JP2001277109A - Backing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backing film, facilitating the mounting/demounting of a wafer to improve flatness of polishing and generate large wafer holding force, in a backing pad used for polishing the semiconductor wafer by a wax-less method for fixing the wafer. SOLUTION: In a backing pad, used for polishing a semiconductor wafer by a wax-less method for fixing the wafer, this backing film is characterized by a constitution such that this pad is in film shape to be formed with a silicon rubber in one surface of a base film to laminate in its opposite surface a pressure sensitive adhesive layer or a pressure sensitive adhesive double coated tape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backing pad suitable for polishing a semiconductor wafer by a waxless method.

[0002]

2. Description of the Related Art Generally, a semiconductor wafer is subjected to a so-called chemical mechanical polishing method in a finishing process or a multi-layer wiring process for device fabrication.
According to g), mirror polishing and planarization of an interlayer insulating film and a conductive film are performed. In such polishing, as a method of holding a wafer on a polishing carrier, the following objects and methods have been adopted. Wax method of applying wax for bonding the wafer to one side of the wafer (Japanese Patent Laid-Open No. 05-013391, etc.) Waxless method by vacuum suction Using a backing pad made of a porous resin, for example, a polyurethane resin porous material, water is applied to the wafer. The waxless method of sticking is used. (Such as JP-A-06-23664)

[0003]

Each of the above-described wafer holding methods has a problem as described above. In the wax method, the nonuniformity of the thickness of the adhesive layer (wax layer) is directly reflected on the flatness, parallelism, and the like of the polished wafer. Therefore, it is important to make the thickness of the adhesive layer uniform. However, it is very difficult to make the thickness of the adhesive layer uniform. For this reason, various methods have conventionally been adopted. For example, in Japanese Patent Application Laid-Open No. Hei 5-13391, a method is used in which particles having a uniform particle diameter are put into wax, and a wafer is attached and pressed so as to have a uniform thickness. I have. However, even if the uniformity can be achieved by such a method, the wax method has a problem that the wafer process becomes complicated because it is necessary to remove the wax from the wafer after polishing the wafer.

The waxless method solves the above-mentioned disadvantages of the wax method.
There is an advantage that removal is unnecessary. The waxless method by vacuum suction has these advantages, but pin holes for vacuum suction must be opened in the backing plate, and the shape is reflected on the polished surface depending on the size and shape of these holes. There is a problem that it is done.

[0005] In the waxless method using a backing pad, a urethane resin porous material using a closed cell is generally widely used, and the foam layer is impregnated with water, and the wafer is held in water. This method has the advantage that the wafer can be easily held and easily removed, but when holding the wafer, sufficient water is removed so that there is no excess water between the backing pad and the wafer. There is a need. If the excess water is not removed well, there is a disadvantage that uneven polishing is caused when polishing is performed. Further, in recent years, the diameter of a wafer to be processed has become extremely large, and it becomes more difficult to remove unnecessary moisture. Further, depending on the type of the surface layer to be polished, there is a problem that the frictional resistance at the time of polishing is large, and sometimes the pad that has been wetted comes off during polishing.

In order to solve the problem that the wafer is peeled off, Japanese Patent Application Laid-Open No. 6-61202 discloses that a silicone resin is directly coated on a backing plate.
An attempt is made to hold the wafer with the silicone resin layer.
This improves flatness and holding power, but if the pretreatment is complicated to coat the silicone resin layer, or if the silicone layer has deteriorated, it is necessary to replace or recoat the entire back plate again. There is a problem that becomes.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a backing pad for fixing a wafer used for polishing a semiconductor wafer by a waxless method, in which the wafer can be easily attached and detached and the flatness of the polishing is good. This provides a backing film having a large wafer holding force.

That is, the present invention relates to a backing pad for fixing a wafer used for polishing a semiconductor wafer by a waxless method, wherein the pad is in the form of a film, and a silicone rubber is formed on one surface of a base film;
A backing film characterized in that an adhesive layer or a double-sided tape is laminated on the opposite surface. In the present invention, the pressure-sensitive adhesive layer laminated or adhered to one surface of the base film can be easily attached to the backing plate of the polishing apparatus, and can be easily replaced. Further, by providing a silicone resin layer on the side opposite to the adhesive layer, the silicone resin layer can firmly hold the wafer with good flatness.

