JPS60182128A - Thin film forming device - Google Patents

Abstract

PURPOSE:To prevent an undesired film from forming on the inner surface of a light incident window of a reaction vessel by blowing inert gas to the inner surface of the window, thereby preventing stock gas which contributes to the accumulation from contacting with the inner surface of the window. CONSTITUTION:A gas nozzle 17 for preventing the cloud of a light incident window is provided on the inner surface of a light incident window 12 of a reaction vessel 11. Inactive rare gas such as hydrogen or halogen is supplied to the nozzle 17. The nozzle 17 is formed of a stainless steel pipe, and a plurality of gas injection holes are formed toward the window 12 at the pipe. Thus, inactive gas is blown to the inner surface of the window 12 of the vessel 11, thereby eliminating the stock gas which contributes to the accumulation of the film on the inner surface of the window 12. Then, no undesired film is formed on the inner surface of the window 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thin film forming apparatus using a photo-excited gas phase chemical reaction, and particularly to a thin film forming apparatus which is excellent in mass productivity and workability.

[Background of the invention]

A method of activating the reaction with light energy (hereinafter referred to as photoCVD method) is one of the methods for forming thin films by gas phase reaction.
It has been known. Compared to reaction activation using thermal energy, plasma, etc., activation using light energy allows the reaction to occur at a lower temperature, and is also widely used because it allows stable thin film formation without damage from electromagnetism or accelerated charged particles. A range of applications are considered. As light energy, laser light, mercury lamp, halogen lamp, deuterium lamp, etc. are known. Among these, mercury lamps are often used from the viewpoints of wavelength, intensity, irradiation area, ease of handling, etc. suitable for reaction activation. In particular, a reaction in which the resonance line of a low-pressure mercury lamp is used as excitation light and mercury vapor is added to the raw material to utilize the sensitizing effect is widely used because of its good effect.

A conventional thin film forming apparatus using the optical CV method is shown in FIG. The device is roughly divided into a reaction system 10 and a reaction gas supply system 20.
, the exhaust system 30 consists of three parts.

The reaction system 10 includes a reaction container 11, an excitation light source 13, a substrate support 14, and a heating source 15 thereof. The reaction vessel 11 is equipped with a light entrance window 12 made of transparent quartz or the like that transmits excitation light. Film-forming substrates, for example silicon wafers 1G, are arranged on a substrate support stand 14 in a reaction vessel 11, and excitation light is irradiated almost perpendicularly onto the surface of the silicon wafer 16. As the heat source 15, a resistance heater, an infrared lamp, or the like is used.

The reaction gas supply system 20 supplies monosilane (SiH4), oxygen (02), ammonia (NH3), and nitrous oxide (N2).
o), raw material gas such as phosphine (PH3) is passed through the flowmeter 21
Through the reactor, a liquid raw material such as hydrazine (N2H4) is supplied to the reaction vessel 11 using a carrier gas. Further, mercury vapor as a sensitizer is supplied to the reaction vessel 11 by flowing a reaction gas or other carrier gas through a mercury evaporator 22 in a constant temperature bath.

In the exhaust system 30, an exhaust device 31 such as a rotary pump or a booster pump is used to replace the gas in the reaction vessel 11 and adjust the pressure of the atmosphere during the reaction. Additionally, a trap and removal device 32 for unreacted gas and reaction products is added.

The problem here is the following regarding the reaction system 10.

A film is also deposited on the inner surface of the excitation light entrance window 12 of the reaction vessel IJ, resulting in poor transmittance of the excitation light. Since the rate of photochemical reaction, that is, the rate of film deposition, is proportional to the intensity of the excitation light, when the transmittance of the excitation light decreases, the rate of film deposition decreases, and furthermore, the reaction stops, making it impossible to obtain the desired film thickness.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film forming apparatus that prevents the formation of an undesired film on the inner surface of a light entrance window of a reaction vessel, and thereby has good workability and mass productivity.

[Summary of the invention]

The present invention is characterized by a thin film forming apparatus that sprays an inert gas onto the inner surface of the light entrance window of a reaction vessel to prevent source gas contributing to film deposition from coming into contact with the inner surface of the light entrance window.

[Embodiments of the invention]

The present invention will be explained in detail below using examples.

Figure 2 shows an embodiment of the apparatus of the present invention.
An inert gas supply nozzle that does not produce any substances is installed to spray the inert gas onto the inner surface of the light entrance window. The same parts as in Fig. 1 are indicated by the same number -m. The reaction vessel 11 is made of stainless steel and has a diameter of 200 m and a height of 80 m.
A light entrance window 12 is provided, which has a circular box shape of 2.0 mm in diameter and is made of transparent quartz, especially synthetic quartz that has good transmittance for short wavelength light such as vacuum ultraviolet light. The substrate support stand 14 is made of aluminum and can be rotated from the outside in order to make the deposited film thickness uniform. The heating source 15 is a resistance heater equipped with a temperature regulator, and the heating source 15 is a resistance heating heater equipped with a temperature regulator.
6 can be maintained at a desired temperature.

The excitation light source 13 is a low-pressure mercury lamp that emits resonance lines at wavelengths of 185'nrn and 254 nm. Although not shown in the drawings, the space between the lamp house and the light entrance window 12 of the reaction vessel 11 is replaced with nitrogen gas to prevent light absorption, particularly ozone generation.

