JP3460712B2 - Polishing pad cushion layer and polishing pad using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, resin plates for information recording, ceramic plates, and other materials requiring high surface flatness. The present invention relates to a polishing pad cushion layer that performs a flattening process stably at a high polishing rate. The polishing pad of the present invention is particularly preferably used in a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer and the like formed thereon before further laminating and forming these layers. is there.

[0002]

2. Description of the Related Art A semiconductor integrated circuit (IC, LSI) is a typical material that requires a high degree of surface flatness.
A single crystal silicon disk called a silicon wafer for manufacturing a. Silicon wafer is IC, LS
In the manufacturing process such as I, in order to form a reliable semiconductor junction of various thin films used for circuit formation, it is required to finish the surface with high precision in each thin film manufacturing process.

Generally, a polishing pad is fixed to a rotatable supporting disk called a platen, and a semiconductor wafer is fixed to a disk called a polishing head capable of rotating and revolving. Polishing and flattening are performed by adding a polishing slurry in which fine particles (abrasive grains) are suspended in the gap between the polishing pad and the wafer by the rotational movement of both. At this time, as the polishing pad moves on the wafer surface, the abrasive grains are pressed onto the wafer surface at the contact points. Therefore, the work surface is polished by the sliding dynamic friction between the wafer surface and the abrasive grains. Such polishing process is usually called CMP polishing process.

Conventionally, as the polishing layer of the polishing pad used for the above-mentioned high-precision polishing, the porosity is generally 30 to 3
About 5% polyurethane foam sheet is used. However, the polyurethane foam sheet has an excellent local flattening ability, but has a compressibility of 0.5 to 1.
It is as small as about 0%, and therefore, it is difficult to apply a uniform pressure to the entire surface of the wafer because the cushioning property is insufficient. Therefore, usually, a soft cushion layer is separately provided on the back surface of the polyurethane foam sheet and polishing is performed.

[0005]

However, the cushion layer of the conventional polishing pad using the polyurethane sheet has the following problems. (1) As the cushion layer, resin-impregnated non-woven fabric having continuous cavities is widely used. There are problems such as changes. (2) Polyurethane foams with independent cavities are beginning to be used, but it is difficult to stabilize the foaming state in the manufacturing process, and the presence of cavities causes a deformation of the cavities when a load is applied, Have time to recover. That is, the problem that the residual strain with respect to the repeated load is large remains, and the cushion layer is deformed with respect to the repeated load from the wafer during polishing, causing a problem in the polishing characteristics.

An object of the present invention is to solve the above problems by forming a cushion layer with a composition having a small residual strain (hysteresis) against a compressive load.

[0007]

The present invention relates to a cushion layer for a polishing pad, which is characterized by reducing a change in compression characteristics by using a composition having less hysteresis. That is, a cushion layer for a polishing pad, which is attached to the surface of the polishing layer opposite to the polishing surface, and is patterned on the surface of the cushion layer on the platen adhesion side.
It has been subjected to uneven processing by
Cushion layer polishing pad, wherein the compression recovery ratio of 90% or more that relates. Compression recovery rate (%) = 100 (T ₃ −T ₂ ) / (T ₁ −T
₂ ) T ₁ : 30 kPa (300 g / cm ² ) from no load
Thickness of the sheet when applying the stress of 60 ksec for 60 seconds, a stress of 180 kPa is applied for 60 seconds from the state of T ₂ : T _1.
The thickness of the sheet when it is loaded : T ₃ : T ₂ ;
Sheet thickness when stress of 0 kPa is applied for 60 seconds

In the polishing layer of the polishing pad, when the Shore D hardness is less than 50, the hardness is too low and the compressibility is 2.0.
% Or more, there may occur a problem that the flattening accuracy of the object to be polished decreases. Even if the compression recovery rate is less than 50%, consolidation may still occur, which is not preferable.

