 100 parts by weight of the carboxyl group-containing hydrophilic polymer.

Specific examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene styrenated phenyl ethers, polyoxyethylene and polyoxypropylene blocks. A copolymer or the like can be used.

It is presumed that the surfactant as described above may have a function of being adsorbed to the carboxyl group-containing hydrophilic polymer in the pressure-sensitive adhesive layer 3 to form a complex, thereby giving the pressure-sensitive adhesive layer 3 tackiness. However, if the amount of the surfactant is too small, the tackiness cannot be obtained. On the other hand, if the amount is too large, it comes in contact with water and flows out during polishing, which is not preferable.

Therefore, the surfactant is usually used in an amount of 10 to 500 parts by weight, preferably 20 to 150 parts by weight, based on 100 parts by weight of the carboxyl group-containing hydrophilic polymer.

In the pressure-sensitive adhesive layer 3 according to the present invention, if necessary,
A hydrophilic plasticizer such as a water-soluble polyhydric alcohol, a tackifying resin, a water-soluble polymer, a pigment, a dye, a defoaming agent, a preservative and the like can be added.

To provide the pressure-sensitive adhesive layer 3 containing the above components on the surface of the substrate 2, a hydrophilic polymer containing a carboxyl group,
When a coating liquid for forming a pressure-sensitive adhesive layer containing a surfactant, a solvent, a cross-linking agent, and optionally a base is prepared, and the coating liquid is applied to the substrate 2 and then heated and dried, a carboxyl group is formed. At least a part of the carboxyl group of the containing hydrophilic polymer is partially neutralized, and the polymer is partially crosslinked,
The adhesive layer 3 is formed.

As the solvent used when the pressure-sensitive adhesive layer 3 is formed on the substrate 2, water or one or more hydrophilic solvents such as methanol, ethanol, isopropanol, acetone, methyl ethyl ketone and ethyl ether are preferably used. In addition, hydrophobic solvents such as ethyl acetate and toluene,
If desired, it can be used as a mixed solvent in addition to the hydrophilic solvent as described above.

The pressure-sensitive adhesive containing each component as described above swells when contacted with water and exhibits excellent water-sealing property, and wafer polishing dust does not enter between the pressure-sensitive adhesive layer and the wafer surface. The pattern formed in can be sufficiently protected. Moreover, after polishing, it can be easily peeled off from the wafer adhesive layer, so the wafer will not be damaged during peeling, and even if the adhesive adheres to the wafer surface, it can be easily washed off with water. be able to.

Next, a method for polishing the back surface of the wafer using the wafer polishing protection sheet 1 according to the present invention will be described.

When the peelable sheet 4 is provided on the upper surface of the wafer polishing protective sheet 1 according to the present invention, the peelable sheet 4 is removed, and then the adhesive layer 3 is subjected to polishing treatment on the back surface of the wafer A. Affix. At this time, it is adhered onto the adhesive layer 3 so that the wafer surface on which the pattern 5 is formed is in contact with the adhesive layer 3 as shown in FIG.

In such a state, the back surface 6 of the wafer is polished by a grinder 7 or the like to remove the oxide film and the like formed on the back surface 6 of the wafer, and the thickness of the wafer A is adjusted to a desired thickness. At this time, purified water is sprayed onto the wafer A to wash away the wafer polishing dust and remove the heat generated during polishing.

Next, after the polishing is completed, the protective sheet 1 is peeled off from the wafer A. At this time, an adhesive or the like may adhere to the surface of the wafer A on which the pattern 5 is formed. The adhered adhesive B can be easily washed off with purified water C.

As described above, in the wafer polishing protection sheet 1 according to the present invention, since the pressure-sensitive adhesive containing the specific component is used as the pressure-sensitive adhesive, even if the pressure-sensitive adhesive is attached to the wafer surface, the pressure-sensitive adhesive is triclenized. It can be removed by washing with purified water without using an organic solvent such as, and therefore, there is no risk of adversely affecting the human body or causing a fire. Moreover, in the past,
Although two steps of cleaning the surface of the wafer having the adhesive attached thereto with an organic solvent such as trichlene and then with purified water are necessary, in the present invention, the surface of the wafer having the adhesive attached is purified water, for example, ultrasonic waves. Since the cleaning may be performed using a cleaning device or the like, the cleaning can be performed in one step.

