Method of recycling abrasive slurry

Abstract

A method of recycling an abrasive slurry for recycling a slurry that: contains colloidal silica; and has been used in polishing semiconductor wafer(s) is provided. The method includes: adding a dispersant to the used slurry having been collected so as to prevent the used slurry from being gelled; irradiating ultrasound to the used slurry having been added with the dispersant so as to disperse a gelled portion and aggregated silica in the used slurry; and, by using a filter, removing a foreign substance contained in the used slurry having been irradiated with the ultrasound.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method of recycling an abrasive slurry for recycling a used slurry having been used in polishing semiconductor wafer(s).[0003]2. Description of Related Art[0004]Polishing of semiconductor wafer(s) is generally classified into two major categories of rough polishing and finish polishing according to surface roughness to be made on the semiconductor wafer(s).[0005]In finish polishing, where ultra-fine surface roughness is required to be made, the semiconductor wafer(s) is usually polished with an ammonia-base colloidal silica slurry having been added with a water-soluble polymer such as ethylcellulose.[0006]The colloidal silica slurry having been used in finish polishing has conventionally been discarded because the slurry may contain metal contamination originating from components of a polishing apparatus, a giant silica solid formed by aggregation of silica in the slurry, and the like....

AI Technical Summary

Benefits of technology

[0015]An object of the invention is to provide a method of recycling an abrasive slurry, by which a used slurry having been used in polishing semiconductor wafer(s), particularly a slurry having been used in finish polishing, can be recycled, so that considerable reduction in slurry usage can contribute to reduction in manufacturing cost of the semiconductor wafer(s).

[0024]According to the aspect of the invention, while the used slurry is prevented from being gelled by the addition to the dispersant to the used slurry, the gelled portion of the slurry and the aggregated silica are dispersed by the irradiation of ultrasound, and foreign substance(s) contained therein is removed by the filter. Thus, foreign substance(s) can be efficiently removed by the filter while an amount of silica contained in the slurry can be prevented from being reduced due to a capture of gelled and aggregated silica by the filter. With this arrangement, the used slurry can be favorably recycled.

[0027]According to the aspect of the invention, by adjusting the pH value in advance, the slurry and silica can be further prevented from being aggregated.

[0030]According to the aspect of the invention, by supplementing the water-soluble polymer, the viscosity of the used slurry can be suitably adjusted. In this manner, an abrasive slurry suitable for recycling can be obtained.

[0036]According to the aspect of the invention, the metal ion having been mixed into the slurry during polishing can be removed. Thus, when semiconductor wafer is polished with the used slurry, it is possible to prevent the semiconductor wafer(s) from being contaminated by metal ion.

Problems solved by technology

However, the methods disclosed in the above Documents are not sufficiently applicable in retrieving and recycling the above-described colloidal silica slurry, and the following problems are pertinent to the methods.

Thus, even when the slurry experiences filtration by a filter, such gel-like aggregation can easily clog the filter.

The methods disclosed in the above Documents cannot solve all the problems although the methods may be able to solve one of the problems.

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