Further, in order to solve the above problems, the rigidity of the polishing layer is increased to improve the flattening accuracy, but the in-plane uniformity is lowered. Therefore, provide a cushion layer,
It is required that the pad as a whole have a high compression rate and compression recovery rate.

The cushion layer for a polishing pad according to the present invention has a compression recovery rate of 90% or more. When the compression recovery rate is lower than 90%, the in-plane uniformity during polishing is poor, and the polishing rate changes largely when polishing is continuously performed. The compression rate and compression recovery rate in the present invention are represented by the following formulas. Compression ratio _{(%) = 100 (T 1} -T 2) / T 1 compression recovery rate _{(%) = 100 (T 3} -T 2) / (T 1 -T
₂ ) T ₁ : 30 kPa (300 g / cm) from no load
The thickness of the sheet when the stress of ² ) is applied for 60 seconds T ₂ : The sheet thickness when the stress of 180 kPa is applied for 60 seconds from the state of T ₁ : The state of the sheet thickness T ₃ : T ₂ is left unloaded for 60 seconds, It is the thickness of the sheet when a stress of 30 kPa is applied again for 60 seconds.

The polishing pad cushion layer of the present invention is a
Uneven processing by patterning on the Latin adhesive side surface
It has been subjected. By subjecting the surface of the polishing pad cushion layer on the platen adhesion side to unevenness processing by patterning , the adhesion area between the platen and the cushion layer is reduced, which increases the applied stress and increases the amount of compressive strain (compressibility increases). It is possible to disperse the local stress generated during polishing and improve the uniformity.

The polishing pad cushion layer of the present invention may be made of a photo-curing resin, a thermosetting resin or a thermoplastic resin, and the cushion layer surface is patterned.
Considering that the unevenness processing is performed , a photo-curable resin is preferable.

[0013] The light mentioned here, for example, visible light, ultraviolet light, electron beam, but the present invention is a laser beam and the like are those limited to patterning the cushion layer surface
Any light can be used as long as it can be used to perform the uneven processing .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The compound having rubber elasticity of the composition forming the cushion layer for a polishing pad of the present invention is not limited as long as it is a resin having a small hysteresis and a rubber-like property and a high compressibility. Butadiene polymer, isoprene polymer, styrene-butadiene copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butadiene-styrene block copolymer, acrylonitrile- Butadiene copolymer,
Examples thereof include urethane rubber, epichlorohydrin rubber, chlorinated polyethylene, silicone rubber, polyester-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, urethane-based thermoplastic elastomer, and fluorine-based thermoplastic elastomer.

When the resin has photosensitivity, a photocurable compound can be mixed. The compound is not limited as long as it is a compound that is cured by light. For example,
Those having an ethylenically unsaturated group are mentioned, and as acrylates or methacrylates of polyhydric alcohols, diethylene glycol dimethacrylate, tetraethylene glycol diacrylate, hexapropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, 1, 6
-Hexanediol diacrylate, 1,9-nonanediol diacrylate, dipentaerythritol pentaacrylate, trimethylolpropane trimethacrylate, oligobutadienediol diacrylate, lauryl methacrylate, polyethylene glycol diacrylate, N, N-dimethylaminopropyl methacrylamide , Trimethylolpropane triacrylate, trimethylolpropane trimethacrylate and the like.

As the epoxy acrylate, 2,2-
Bis (4-methacryloxyethoxyphenyl) propane, 2,2-bis (4-acryloxyethoxyphenyl) propane, bisphenol A, acrylic acid or methacrylic acid adduct of epichlorohydrin type epoxy resin, etc. As the acrylate or methacrylate having, low molecular weight unsaturated polyester such as phthalic anhydride-neopentyl glycol-acrylic acid condensate, etc., addition product of trimethylolpropane triglycidyl ether with acrylic acid or methacrylic acid, trimethylhexamethylene diisocyanate A urethane acrylate compound or a urethane methacrylate compound obtained by the reaction of a dihydric alcohol with an acrylic acid monoester or a methacrylic acid monoester, a methoxypolyethylene glycol acrylate , Methoxy polypropylene glycol acrylate, methoxy polypropylene glycol methacrylate, phenoxy polyethylene glycol acrylate, phenoxy poly polyethylene glycol methacrylate, phenoxy polypropylene glycol acrylate, phenoxy polypropylene glycol methacrylate, nonyl phenoxy polyethylene glycol acrylate, nonyl phenoxy polyethylene glycol methacrylate, nonyl phenoxy polypropylene glycol acrylate, Examples thereof include nonylphenoxy polypropylene glycol methacrylate. These may be used alone or in combination of two or more.

