JP2001244223A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad where fluctuation in polishing speed and accuracy is small even if the thickness of the polishing pad is reduced by dressing. SOLUTION: This polishing pad is used for polishing a surface, particularly, for flattening a semiconductor wafer or forming wiring, and consists of a macromolecular porous body. In this case, the polishing surface has at least one independent bubble per cm2 with an average hole diameter of 0.3 mm or more, and at least 100 independent bubbles per cm2 with an average hole diameter of 0.1 mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a surface by a combination of a mechanical action and a chemical action used for flattening a semiconductor wafer and forming a wiring (hereinafter, referred to as a CMP method). Polishing pad to be used.

[0002]

2. Description of the Related Art As semiconductor wafers have been multi-layered due to their higher integration density, it has become important to finish the surface flat. For this purpose, the surface of the semiconductor wafer is polished by a CMP method. Things are starting to happen. In this method, polishing is performed by a polishing pad while a slurry comprising an abrasive and a chemical component is supplied to the surface of a semiconductor wafer.

As a polishing pad used for this polishing, a polishing pad made of a nonwoven fabric impregnated with a polyurethane resin, a foamed polyurethane resin or the like is generally used. The surface of the polishing pad on the side of polishing the semiconductor wafer is generally hard, and a hardness of about 55 in Shore D standard is used.

In the polishing process, a silica slurry in which fine-particle silica is dispersed in water is usually used, and the pad surface is processed to uniformly supply the slurry to the pad surface. For example, in general, FIGS.
As shown in FIG. 5, holes 2 are formed in the surface of the foamed polyurethane to hold the slurry. As the holes 2, for example, holes 2 having a diameter of 1.5 mm are formed over the entire surface of the polishing pad at intervals of 5 mm. The holes 2 are formed by punching or the like after molding the foamed polyurethane. Further, in order to smoothly supply the abrasive, as shown in FIGS. 5 and 6, grooves 3 having a lattice shape, a radial shape, a concentric shape, a spiral shape, or the like are provided on the surface of the foamed polyurethane. The grooves 3 are generally provided by cutting or the like after molding urethane foam.

[0005]

The hole 2 or the groove 3 is formed by post-processing after forming urethane foam by punching or cutting. For example, if holes having a diameter of 1.5 mm are provided at 5 mm intervals as in the above-described example, if the size of the polishing pad is 600 mmΦ, the number of holes increases to several hundreds or more, and the processing operation requires large cost and time. I have. The polishing pad is dressed as dressing as a measure to reduce the polishing rate due to clogging caused by polishing and to reduce polishing accuracy due to uneven wear of the pad surface. The dressing causes a new polishing surface to appear on the polishing pad surface, which has the effect of restoring the polishing accuracy and polishing speed. However, the thickness of the polishing pad decreases with dressing, and the depths of the holes 2 and the grooves 3 are reduced. Decrease. When the depth decreases, the amount of the polishing agent held in the holes 2 and the grooves 3 changes, so that the polishing speed and polishing accuracy of the semiconductor wafer change, which causes variation in polishing quality. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a polishing pad having less variation in polishing rate and polishing accuracy even when the thickness of the polishing pad is reduced by dressing.

[0006]

That is, the present invention relates to a polishing pad used for surface polishing, particularly for flattening a semiconductor wafer and forming wiring, which is made of a porous polymer material and whose polishing surface is 0.3 mm. 1 closed cell with the above average pore size / cm
100 or more closed cells having an average pore diameter of ² or more and 0.1 mm or less
The present invention relates to a polishing pad characterized in that the polishing pad has at least one polishing pad / cm ² .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1 and FIG.
A group and 6 closed cells having a small pore size are homogeneously contained (see FIGS. 1 and 2). When the cut surface is observed, the closed cells having a large pore size are 0.3 mm or more, preferably 0.5 to 2 m.
m having an average pore diameter of 1 / cm ² or more, preferably 2
5 / cm ² or, small closed cells having a pore diameter of preferably 0.1mm or less that of the average pore size of 0.01~0.08mm 100 / cm ² or more, preferably having 300 to 800 pieces / cm ² It becomes. Large closed cell diameter of 0.3
If it is less than mm, the function of supplying the abrasive to the entire surface is reduced, and the polishing rate is reduced. On the other hand, if the diameter of the closed cell having a small pore diameter exceeds 0.1 mm, the local holding ability of the abrasive is reduced, and the polishing rate is undesirably reduced.

The material of the porous polymer according to the present invention is not particularly limited, but a thermosetting resin having a small creep characteristic is preferable. Examples thereof include epoxy resins, polyester resins, polyurethane resins, dicyclopentadiene resins, phenol resins, urea resins, and melamine resins. Among these, polyurethane resins are preferable because of their excellent wear resistance. As a means for forming closed cells having different pore sizes, it is possible to use a foaming agent having a different particle size.However, it is possible to mix small-sized plastic hollow particles with a thermosetting resin containing a foaming agent and foam the mixture. Thereby, a polymer porous body in which closed cells having a large pore size and closed cells having a small pore size are uniformly dispersed can be obtained.