Further, in the present invention, the base film is preferably a polyester film. By using a polyester film as the base film, an inexpensive back film having sufficient strength can be provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester film of the present invention can be arbitrarily used as long as it contains polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate or the like as a main component. As the polyester film, an easily adhesive polyester film obtained by treating the surface with an actinic ray or laminating a compound for improving the adhesiveness on the surface of the polyester film can be used. In this case, the silicone rubber film can be used. Can reduce the amount of the adhesion improver. That is, the interface ray peel strength of the silicone rubber layer and the polyester film is set by the above-mentioned actinic ray treatment, selection of the easily-adhesive polyester film, and the combination of the amount of the adhesiveness improver and the like. It is preferably at least 4 N / 20 mm, more preferably at least 6 N / 20 mm, even more preferably at least 8 N / 20 mm.

Examples of the above-mentioned treatment method using actinic radiation include corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, flame treatment, and the like. Acrylic compounds or blends thereof are mentioned. The method of laminating the easy-adhesion layer may be a so-called in-line method of laminating at the time of film formation, or a so-called off-line method of laminating the formed film. In addition, a film obtained by treating the surface of the easy-adhesion layer of the film having the easy-adhesion layer laminated thereon with the above-mentioned active ray can be used, but is not limited thereto.

In the present invention, the silicone rubber layer is preferably a silicone rubber composition obtained by blending 0.2 to 20 parts by weight of a polyhydric alcohol methacrylate ester with 100 parts by weight of silicone rubber. Is preferred. Since the silicone rubber layer is produced from a silicone rubber composition in which 0.2 to 20 parts by weight of a polyhydric alcohol methacrylate is blended with respect to 100 parts by weight of the silicone rubber, the interfacial peel strength between the silicone rubber film and the polyester film is as described above. It is possible to increase the thickness to 4 N / 20 mm or more, preferably 6 N / 20 mm or more, particularly preferably 8 N / 20 mm or more, so that the silicone rubber layer peels off from the interface with the polyester film after bonding to the above device. Not even.

The silicone rubber used in the present invention has an average
Ordering formula: Ra SiO_{(4-a) / 2}Organopolysilos represented by
It is a xan. In the above formula, R is a substituted or unsubstituted monovalent carbon
A hydrogen group, such as a methyl group, an ethyl group,
Alkyl such as benzyl, butyl, pentyl and hexyl
Group, vinyl group, allyl group, butenyl group, pentenyl group,
Alkenyl group such as hexenyl group, phenyl group, tolyl
Group, xylyl group, aryl group such as naphthyl group, cyclope
Cycloalkyl groups such as methyl group and cyclohexyl group,
Aralkyl groups such as benzyl group and phenethyl group, 3-chloro
Propyl group, 3,3,3-trifluoropropyl group
Halogenated alkyl groups and the like, preferably methyl
Group, vinyl group, phenyl group, 3,3,3-trifluoro
Propyl group. In the above formula, a is 1.9 to 2.1.
Is a number within the range. The silicone rubber component is
It is expressed by the average unit formula, but the specific siloki
As the sun unit, for example, R_ThreeSiO_1/2Unit, R_Two
(HO) SiO_1/2Unit, R _TwoSiO_2/2Unit, RSi
O_3/2Units and SiO_4/2Units.

The main component of the silicone rubber component in the present invention
Is R_TwoSiO_2/2Unit and R_ThreeSiO _1/2Unit or
R_Two(HO) SiO_1/2Linear polymerization requiring units
Body and possibly small amounts of RSi O_3/2Units and / or
Or R_ThreeSiO_1/2Contains a unit and has a partially branched structure
Can have. Some of the silicone rubber components
As R_ThreeSiO_1/2Units and SiO_4/2From units
Resinous polymers can be blended. in this way
The silicone rubber component is a mixture of two or more polymers.
You may. In addition, the composition is an addition reaction-curable silicone.
In the case of a rubber composition, it is represented by the above average unit formula.
At least two Rs in the organopolysiloxane are
It must be a alkenyl group.

