KR20020004732A - Cleaning method for polishing pad used for preventing micro scratch - Google Patents

Abstract

PURPOSE: A method of cleaning a polishing pad preventing a micro scratch is provided to prevent a micro scratch from particles of slurry formed on a center portion of a polishing pad by injecting uniformly deionized water on the center portion of the polishing pad. CONSTITUTION: A discharge operation of a slurry discharged in a polishing process is stopped(S201). Deionized water is injected from a nozzle to a center portion of a polishing pad(S202). The deionized water is injected uniformly to the surface of the rotating polishing pad and a head assembly. The polishing pad is cleaned by injecting uniformly the deionized water. The number of the nozzle is one or more. A slurry is removed from a surface of the polishing pad by using a rotary force of the polishing pad(S203). The injection operation of the deionized water is stopped from the nozzle(S204).

Description

Cleaning method of polishing pad to prevent microscratches {CLEANING METHOD FOR POLISHING PAD USED FOR PREVENTING MICRO SCRATCH}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a semiconductor wafer in a polishing facility for manufacturing a semiconductor device, and more particularly, to a method for effectively cleaning a slurry in which contaminants accumulate during use in a chemical mechanical polishing process. will be.

Thin substrates such as silicon substrates and wafers used in semiconductor manufacturing are polished and planarized using CMP systems. In general, the polishing process is performed by a relative rotational movement of a carrier plate and a polishing pad on which a wafer is mounted. The carrier plate has a retaining ring in contact with the polishing pad. In the polishing process, a slurry is supplied to promote polishing. The slurry is a mixture of abrasive particles and water, and water is usually used as DIW, and small solid particles in water are suspended or suspended in a thin porridge. It is said to be in a state. Normally, the polishing pad and the substrate rotate at different rotational speeds to make relative rotational movements.

However, when the polishing process is performed several times, large particles are formed by contamination of the facility, which causes micro scratches during the polishing process. Since this damages the wafer and adversely affects the semiconductor yield, in order to prevent micro-scratches, a method of removing the slurry used in the cleaning process after the polishing process is mainly used.

However, the conventional polishing equipment does not effectively remove the slurry in this cleaning process, so that the slurry remains in the center portion. This is because, when cleaning using ultrapure water, the ultrapure water is mostly injected from a position slightly away from the center and spread outward due to the centrifugal force, so that the ultrapure water is not effectively distributed to the center portion of the polishing pad. When the slurry remaining in the center part is accumulated continuously while the process is repeated and a certain amount is accumulated, the slurry accumulated in the center of the polishing pad is introduced along the pad groove formed on the surface of the polishing pad by the rotation of the head during the polishing process. It will cause micro scratches.

An object of the present invention is to provide a method for cleaning a polishing pad for preventing micro-scratches caused by slurry large particles accumulated in the center of the polishing pad when the polishing process is repeatedly performed as described above.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view schematically showing the configuration of a polishing apparatus applying a polishing pad cleaning method for preventing micro scratches, which is an embodiment of the present invention;

2 is a process flowchart for explaining a process of the polishing pad cleaning method of the present invention;

3A and 3B are graphs showing a tendency of defects that occur according to the number of wafers in the prior art and the present invention; And

4A and 4B are graphs showing that the KLA tendency decreases when the cleaning method of the present invention is applied.

* Explanation of symbols for main parts of the drawings

1: head assembly

2: polishing pad

3: slurry arm

4: Nozzle

In order to achieve the above object, the present invention is arranged so that deionized water (DIW) can be sprayed on the center of the polishing pad when cleaning the polishing pad to prevent the slurry from accumulating in the center of the polishing pad as conventionally It was presented how to.

According to a feature of the present invention, a method for cleaning the entire surface of the polishing pad by directly supplying from the upper center portion to the central portion, compared to conventional equipment spraying pure water at a point of 1/4 to 1/3 of the radius of the polishing pad. It is adopted.

Hereinafter, with reference to the accompanying drawings, the configuration and operation of a specific embodiment of the present invention will be described in detail.

