JP3455517B2 - Urethane molded product containing cavities for polishing pad, polishing sheet and polishing pad - 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 void-containing urethane molded product for a polishing pad that performs a flattening process stably and at a high polishing rate, a polishing sheet and a polishing pad obtained from the urethane molded product. 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. By rotating the both, a relative speed is generated between the platen and the polishing head, and polishing slurry is added by adding polishing slurry in which fine particles (abrasive grains) are suspended in the gap between the polishing pad and the wafer. The flattening process is performed. 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.

The polishing operation in the CMP polishing step is carried out by holding the abrasive grains in a slurry in which fine particles (abrasive grains) are suspended in a polishing pad to be used. Therefore, the higher the retention density of the abrasive grains on the polishing pad, the higher the polishing rate. Therefore, as the polishing pad, a porous material having a large number of pores is usually used, and by holding the abrasive grains in the pores, it is possible to increase the retention density of the abrasive grains and increase the polishing rate. It is being appreciated. here,
In order to stabilize the polishing rate, it is necessary to suppress the variation in the porosity of the porous material.

Conventionally, a polyurethane foam sheet having a porosity of about 30 to 35% is generally used as a polishing pad used for the above-mentioned high-precision polishing. Also,
The technique described in JP-A-8-500622, which discloses a polishing pad in which hollow microspheres, water-soluble polymer powder or the like is dispersed in a matrix resin such as polyurethane, is also known.

[0006]

However, the conventional polishing pad using a polyurethane sheet has the following problems.

In the conventional manufacture of void-containing urethane molded products, a raw material composition containing an uncured urethane prepolymer is put into a mold and allowed to cure, and the resulting void-containing urethane molded products are sliced into a polishing sheet. However, the void ratio varies in the depth direction of the urethane molded product due to the difference in specific gravity from the matrix layer. If this molded product is formed into a sheet by mechanical processing such as slicing and a polishing pad is obtained from the polishing sheet, the void content in each polishing pad varies even within the same lot due to the above reasons.

This variation in the contained void ratio causes variations in the retention density of the abrasive grains, that is, variations in the polishing rate of the polishing pad obtained from the same lot. Also, the size of the cavity varies both inside and outside.

Generally, in CMP polishing, the work of scraping off the pad surface called dressing is carried out using a diamond grindstone or the like to expose the surface with exposed pores and reuse the same as in the initial state. Be seen. At this time, if there is a variation in the contained void ratio in the depth direction, there will be a variation in the exposed void ratio on the surface of the same polishing pad after dressing. That is, even with the same polishing pad, the polishing rate becomes unstable.

An object of the present invention is to reduce the variation in the void ratio of the void-containing urethane molded article and to reduce the variation in the polishing rate of the obtained polishing pad within the lot and within the same pad.

[0011]

The present invention relates to a void-containing urethane molded article for a polishing pad, which is obtained by charging a raw material composition containing an uncured urethane prepolymer and a polymer foaming microelement into a mold and curing the composition. The urethane molded article has a thickness of 100 mm or less, 20 mm or more, and
Apparent specific gravity of the upper layer, middle layer, and lower layer of the urethane molded product
Within 5% based on the apparent specific gravity of the upper layer
Polishing pad cavity containing urethane molded product, wherein that relates. In the present invention, the difference in apparent specific gravity is preferably within 3% based on the apparent specific gravity of the upper layer portion.

The polishing pad formed from the void-containing urethane molding for a polishing pad has a small variation in the void content in the lot and in the thickness direction of the pad itself. Therefore, the variation in the polishing rate is small, and the stable polishing rate is small. It will be obtained.

The porosity can be measured by the following method. The obtained void-containing urethane molded product is sliced into a sheet, and the void ratio of each polishing sheet is measured.
The porosity is calculated by the following formula 1. Porosity (%) = 100 × (true specific gravity−apparent specific gravity) / true specific gravity (Equation 1) The apparent specific gravity is measured according to the description of Examples.

