JP2002192454A - Method of manufacturing for cavity-containing urethane molding, and abrasive pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To productively provide an abrasive pad that is highly uniform in polishing characteristics with another in the same lot, and that shows few changes in the polishing characteristics during polishing and is homogeneous or without a difference in characteristics between the inner and outer circumferential portions. SOLUTION: A method of manufacturing for an abrasive pad produces the abrasive pad by putting and curing an uncured urethane prepolymer in a die and slicing a resultant cavity-containing urethane block, wherein the thickness of the block is set between 5 mm and 100 mm inclusive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 and ceramic plates, etc., which require high surface flatness. The present invention relates to a polishing pad for performing a flattening process stably at a high polishing rate and a method for manufacturing the same. The polishing pad of the present invention is preferably used particularly in a step of flattening a silicon wafer and a device on which an oxide layer, a metal layer, and the like are formed, before further laminating and forming these layers. is there.

[0002]

2. Description of the Related Art Semiconductor integrated circuits (ICs, LSIs) are typically used as materials requiring high surface flatness.
And a disk of single-crystal silicon called a silicon wafer. Silicon wafer, IC, LS
In a manufacturing process such as I, in order to form a reliable semiconductor junction of various thin films used for forming a circuit, it is required to finish the surface with high precision and flatness in each thin film forming process.

Generally, a polishing pad is fixed to a rotatable support disk called a platen, and a semiconductor wafer is fixed to a disk called a polishing head capable of revolving and revolving. The relative rotation between the platen and the polishing head is generated by the two rotational motions, and a polishing slurry in which fine particles (abrasive grains) are suspended in a gap between the polishing pad and the wafer is added, so that polishing, A flattening process is performed. At this time, as the polishing pad moves over the wafer surface, the abrasive grains are pressed onto the wafer surface at the contact points. Therefore, the working surface is polished by a sliding dynamic frictional action between the wafer surface and the abrasive grains. Such polishing is usually referred to as CMP polishing.

The polishing operation in the CMP polishing step is performed by holding abrasive grains in a slurry in which fine particles (abrasive grains) are suspended on a polishing pad to be used. Therefore, the polishing rate increases as the holding density of the abrasive grains on the polishing pad increases. For this reason, a porous material having a large number of holes is usually used as a polishing pad, and by holding the abrasive particles in the holes, it is possible to increase the holding density of the abrasive particles and increase the polishing rate. Have been done. here,
In order to stabilize the polishing rate, it is necessary to suppress the variation in the cavity density 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 Japanese Patent Publication No. Hei 8-500622, which discloses a polishing pad in which hollow microspheres or a water-soluble polymer powder or the like is dispersed in a matrix resin such as polyurethane, is also known.

[0006]

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

In the production of a conventional void-containing urethane molded product, an uncured urethane prepolymer is put into a mold and cured, and the resulting void-containing urethane block is sliced to obtain a polishing pad. Causes a variation in the cavity density in the depth direction of the block. If this molded product is formed into a sheet by machining such as slicing and a polishing pad is obtained from the sheet, the density of cavities contained in each polishing pad varies within the same lot for the above-described reason.

[0008] The variation in the density of the contained cavities causes the variation in the holding density of the abrasive grains, that is, the variation in the polishing rate of the polishing pad obtained from the same lot. Also, the size of the cavity varies between inside and outside.

In general, in CMP polishing, clogging is performed by dressing a pad surface using a diamond grindstone or the like, and as in the initial state, a work of exposing a surface with exposed holes and reusing the same is performed. Will be At this time, if there is a variation in the density of the contained cavities in the depth direction, a variation in the density of the cavities exposed on the surface after dressing occurs in the same polishing pad. That is, the polishing rate becomes unstable even with the same polishing pad.

An object of the present invention is to reduce the variation in the cavity density of the void-containing urethane molded product, and to reduce the variation in the polishing rate of the polishing pad obtained therefrom within a lot and within the same pad.

[0011]

According to the present invention, there is provided a urethane block having a length in the depth direction of 100 mm or less, preferably 80 mm or less, more preferably 50 mm or less in the production of a void-containing urethane block for a polishing pad. It is characterized by reducing the variation in the density of the voids contained in urethane.

[0012] The polishing pad obtained by the above-described manufacturing method has a small variation in the contained cavity density in the lot and in the thickness direction of the pad itself, so that a variation in the polishing rate is small and a stable polishing rate can be obtained. .

