KR20080062043A - Chemical mechanical polishing method for preventing defects due to post cleaning - Google Patents

Abstract

A CMP method for preventing defects due to a post cleaning process is provided to remove foreign materials by performing a second polishing process using deionized water. A wafer is loaded into a chemical mechanical polishing apparatus(S21). A first polishing process is performed by using a slurry and a polishing pad(S22). A post-cleaning process for the first polished wafer is performed(S23). A second polishing process for the wafer is performed by using only deionized water(S24). A rinse process and a dry process for the wafer are performed(S25). The wafer is discharged from the CMP apparatus(S26). The post-cleaning process is performed by using a roll brush.

Description

Chemical Mechanical Polishing Method for Preventing Defects Due to Post Cleaning}

1 is a process flow chart of a chemical mechanical polishing method according to the prior art.

Figure 2 is a photographic illustration showing the foreign matter of the wafer caused by the post-cleaning of the chemical mechanical polishing method according to the prior art.

3 is a process flow chart of a chemical mechanical polishing method according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing technique of a semiconductor device, and more particularly, to a chemical mechanical polishing method capable of preventing a defect from occurring due to post-cleaning of a chemical mechanical polishing process.

As the semiconductor device has high performance, high integration, and high density, the structure of the device tends to be more multilayered, and the unevenness of the surface tends to increase. If the step height of the surface becomes large, since the depth of focus of the surface is limited during the exposure process, it is difficult to integrate the fine line width. Therefore, the surface planarization process is essential. Conventional planarization techniques include spin on glass (SOG), reflow, and etch back.

However, although these conventional planarization techniques are effective in planarizing the chip size, it is difficult to achieve sub-micron flatness for the interlayer insulating film of the multilayer interconnection when applied to a semiconductor device requiring a wiring width of 0.35 µm or less. As a technology capable of a wide range of planarization, a chemical mechanical polishing (CMP) technique, which performs polishing by chemical reaction at the same time as mechanical polishing, has emerged.

The chemical mechanical polishing technique uses the frictional force of slurry and pad to process the wafer surface, so the influence of slurry and pad is large. In addition, since the post-cleaning step of the chemical mechanical polishing process has a large effect on the yield of the semiconductor device, a lot of researches have recently been made on the post-cleaning method.

A typical post-cleaning method is a method of removing abrasive particles adsorbed on a wafer surface by applying ultrasonic waves while the wafer is immersed in a cleaning tank containing ultrapure water or a specific chemical liquid. There is also a method of removing abrasive particles adsorbed on the wafer surface using a brush while spraying ultrapure water or a specific chemical liquid. In addition, these two systems may be used in parallel.

However, if the equipment or apparatus used for cleaning, such as a brush, is contaminated, the particles remain on the wafer even after the post-cleaning is completed. Such foreign matters cause a back side pressure error in a subsequent metallization deposition process, or a defocus or alignment miss in an exposure process. These are the factors causing a big problem in the yield of the wafer.

1 is a process flow chart of a chemical mechanical polishing method according to the prior art. As shown in FIG. 1, in the conventional chemical mechanical polishing method, a wafer is introduced into a facility (S11), and then subjected to a first polishing step (S12) using a slurry and a second polishing step (S13) using ultrapure water. The wafer is discharged (S16) through at least one post-cleaning process (S14) and a rinse and drying process (S15). In the conventional chemical mechanical polishing method, foreign matter may be generated on the wafer due to post-cleaning (S14), and FIG. 2 is a photograph showing such an example.

It is therefore an object of the present invention to prevent defects in the wafer due to post-cleaning of the chemical mechanical polishing process.

In order to achieve this object, the present invention provides a chemical mechanical polishing method of the following configuration.

