JPH05109683A - Removal of metallic impurity in semiconductor silicon wafer cleaning fluid - Google Patents

Abstract

PURPOSE:To remove metallic impurities in a silicon wafer cleaning fluid easily and effectively by a method wherein a silicon film for gettering, an oxide film on the surface of which is removed, is immersed in the silicon wafer cleaning liquid and the metallic impurities in the cleaning liquid are made to adsorb on the silicon film surface for getter use. CONSTITUTION:Ammonia hydrogen peroxide water (NH4OH/H2O2/H2O) is used as a semiconductor silicon wafer cleaning fluid. After a cleaning tank is filled with this cleaning liquid, a silicon film for getter use, an oxide film on the surface of which is removed, is immersed in the cleaning fluid. By immersing the silicon film for getter use in the cleaning fluid, the oxide film on the surface of which is removed and whose surface is activated, in the cleaning fluid, metallic ions, such as aluminum ions, iron ions and zinc ions, in the cleaning fluid adsorb on the activated silicon film surface and the cleaning fluid is cleaned. After the silicon film for getter use is taken out from the cleaning fluid, a silicon wafer for cleaning use, which is used as a product, is immersed in the cleaned cleaning liquid to perform a cleaning of the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for effectively removing contaminant metals in a cleaning liquid in a semiconductor silicon wafer cleaning process.

2. Description of the Related Art Regarding silicon wafers, which are the material for semiconductor integrated circuits such as VLSI, as the density and density of devices increase, trace contamination of silicon wafers has a great influence on device quality. It started to come. Contamination includes particle contamination in which fine particles adhere to the surface of the silicon wafer to cause shape defects, and heavy metal ions such as alkali metals, iron, and copper that adhere to the surface of the silicon wafer as metal impurities, causing metal defects. Are known. As a method of preventing particle contamination, a method of filtering the cleaning liquid with a fine mesh filter is known, but there is a problem that fine particles smaller than the mesh diameter cannot be removed, and a method of using a dummy wafer instead of the filter is proposed. (Japanese Patent Laid-Open No. 2-292825). However, this method does not consider metal contamination.
On the other hand, gettering is generally performed as a method of removing metal impurities on the wafer surface, but if gettering is not performed properly, there is a problem that it may cause contamination rather than gettering. Therefore, it is desirable to finally clean the silicon wafer in an environment where metal contamination does not occur in advance, but it is extremely difficult to eliminate metal impurities mixed in from piping etc. even if a new cleaning liquid is used. First, it is necessary to remove metal impurities in the liquid in the cleaning tank.

[0002]

Means for Solving the Problem: The present invention provides a method for effectively removing metal impurities in a silicon wafer cleaning liquid by a simple means. According to the present invention, the getter silicon from which the oxide film on the surface has been removed is immersed in the silicon wafer cleaning liquid, and the metal impurities in the silicon wafer cleaning liquid are adsorbed on the getter silicon surface to be removed. A method for removing metal impurities in a wafer cleaning liquid is provided.

Ammonia hydrogen peroxide solution (NH ₄ OH / H ₂ O ₂ / H ₂ 0) is usually used as a cleaning solution for semiconductor silicon wafers. After filling the cleaning bath with the cleaning liquid, getter silicon from which the oxide film on the surface is removed is immersed in the cleaning liquid. As the getter silicon, another silicon wafer from which the oxide film on the surface is removed can be used. Note that particle-shaped or block-shaped silicon may be used as the getter silicon. The oxide film on the surface of the getter silicon can be removed by washing the surface of the silicon with a hydrofluoric acid solution or the like. The surface of the getter silicon is etched by hydrofluoric acid, and the natural oxide film formed on the surface of the silicon is removed and activated. By immersing the getter silicon whose surface is activated by removing the oxide film into the cleaning liquid, metal ions such as aluminum, iron, and zinc in the cleaning liquid are adsorbed on the activated silicon surface to clean the cleaning liquid. The immersion time may be about 5 to 10 minutes. After removing the getter silicon from the cleaning liquid, the cleaning silicon wafer to be a product is immersed in the cleaned cleaning liquid to clean the wafer. The getter silicon that has adsorbed metal ions can be reused by treating it with hydrofluoric acid again and etching the surface to activate it.

[0004]

[Example] A getter silicon wafer whose surface was activated by removing the oxide film by hydrofluoric acid treatment was dipped in ammonia hydrogen peroxide solution (NH ₄ OH / H ₂ O ₂ / H ₂₀ ) for 5 to 10 minutes. After taking out, the silicon wafer to be the product was immersed and washed according to the usual conditions. The metal concentration on the surface of the silicon wafer after cleaning is shown in FIG. On the other hand, for comparison, cleaning was performed by a conventional method that does not use a getter silicon wafer. The results are also shown in FIG. As shown,
The concentrations of iron, zinc and aluminum on the surface of the silicon wafer cleaned with the cleaned cleaning solution are reduced to about 1/10 of those of the uncleaned cleaning solution.

[0005]

According to the method of the present invention, since metal impurities in a silicon wafer cleaning liquid can be easily and effectively removed, metal contamination of the silicon wafer in the cleaning step can be prevented and high-quality silicon can be obtained. Wafers are obtained and product yield is improved.

[Brief description of drawings]

FIG. 1 is a graph showing the metal concentration on the surface of a silicon wafer when the method of the present invention and the conventional cleaning method are performed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Etsuro Morita 1-297 Kitabukuro-cho, Omiya-shi, Saitama Prefecture Central Research Laboratory, Mitsubishi Materiali Co., Ltd. (72) Inventor Yasushi Shimane 1-297 Kitabukuro-cho, Omiya-shi, Saitama Prefecture Central Research Institute Co., Ltd.

Claims (1)

[Claims] 1. A semiconductor silicon wafer, characterized in that a getter silicon from which an oxide film on the surface has been removed is dipped in a silicon wafer cleaning liquid to adsorb metal impurities in the silicon wafer cleaning liquid to the surface of the getter silicon to remove it. Method for removing metallic impurities from cleaning liquid.