The density of the contained cavities can be measured by the following method. (1) The obtained void-containing urethane molded product is sliced into sheets, and the void ratio of each sheet is measured. The porosity is calculated by the following equation (1): porosity (%) = 100 × (true specific gravity−apparent specific gravity) / true specific gravity. That is, it can be calculated by measuring the apparent specific gravity. (2) The obtained void-containing urethane molded product is sliced into a sheet, and the sheet is sliced to a certain thickness and observed under a microscope. The cavity density is measured by capturing the image with a device such as a CCD camera and processing the image.

That is, the present invention is characterized in that the thickness difference of the void-containing urethane molded article is regulated to reduce the difference in the contained void density in the vertical direction of the molded article.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The void-containing urethane molded article of the present invention is obtained by polymerizing an isocyanate group-containing compound (polyisocyanate compound) and an active hydrogen group-containing compound (polyol compound) as a matrix. As a method for containing cavities, polymer foamed microelements (for example, Expancel (Nippon Philite)
Co., Ltd.) is dispersed and polymerized, foamed by mechanically stirring and bubbling, and a compound that generates a gas during the polymerization reaction is added. Among them, the method can be suitably adapted to a method using a polymer foamed microelement. Alternatively, a surfactant is added to one of the isocyanate group-containing compound and the active hydrogen group-containing compound, mixed with a non-reactive gas, and stirred to disperse the fine bubbles to form a bubble dispersion liquid, and polymerize the bubble dispersion liquid. It is formed by things.

The isocyanate compound is not particularly restricted but includes 4,4'-diphenylmetadisocyanate,
2,4'-diphenylmethane diisocyanate, 2,4
-Aromatic diisocyanate compounds such as toluene diisocyanate and 2,6-toluene diisocyanate, aliphatic diisocyanate compounds such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and 1,6-hexamethylene diisocyanate (HDI), and hydrogenation 4,4'-diphenylmethane diisocyanate (HMDI, trade name Hylen-W, manufactured by Huls),
Alicyclic diisocyanate compounds such as 1,4-cyclohexane diisocyanate (CHDI) and norbornane diisocyanate; The above compounds may be used alone or in combination.

In addition to the above-mentioned diisocyanate compound, 3
A polyfunctional polyisocyanate compound having a functional or higher functionality can also be used. As polyfunctional isocyanate compounds, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (Bayer) or trade name duranate (Asahi Kasei Kogyo). When these trifunctional or higher functional polyisocyanate compounds are used alone, they tend to gel during the synthesis of the prepolymer, and thus are preferably used by adding to the diisocyanate compound.

The active hydrogen group-containing compound is not particularly limited, but is an organic compound having at least two or more active hydrogen atoms, and a compound generally called a polyol compound or a chain extender in the 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 include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH).

The polyol compound is an oligomer having a molecular weight of about 500 to 10,000 based on a terminal group determination method,
The following polyether polyols and polyester polyols are exemplified.

The polyether polyols include polyoxypropylene polyols 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 adding ethylene oxide, polyols obtained by adding butylene oxide, styrene oxide, etc., and poly obtained by adding tetrahydrofuran to the polyhydric alcohol by ring-opening polymerization. Oxytetramethylene polyols can be exemplified. Copolymers using two or more of the above-mentioned cyclic ethers can also be used.

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

The above-mentioned void-containing urethane molded article 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 even more preferably 50 mm or less. In particular, it is preferably 35 mm or less.

If it is 100 mm or more, the distribution of the cavities due to the movement of the cavities during curing becomes large. In addition, the heat of the curing reaction inside is difficult to escape, and the inside of the block becomes hot, so the cavities expand and the size of the inner and outer cavities varies, and especially in the case of hollow beads, re-expansion causes a comparison with the upper and lower and peripheral parts The inner cavity becomes larger. Further, when the internal cavity is expanded and hardened, when the internal cavity is cooled, the cavity shrinks and the block is distorted. When the block is sliced, the pad itself becomes distorted.

Further, the block is maintained as an post cure in an environment at 70 to 180 ° C. for several hours, and is reacted with moisture in the air to completely cure or to crush excess isocyanate groups. In this case, the temperature does not become uniform immediately after the post-curing, or moisture does not enter the inside immediately, so that the uniformity of the quality in the block is also deteriorated.

When a polishing pad is obtained by slicing such a thick block, a pad having a different polishing characteristic is obtained depending on the position of the slice, or the polishing characteristic changes due to the pad being cut off during polishing. I can. Further, even in the same pad, the polishing characteristics are different between the center and the outer peripheral portion, so that uniform polishing may not be performed.