In order to enhance the photocurability of the photocurable compound, a photopolymerization initiator, a sensitizer or the like can be added. These are not particularly limited and are used depending on the light source and wavelength range to be used. The photopolymerization initiator used in this case is not limited, and it is a compound that absorbs light to cause cleavage or the like to generate a polymerization active species and initiate a polymerization reaction or the like. For example, when ultraviolet rays near the i-line (365 nm) are used as the light source, the aromatic ketones include benzophenone, 4,4′-bis (dimethylamino) benzophenone, 4-methoxy-4′-dimethylaminobenzophenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-ethylanthraquinone, enanthrenequinone, etc. As benzoins, methylbenzoin, ethylbenzoin, etc., and as benzyl derivatives , Benzyl dimethyl ketals and isodazoles include 2- (o-
Chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (m-
Methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-diphenylimidazole dimer, 2- (p -Methoxyphenyl)
-4,5-diphenylimidazole dimer, 2- (2,
Examples of acridine derivatives such as 4-dimethoxyphenyl) -4,5-diphenylimidazole dimer include 9-phenylacridine, 1,7-bis (9,9'-acridinyl) heptane, N-phenylglycine and the like. To be These may be used alone or in combination of two or more.

The present invention can also be carried out using a photosensitive sheet currently used in the printing field and the like. Further, the compression rate can be further increased by mixing the plasticizer. It is not particularly limited, and examples thereof include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, ditridecyl phthalate, butylbenzyl phthalate. , Dicyclohexyl phthalate, phthalates such as tetrahydrophthalate, di-2-ethylhexyl adipate, dioctyl adipate, diisononyl adipate, diisodecyl adipate, bis-adipate bis (butyldiglycol), di-n-alkyl adipate, Di-2-ethylhexyl azelate, dibutyl sebacate, dioctyl sebacate, di-2-ethylhexyl sebacate, dibutyl maleate, di-2-ethylhexyl maleate, dib fumarate Such as aliphatic dibasic acid ester, triethyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, chlorinated paraffin, acetyl tributyl acetyl citrate, epoxy Examples include plasticizers and polyester plasticizers. Can be mentioned.

As a means for imparting a higher compression rate to the cushion layer, a method of forming a groove structure or a halftone dot structure on the platen bonding surface side of the cushion layer is suitable. The shape and size cannot be limited because they differ depending on the polishing apparatus, polishing conditions, and the object to be polished, but, for example,
As for the shape, perforations (through holes), concentric circular grooves, XY, which are used for the surface irregularities of the polishing layer, are used.
Examples include lattices, cylinders, polygonal prisms, polygonal pyramid aggregates, and composites of these. The size is not limited because it changes depending on the required compression characteristics, but the maximum depth is the thickness of the cushion layer.

The method for manufacturing the polishing pad cushion layer according to the present invention will be described below. Even when another resin is used, the cushion layer can be prepared by a method similar to this method.

In the present invention, first, a polymer, a monomer, and a plasticizer, to which the above-mentioned additives such as a photoinitiator are added, are melt-mixed to prepare a mixture, which is then molded into a sheet.
The melt-mixing method is not limited, but a method in which the temperature is raised above the Tg (glass transition temperature) of the polymer in the twin-screw extruder and melt-mixed can be used. Further, the sheet processing method is not limited, but a conventionally known method can be applied. For example, there are methods such as roll coating, knife coating, doctor coating, blade coating, gravure coating, die coating, reverse coating, spin coating, curtain coating, and spray coating. Also,
It is also possible to perform die molding by pouring into a designated die or the like.