The molecular structure of the silicone rubber component is not particularly limited, and may be, for example, linear, partially branched linear, branched, or resinous. , A linear polymer, or a mixture mainly composed of a linear polymer. Such silicone rubber components include, for example, dimethylpolysiloxane having trimethylsiloxy groups at both ends of molecular chains, methylvinylpolysiloxane having trimethylsiloxy groups at both ends of molecular chains, methylphenylpolysiloxane having trimethylsiloxy groups at both ends of molecular chains, and methylphenylpolysiloxane. Trimethylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer at both ends of chain, trimethylsiloxy group-blocked dimethylsiloxane / methylphenylsiloxane copolymer at both ends of molecular chain, dimethylsiloxane / methyl-blocked trimethylsiloxy group at both ends of molecular chain 3,3-trifluoropropyl) siloxane copolymer, molecular chain terminal trimethylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, molecular chain terminal dimethyl Nylsiloxy group-blocked dimethylpolysiloxane, molecular chain terminal dimethylvinylsiloxy group-blocked methylvinylpolysiloxane, molecular chain terminal dimethylvinylsiloxy group-blocked methylphenylpolysiloxane, molecular chain terminal dimethylvinylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane Copolymer, dimethylvinylsiloxy-group-blocked dimethylsiloxane / methylphenylsiloxane copolymer with both ends of molecular chain, dimethylsiloxane-methyl (3,3,3-trifluoropropyl) siloxane-copolymer with both ends of molecular chain dimethylvinylsiloxy-group Coupling, dimethylvinylsiloxy group-blocked dimethylsiloxane at both ends of molecular chain
Methylvinylsiloxane / methylphenylsiloxane copolymer, dimethylpolysiloxane with silanol groups at both ends of molecular chain, methylvinylpolysiloxane with silanol groups at both ends of molecular chain, methylphenylpolysiloxane with silanol groups at both ends of molecular chain, both ends of molecular chain Silanol group-blocked dimethylsiloxane / methylvinylsiloxane copolymer, molecular chain terminal silanol group-blocked dimethylsiloxane / methylphenylsiloxane copolymer, molecular chain terminal silanol group-blocked dimethylsiloxane / methyl (3,3
3-trifluoropropyl) siloxane copolymer, dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer with silanol groups at both ends of molecular chain, dimethylpolysiloxane with trimethoxysiloxy groups at both ends of molecular chain, tris at both ends of molecular chain Methoxysiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer, molecular chain terminal trimethoxysiloxy group-blocked dimethylsiloxane / methylphenylsiloxane copolymer, molecular chain terminal trimethoxysiloxy group-blocked dimethylsiloxane / methylvinylsiloxane / methyl Phenylsiloxane copolymer, organopolysiloxane copolymer comprising R ₃ SiO _1/2 units and _{SiO 2/2} units, R ₂ SiO
Organopolysiloxane copolymers consisting of _2/2 units and RSi O _3/2 units, R ₃ Si O _1/2 units and R ₂ Si O _2/2
And organopolysiloxane copolymers consisting of RSiO _3/2 units and a mixture of two or more of these. The viscosity of the silicone rubber component at 25 ° C.
Although not particularly limited, practically, it is preferably 100 centistokes or more, particularly preferably 1,000 centistokes or more.

The methacrylic acid ester of a polyhydric alcohol used in the present invention is an ester compound obtained by esterifying two or more alcoholic hydroxyl groups of a polyhydric alcohol having two or more alcoholic hydroxyl groups with methacrylic acid,
For example, ethylene glycol dimethacrylate, 1,3 butanediol dimethacrylate, 1,4 butanediol dimethacrylate, 1,6 hexanediol dimethacrylate, neopentyl glycol dimethacrylate,
2,2'bis (4-methacryloxydiethoxyphenyl) pron, glycene dimethacrylate, glycentrimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, tetramethylolmethane dimethacrylate And tetramethylolmethanetrimethacrylate, tetramethyloltetramethacrylate, and the like, and a compound containing three or more methacrylates is particularly preferable. In addition, any one of the above compounds may be used alone, or two or more of them may be used in combination.

The compounding amount of the methacrylic acid ester is 0.2 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the silicone rubber. Has an insufficient adhesive strength. On the other hand, if it exceeds 20 parts by weight, the effect of improving the adhesive strength reaches saturation and the physical properties of the silicone rubber deteriorate. The methacrylic acid ester serves as an adhesiveness improver for the silicone rubber composition.If necessary, a reinforcing filler, a pigment, a dye, an antioxidant, an antioxidant, a release agent, A flame retardant, a thixotropic agent, a dispersant for a filler, a co-crosslinking agent and the like can be added.

The method of compounding the above compounding agent with the silicone rubber is not particularly limited. For example, when a silicone rubber compound is produced, two rolls, a Banbury mixer,
It may be carried out using a rubber kneading machine such as a dough mixer (kneader). In the case where silicone rubber is dissolved in a solvent and a film is formed by a casting method, the silicone rubber compound is dissolved in the solvent to prepare a solution. At this time, it may be carried out by a method of adding and blending to the obtained solution.