The chemical mechanical polishing method according to the present invention comprises the steps of injecting a wafer into a chemical mechanical polishing facility, performing a first polishing process using a slurry and a polishing pad on the wafer, and performing the first polishing on the wafer. Performing a post-cleaning process on the wafer, performing a second polishing on the wafer on which the post-cleaning process is completed, using only ultrapure water, and rinsing and drying the wafer on which the second polishing is completed. And discharging the wafer from which the rinse and drying process is completed from the chemical mechanical polishing facility.

In this chemical mechanical polishing method, the post-cleaning process may use a roll brush. In addition, it is preferable that the pressure of the second polishing process is about 30 hPa, and the RPM per minute (RPM) is half the level of the first polishing process.

Example

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. However, in describing the embodiments, descriptions of technical contents that are well known in the art to which the present invention pertains and are not directly related to the present invention are omitted. This is to more clearly communicate without obscure the core of the present invention by omitting unnecessary description.

Abrasive particles used in chemical mechanical polishing processes play an important role for wafer planarization. However, after polishing, abrasive particles adsorbed on the wafer surface and backside must be removed. Various cleaning methods have been introduced for this purpose, but there are still limitations. In particular, the problem caused by contamination of post-cleaning equipment or tools has no solution.

3 is a process flowchart of a chemical mechanical polishing method according to an embodiment of the present invention.

Referring to FIG. 3, first, a wafer is introduced into a chemical mechanical polishing facility (S21). The wafer once introduced into the facility is moved within the facility by means of a transfer robot or the like. The wafer is first transferred to the top of the polishing pad. Thereafter, the polishing head performs the first polishing by using the slurry and the polishing pad while the polishing head adsorbs and fixes the wafer (S22).

Subsequently, the post-cleaning process is performed without performing the second polishing process using ultrapure water (DI water) as in the related art (S23). The post-cleaning process uses a roll brush.

Subsequently, the second polishing is performed using only ultrapure water (S24). The second polishing process sprays ultrapure water at a predetermined pressure while rotating the wafer in a rotary chuck. Therefore, fine polishing is performed by the pressure of the ultrapure water sprayed, and it is possible to remove any foreign matter that may be present. The second polishing process uses only ultrapure water to prevent contamination by the chemical liquid, and proceeds after the post-cleaning process (S23), so that foreign matters on the wafer due to contamination of the cleaning equipment or the tool can be removed. The pressure used in the second polishing process is about 30 hPa, and the RPM per minute (RPM) is lowered to half the level of the first polishing process.

Subsequently, the wafer is discharged from the facility (S26) through a normal rinsing and drying process (S25). The rinse and dry process S25 is carried out, for example, in a spin rinse dryer.

So far, the chemical mechanical polishing method for preventing defects caused by post-cleaning according to the present invention has been described. In the present specification and drawings, preferred embodiments of the present invention have been disclosed, and although specific terms have been used, these are merely used in a general sense to easily explain the technical contents of the present invention and to help the understanding of the present invention. It is not intended to limit the scope. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

As described above, the present invention does not proceed with the second polishing step using ultrapure water immediately after the first polishing step using the slurry and the polishing pad. And the second polishing process using ultrapure water proceeds after the post-cleaning process. Therefore, even if foreign matter remains on the wafer due to contamination of the cleaning equipment or tools in the post-cleaning process, it may be removed through the second polishing process using ultrapure water, and the wafer failure due to the post-cleaning may be prevented.

Claims (4)

Introducing a wafer into a chemical mechanical polishing facility; Performing a first polishing on the wafer using a slurry and a polishing pad; Performing a post-cleaning process on the wafer on which the first polishing is completed; Performing a second polishing using only ultrapure water on the wafer on which the post-cleaning process is completed; Rinsing and drying the wafer on which the second polishing is completed; And Ejecting the wafer from which the rinsing and drying process is completed from the chemical mechanical polishing facility; Chemical mechanical polishing method comprising a. The method of claim 1, And the post-cleaning process uses a roll brush. The method of claim 1, And the pressure of the second polishing process is about 30 hPa. The method of claim 1, The RPM per minute of the second polishing process is about half the level of the first polishing process.

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