In order to further increase the compressibility of the sheet produced by the above method, patterning is performed by a light wavelength suitable for the composition using a conventionally known photolithography method, and a desired shape portion is formed on one surface of the sheet. Light cure. The uncured portion is washed away with a solvent to form an uneven shape.

When a load is applied to the cushion layer thus obtained, the stress concentrates on the bottoms of the projections of the projections and depressions formed by patterning. If the protrusions are formed so as to be uniformly dispersed in the pad surface, the protrusions are uniformly recessed and a cushioning effect is exhibited. The thickness of the cushion layer in the present invention is not particularly limited, but is preferably 0.5 mm to 5 mm. Furthermore, 0.5-
2 mm is preferable. The polishing pad of the present invention can be produced by attaching a polishing layer made of polyurethane to the surface of the cushion layer opposite to the platen-bonding side with an adhesive tape.

[0024]

[Example] Hardness According to JIS-6253, the measurement sample thickness is 6 mm.
Above, the measurement was performed using the Shore A hardness tester.

Compressibility and compression recovery rate The cushion layer after processing was cut into a circle having a diameter of 7 mm to obtain a measurement sample. Using this measurement sample, diameter 5 mm
Using the cylindrical indenter of the
Using a (thermo-mechanical analyzer), T1 to T3 were measured at 25 ° C. and determined by the following formula. Compression rate (%) = 100 (T1-T2) / T1 Compression recovery rate (%) = 100 (T3-T2) / (T1-T
2) T1: Thickness of the sheet when a load of stress of 30 kPa (300 g / cm ² ) is held for 60 seconds from an unloaded state (μ
m) T2: From the state of T1, load a stress of 180 kPa to 60
Thickness of sheet when held for seconds (μm) T3: Remove the load from the state of T2, leave for 60 seconds, and then again
It is the thickness (μm) of the sheet when a load of stress of 30 kPa is held for 60 seconds.

Polishing Evaluation A wafer having a SiO2 film with a thickness of 5000 Å formed on the surface of single crystal silicon was used as a processing material for evaluation, and polishing evaluation was performed under the following conditions.

As the polishing apparatus, a general nano-factor / NF-300 (corresponding to φ3 inch) as a test polishing apparatus was used. As the polishing slurry, silica (SiO2) slurry (manufactured by Fujimi Co., Ltd.) was used. The wafer to be processed is held on the polishing head under the condition of water adsorption / standard backing material (S = R301), the polishing pad sample is attached and fixed to the platen (polishing pad support), and the polishing pressure is 20 kPa (200 g). / Cm ² ),
Polishing head rotation speed 25 rpm and platen rotation speed 75 r
As pm, polishing operation was performed at a polishing slurry supply rate of 25 cc / min for 2 minutes, and an interference type film thickness measuring device manufactured by Otsuka Electronics Co., Ltd. was used for measuring the film thickness of the oxide film. The polishing rate was measured.

Uniformity Evaluation After polishing, the in-plane film thickness was measured for 14 polishing surfaces of a wafer having a diameter of 7.62 cm (φ3 inch), and the formula 100 was used.
The numerical value (%) was calculated by x (maximum film thickness-minimum film thickness) / (maximum film thickness + minimum film thickness) to evaluate the uniformity of the entire wafer surface.

