JP2935915B2 - Method for cleaning silicon with HF gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning silicon by removing silicon deposited on a thin film forming apparatus or a jig of the apparatus with HF gas without damaging the apparatus or the jig itself.

[0002]

2. Description of the Related Art Conventionally, in thin film forming processes such as semiconductor manufacturing and photosensitive drum manufacturing, that is, methods such as CVD, vacuum deposition, PVD, silicon epitaxy, etc., only an object for forming a thin film is required. In addition, a large amount of deposits and deposits are generated not only in the members of the apparatus, various jigs, and the like.

A similar phenomenon occurs when an amorphous silicon film is formed by a CVD method in a thin film forming apparatus.

As a means for removing these, there are usually strong acids,
Washing with strong liquid such as an alkali, mechanical polishing, CF _4, SF
₆ , a method of cleaning in a plasma atmosphere using NF ₃ or the like as a cleaning gas has been implemented.

[0005] However, the method using washing with a strong acid or strong alkali or mechanical polishing has a problem that the apparatus must be stopped for a long period of time, the operation is complicated, and the apparatus and jigs are damaged. In addition, the method of cleaning under a plasma atmosphere using CF ₄ , SF ₆ , NF ₃ or the like has a problem that a plasma atmosphere is required, so that restrictions on the apparatus are large.

[0006]

Means for Solving the Problems In view of the above problems, the present inventors have made intensive studies and as a result, have obtained H at a relatively low cost.
The inventors have found that the silicon film formed by the CVD method can be removed without damaging the substrate even at around room temperature using F gas, and the present invention has been achieved.

That is, according to the present invention, there is provided a method of removing amorphous silicon deposited on a thin film forming apparatus or a jig of the apparatus by contacting the silicon with a gas containing HF gas having a very low moisture content.
An object of the present invention is to provide a method for cleaning silicon using F gas.

First, the deposit of the thin film forming apparatus or jig which is the object of the present invention is a silicon film or powder. Normally, in the above-mentioned thin film forming apparatus, a Si-containing compound gas such as silane, halogenated silane or the like is applied to a target substrate by plasma CV
A method of forming a film by performing D or LPCVD is used. When a film is formed by the above method, silicon is deposited in a film or powder form on an apparatus or a jig other than the intended place. The present invention is intended to remove such a deposit.

The conditions for performing CVD are plasma CVD.
500 ° C or less, about 10 Toor or less, LPCVD 6
Although the temperature is 0.1 ° C. or less and 0.1 to several Torr, the silicon film or powder deposited under this condition is hard to become crystalline Si and is amorphous having a composition of SiHx (x = 1.0 or less). is there.

Accordingly, the conditions for removing the deposited silicon become more severe as the crystallization proceeds, and if the deposited material is sufficiently heated to be crystallized, it becomes difficult to remove the deposited material with HF gas.

When cleaning a silicon film formed by a plasma CVD method, N ₂ is used as a diluent gas, and the concentration (Vol%) and the cleaning temperature are examined.
When the gas concentration is 1 Vol%, cleaning can be performed in a short time at around 300 ° C., but as the HF gas concentration increases, the temperature decreases. It was found that the cleaning process could be performed.

A film formed by LPCVD requires more severe conditions. Next, the cleaning method is as follows. In order to remove deposits dispersed in the entire apparatus, a gas containing HF gas is introduced into the apparatus, or when the thin film forming apparatus is not so large, the entire apparatus is cleaned. It is possible to adopt two methods, that is, a method of introducing a gas containing HF gas into a cleaning device and introducing a gas containing HF gas.

Similarly, in the case of a jig, a gas containing HF gas is introduced into the apparatus using a thin film forming apparatus, or the jig is put into a cleaning apparatus and a gas containing HF gas is introduced. These two methods can be adopted.

When performing cleaning, HF is
The introduction of the cleaning gas is stopped after the introduction of the gas containing the gas to a certain pressure, and the cleaning gas is allowed to stand still for a certain period of time. it can.

