JPH0957608A - Polishing pad and polishing method for work to be surface-treated using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad and a polishing method, capable of performing polishing well even if the polished surface of a work to be surface- treated such as a large-aperture semiconductor wafer has the large area. SOLUTION: A polishing pad 10 is constituted by sticking a soft porous sheet 12 to serve as an absorbing, holding and discharging layer for abrasive fluid L onto the lower surface of a polishing cloth 11 on which many through holes 11A are provided at specified pitches. In a polishing method, the polishing pad 10 is fixed on the front surface of a polishing surface plate 31 so that the polishing cloth 11 side may face to the outside, and abrasive fluid is supplied onto the front surface of the polishing pad 10 in the downstream polishing surface plate which has polished the semiconductor wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing pad suitable for polishing a surface-treated workpiece having a particularly large surface to be polished, such as a semiconductor wafer, and a surface using the same. The present invention relates to a polishing method for a processed workpiece.

[0002]

2. Description of the Related Art First, a polishing pad currently in use and a polishing method for a surface-treated workpiece using the same will be described with reference to FIGS. 5 is a cross-sectional view of a current polishing pad fixed to a polishing platen, FIG. 6 is a schematic partial plan view of a current polishing apparatus, and FIG. 7 is shown in FIG. It is a sectional view on the AA line of a polisher.

Since the conventional polishing pad is made of a resin such as polyurethane having a flat surface without irregularities, when polishing a large-diameter semiconductor wafer or the like, the polishing liquid is a semiconductor. It was difficult to penetrate from the outer peripheral portion of the wafer to the central portion, and polishing with good in-plane uniformity could not be performed. Therefore, in order to improve the in-plane uniformity of the polishing, as shown in FIG. 5, in the current polishing pad 1, a large number of liquid reservoir holes 2 are formed on the surface thereof and the liquid reservoir holes 2 are polished. The liquid is stored, and the surface 3 excluding the liquid storage holes 2 polishes the surface to be polished of the surface-treated workpiece. The polishing pad 1 may be made of, for example, a polyurethane foam material, in which case the foam hole serves as the liquid reservoir hole 2. There is also a polishing pad 1 made of, for example, a polyurethane sheet-like non-woven fabric, and the liquid reservoir holes 2 in this case are groove-shaped or groove-shaped holes formed by pressing in a grid pattern. In some cases. In any case, the liquid reservoir hole 2 does not penetrate in the thickness direction of the polishing pad 1 and has a bottom.

In the case of polishing a semiconductor wafer which is a surface-treated workpiece, the polishing pad 1 is used and the polishing apparatus 30 having the configuration shown in FIGS. 6 and 7 is used. This polishing apparatus 30 has, for example, a diameter of the semiconductor wafer S of 2
A disk-shaped polishing platen 31 having a flat surface with an area having a diameter more than twice and rotating in the direction of arrow Ra at, for example, 30 rpm around a rotating shaft 32, and a surface to be surfaced above the polishing platen 31. A semiconductor wafer S, which is a processed product, is held by a means such as a vacuum chuck device 33 having a porous structure, and is rotated from the rotation axis 32 during polishing, for example, to the center of the radius of a polishing platen 31. There is a shaft 34, for example, at 30 rpm, which is the same as the number of rotations of the polishing platen 31,
It is composed of a holding plate 35 that can rotate in the same rotation direction as the arrow Rb, and a nozzle 37 that supplies the polishing liquid L to the center of rotation of the polishing platen 31. . Reference numeral 36 is a through hole 36 opened in the center of the rotary shaft 34 and communicating with the vacuum chuck device 33.
And is connected to a vacuum pump (not shown).

In polishing the semiconductor wafer S,
The vacuum pump is operated to hold the surface to be polished downward in a horizontal state by the vacuum chuck device 33, while the polishing pad 1 is placed on the horizontal surface of the polishing platen 31 and the polishing surface 3 is placed upward. Stick with an adhesive, etc., and then polish this surface plate 3
1 is rotated in the direction of the arrow Ra at the number of rotations, the polishing liquid L is supplied to the surface 3 of the polishing pad 1 from the nozzle 37, and the holding plate 35 holding the semiconductor wafer S is indicated by the number of rotations. The surface to be polished of the semiconductor wafer S is the surface 3 of the polishing pad 1 while being lowered while rotating in the direction of Rb.
And press it with a predetermined pressing force. In this way, the surface to be polished of the semiconductor wafer S is polished.

