JPH01196129A - Formation of thermal oxide film on semiconductor wafer - Google Patents

Abstract

PURPOSE:To assure a semiconductor wafer with a clean thermal oxide film by forming the thermal oxide film thicker than a predetermined one, removing the surface of the same by etching to a desired thickness, and thereafter washing said surface with a non-etching solution. CONSTITUTION:First, a thermal oxide film (silicon oxide film) 11 is formed thicker than a desired one, and then a silicon wafer 10 is dipped into a clean solution containing fluoride ions which can etch the film 11 to etch the surface of the same up to a desired thickness. The etching substantially removes dust 12 adhering to the surface of the film 11. Thereafter, the silicon wafer 10 is taken out, and an etchant is removed from the surface of the wafer 10 by washing, and then the film 11 is washed by a clean solution of no capability of etching such as hydrochloric acid-aqueous hydrogen peroxide-wafer, and relatively small dust 12 is removed, for the next process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a thermal oxide film on a semiconductor wafer.

[Conventional technology]

Generally, ICs are manufactured from semiconductor wafers such as silicon wafers.
During the production of semiconductor devices such as these, the formation of a thermal oxide film on a semiconductor wafer is repeated many times.

Conventionally, in order to form a thermal oxide film on the surface of a semiconductor wafer, such as a silicon wafer, the silicon wafer is mounted on a processing jig (boat) made of heat-resistant material and placed inside the core tube of an electric furnace. This is done by thermal oxidation treatment.

The film thickness is controlled by calculations based on the type of atmosphere and temperature. When the thermal oxide film reaches the desired thickness, it is pulled out of the furnace, and after the temperature of the silicon wafer has been lowered to room temperature, it is directly injected into the wafer. Alternatively, a simple cleaning process may be performed before proceeding to the next process.

[Problem to be solved by the invention]

However, according to the conventional method for forming a thermal oxide film, the semiconductor wafer 1 is exposed to the
As shown in the figure, minute dust 2 easily adheres to the semiconductor wafer 1, and when a thermal oxide film 3 is formed by thermal oxidation treatment with the dust 2 attached, the dust 2 is firmly bonded onto the semiconductor wafer 1. It has become what is called a "burned-in" state,
cannot be easily removed.

Further, the dust 2 on the semiconductor wafer 1 has an adverse effect on subsequent processes, causing problems during mask alignment in the lithography process, and deteriorating the characteristics and quality of devices to be formed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for forming a thermal oxide film on a semiconductor wafer, which can clean the thermal oxide film.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention involves forming a thermal oxide film thicker than a desired thickness during thermal oxidation treatment of a semiconductor wafer, and then removing the surface of the thermal oxide film to the desired thickness by etching. After that, the surface of the thermal oxide film is cleaned with a chemical solution that has no etching properties.

[For production]

According to the above means, relatively large dust particles are removed by etching, and relatively small dust particles are removed by cleaning with a chemical solution.

Etching is performed by immersion in a clean solution capable of etching thermal oxide films.

Chemical solutions used for cleaning include hydrochloric acid-hydrogen peroxide-water,
A clean solution such as aqueous ammonia-hydrogen peroxide-water or sulfuric acid-hydrogen peroxide solution may be used.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

When thermally oxidizing the silicon wafer 10, first, the first
As shown in the figure, a thermal oxide film (silicon oxide film) 11 is formed thicker than a desired thickness, and then a silicon wafer 10 is placed in a clean solution containing fluoride ions capable of etching the thermal oxide film 11. Then, as shown in FIG. 2, the surface of the thermally oxidized film was etched to a desired thickness. By this etching, most of the dust 12 stuck to the surface of the thermal oxide film 11 was removed.

Thereafter, the silicon wafer 10 is taken out, the etchant is removed from the surface of the silicon wafer 10 by washing with water, etc., and then a clean chemical solution that does not have the ability to etch the thermal oxide film j1, such as hydrochloric acid-hydrogen peroxide-water, ammonia water-hydrogen etchant, etc. Wash with oxidized oxygen water - water, sulfuric acid - hydrogen oxide water, etc. to remove relatively small dust [2] as shown in Fig. 3 before proceeding to the next step.

Here, an untreated silicon wafer A1 after thermal oxidation treatment, a silicon wafer A1 with only etching treatment, and a silicon wafer C subjected to chemical cleaning treatment.
Table 1 shows the comparison of the number of dust particles.

Table-1 The number of dust particles is 50 silicon wafers (1' diameter
00 mm) and was measured using a dedicated dust counter.

Therefore, although etching treatment alone is effective in removing relatively large dust particles, it is not very effective in removing relatively small dust particles. It was found that the method was effective in removing even small particles of dust, and that a cleaner thermal oxide film surface could be obtained.

Separately, when only cleaning was performed without etching, there was no significant change in the amount of dust.
It was also confirmed that the effect was small.

Although the above embodiment describes a method for forming a thermal oxide film on a silicon wafer, the present invention is not limited thereto (for example, it can also be applied to forming a thermal oxide film on a germanium wafer or other semiconductor wafers).

〔Effect of the invention〕

As described above, according to the present invention, relatively large dust particles are removed by etching, and relatively small dust particles are removed by cleaning with a chemical solution, making it possible to obtain a semiconductor wafer with a clean thermal oxide film. .

[Brief Description of the Drawings] Figures 1 to 3 show one embodiment of the present invention.
2 and 3 are cross-sectional views of a silicon wafer after a thermal oxidation process, an etching process, and a chemical cleaning process, respectively, and FIG. 4 is a cross-sectional view of a silicon wafer according to a conventional method. 10... Silicon wafer 11... Thermal oxide film 12... Dust

Claims (1)

[Claims] During thermal oxidation treatment of semiconductor wafers, after forming a thermal oxide film thicker than the desired thickness, the surface of the thermal oxide film is removed by etching to the desired thickness, and then the surface of the thermal oxide film is etched without etching properties. A method for forming a thermal oxide film on a semiconductor wafer, the method comprising cleaning with a chemical solution.