As the foaming agent, a chemical foaming agent such as bicarbonate, azo compound, hydrazine compound, semicarbazozide compound, azide compound, triazole compound, nitroso compound and the like, water and the like can be used. By using 0.1 to 2 parts by weight per part, a porous body having an expansion ratio of about 1.5 to 2 times can be obtained. As the plastic hollow particles, particles composed of an acrylic resin, an acrylonitrile-vinylidene chloride copolymer, a phenol resin or the like can be used. Among these, hollow particles made of an acrylonitrile-vinylidene chloride copolymer can be preferably used because the shape is close to a true sphere and the particle diameter can be adjusted. The amount of the hollow particles is 0.5 to 100 parts by weight of the base resin.
5 parts by weight, preferably 1 to 3 parts by weight.

The polishing pad according to the present invention is a polymer porous body having a group of closed cells having different pore diameters. Since closed cells having a large pore diameter and closed cells having a small pore diameter are uniformly distributed, the polishing pad of the polishing pad has Even if the thickness decreases due to wear, new large diameter holes appear one after another, so there is no need to separately provide holes and grooves unlike conventional polishing pads, and the variation in polishing speed and polishing accuracy of semiconductor wafers is improved. Is done.

[0011]

The embodiments of the present invention will be described below with reference to examples. Example 1 The materials shown in Table 1 were degassed and mixed in a vacuum vessel for 10 minutes, filled in a mold at a mold temperature of 60 ° C., and a molded product having a thickness of 10 mm was obtained. Heat treatment was carried out to completely cure. Then, it was sliced to a thickness of 2 mm to obtain a polishing pad. Table 2 shows the specifications of the obtained polishing pad. For comparison, a urethane foam using water as a foaming agent in a polyurethane resin as a prior art product was used as a material.
The case where the groove 3 is present as shown in FIGS. 5 and 6 and the case where the groove 3 is not present were also implemented. A polishing pad shown in Table 2 was wrapped by Nippon Engis Co., Ltd. (trade name: I
MPTEC 10DVT), 0.45MP load
a, contained 12% by weight of fumed silica under the conditions of a rotation speed of 60 rpm, polishing for 2 minutes, and dressing for 2 minutes;
A polishing test was performed on a silicon thermal oxide film formed on a silicon wafer using a silica slurry of H11. Table 3 shows the obtained results.

[0012]

[Table 1] Polyol: High cast N4014A (trade name) Polyisosonate: High cast N4014B (trade name) Hollow particles: Microsphere F-80 (trade name)

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

As is evident from the results shown in Table 3, according to the present invention, it is possible to provide a polishing pad with less variation in polishing rate and polishing accuracy even when the thickness of the polishing pad is reduced by dressing. It has become possible.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG. 2;

FIG. 3 is a plan view showing an example of a conventional polishing pad.

FIG. 4 is a sectional view taken along line BB in FIG. 3;

FIG. 5 is a plan view showing another example of a conventional polishing pad.

FIG. 6 is a cross-sectional view taken along the line CC in FIG. 5 (in FIGS. 3 to 6, the shape of fine holes generated in the case of urethane foam is omitted)

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polishing pad 2 hole 3 Groove 4 Polishing surface 5 Large diameter hole 6 Small diameter hole

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ryoji Kose 1150 Goshomiya, Odate, Shimodate-shi, Ibaraki F-term in Goshomiya Office, Hitachi Chemical Co., Ltd. 3C058 AA07 AA09 CA01 CB01 DA02 DA12 4F071 AA25X AA33 AA34X AA39 AA41 AA42 AA43 AA53 AA76 AE01 AF22 AH16 DA13 DA20 4F074 AA37 AA48 AA49 AA59 AA63 AA64 AA65 AA78 BA03 BA13 BA14 BA15 BA16 BA17 BA18 BA20 CA23 DA02 DA03 DA12 DA56

Claims (4)

[Claims] 1. A polishing pad used for surface polishing of an object surface, which is made of a polymer porous material and whose polishing surface is 0.3
1 / cm ² or more closed cells with an average pore size of
100 closed cells having an average pore diameter of 0.1 mm or less / cm
A polishing pad comprising ^two or more polishing pads. ^2. A thermosetting resin foam in which the polymer porous body has at least one closed cell having an average pore size of 0.3 mm or more / cm ² , and plastic hollow particles having an average particle size of 0.1 mm or less. The polishing pad according to claim 1, comprising: 3. The thermosetting resin foam is a polyurethane resin foamed with a chemical foaming agent or water as a foaming agent,
3. The polishing pad according to claim 1, wherein the plastic hollow particles are an acrylonitrile-vinylidene chloride copolymer. 4. The polishing pad according to claim 1, wherein the polishing pad is used for flattening the surface of a semiconductor wafer.