[0006]

However, even if the polishing apparatus 30 and the polishing pad 1 are used for polishing, the polishing liquid L is used.
Remains in the liquid reservoir hole 2 of the polishing pad 1 and the replacement thereof is bad, so that the polishing result is not so good. Moreover, since the diameter of semiconductor wafers has been recently increased, in-plane uniformity of polishing is particularly required for polishing semiconductor wafers of this large diameter. Therefore, it is necessary to develop a good polishing pad and polishing method. It has been demanded. An object of the present invention is to solve such a problem, and a polishing pad and a polishing method capable of satisfactorily polishing even a surface to be polished of a surface-treated workpiece having a large area. The purpose is to obtain.

[0007]

Therefore, according to the polishing pad of the present invention, a flexible porous material serving as a layer for absorbing, holding and discharging a polishing liquid is formed on the lower surface of a polishing cloth having a large number of through holes formed at a predetermined pitch. The problem was solved by adopting a structure in which a quality sheet is attached.

Further, in the polishing method of the present invention, the surface is finished to be a flat surface, and the polishing pad of the present invention is placed on the surface of a polishing platen which rotates at a predetermined number of revolutions with the polishing surface side being outside. The polishing surface of the polishing cloth is fixed, and the surface to be polished of a surface-treated workpiece such as a semiconductor wafer is fixed to the surface of the polishing cloth at a predetermined rotation number about a rotation axis different from the rotation axis of the polishing surface plate. And abutting while rotating in the same rotation direction, in such a polishing state of the surface-treated workpiece and the polishing pad, the downstream side immediately after polishing the surface to be polished of the surface-treated workpiece The problem has been solved by adopting a method of supplying a polishing liquid to the surface of the polishing pad on the polishing platen.

Therefore, according to the polishing pad of the present invention and the method of polishing a surface-treated workpiece using the same, the polishing cloth is uniformly polished by the cushioning action of the flexible porous sheet. The flexible porous sheet can be brought into contact with the surface, and due to the pumping action of this flexible porous sheet,
Since the polishing liquid can be absorbed, retained, and discharged, the polishing rate in the surface to be polished becomes constant, and polishing with good uniformity can be performed. Furthermore, since the polishing method of the present invention employs a method of supplying a polishing liquid to the polishing pad surface on the downstream polishing plate immediately after polishing the surface-treated workpiece, a predetermined pressing force is applied. The flexible porous sheet that has been pressed with can automatically absorb the fresh polishing liquid supplied by its restoring action.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a polishing pad of the present invention and a method for polishing a surface-treated workpiece using the same will be described with reference to FIGS. FIG. 1 is an enlarged cross-sectional view of a polishing pad according to a first embodiment of the present invention fixed to a polishing platen, and FIG. 2 is a schematic view showing an embodiment of a polishing apparatus of the present invention. 3 is a plan view of a portion, FIG. 3 is a cross-sectional view of the polishing apparatus shown in FIG. 2 taken along the line AA, and FIG. 4 is a second embodiment of the present invention shown in a state of being fixed to a polishing surface plate. It is an expanded sectional view of a polishing pad. Note that FIGS.
The same reference numerals are given to the same components as those shown in FIG.

In FIG. 1, reference numeral 10 indicates a polishing pad which is a first embodiment of the present invention. This polishing pad 10
Is a polishing cloth 11 in which a large number of independent fine through holes 11A and polishing surfaces 11B are formed at a predetermined fine pitch, and a polishing liquid absorbed on the lower surface thereof,
It is formed in a double structure with a flexible porous sheet (hereinafter, simply abbreviated as “porous sheet”) 12 serving as a holding and discharging layer. The polishing cloth 11 has, for example, a thickness of 1 to 3.
mm polyester resin non-woven fabric, through-hole 11
The diameter of A is about 1 to 10 mm, and the most preferable diameter is 2 to 3 mm. Further, the porous sheet 12 is, for example, a foamed body of polyester resin having a thickness of 1 to 3 mm, and is an elastic body formed by connecting pores like a sponge-like sheet.

Next, the operation and effect of the polishing pad 10 having such a structure will be described. The polishing liquid supplied to the surface of the polishing pad 11 first enters through the through holes 11A and is absorbed and retained in the layer of the porous sheet 12. When polishing a large-diameter semiconductor wafer S, which is a workpiece to be surface-treated, with the polishing surface 11B of the polishing pad 10 in which the polishing liquid is held in this manner, the surface to be polished of the semiconductor wafer S is polished as described above. While being pressed against the surface 11B, the surface to be polished of the semiconductor wafer S is polished by the frictional force generated by the pressing force in that case and the supply of the polishing liquid.