That is, the present invention is characterized in that the difference in the void content in the vertical direction of the urethane molded product is reduced by regulating the thickness of the void-containing urethane molded product. Further, the present invention is a method for producing a polishing sheet, which comprises forming a cavity-containing urethane molded article for a polishing pad by slicing,
And a polishing sheet produced by the method. Further, the present invention relates to a polishing pad manufactured by laminating a cushion layer on the polishing sheet.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The void-containing urethane molded article for a polishing pad according to the present invention comprises an isocyanate group-containing compound (
It is obtained by polymerizing a polyisocyanate compound) and an active hydrogen group-containing compound (polyol compound) as a matrix. As a method of containing a cavity,
It is formed by a method of dispersing and polymerizing polymer foam microelements (for example, Expancel (Nippon Phyllite Co., Ltd.)).

The isocyanate compound is not particularly limited, and 4,4'-diphenylmethadiisocyanate,
2,4'-diphenylmethane diisocyanate, 2,4
-Aromatic diisocyanate compounds such as toluene diisocyanate and 2,6-toluene diisocyanate, ethylene diisocyanate, aliphatic diisocyanate compounds such as 2,2,4-trimethylhexamethylene diisocyanate and 1,6-hexamethylene diisocyanate (HDI), hydrogenation 4,4'-diphenylmethane diisocyanate (HMDI, trade name: Hiren-W, manufactured by Huls), 1,4-cyclohexane diisocyanate (CH
DI), alicyclic diisocyanate compounds such as norbornane diisocyanate, and the like. The above compounds may be used alone or in combination.

In addition to the above diisocyanate compound, 3
It is also possible to use a polyfunctional isocyanate compound having a functionality or higher. As the polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (Bayer Co.) and trade name Duranate (manufactured by Asahi Kasei Corporation). When these trifunctional or higher polyisocyanate compounds are used alone, they tend to gel during the synthesis of the prepolymer, so it is preferable to use them by adding them to the diisocyanate compound.

The active hydrogen group-containing compound is not particularly limited, but it is an organic compound having at least two active hydrogen atoms, and a compound usually called a polyol compound or a chain extender in the technical field of polyurethane is used. be able to. The active hydrogen group is a functional group containing hydrogen that reacts with an isocyanate group, and examples thereof include a hydroxyl group, a primary or secondary amino group, and a thiol group.

The polyol compound is an oligomer having a molecular weight of about 500 to 10,000 as determined by the terminal group quantitative method,
The following polyether polyols and polyester polyols may be mentioned.

The polyether polyol is a polyoxypropylene polyol obtained by adding propylene oxide to one or more polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin and trimethylolpropane. , Polyoxyethylene polyols obtained by addition of ethylene oxide, butylene oxide, polyols obtained by addition of styrene oxide, etc., and polys obtained by addition of tetrahydrofuran to the polyhydric alcohol by ring-opening polymerization. Oxytetramethylene polyols can be illustrated. Copolymers using two or more of the above cyclic ethers can also be used.

As the polyester polyol, one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol glycerin, trimethylolpropane, pentaerythritol or other low molecular weight polyhydric alcohol is used. Glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, hydrogenated dimer or other low molecular weight dicarboxylic acid or a condensation polymer with two or more kinds of oligomeric acids, Examples include polyols such as ring-opening polymers of cyclic esters such as propiolactone, captolactone and valerolactone.

The void-containing urethane foam molded product is generally formed in a block shape. The thickness of the block at this time is
It is preferably 100 mm or less, more preferably 70 mm or less, and further preferably 50 mm or less. It is particularly preferably 35 mm or less.

If it is thicker than 100 mm, the cavities move widely during curing, resulting in a large variation in the cavity distribution. In addition, since the heat of curing reaction inside does not escape easily and the temperature inside the block becomes high, the cavities expand and the sizes of the cavities inside and outside vary. The inner cavity becomes larger. Further, the internal cavity is hardened in the expanded state, and when it is cooled, the cavity shrinks and the block is distorted, and when this is sliced, the polishing sheet itself becomes distorted.

