JPH10294301A - Method for polishing semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the clogging of the polishing cloth used in CMP securely and to prevent the occurrence of damages. SOLUTION: In the process for polishing a semiconductor water with polishing agent being flowed in a polishing cloth 7 in a semiconductor wafer, ice is included in the solid component of the polishing agent. Furthermore, the ice remaining at a vacuum part 9 at the surface of the polishing cloth 7 is melted by heating the polishing cloth 7 after the polishing is finished. Thus, the stable control of the polishing amount is performed, and the damage occurring in the semiconductor wafer is prevented. In this way, the reduction in yield is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for performing mechanical chemical polishing, which is a step of flattening a semiconductor wafer.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, as a method for flattening a semiconductor wafer, CMP (Chemical Mechanical Polishing) is hereinafter referred to as CMP.
ing) is used. In CMP,
For example, a polishing cloth made of polyurethane and an abrasive obtained by suspending SiO2 particles having a particle diameter of 5 to 300 nm in an alkaline solution such as KOH or amine is used. For example, polishing is performed by a polishing apparatus shown in FIG. Will be

In the polishing apparatus shown in FIG. 2, a polishing cloth 3 is set on a turntable 2 and rotates with the rotation of a main shaft 1. The wafer 6 is held by the rotary head 5 by suction, and rotates while being pressed by the pressing shaft 4. When viewed from the wafer 6, the wafer 6 itself rotates and the polishing pad 3 revolves. Further, the pressurizing shaft 4 may swing with respect to the main shaft 1 by forward and backward movement.

[0004] As the polishing process is performed, SiO2 particles contained in the polishing agent are clogged in the pores on the surface of the polishing cloth, and this lowers the polishing rate. It becomes difficult to control the amount of polishing. In order to prevent this, it is necessary to dress the polishing cloth 3 periodically.

As a method of dressing the polishing cloth 3, clogging of the polishing cloth surface and removal of foreign substances have been carried out by brushing using a diamond electrodeposition jig or a ceramic blade while flowing water through the polishing cloth 3. .

[0006]

However, in the above-mentioned conventional method, since it is performed by brushing using a diamond electrodeposition jig or a blade, it is difficult to reliably remove clogging on the polishing cloth surface. In addition to this, there is a problem that the surface of the polishing pad is scratched.

FIG. 3 shows a state in which SiO 2 particles (abrasive solid component) contained in the abrasive are clogged in the pores 9 on the surface of the polishing cloth 3 made of the abrasive main material 7. I have. This makes it difficult to restore the polishing rate to its original state even after dressing.
FIG. 4 shows a state in which the surface of the polishing pad is scratched. As a result, the surface of the polished semiconductor wafer may be damaged, resulting in a decrease in the yield of the semiconductor device.

Accordingly, an object of the present invention is to provide a method for polishing a semiconductor wafer which can suppress generation of scratches on a polishing cloth and reliably remove clogging of the polishing cloth by including ice in a solid component of the polishing slurry. The purpose is to do.

[0009]

According to a method of polishing a semiconductor wafer of the present invention, in the step of polishing the semiconductor wafer while adding a polishing agent between the semiconductor wafer and the polishing pad, the solid component of the polishing agent is mixed with ice. And polishing the semiconductor wafer. According to one aspect of the method of polishing a semiconductor wafer of the present invention, the method further comprises, after the polishing step, a step of melting the ice on the polishing cloth by heating the polishing cloth. According to one aspect of the method for polishing a semiconductor wafer of the present invention, the polishing agent is an alkaline aqueous solution. According to one aspect of the method of polishing a semiconductor wafer of the present invention, in the step of melting ice on the polishing cloth, the ice on the polishing cloth is melted by flowing hot water on the polishing cloth.

Since the abrasive of the present invention uses a solid component as ice, even if ice is clogged in the pores on the surface of the polishing cloth, even if mechanical dressing is not performed,
Since the ice melts, clogging can be eliminated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described. FIG. 2 as described above
In the polishing apparatus shown in FIG. 1, an alkaline aqueous solution containing ice is flowed as an abrasive onto the polishing pad 3 to remove the semiconductor wafer 6.
During polishing, the polishing agent is made to exist between the semiconductor wafer 6 and the polishing pad 3 to promote polishing.

After the polishing process is completed, ice particles on the polishing cloth or ice particles (8 in FIG. 3) entering pores on the polishing cloth surface (9 in FIG. 1) generate frictional heat due to polishing, or Dissolves at atmospheric temperature.

As described above, according to the present invention, even if dressing is not performed, clogging unlike the related art does not occur. Therefore, the polishing pad does not deteriorate as shown in FIG.

Next, a second embodiment of the present invention will be described. In the first embodiment described above, when the polishing process is continuously performed, the temperature of the polishing cloth surface is constantly cooled, and ice on the polishing cloth may not be completely melted.
The second embodiment is an embodiment for this case. After performing the processing of the first embodiment described above, the polishing pad 3 is heated. For example, by flowing warm water of about 40 ° C. on the polishing cloth 3, ice particles on the polishing cloth or ice particles (8 in FIG. 3) entering pores (9 in FIG. 1) of the polishing cloth surface become Can be forcibly dissolved.

As described above, according to the present invention, even if dressing is not performed, clogging unlike the related art does not occur. Therefore, the polishing pad does not deteriorate as shown in FIG.

[0016]

As described above, according to the present invention, in the conventional polishing method, dressing for causing clogging of the polishing pad was required, but in the method of the present invention, clogging of the polishing pad was surely removed. Therefore, the polishing rate in the CMP process can be stably maintained, and therefore, the polishing amount can be easily controlled. Further, since the generation of scratches on the polishing cloth can be suppressed, the scratches transferred to the semiconductor wafer can also be prevented, so that the yield can be prevented from lowering due to the scratches. Further, by suppressing the occurrence of scratches on the polishing pad, deterioration of the polishing pad can be prevented, the frequency of replacement of the polishing pad can be reduced, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a polishing cloth surface portion according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an apparatus showing a state where a CMP process is being performed.

FIG. 3 is a cross-sectional view of a surface portion of a polishing cloth in which clogging has occurred.

FIG. 4 is a cross-sectional view of a surface portion of a polishing cloth having a rough surface and scratches.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spindle 2 Rotary table 3 Polishing cloth 4 Pressure shaft 5 Rotating head 6 Semiconductor wafer 7 Polishing cloth main material 8 Abrasive solid component 9 Void

Claims (4)

[Claims] In the step of polishing the semiconductor wafer while adding a polishing agent between the polishing pad and the semiconductor wafer, the solid component of the polishing agent contains ice, and the semiconductor wafer is polished. Polishing method for a semiconductor wafer. 2. The method of polishing a semiconductor wafer according to claim 1, further comprising a step of heating the polishing cloth to melt ice on the polishing cloth after the polishing step according to claim 1. 3. The method according to claim 1, wherein the polishing agent is an alkaline aqueous solution. 4. The step of melting ice on the polishing cloth,
The method according to claim 2, wherein ice on the polishing cloth is melted by flowing hot water over the polishing cloth.