The polishing liquid crushes the layer of the porous sheet 12 by the pressing force during polishing, and is discharged through the through holes 11A in the crushed portion, and is applied to the surface to be polished of the semiconductor wafer S being polished. It overflows and is supplied to the entire surface to be polished. Next, when the polishing pressure is no longer applied, the layer of the porous sheet 12 in the crushed portion swells in an attempt to restore the original state, but at this time, the polishing liquid is automatically absorbed.

The layer of the porous sheet 12 during polishing supplies the polishing liquid to the entire surface to be polished of the semiconductor wafer S while performing a so-called pumping action of repeating absorption, retention and discharge of the polishing liquid in this manner. Therefore, the polishing rate in a wide surface to be polished becomes constant, and polishing with good uniformity can be performed.

Next, with reference to FIG. 2 and FIG. 3, a polishing apparatus for polishing by utilizing the delicate action of the polishing pad 10 described above and a polishing method using the same will be described. The polishing apparatus 30A having the configuration shown in FIGS. 2 and 3 includes, for example, a flat surface having an area having a diameter twice or more the diameter of the semiconductor wafer S, and the arrow R at the rotation axis 32 at 30 rpm, for example.
A disk-shaped polishing platen 31 that rotates in the direction of a, and a semiconductor wafer S, which is a surface-treated workpiece, are provided above the polishing platen 31 by means such as a vacuum chuck device 33 having a porous structure. The rotating shaft 34 is held at the center of the radius of the polishing platen 31 and is separated from the rotating shaft 32 during polishing.
For example, the number of rotations of the polishing platen 31 is equal to 3
It is the same as the construction of the above-mentioned working polishing apparatus 30 in that it is constituted by a holding plate 35 capable of rotating at 0 rpm in the same rotation direction as indicated by the arrow Rb. Reference numeral 36 is a through hole 36 opened in the center of the rotary shaft 34 and communicating with the vacuum chuck device 33, and is connected to a vacuum pump (not shown).
It is similar to the polishing device 30.

In the polishing apparatus 30A of the present invention, a nozzle 37 is disposed above the polishing platen 31 on the downstream side immediately after polishing the surface to be polished of the semiconductor wafer S, and the polishing platen is provided. The polishing liquid is supplied to the surface of the polishing pad 10 attached to the surface of 31.

When the semiconductor wafer S is polished by using the polishing apparatus 30A having such a structure, the vacuum pump is operated so that the surface to be polished is faced down.
While holding the polishing pad 10 in a horizontal state by using an adhesive or the like with the polishing surface 3 facing upward on the horizontal surface of the polishing platen 31, and then rotating the polishing platen 31 by the rotation. Rotate by the number in the direction of arrow Ra, and polish pad 1
The polishing liquid L is supplied from the nozzle 37 to the surface 3 of the semiconductor wafer S, and the holding plate 35 holding the semiconductor wafer S is lowered while rotating in the direction of the arrow Rb at the number of rotations. It is brought into contact with the surface 3 of the polishing pad 1 and pressed with a predetermined pressing force.

When the polishing pad 10 is sequentially and partially pressed against the holding plate 35 and the semiconductor wafer S, the layer of the porous sheet 12 in the pressed portion is crushed and held by the layer. The polishing liquid L present is discharged through the through holes 11A in the crushed portion, overflows the polishing surface 11B and the surface to be polished of the semiconductor wafer S being polished, and is supplied to the entire surface to be polished. . Next, as the polishing platen 31 rotates, the portion of the porous sheet 12 that is crushed by the pressing force of the semiconductor wafer S changes sequentially, and the porous sheet to which the pressing force has been applied until now is changed. 12
When the pressing force is no longer applied to the portion, the pressed portion bulges in an attempt to restore to the original state, and at this time, the polishing constant on the downstream side immediately after polishing the surface to be polished of the semiconductor wafer S is finished. The fresh polishing liquid L sequentially supplied from the nozzle 37 arranged above the disk 31 is automatically absorbed and held by the pumping action. In this way, the semiconductor wafer S is polished in a state where the polishing rate in the surface to be polished is constant and with uniform polishing.

Next, referring to FIG. 4, the second embodiment of the present invention will be described.
The polishing pad 20 which is an embodiment of the above will be described. In the polishing cloth 11 of the first embodiment, a part of the polishing liquid L absorbed and retained in the portion of the porous sheet 12 to which the pressing force has been applied escapes in the horizontal direction, and the periphery of the pressed portion. Therefore, the polishing efficiency tends to be reduced. The polishing pad 20 of the second embodiment of the present invention shown in FIG. 4 improves on this drawback.