Furthermore, the void-containing urethane foam molded article is maintained as a post-cure in an environment of 70 to 180 ° C. for several hours to react with moisture in the air to be completely cured,
Although excess isocyanate groups may be crushed, if the urethane molded product is thicker than 100 mm, the temperature may not be uniform even during post-cure, or moisture may not quickly penetrate into the interior. The homogeneity of quality within the molding is impaired.

When a polishing sheet is obtained by slicing such a thick urethane molded product, a polishing sheet having different polishing characteristics is obtained depending on the position of the slice, or the polishing characteristics are changed by scraping the pad during polishing. I can do it. Further, even in the same pad, polishing characteristics may differ between the center and the outer peripheral portion, and uniform polishing may not be possible.

If it is too thin, there is a risk that the urethane molded article will bend when it is handled, and it is necessary to keep the mold accurately horizontal, and further productivity is impaired. Therefore, it is necessary to have a thickness of 20 mm or more. is there. If the size of the urethane molded product is rectangular, the shorter side is 50
It is preferably cm or more, more preferably 60 cm or more, further preferably 70 cm or more, particularly preferably 80 cm or more. In particular, in the case of such a large-sized polishing pad, reaction heat is likely to be accumulated inside, which is effective in applying the present invention.

In the void-containing urethane foam molded product thus obtained, the difference in apparent specific gravity between the upper layer portion, the middle layer portion and the lower layer portion is within 5% based on the apparent specific gravity of the upper layer portion .
It is preferably within 4%, particularly within 3%
Is preferred. Incidentally, since the urethane molded product is usually slightly expanded in the mold and the central part is bulged, the bulged part is removed and then sliced. The upper layer portion here is the peripheral portion of the polishing sheet obtained by removing 1.5 mm from the uppermost surface of the urethane molded product after removing the raised portion, and slicing it with a thickness of 1.27 mm from this, and the lower layer portion is This is a peripheral portion of a polishing sheet obtained by removing 1.5 mm from the lowermost surface of a urethane molded product and slicing it to a thickness of 1.27 mm. The middle layer portion is a peripheral portion of a sheet sliced at a thickness of 1.27 mm including the midpoint of the thickness of the urethane molded product from which the raised portion is removed. The peripheral portion is a portion within 10 cm from the end surface of the sheet.

The above-mentioned urethane molded product is sliced into a polishing sheet having a predetermined thickness by using a slicer (canna system, band saw system, etc.). The thickness of the polishing sheet at this time is 0.5 m
It is preferably about m to 25 mm, and further, CM
In the case of a polishing pad for P, it is preferably 0.7 mm to 1.7 mm. The total thickness unevenness is preferably R ≦ 50 μm, more preferably R ≦ 20 μm, and even more preferably R ≦ 10 μm.

The above-mentioned polishing sheet is used after being punched into a predetermined size. The shape of the present polishing sheet is selected according to the device used and the like, and may be any of square, rectangular, polygonal, circular, etc., but it is preferably circular. In the case of a circular shape, the diameter is preferably 50 cm or more, more preferably 60 cm or more, further preferably 70 cm or more, and particularly preferably 80 cm or more. In addition, PEF is applied to a polishing sheet punched to a specified size.
It is preferable that a cushion layer of (independently foamed polyethylene foam) is attached using a double-sided tape to form a polishing pad of a laminate.

When performing a polishing operation using the polishing pad of the present invention, it is a preferable mode to use a known auxiliary agent, for example, a lubricant or an abrasive, specifically, alumina, ceria, Examples thereof include abrasives such as silica and slurries in which these are dispersed / suspended in water or a liquid organic compound.

[0031]

[Example] (Measurement of apparent specific gravity) The apparent specific gravity is a small piece (1 cm) sampled from an abrasive sheet obtained by slicing the urethane molded product in the thickness direction.
Accurately measure the weight of × 1.5cm, and use the small piece to obtain a high-precision electronic hydrometer ED-120T (MIRAG)
(Manufactured by Company E) to determine the apparent specific gravity. The void ratio (%) in the thickness direction of the urethane molded product can be obtained by substituting this value into the above-mentioned formula 1.