(Sample 1) Styrene as a polymer
Butadiene copolymer (JSR, SBR1507) 8
4 parts by weight, 1 lauryl methacrylate as a monomer
0 parts by weight, benzyl dimethyl ketal as a photoinitiator 1
By weight, 5 parts by weight of liquid isoprene as a plasticizer was blended, melt-mixed by a twin-screw extruder, and then extruded by a T-die. The sheet was sandwiched on both sides with a PET film having a thickness of 100 μm and pressed with a roll so that the sample thickness was 2 mm, to mold an uncured cushion sheet. Both surfaces of this uncured cushion sheet were irradiated with ultraviolet rays for 10 minutes by a high-pressure mercury lamp (manufactured by Oak Co.) to cure the entire surface, and then the PET film was peeled off to obtain Sample 1.

(Sample 2) An uncured cushion sheet (sample thickness 2 mm) obtained in the process of preparing Sample 1
After irradiating ultraviolet rays from one side of the above for 2 minutes, PE on the other side
T was peeled off, and a halftone dot negative (light-transmitting part diameter 0.
6 mm, halftone dot center distance 1.2 mm) was placed, and ultraviolet rays were irradiated from the negative surface for 1 minute. The cushion sheet after irradiation was rubbed with a nylon brush while being immersed in a mixed solvent of toluene / methyl ethyl ketone (1/1 weight) to wash away the uncured portion. The resulting uneven cushion sheet is dried in an oven at 60 ° C, and the uneven surface is exposed to ultraviolet light for 10 hours.
It was irradiated for a minute and cured. The PET sheet on the back surface was peeled off to obtain Sample 2. In addition, the concave portion of the sample 2 is 0.
It was 6 mm deep.

(Sample 3) Sample 3 was a commercially available non-woven fabric type cushion layer, SUBA400 (manufactured by Rodel). The characteristic values of the sample are shown below.

[0032]

[Table 1]

As the polishing layer, a commercially available polyurethane polishing pad, IC-1000 (manufactured by Rodel) was used, and a double-sided adhesive tape (double tack tape, Sekisui Chemical Co., Ltd.) was attached to the opposite surface to the polishing surface. Each sample was laminated on the polishing layer. Also, a double-sided adhesive tape was attached to the surface of the cushion layer to be adhered to the platen to form a polishing pad. This polishing pad was attached to the platen of the polishing machine and the polishing characteristics were evaluated. The results are shown below.

[0034]

[Table 2]

[0035]

In the polishing pad of the present invention, a composition having less hysteresis is used for the cushion layer , and the platen thereof is used .
Concavo-convex processing by patterning is applied to the adhesive side surface
It is possible to reduce the change in compression characteristics by using
In- plane uniformity , which has a trade-off relationship,
It is a polishing pad that is extremely effective in achieving both flattening characteristics.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-249709 (JP, A) JP-A-2000-232082 (JP, A) JP-A-2000-117619 (JP, A) JP-A-7-149939 ( JP, A) JP 10-217112 (JP, A) JP 2-250766 (JP, A) JP 7-164307 (JP, A) JP 9-117855 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B24B 37/0 H01L 21/304 622

Claims (3)

(57) [Claims] 1. A cushion layer for a polishing pad, which is bonded to the surface of the polishing layer opposite to the polishing surface, wherein patterning is performed on the surface of the cushion layer on the platen bonding side.
A cushion layer for a polishing pad, which has been subjected to a concavo-convex processing treatment and has a compression recovery rate of 90% or more represented by the following formula . Compression recovery rate (%) = 100 (T ₃ −T ₂ ) / (T ₁ −T
₂ ) T ₁ : 30 kPa (300 g / cm ² ) from no load
Thickness of the sheet when applying the stress of 60 ksec for 60 seconds, a stress of 180 kPa is applied for 60 seconds from the state of T ₂ : T _1.
The thickness of the sheet when it is loaded : T ₃ : T ₂ ;
Sheet thickness when stress of 0 kPa is applied for 60 seconds 2. The cushion layer for a polishing pad according to claim 1 , which contains a compound having rubber elasticity. Wherein according to the surface opposite to the polishing surface of the polishing layer to claim 1
Or bonding the polishing pad and the second cushion layer polishing pad according.