The polishing pad 20 corresponds to the polishing pad 1 described above.
The welding line 13 is formed in a unit of an area where a suitable number of the through holes can face and exist on the porous sheet 12A of 0. Therefore, these welding lines 13 play the role of a barrier, and due to the existence of the welding lines 13, the welding lines 13
The polishing liquid L absorbed and retained in the unit area portion surrounded by is discharged only from the limited number of through holes 11A of the polishing cloth 11 existing on the upper surface thereof, and the polishing liquid L of the adjacent other unit area portion is discharged. It does not flow into the through hole 11A.

These welding lines 13 are formed by the porous sheet 12.
Can be formed by instantaneously heating with a grid-like tooth profile formed with an interval width of about 5 to 20 mm. When the porous sheet 12A subjected to such a welding process is adhered to the polishing cloth 11, the weld line 13 has a reduced flexibility and porosity, and therefore has a cushioning effect. The pumping effect is also reduced,
Also, since the flatness of these welded parts has deteriorated,
It is preferable to select the spacing width so that each welding line 13 is not located on the lower surface of the through hole 11A, that is, is located on the lower surface of the cloth portion of the polishing cloth 11.

Therefore, when the polishing pad 20 is used for polishing, the polishing liquid L absorbed and held in a unit area portion by the function of the welding line 13 is discharged only from the through hole 11A in the portion to which the pressing force is applied. As a result, it is efficiently polished.

[0023]

As described above, according to the polishing pad of the present invention and the method for polishing a surface-treated workpiece using the same, the cushioning action of the flexible porous sheet allows the polishing cloth to be evenly surfaced. The flexible porous sheet can be brought into contact with the surface to be polished of the processed material, and the polishing liquid can be absorbed, retained, and discharged by the pumping action of the flexible porous sheet. The difference in polishing rate at the outer peripheral portion can be reduced, and extremely uniform polishing can be performed.
Therefore, the yield is improved.

Furthermore, since the polishing method of the present invention employs a method of supplying the polishing liquid to the surface of the polishing pad on the polishing platen on the downstream side immediately after the surface-treated workpiece is completely polished, The flexible porous sheet that has been pressed by the pressing force automatically absorbs the supplied fresh polishing liquid by its restoring action, and constantly discharges this fresh polishing liquid to the surface to be polished. In addition, a number of excellent effects such as improved polishing efficiency can be obtained.

[Brief description of drawings]

FIG. 1 shows the first of the present invention shown in a state of being fixed to a polishing platen.
FIG. 3 is an enlarged cross-sectional view of a polishing pad that is an example of the above.

FIG. 2 is a partial plan view schematically showing an embodiment of the polishing apparatus of the present invention.

3 is a cross-sectional view of the polishing apparatus shown in FIG. 2 taken along the line AA.

FIG. 4 shows a second embodiment of the present invention shown in a state of being fixed to a polishing platen.
FIG. 3 is an enlarged cross-sectional view of a polishing pad that is an example of the above.

FIG. 5 is an enlarged cross-sectional view of a current polishing pad shown in a state of being fixed to a polishing platen.

FIG. 6 is a partial plan view schematically showing a current polishing apparatus.

7 is a cross-sectional view taken along the line AA of the polishing apparatus shown in FIG.

[Explanation of symbols]

 10 Polishing pad which is the first embodiment of the present invention 11 Polishing cloth 11A Through hole 11B Polishing surface 12 Flexible porous sheet 12A Flexible porous sheet 13 Welding line 20 It is the second embodiment of the present invention. Polishing pad 30A Polishing device 31 Polishing platen 35 Holding plate 37 Nozzle L Polishing liquid S Semiconductor wafer

Claims (3)

[Claims] 1. A flexible porous sheet serving as a layer for absorbing, holding, and discharging a polishing liquid is attached to the lower surface of a polishing cloth having a large number of through holes formed at a predetermined pitch. Polishing pad to be used. 2. The polishing pad according to claim 1, wherein the flexible porous sheet is provided with a welding line in a unit of an area in which a predetermined number of the through holes can face and exist. . 3. The surface is finished to be a flat surface, and the polishing pad according to claim 1 is fixed to the surface of a polishing surface plate that rotates at a predetermined rotation speed, with the polishing cloth side facing outward, and the polishing is performed. The surface to be polished of the surface-treated workpiece is brought into contact with the surface of the cloth while rotating in the same rotation direction as the polishing surface plate at a predetermined number of rotations around a rotation axis different from the rotation axis of the polishing surface plate. Then, in the polishing state of such a surface-treated workpiece and a polishing pad, the polishing pad surface on the polishing platen on the downstream side immediately after finishing polishing the surface to be polished of the surface-treated workpiece A method for polishing a surface-treated workpiece, which comprises polishing while supplying a polishing liquid.