(Preparation of Cavity-Containing Polyurethane Molded Product 1) Adiprene L-325 melted and temperature-controlled at 80 ° C.
(Isocyanate-terminated prepolymer, NCO = 9.25
%, Manufactured by Uniroyal Corporation) (first component) 3000 parts by weight, 19 parts by weight of a silicon foam stabilizer SH-192 (manufactured by Toray Dow Corning Silicon Co., Ltd.) as a surfactant, and Expancel 551DE (as a hollow bead) ( 90 parts by weight of Nippon Ferrite Co., Ltd. was mixed and stirred with a whipping mixer (stirring blade rotation number = 3500 rpm) for about 5 minutes until a cream-like (meringue state) was obtained to obtain an air bubble dispersion liquid 1. Transfer this air bubble dispersion liquid 1 to a planetary mixer, and
Cure amine MT (methylene bis-
0-chloraniline, manufactured by Ihara Chemical Co., Ltd. (No. 2
770 parts by weight of (Component) was added and mixed for about 2 minutes. The liquid mixture has fluidity and has a width of 700 mm and a depth of 7 within the pot life.
A cavity-containing polyurethane molded product 1 was prepared by casting in an oven mold of 00 mm to a height of 80 mm and curing it, and performing post cure for 6 hours in an oven whose temperature was adjusted to 110 ° C ± 10 ° C.

(Preparation of Cavity-Containing Polyurethane Molded Product 2) A mixed solution was prepared in the same manner as the above-mentioned molded product. This mixed solution was cast into an oven mold similar to the above at a height of 120 mm and cured within a pot life of fluidity at 110 ° C. ± 1.
Post-curing was performed for 6 hours in an oven whose temperature was adjusted to 0 ° C. to prepare void-containing polyurethane molded product 2.

(Preparation of Cavity-Containing Polyurethane Molded Product 3) A mixed solution was prepared in the same manner as the above-mentioned molded product. This mixed liquid is fluid and has a width of 830 mm and a depth of 830 within the pot life.
6 mm in an oven whose temperature is adjusted to 110 ° C ± 10 ° C.
Post-curing was performed for a time to prepare a void-containing polyurethane molded product 3.

Example 1 (Preparation of Polishing Pad 1) While heating the void-containing polyurethane molded article 1 to about 50 ° C., it was sliced to a thickness of 1.27 mm with a slicer (VGW-125 manufactured by Amitech Co., Ltd.) and a polishing sheet 60 sheets were obtained. The raised portion was removed and then sliced. These polishing sheets are sequentially processed from the top of the molded body (1-1).
(-59). Further, the polishing sheet corresponding to the lower layer portion was sliced to 1.27 mm after removing the slice by 1.50 mm from the bottom portion to obtain (1-60). Small pieces for measuring the porosity were sampled from the periphery of each polishing sheet. Table 1 shows some of the porosity results. Also, each polishing sheet is 24 inc
It was punched into a hφ size disc. Double-sided tape (double tack tape # 57 manufactured by Sekisui Chemical Co., Ltd.)
82) was used to attach PEF (independent foaming polyethylene foam), which is a cushion layer, to obtain a polishing pad.
Furthermore, a double-sided tape (double tack tape # 5673, manufactured by Sekisui Chemical Co., Ltd.) was attached to this PEF to obtain a polishing pad of a laminate. A sheet number is assigned to each laminate polishing pad, and the polishing pad (1-
Numbered 1) to (1-60).