Further, since the wafer polishing protection sheet 1 according to the present invention is adhered to the wafer A with sufficient adhesive force when polishing the back surface of the wafer A, wafer polishing dust is generated between the wafer surface and the adhesive sheet. The pattern formed on the surface of the wafer does not get destroyed.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 a) Carboxyl group-containing hydrophilic polymer aqueous emulsion of butyl acrylate / methyl methacrylate / methacrylic acid (50/30/20 wt%) obtained by emulsion polymerization (polymer concentration 42
% By weight), 4 parts by weight of a polyoxyethylene alkylphenyl ether phosphate-based anionic surfactant which is liquid at room temperature, 80 parts by weight of isopropyl alcohol, and 6 parts by weight of triethanolamine are mixed and stirred for 4 hours. A viscous 4,000 cp mixture was prepared.

b) Next, 0.9 part by weight of sorbitol polyglycidyl ether (epoxy equivalent 170) was added, stirred, and then coated on a polyethylene terephthalate film so that the dry coating thickness was about 30 μm. Then, after hot air circulation drying at 80 ° C. for 4 minutes to form a pressure-sensitive adhesive layer, a film-type separator was attached to the pressure-sensitive adhesive surface and cured for 1 week to prepare a protective sheet used in the present invention.

c) This protective sheet has a diameter of 5 inches and a thickness of 0.
It was attached to the surface of a 5 mm semiconductor wafer using a pressure roll with a load of 1 kg. This sample was accurately fixed to the grind device so that the back surface of the wafer was facing up, and was abraded for 5 minutes under water spray with a water pressure of 30 kg / cm ² , the protective sheet did not peel off during abrading, and the wafer cracked. Without any damage, the surface of the wafer was not damaged. (Abrasivity) d) Next, when the strong adhesive film was attached to the protective sheet and the protective sheet was peeled from the wafer, the peeling was extremely easy and the wafer was not damaged. (Peelability) e) Slight contamination of the pressure-sensitive adhesive composition was observed on the wafer surface, but it was easily removed by ultrasonic cleaning with pure water, and no residue was observed on the wafer surface. I couldn't do it. (Washability) Example 2 a) 28 parts by weight of an aqueous emulsion of the carboxyl group-containing hydrophilic polymer used in Example 1, 8 parts by weight of a cationic surfactant of ethylene oxide-added coconut amine liquid at room temperature, isopropyl 80 parts by weight of alcohol was mixed and stirred for 44 hours to prepare a mixed solution.

Next, a protective sheet was prepared in the same manner as in Example 1, b), and the abrasiveness, releasability and washability were examined in the same manner as in c), d) and e). The property was good as in Example 1.

Examples 3 to 8 According to the same manner as in Example 1, a mixed solution having the composition shown in Table 1 was prepared, and then a protective sheet was prepared.
The washability was examined. As a result, in all cases,
The water washability was good as in Example 1.

Comparative Example 1 In Example 1, the composition of Table 1 was adjusted so that the total amount of the cross-linking agent, sorbitol polyglycidyl ether used, reacted with the carboxyl groups of the hydrophilic polymer, and the amount of the remaining carboxyl groups was almost the same. A group-containing hydrophilic polymer (polymer concentration 42% by weight) was emulsion polymerized, and a mixed solution was prepared in the same manner as in Example 1, a).

Next, a protective sheet was prepared in the same manner as in Example 1 in which no cross-linking agent was used, and the polishing property, peeling property, and water washability were examined. As a result, polishing could be performed without any problems. However, since the adhesive strength was too strong to peel off, the wafer was damaged when I tried to peel it off.