In the present invention, a cloth or film mainly composed of poly-4-methylpentene-1 or a cloth or film composed of an ethylene / methyl methacrylate copolymer is laminated on the surface of the silicone rubber layer as a cover sheet. A preferred configuration is preferred. As a result, it is possible to prevent adhesion of dirt on the surface of the silicone layer of the film.

In the present invention, the method of laminating the silicone rubber layer on the polyester film is optional. For example, a solution obtained by dissolving the silicone rubber composition in a solvent is applied to the surface of the polyester film and dried to form a silicone rubber layer. A method of forming a thin film, a method of extruding a silicone rubber composition on the surface of a polyester film under high pressure to form a thin film of silicone rubber, and the like can be mentioned. In the case of liquid silicone rubber, a method of coating without dilution with a solvent may be used. In addition, the thickness composition ratio of the silicone rubber film and the polyester film in the present invention can be arbitrarily set according to the use of the composite.

The crosslinking method is not particularly limited. For example, a peroxide compound is compounded in a silicone rubber composition,
After laminating by the above method, the laminate may be subjected to a heat treatment to be crosslinked, or may be crosslinked by irradiation with an actinic ray such as an ultraviolet ray, an electron beam, or a γ ray. The addition of various auxiliaries in these crosslinking treatments is not limited at all. Then, in the present invention, after laminating a silicone rubber layer and a cover sheet on the polyester film in this order, the above crosslinking treatment is performed, and then the cover sheet is peeled off to form a composite of the polyester film and the silicone rubber film. To manufacture.

Further, in the present invention, a groove may be formed on the surface of the silicone rubber layer, which is the layer holding the wafer, for the purpose of easily removing excess air and water. The shape of the groove processing is not particularly limited, but is preferably a lattice shape or a radial shape from the center of the back film.

The distance between the grooves, the width of the grooves, the depth of the grooves, and the cross-sectional shape of the grooves are not particularly limited, but the distance between the grooves is preferably 30 mm or less, more preferably 20 mm or less.
mm or less is good. The width of the groove is preferably 5 mm or less, more preferably 2 mm or less. If the width of the groove is larger than that, the shape of the groove will affect the surface condition of the wafer when polished. Further, the depth of the groove is preferably 20 μm or more.

[0024]

Example 1 A commercially available high-strength silicone rubber compound ("KE" manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silicone rubber compound.
555-U ") and a commercially available silicone rubber compound for general molding (" KE958- "manufactured by Shin-Etsu Chemical Co., Ltd.)
U ") in a weight ratio of 60:40, and kneaded at 100 to 200 ° C using two rolls to form a rubber sheet having a thickness of 3 mm. The unvulcanized rubber sheet was cut into 1 cm square strips, and the weight ratio of the strips to toluene was 2%.
It was weighed so as to be 3%, put into a stirrer equipped with a vacuum defoaming device together with toluene, and stirred at atmospheric pressure for 15 hours to dissolve the small pieces in toluene. Then, trimethylolpropane trimethacrylate was added to the solution. After adding 2 parts to 100 parts of the silicone rubber compound and stirring uniformly, the vacuum defoaming device was driven and the gauge pressure was -7.
The mixture was further stirred for 20 minutes under a vacuum of 50 mmHg and defoamed.

Next, the silicone rubber solution obtained by the above-mentioned dissolution and defoaming is supplied to a roll coater, and the corona-treated surface of a 75 μm-thick polyethylene terephthalate film (Cosmoshine A4100 manufactured by Toyobo Co., Ltd.) is treated. After drying, it was coated so as to have a thickness of 150 μm, subsequently introduced into an oven, dried at 80 ° C., and a silicone rubber-side surface having a thickness of 35 μm comprising a copolymer of poly-4-methylpentene-1 was obtained. A mat-processed film ("Opulan X-60YMT4", manufactured by Mitsui Petrochemical Co., Ltd.) is stacked so that the mat-processed surface faces the silicone rubber, and is continuously laminated while being pressed with a pressure roll at a pressure of 5 kgf / cm ^2. The obtained laminate was further continuously guided to an electron beam irradiation device (200 KV, 15 Mrad) to perform a crosslinking treatment, and then the cover sheet was removed. And the total thickness of a silicone rubber film and the polyester film 225
A μm composite was obtained, which was wound into a roll. Further, using a roll laminator, this roll was laminated with a double-sided adhesive tape (# 761 manufactured by Teraoka Co.) on the polyester surface of the film to obtain a backing film.