Comparative Example 1 (Preparation of Polishing Pad 2) The void-containing polyurethane molded product 2 was sliced in the same manner as above to obtain 92 polishing sheets having a thickness of 1.27 mm. These polishing sheets are sequentially arranged from the upper part of the formed body (2-1) to
Numbered (2-91). Pieces for voidage measurement were sampled from each sheet. Some porosity results are shown in Table 1. Further, a polishing sheet for the lower layer portion was obtained in the same manner as in Example 1 (2-92). Further, each polishing sheet was punched into a disc shape of 24 inchφ size. PEF was attached to this polishing sheet as described above to obtain a polishing pad of a laminated body. Sheet numbers were assigned to the respective laminated body polishing pads, and the polishing pads (2-1) to (2-92) were numbered. (Example 2) (Preparation of polishing pad 3) The void-containing polyurethane molded product 3 was sliced in the same manner as described above to obtain 12 polishing sheets having a thickness of 1.27 mm. Further, a polishing sheet for the lower layer portion was obtained in the same manner as in Example 1 (3-13). These polishing sheets were numbered (3-1) to (3-13) in order from the top of the formed body.
A small piece was sampled from each polishing sheet for the measurement of porosity. Some porosity results are shown in Table 1.
Further, each polishing sheet was punched into a disk shape of 30 inchφ size. PE as described above on this polishing sheet
F was bonded to obtain a polishing pad of a laminated body. Sheet numbers were assigned to the respective laminated body polishing pads, and the polishing pads (3-1) to (3-13) were numbered.

[0037]

[Table 1]

(Measurement of Polishing Speed) The polishing characteristics of the obtained polishing pad were evaluated by a CMP polishing apparatus (SPP-600S manufactured by Okamoto Machine Tool Co., Ltd.) using a silicon wafer on which an oxide film was deposited. At this time, 150 g / m of silica slurry (RD97001 manufactured by Fujimi Incorporated) adjusted to pH 11 was used as the slurry.
polishing flow of 350 g / cm ² , while flowing at a flow rate of in,
Polishing pad rotation speed 35 rpm, wafer rotation speed 33 rpm
A polishing experiment was conducted at. As a wafer used for evaluation, a 6-inch silicon wafer having a thermal oxide film deposited thereon in a thickness of 1 μm was used, and an average polishing rate after polishing to 0.5 μm was obtained. Table 2 shows the polishing rate results of the polishing pads in Examples and Comparative Examples. In addition, the polishing pad obtained in Example 2 was further punched into 24 inchφ for use in order to match with the evaluation machine.

[0039]

[Table 2]

[0040]

According to the present invention, a polishing pad having high uniformity of polishing characteristics in the same lot can be obtained with high productivity. Further, it is possible to obtain a uniform polishing pad in which there is little change in polishing characteristics during polishing and there is no difference in characteristics between the inner circumference and the outer circumference of the pad.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Shimomura 2-1-1 Katata, Otsu City, Shiga Toyo Spinning Co., Ltd., Research Institute (72) Inventor Hiroshi Seyanagi 1--17, Edobori, Nishi-ku, Osaka City, Osaka Prefecture No. 18 Toyo Tire & Rubber Co., Ltd. (72) Inventor Kazuyuki Ogawa 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Tire & Rubber Co., Ltd. (56) Reference JP 2000-344850 (JP, A) JP HEI 2-250766 (JP, A) JP-A-11-204468 (JP, A) International publication 00/012262 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) B24B 37/00 H01L 21/304 622 C08J 5/14 CFF

Claims (5)

(57) [Claims] 1. An uncured urethane prepolymer and high
A cavity-containing urethane molded article for a polishing pad, which is obtained by charging a raw material composition containing a molecularly foamed microelement into a mold and curing the composition, wherein the urethane molded article has a thickness of 100.
mm or less, 20 mm or more, and the urethane molded product
The difference in apparent specific gravity between the upper layer, middle layer and lower layer is
The void-containing urethane molded article for a polishing pad , which has an apparent specific gravity of 5% or less . 2. The void-containing urethane molded article for a polishing pad according to claim 1, wherein the difference in apparent specific gravity is within 3% based on the apparent specific gravity of the upper layer portion. 3. A method for producing a polishing sheet, which comprises forming the void-containing urethane molded article for polishing pad according to claim 1 or 2 by slicing. 4. A polishing sheet produced by the method according to claim 3. 5. A polishing pad manufactured by laminating a cushion layer to the polishing sheet according to claim 4.