Comparative Example 2 A mixed solution having the same composition as in Example 3 was prepared, except that the polyoxyethylene nonylphenyl ether nonionic surfactant (HLB13.7) was used as the anionic surfactant and the cationic surfactant of Example 3. A protective sheet was prepared in the same manner.

When the abrasiveness, peelability and water washability of this protective sheet were examined in the same manner as in Example 3, polishing and peeling could be carried out without problems, but contamination of the wafer surface due to bleeding of the surfactant was remarkable and pure water was used. Although the residue could be completely removed by ultrasonic cleaning with, it took a long time for cleaning.

Comparative Example 3 To 100 parts by weight of a butyl acrylate / vinyl acetate / acrylic acid copolymer (toluene / ethyl acetate as a main solvent) (polymer concentration 30% by weight), 10 parts by weight of an isocyanate-based curing agent was added to prepare Example 1 and A protective sheet was prepared in the same manner.

When the polishing property, peeling property, and water washing property of this protective sheet were examined in the same manner as in Example 1, polishing and peeling could be performed without problems, but slight contamination by the pressure-sensitive adhesive composition was observed on the wafer surface. Ultrasonic cleaning with pure water was performed, but the residue could not be easily removed.

[Brief description of drawings]

1 and 2 are cross-sectional views of a polishing protection sheet according to the present invention, and FIGS. 3 and 4 are explanations when polishing the back surface of a wafer using the polishing protection sheet according to the present invention. It is a figure. 1 ... Abrasive protective sheet, 2 ... Base material 3 ... Adhesive layer, A ... Wafer B ... Residual adhesive, C ... Water

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Narita 1-1502 Yoshikawa housing complex, Yoshikawa-cho, Kita-Katsushika-gun, Saitama Prefecture (72) Inventor Katsuhisa Taguchi 2-14-18 Chuo, Warabi-shi, Saitama Invention Author Yoshitaka Akida 7-3 Tsuji, Urawa City, Saitama Prefecture (72) Inventor Takanori Saito 318-310, Kamikomachi, Omiya City, Saitama Prefecture (56) References JP 62-101678 (JP, A)

Claims (4)

[Claims] 1. A partially crosslinked product of a hydrophilic polymer containing a carboxyl group in which at least a part of a carboxyl group is partially neutralized, and (ii) an anionic surfactant and a cation on one surface of a substrate. A protective sheet for wafer polishing, which is provided with an adhesive layer containing at least one liquid surfactant at room temperature selected from the group consisting of organic surfactants. 2. A partially crosslinked product of a carboxyl group-containing hydrophilic polymer in which at least a part of carboxyl groups is partially neutralized, and (ii) an anionic surfactant and a cation on one surface of a substrate. At least one liquid surfactant at room temperature selected from the group consisting of organic surfactants (iii)
A wafer polishing protection sheet provided with a pressure-sensitive adhesive layer containing a nonionic surfactant. 3. A partially crosslinked product of a hydrophilic polymer containing a carboxyl group in which at least a part of the carboxyl group is partially neutralized, and (ii) an anionic surfactant and a cation on one surface of a substrate. Of a wafer polishing protective sheet provided with a pressure-sensitive adhesive layer containing at least one liquid surfactant at room temperature selected from the group consisting of organic surfactants on the patterned wafer surface. Then, after polishing the back surface of the wafer while supplying water to the back surface of the wafer, the protective sheet is peeled off from the back surface of the wafer. 4. A partially crosslinked product of a hydrophilic polymer containing a carboxyl group in which at least a part of the carboxyl group is partially neutralized, and (ii) an anionic surfactant and a cation on one surface of a substrate. At least one liquid surfactant at room temperature selected from the group consisting of:
i) A wafer polishing protective sheet provided with a pressure-sensitive adhesive layer containing a nonionic surfactant is attached to the patterned wafer surface, and then water is supplied to the wafer back surface to clean the wafer back surface. A method for polishing a wafer surface, which comprises peeling a protective sheet from the back surface of the wafer after polishing.