If the block is too thin, there is a danger of breaking when handling the block, and it is necessary to keep the mold accurately horizontal, and furthermore, the productivity is deteriorated, so that the block is 5 m.
m or more, preferably 10 mm or more. When the size of the block is rectangular, the shorter side is preferably 50 cm or more, more preferably 60 cm or more, even more preferably 70 cm or more.
Particularly preferably, it is 80 cm or more. In particular, in the case of such a large pad, reaction heat tends to be trapped inside, which is effective for applying the present invention.

The block thus obtained preferably has a difference in apparent specific gravity between the upper, middle and lower layers of 5% or less based on the apparent specific gravity of the upper layer. Furthermore, it is preferably within 4%, and particularly preferably within 3%. In addition, since the block usually expands slightly in the mold and bulges at the center, the bulge is removed and sliced later. The upper layer portion referred to here is a peripheral portion of a sheet obtained by removing 1.5 mm from the uppermost surface of the block after removing the swelling portion and then slicing the block to a thickness of 1.27 mm, and the lower layer portion is a block portion. Is a peripheral portion of a sheet sliced at a thickness of 1.27 mm from which 1.5 mm has been removed from the uppermost surface. The middle layer portion is the peripheral portion of the slice sheet having a thickness of 1.27 mm including the midpoint of the thickness of the block from which the raised portion has been removed.
In addition, the peripheral portion is a portion 10 cm inside the end cotton of the sheet.

The above blocks are sliced (canna type,
The sheet is sliced into a sheet having a predetermined thickness by a band saw method or the like. The sheet thickness at this time is often about 0.5 mm to 25 mm, and more preferably 0.7 mm to 1.7 mm in the case of a pad for CMP. The thickness unevenness of the whole is preferably R ≦ 50 μm, more preferably R ≦ 20 μm, and even more preferably R ≦ 10 μm.

A polishing pad is punched out of the sheet into a predetermined size. The shape of the polishing pad is selected depending on the device to be used and may be any of a square, a rectangle, a polygon, a circle, etc., but is preferably a circle. In the case of a circular shape, the diameter is preferably at least 50 cm, more preferably at least 60 cm, further preferably at least 70 cm, particularly preferably at least 80 cm.

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

[0031]

EXAMPLES (Measurement of apparent specific gravity) The apparent specific gravity was determined by accurately measuring the weight of a small piece (1 cm x 1.5 cm) sampled from a sheet obtained by slicing the above molded product in the thickness direction, and further using the small piece. High precision electronic hydrometer ED-1
It measured by 20T (made by MIRAGE), and apparent specific gravity was calculated | required. By substituting this value into the above equation (1), the cavity density in the thickness direction of the molded product can be obtained.

(Preparation of Hollow-Containing Polyurethane Block 1) Adiprene L-3 melted and temperature-controlled to 80 ° C.
25 (isocyanate terminated prepolymer, NCO = 9.
25% Uniroyal Co.) (1st component) Silicon foam stabilizer SH-192 as a surfactant in 3000 parts by weight
19 parts by weight (manufactured by Toray Dow Corning Silicone Co., Ltd.) and 90 parts by weight of Expancel 551DE (manufactured by Nippon Ferrite Co., Ltd.) as hollow beads were mixed, and the mixture was mixed with a whipping mixer (stirrer blade rotation speed = 3500 rpm). 5 minutes,
The mixture was stirred until it became a cream (meringue state) to obtain a foam dispersion liquid 1. This bubble dispersion liquid 1 was transferred to a planetary mixer and melted at 120 ° C. and kept warm to cure amine MT (methylenebis-0-chloroaniline, Ihara Chemical Co., Ltd.)
(The second component) (770 parts by weight) and mixed for about 2 minutes. 700 m width within the pot life with fluidity
m, height 80m in 700mm depth oven mold
m and cured, and post-cured for 6 hours in an oven adjusted to a temperature of 110 ° C. ± 10 ° C. to prepare a void-containing polyurethane block.

(Preparation of Hollow-Containing Polyurethane Block 2) A mixed solution was prepared in the same manner as in the above-mentioned molded article. This mixture was poured into an oven mold similar to the above to a height of 120 mm within a usable life having fluidity, and was cured.
Post-curing was performed for 6 hours in an oven adjusted to a temperature of ± 10 ° C. to prepare a void-containing polyurethane block 2.

(Preparation of Hollow-Containing Polyurethane Block 3) A mixed solution was prepared in the same manner as in the above-mentioned molded article. This mixed liquid is supplied to a potable fluid within a pot life of 830 mm and a depth of 8 mm.
A 20 mm height was cast into a 30 mm oven mold and cured, and post-curing was performed for 6 hours in an oven adjusted to a temperature of 110 ° C. ± 10 ° C. to produce a void-containing polyurethane block 3.