The HF gas used preferably has a minimum water content, and preferably has a water content of 0.1 Vol% or less. If the water content is high, the apparatus is corroded, which is not preferable.
The metal impurities are preferably as small as possible, and the purity of the HF gas is preferably 99.9 Vol% or more.

When cleaning is performed, only HF gas may be introduced into the apparatus. However, depending on conditions, an inert gas such as Ar or N ₂ may be mixed and used as a cleaning gas as described above. Good.

An apparatus for performing cleaning includes:
As described in detail in Japanese Patent Application No. 3-38840 proposed by the present applicant, a heating device equipped with a temperature controller is provided. It has.

The material of the container is determined by the temperature at which the cleaning is performed, but since a very high temperature is not required, the cleaning can be sufficiently performed with various kinds of stainless steel, aluminum, Monel, Inconel or the like.

By the method as described above, the deposits deposited on the thin film forming apparatus and the jig can be cleaned relatively easily.

[0020]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 5 Monosilane was used as a raw material, and plasma CVD was performed at 250 ° C.
The amorphous silicon film formed on the SUS430 is set in a cleaning device, and the HF gas is diluted with N ₂ ,
Gases having HF gas concentrations of 1, 10, 20, 50, and 100 Vol% were introduced into the apparatus, and 100 to 34 as shown in Table 1.
A cleaning process was performed at a temperature of 0 ° C., and the film thickness before and after the cleaning was indirectly evaluated by irradiating fluorescent X-rays with the peak intensity of Si atoms in the film. X-ray fluorescence was measured using a system 3270 manufactured by Rigaku Denki Kogyo under the conditions of 50 KV, 50 mA, and a measurement area of 30φ.

[0022]

[Table 1]

As can be seen from the results shown in Table 1, it was found that the higher the HF gas concentration, the lower the temperature of the cleaning atmosphere and the easier the cleaning process in a short time. Examples 6 to 8 Monosilane was used as a raw material, and LPCVD was performed at 500 ° C.
Amorphous silicon formed on US430 is set in a cleaning device, and only HF gas is introduced into the device.
The treatment was performed under the conditions shown in Table 2. Evaluation of film thickness was performed in Example 1.
This method is the same as that of the method described above.

[0024]

[Table 2]

As can be seen from the table, it was found that the film formed by LPCVD can remove amorphous silicon at a temperature of 200 ° C. or more. Comparative Examples 1 to 3 Using monosilane as a raw material, LPCVD was performed at 700 ° C.
Polysilicon formed on US430 was placed in a cleaning apparatus, and only HF gas was introduced into the apparatus, and processing was performed under the conditions shown in Table 3. Evaluation of the film thickness is performed in the same manner as in Examples 1 to 5.

[0026]

[Table 3]

As can be seen from the results in the table, 150 to 30
It was found that the polysilicon could not be removed even at a temperature of 0 ° C. Comparative Examples 4 to 6 The same processes as Comparative Examples 1 to 3 were performed using commercially available silicon wafers. The etching depth was measured by masking a part of the wafer with Al, treating with HF gas, peeling off the Al mask with hydrochloric acid, and measuring the level difference with a surface roughness meter (manufactured by Kosaka Laboratories). The results are also shown in Table 4.

[0028]

[Table 4]

As can be seen from the results, 150-300 ° C.
It was found that the silicon crystal could not be removed even at this temperature.

[0030]

The cleaning method of the present invention, which is performed using high-purity HF gas, is performed by a halogen-containing compound such as CF _{4 in} a plasma atmosphere or by a CVD method which has been cleaned by a wet method using an aqueous solution of sodium hydroxide. The deposited silicon can be easily cleaned.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-138473 (JP, A) JP-A-1-94624 (JP, A) Patent 2901778 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09K 13/08 C23C 16/44 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A method of cleaning silicon using an HF gas for removing amorphous silicon deposited on a thin film forming apparatus or a jig of the apparatus by contacting the silicon with a gas containing an HF gas having a very small amount of moisture.