FIG. 1 is a view schematically showing a polishing pad cleaning method preventing micro-scratches according to an embodiment of the present invention, and FIG. 2 is a flowchart illustrating a process of the polishing pad cleaning method of the present invention.

The polishing apparatus in which the polishing pad cleaning method of the present invention is used is, as shown in FIG. 1, a head assembly 1 and a polishing pad composed of a carrier platen and a retaining ring. And a nozzle 4 for injecting the slurry and the pure water and a slurry arm 3 for supporting the slurry 4. As shown in FIG. 1, the slurry arm is located near the center so that the slurry and pure water are injected into the center of the polishing pad.

The cleaning process of the polishing pad is as shown in FIG. Looking at this in detail as follows. First, the step of stopping the discharge of the slurry (slurry) discharged in the polishing process (S201), the step of spraying pure water in the vicinity of the polishing pad center so that the pure water falls in the center of the polishing pad in the nozzle (S202), the rotational force of the polishing pad Thereby removing the slurry on the surface of the polishing pad (S203) and blocking the discharge of the pure water injected from the nozzle (S204). Each step will be described in detail as follows. The number of nozzles mounted on the slurry arm may be one or more. In step S201, the slurry sprayed during the polishing process is blocked and pure water is injected into the center of the polishing pad in step S202. Pure water sprayed in step S202 is spread evenly hit the head assembly in the a direction on the surface of the polishing pad rotated in the b direction of FIG. Step S203 is a step in which the entire surface of the polishing pad is cleaned by the evenly spread pure water. As shown in FIG. 1, since pure water falls to the center portion of the polishing pad, the possibility of slurry accumulation in the center portion disappears. Step S204 is a step of blocking the supply of pure water when the cleaning process is completed. This is followed by a subsequent process of polishing the wafer.

3 is a graph showing a tendency of defects occurring according to the number of wafers according to the prior art and the present invention, and FIG. 4 is a graph showing a decrease in the KLA tendency when the cleaning method of the present invention is applied.

3 and 4, it can be seen that defects are greatly reduced when the polishing pad is cleaned by applying the present cleaning method. FIG. 3 shows the results of defect measurements on polished wafers evaluated by SURFSCAN, with the horizontal axis representing the number of wafers to be polished and the vertical axis representing the total defects measured (SURFSCAN total defect). As shown in FIG. 3, the number of defects that greatly increased after 1000 wafers (see FIG. 3A) can maintain the number of defects (see FIG. 3B) without diverging by applying the cleaning method of the present invention. 4 is a graph of before and after applying the improvement method for the two facilities KLA evaluation trend, which is a measure of the quantitative trend of defects. As shown in FIG. 4, it can be seen that the trend of KLA evaluation is that the defects are reduced in quantity when the cleaning method of the present invention is applied.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications are within the scope of the appended claims.

When the polishing pad cleaning method of the present invention is applied to a semiconductor manufacturing facility, it is possible to effectively remove the slurry macroparticles generated while accumulating at the center of the polishing pad as described above, thereby suppressing an increase in defects. The benefit that the increase in defects is suppressed is that it has a great effect in suppressing micro scratches by the macroparticles contained in the slurry.

Claims (1)

A method of cleaning a polishing pad in a polishing apparatus, wherein the polishing pad is used in a polishing process to remove contaminated slurry in manufacturing a semiconductor device, wherein at least one nozzle for injecting the slurry and pure water is disposed above the center of the polishing pad. Blocking the slurry sprayed from the nozzle; Spraying pure water such that pure water falls from the nozzle to the center of the polishing pad; Removing the slurry of the polishing pad by the rotational force of the polishing pad; and Blocking the discharge of the pure water sprayed from the nozzle, The polishing pad cleaning method according to claim 1, wherein the entire surface of the polishing pad is sufficiently cleaned so that the pure water sprayed to the center of the polishing pad diffuses to the front surface according to the rotating polishing pad so that the contaminated slurry does not accumulate in the center.