Example 1 (Preparation of Polishing Pad 1) The polyurethane block 1 containing cavities was sliced to a thickness of 1.27 mm with a slicer (VGW-125 manufactured by Amitec) while heating at about 50 ° C. I got one. The swelling portion was sliced after removal. These sheets were numbered as (1-1) to (1-59) in order from the top of the compact. Also, the sheet corresponding to the lower layer portion was sliced to 1.27 mm after removing the bottom by 1.27 mm, and
60. A small piece for measuring the cavity density was sampled from the periphery of each sheet. Some of the cavity density results are shown in Table (1). Also, 2 from each sheet
A punching polishing pad was obtained in a disk shape of 4 inchφ size. Double-sided tape (Sekisui Chemical Co., Ltd.)
It was bonded to PEF (independently foamed polyethylene foam) using double tack tape # 5782). This PE
F acts as a cushion layer. In addition, this PEF is double-sided tape (double tack tape # 5 manufactured by Sekisui Chemical Co., Ltd.).
673) to obtain a polishing pad of a laminate. A sheet number was assigned to each of the laminate polishing pads, and the respective polishing pads were numbered as polishing pads (1-1) to (1-60).

(Comparative Example 1) (Preparation of Polishing Pad 2) The void-containing polyurethane block 2 was sliced in the same manner as described above to obtain 92 sheets having a thickness of 1.27 mm. These sheets were numbered as (2-1) to (2-91) in order from the top of the formed body. From each sheet, a small piece for measuring the cavity density was sampled. Some cavity density results are shown in Table 1. In addition, a lower layer sheet was obtained in the same manner as in Example 1 (2-9).
2). Also, a polishing pad was punched out from each sheet in a disk shape of 24 inchφ size. PEF was bonded to this polishing pad as described above to obtain a polishing pad of a laminate. A sheet number is assigned to each of the laminate polishing pads, and the polishing pads (2-1) to (2-
92). (Example 2) (Preparation of polishing pad 3) The void-containing polyurethane block 3 was sliced in the same manner as described above to obtain 12 sheets having a thickness of 1.27 mm. Further, a lower layer sheet was obtained in the same manner as in Example 1 (3-13). These sheets were numbered as (3-1) to (3-13) in order from the top of the formed body. From each sheet, a small piece for measuring the cavity density was sampled. Table 1 shows some cavity density results.
Shown in Also, a polishing pad was punched out from each sheet into a disk having a size of 30 inchφ. PEF was bonded to this polishing pad as described above to obtain a polishing pad of a laminate. A sheet number is assigned to each of the laminate polishing pads, and the polishing pads (3-1) to (3) are respectively assigned.
-13).

[0037]

[Table 1]

(Measurement of polishing rate)
CMP polishing equipment (SPP-600 manufactured by Okamoto Machine Tool Co., Ltd.)
In S), the polishing characteristics were evaluated using a silicon wafer on which an oxide film was deposited. At this time, a silica slurry adjusted to pH 11 (manufactured by Fujimi Incorporated) was used as the slurry.
RD97001) at a flow rate of 150 g / min, a polishing load of 350 g / cm ² , and a polishing pad rotation speed of 35.
A polishing experiment was performed at 33 rpm at a wafer rotation speed of 33 rpm. The wafer used for the evaluation was a 6-inch silicon wafer on which a thermal oxide film was deposited at 1 μm, and the average polishing rate when polishing was performed at 0.5 μm was obtained. Table 2 shows the polishing rate results of the polishing pads in Examples and Comparative Examples. Example 2
In order to match the pad obtained in,
Inchφ was used for punching.

[0039]

[Table 2]

[0040]

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

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuo Shimomura 2-1-1 Katata, Otsu-shi, Shiga Inside Toyobo Co., Ltd. Research Institute (72) Inventor Hiroshi Seyanagi 1-17-Edobori, Nishi-ku, Osaka-shi, Osaka 18 Toyo Tire & Rubber Co., Ltd. (72) Inventor Kazuyuki Ogawa 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka F-term in Toyo Tire & Rubber Co., Ltd.

Claims (3)

[Claims] 1. A method in which an uncured urethane prepolymer is put into a mold, and a polishing pad is obtained by slicing a void-containing urethane block obtained by curing, wherein the thickness of the block is 100 mm or less and 5 mm or more. A method for manufacturing a polishing pad. 2. A polishing pad obtained by the method according to claim 1. 3. A void-containing urethane block for obtaining a polishing pad by slicing, wherein the difference in apparent specific gravity between the upper layer, the middle layer and the lower layer of the block is within 5%. Urethane blocks containing cavities for polishing pads.