The obtained backing film was bonded to a backing plate of a polishing machine (SPP600S manufactured by Okamoto Machine Tool Co., Ltd.) using the double-sided tape, and a silicon wafer was pressed against a silicone resin layer on the surface to hold the wafer and perform a polishing experiment. went. At this time, a 6-inch silicon wafer provided with a thermal oxide film of 10,000 angstroms was polished as a wafer used for evaluation. The polishing conditions were as follows: a ceria-based slurry was used as the slurry, the rotation speed of the plate was 50 rpm, and a urethane-based porous pad (Rodel IC10) was used as the polishing pad.
00 / S400). When the polishing load was gradually increased from 100 g / cm ^{2 and the} load at which the wafer could not be held was observed, the wafer did not come off even if the pressure was increased to 1 kg / cm ² .

Example 2 A lattice-shaped groove having a width of 1 mm, a pitch of 10 mm and a depth of 25 μm was formed on the surface of the silicone rubber layer of the backing film material obtained in Example 1. Using the same pad, was evaluated in the same manner as in Example 1, where the wafer gradually increasing progressively polishing load from 100 g / cm ² saw a load can not be held, even if pressurized to 1 kg / cm ² The wafer did not come off.

Example 3 The surface of the silicone rubber layer of the backing film material obtained in Example 1 was subjected to radial groove processing with a width of 1 mm, a pitch of 10 mm and a depth of 25 μm. Using the same pad, was evaluated in the same manner as in Example 1, where the wafer gradually increasing progressively polishing load from 100 g / cm ² saw a load can not be held, even if pressurized to 1 kg / cm ² The wafer did not come off.

Comparative Example 1 Example 1 was repeated, except that the backing plate of the polishing machine was replaced with a urethane foam-based backing pad (NF200 manufactured by Rodale).
The evaluation was performed in the same manner as described above. When a polishing load saw the load on which the wafer can not be held continue to increase gradually from 100g / cm ^2, but it is not that is pressurized up to 300g / cm ² wafer comes off, the wafer is moved can not withstand the frictional resistance However, a phenomenon of hitting the guide supporting the peripheral portion of the wafer occurred, and when the pressure was increased to 400 g / cm ² , a phenomenon that the wafer finally came off the backing film occurred.

Comparative Example 2 A backing plate of a polishing machine was heated to about 80 ° C., and a wax for bonding a sample (Electron wax manufactured by Buehler) was melted at about 80 ° C. and spread thinly and uniformly on the backing plate. When a silicon wafer was attached and the temperature dropped, the same polishing evaluation as in Example 1 was performed. When the polishing load was gradually increased from 100 g / cm ^{2 and the} load at which the wafer could not be held was observed, the wafer did not come off even if the pressure was increased to 1 kg / cm ² . However, the uniformity of the thickness of the oxide film in the plane of the polished wafer was extremely poor. Also, in order to detach the sample, the backing plate must be replaced every time,
The work became extremely complicated.

According to the present invention, there is provided a backing film capable of easily attaching and detaching a wafer, having good flatness of polishing, and having a large wafer holding force.

[0032]

The force for holding the wafer is strong, and the wafer can be easily attached and detached. Moreover, since the adhesive layer is provided on one side, the backing film can be easily replaced.

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Claims (8)

[Claims] 1. A backing pad for fixing a semiconductor wafer, which is used for polishing a semiconductor wafer by a waxless method, wherein the pad is in the form of a film, and silicone rubber is formed on one surface of a base film, and on the opposite surface thereof. A backing film having a configuration in which an adhesive layer or a double-sided tape is laminated. 2. The backing film according to claim 1, wherein said base film is a polyester film. 3. The backing film according to claim 1, wherein the silicone rubber layer is a silicone rubber layer.
A backing film comprising a silicone rubber composition obtained by mixing 0.2 to 20 parts by weight of a polyhydric alcohol methacrylate with respect to 00 parts by weight. 4. The backing film according to claim 1, wherein the surface of said silicone rubber layer is poly-4-
A backing film characterized by laminating a cloth or a film containing methylpentene-1 as a main component as a cover sheet. 5. The backing film according to claim 1, wherein an ethylene.
A backing film characterized by laminating a cloth or film comprising a methyl methacrylate copolymer as a cover sheet. 6. The backing film according to claim 1, wherein a groove is formed in the silicone rubber layer. 7. The backing film according to claim 6, wherein the grooves formed in the silicone rubber layer are lattice-shaped. 8. The backing film according to claim 6, wherein the grooves formed in the silicone rubber layer are radial.