JPS60100423A - Cleaning process of piping - Google Patents

Abstract

PURPOSE:To reduce the downtime of a semiconductor manufacturing device while securing safety of operators by a method wherein piping to be filled with the mixed gas containing silicide gas or silicide is filled with hydrofluoric anhydride gas while the piping to be cleaned is heated. CONSTITUTION:A ribbon heater is supplied with power and a stainless tube 2 is heated up to 150 deg.C while a valve 4 is closed and another valve 3 is opened and hydrofluoric anhydride bomb is also opened to fill the inside of the stainless tube 2 with the hydrofluoric gas draining the same through an exhaust processing vessel 12. After filling the hydrofluoric gas for three hours, the hydrofluoric anhydride bomb is closed and the stainless tube 2 heated at 150 deg.C is further vacuum-drained for three hours. Through these procedures, the concentration of impurities such as C, O, N etc. having influence upon the semiconductor characteristics may be reduced avoiding new adhesion of water, air, oxgen and carbon oxide to inner wall of the stainless tube 2 since the gas tube 2 may be cleaned without being exposed to atmosphere at all.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning dirt attached to the inner wall of a pipe through which a silicide gas such as silane or a mixed gas containing a silicide flows.

Among semiconductor manufacturing equipment, when silicide gas or a mixed gas containing silicide is used as a reactive gas in CVD, plasma CVD, and evixaxial growth equipment, the reactive gas is transported using piping made of materials such as stainless steel. It leads to the reaction chamber. Mainly 5iOL is used on the inner wall of this pipe.
Silicon oxides such as these have adhered to the surface, causing problems in the manufacture of semiconductors. That is, silicon oxide was deposited on the inner wall due to a reaction between oxygen mixed in due to a trace amount of atmospheric leakage and silicide gas during long-term use of 6 months to 1 year. For this reason, a method has been sought for cleaning and removing the dirt on the inner wall in order to improve the characteristics of the manufactured semiconductor device.

The conventional method for cleaning pipes is to remove all the pipes that flow silicide gas or a mixture containing silicide, disassemble them into parts such as stainless steel pipes, mass flow meters, stomp valves, etc., and then clean them using fluoride. hydrogen M solution or hydrofluoric acid,
A mixed solution of nitric acid was used to remove deposits on the inner walls. In this method, the pipes are disassembled once, which takes time to clean, and the operator directly uses chemicals such as hydrogen fluoride solution, hydrogen fluoride, or nitric acid solution, resulting in a high rate of accidents.

The present invention is a heuristic invention discovered through experiments by the inventors who were perplexed by the above problem.

The present invention is characterized by flowing anhydrous hydrogen fluoride gas (purity of 99.9% or more) through a pipe through which a silicide gas or a mixed gas containing a silicide flows, and further heating the pipe to be cleaned.

The present invention connects an anhydrous hydrogen fluoride cylinder to the gas inlet of the piping and simply flows the gas to remove silicon oxide, etc. attached to the inner wall of the piping, so disassembly and assembly of the piping can be omitted, making it possible to manufacture semiconductors. It is safe because the time during which the equipment is stopped is short and the operator does not come into direct contact with chemicals.

In addition, by flowing hydrogen fluoride gas into the piping and heating the entire piping at the same time, the cleaning ability can be increased.
This also leads to a reduction in cleaning time. KaP! ! ) Since the temperature is high, the cleaning ability can be improved, but there are limits depending on the materials used in the piping, such as the mass flow controller and stop valve, and the heat resistance temperature. Generally 15
It can be heated up to 0'C. Also, 100″C or more, 1
By heating up to 50'C, in addition to the cleaning performance mentioned above, oxygen, carbon oxides, air, etc. adsorbed on the inner wall of the pipe are removed.
It has the advantage of being able to remove gases or liquids such as water.

Examples are shown below.

Example 1 FIG. 1 is a schematic diagram of a plasma CVD apparatus and a gas piping system (doping system).

In the drawing, the pipe (2) to be cleaned is sufficiently evacuated using the exhaust pump (10) of the device. Next, valve (3)
Close the valve (4) and purge dry N2 between the valve (4) and the connection to the gas pump (1). In this state, remove the current plug from the connection port (1) to the gas cylinder and attach an anhydrous hydrogen fluoride cylinder.

Next, cover the stainless steel tube (2) with a ribbon heater without any gaps. In this state, the ribbon heater is energized and 15
Heat the stainless steel pipe to 0°C, close the valve (4), open the valve (3) to pass the hydrogen fluoride gas through the stainless steel pipe (2), and open the valve (3) to pass the hydrogen fluoride gas through the inside of the stainless steel pipe (2) for exhaust treatment. Tank (
12). After flowing hydrogen fluoride gas for 3 hours, the anhydrous hydrogen fluoride cylinder was closed and evacuated for another 3 hours while being heated to 150°C.

After this cleaning, silane (Sin
When a solar cell was fabricated by a known plasma CVD method using a silicide gas with H2*ILn > 1), the efficiency of the solar cell was around 5.5% before cleaning, but after the cleaning process of the present invention, the efficiency of the solar cell was approximately 5.5%. With this, the efficiency was 8.5%. In addition, the piping (2') on the exhaust side from the reaction chamber (8), which had previously been contaminated with oil from the exhaust pump (1o), had been cleaned.

As in this example, the gas piping does not come in contact with the atmosphere at all (it can be cleaned, so new water or water is added to the inner wall of the stainless steel pipe).
It was possible to reduce the concentration of impurities such as C10 and N, which affect semiconductor film characteristics, without adsorbing air, oxygen, or carbon oxides at all.

In the present invention, hydrogen fluoride and at the same time have a purity of 99.999%.
It is effective to purge (exhaust treatment) the above inert gases (water or oxygen additives are 3 PPM or less) such as margon, nitrogen, hydrogen, and helium with an inert gas.

[Brief explanation of drawings]

FIG. 1 shows an outline of the plasma CVD apparatus and gas piping. Figure 2 shows a cross section when ribbon heaters are placed on gas piping. 1 is a gas cylinder inlet, and 2.2' is a stainless steel pipe. Patent applicant Commissioner of the Patent Office 1. Display of the case 1982 Patent Application No. 207149 26 Name of the invention Method for cleaning pipes 3, Person who makes Ht1 correction 4, Date of amendment order January 11, 1980 (Shipping date January 31, 1980) 5. Delete column 6 for the brief description of the drawing to be corrected, and from line 9 on page 6 to line 12 on page 6 of the specification of contents of the correction.

Claims (1)

[Claims] 1. By flowing anhydrous hydrogen fluoride (liver) gas through a pipe that flows a silicide gas such as silane and a mixed gas containing a silicide, stains on the inner wall of the pipe can be removed without disassembling the pipe. A method for cleaning piping characterized by removing. 2. A method for cleaning piping according to claim 1, characterized in that the piping to be cleaned is heated. 3. A method for cleaning piping according to claim 1, characterized in that the anhydrous hydrogen fluoride used has a purity of 99.9% or more.