The gas supply system is the one shown in FIG. 1 with another gas supply nozzle 17 for supplying one or a mixture of inert gases such as hydrogen, halogen and its hydrides, nitrogen, argon, and helium. I made it possible. This additional gas supply nozzle consists of a stainless steel pipe with a diameter of 1/4 inch arranged in a ring shape near the inner surface of the light entrance window, and multiple gas ejection holes with a diameter of 0.25 mm facing the light entrance window. ing.

The exhaust system is a rotary one with an exhaust speed of 950 Q/min.
A mechanical booster pump with an evacuation speed of 100 rri'/h was used in combination with the pump.

Experimental Example 1 (Silicone film formation example) A mercury evaporator 22 (mercury vapor pressure 5×10
``'' Torr) into the reaction vessel 11.

The coating substrate 16 was a silicon wafer with a diameter of 3 inches, and the substrate temperature was set at 200'C. Hydrogen 400mΩ is used in the inert gas nozzle 17 to prevent film deposition on the light entrance window.
/min was supplied. The pressure inside the reaction vessel 11 is 1,5
Torr. 2700-320 for 20 minutes reaction
A film is deposited on 〇, and the average film deposition rate is about] 508 mi
It is n. If an inert gas (hydrogen in this example) is not blown onto the inner surface of the light entrance window, an amorphous silicon film will also be deposited on the inner surface of the light entrance window, and within a few minutes the light entrance window will become cloudy and the excitation light will become cloudy. permeation is blocked and the reaction does not proceed, making it impossible to obtain a film thickness of several hundred eight or more.

Experimental example 2 (Silicone film formation example (2)) Mixed gas of 5% monosilane and 95% nitrogen as reaction gas 500 mQ/m
In is supplied to the reaction vessel 11 through the mercury evaporator 22. Hydrogen chloride 100rr+Q/min and nitrogen 200 mQ were supplied to the gas nozzle 17 for preventing film deposition on the light entrance window 12.
/ min of mixed gas is supplied. In order to prevent the mixing of the original gas for film deposition on the substrate and the gas for preventing film deposition on the inner surface of the light incident window and to improve the efficiency of both, a quartz looper 18 (scale plate) is placed between the two. installed. Looper 1
The plate No. 8 was 100 μm thick, 8 sides long, and 4 m apart, and the set angle was perpendicular to the substrate surface, that is, parallel to the speed of excitation light, so as not to impede the irradiation of excitation light and to reduce the conductance of both gases. . The exhaust gas was released to atmospheric pressure. Other reaction conditions were the same as in Experimental Example 1. Approximately 4 in 1 hour reaction
An amorphous silicon film of 0.000 was successfully deposited. Although the average film deposition rate is 678/mi, which is inferior to Experimental Example 1 and the conventional example, it has the advantage of being able to operate under atmospheric pressure and forming a thick film without clouding the light entrance window 12 at all. here,
Hydrogen chloride gas not only prevents direct contact between monosilane and the light entrance window, but also has the effect of etching the amorphous silicon that has undesirably deposited on the inner surface of the light entrance window, making it extremely effective in preventing fogging of the light entrance window. It is true.

Experimental Example 3 (Formation of silicon oxide film) A mixed gas of 5% monosilane and 95% nitrogen as a raw material gas was supplied to the mercury evaporator 22 at 500 rnD,/ri-in.
through, and nitrous oxide chamber 23250 m D, / mi
n is supplied to the reaction vessel 11. Although the substrate 16 is not heated, the temperature is raised to 60 to 70° C. by irradiation with the mercury lamp 13. Nitrogen is supplied at 2000 rn Q /min as an inert gas for preventing film deposition on the inner surface of the light entrance window 12 .

The focus inside the reaction vessel is atmospheric pressure. When forming a silicon oxide film, if pure silicon oxide is formed in the form of a film, clouding of the light entrance window will not occur, but if silicon chemotactic particles adhere, the incident light will be scattered and the excitation light intensity will be reduced. decrease. This tendency is particularly strong in reactions where the film deposition rate is high under atmospheric pressure. Therefore, it is effective to blow an inert gas that does not cause deposits on the inner surface of the light entrance window.

A 1 μm thick silicon oxide film was formed in about 15 minutes of reaction.

Experimental Example 4 (Formation of silicon nitride film) 8 m D of monosilane was used as the raw gas,
/min and ammonia at 72 mΩ/min are supplied to the reaction vessel 11 through the mercury evaporator 22. The substrate 16 was heated to 200°C. Helium 300 rn 07m- is used as an inert gas to prevent deposition on the inner surface of the light entrance window 12.
Supply 1n. The pressure inside the reaction vessel is 3-4 Torr. A film of 2200-270 OA is deposited in a 30-minute reaction, and the average film deposition rate is about 70-9Q8/'min. If an inert gas is not sprayed onto the inner surface of the light entrance window, the reaction will stop in about 15 minutes and it will be difficult to obtain a film thickness of 1000 to 15008 or more.

The above has described in detail the formation of thin films of silicon and its compounds, but when dopants such as phosphorus and boron are further added to these, or other materials such as compound semiconductors, metals and their oxides, carbides, nitrides, etc. The present invention can be similarly applied to thin film formation.

Inert gases that do not cause deposits on the inner surface of the light entrance window include gases that have small light absorption or extinction cross sections such as nitrogen and argon that hardly react, as well as gases that do not cause deposits such as halogens and their hydrides. It is possible to use a gas that has a good etching property when reacting with the etching process. Particularly in the latter case, conductance control plates such as louvers and differential exhaust systems are moved to the right in order to reduce mixing with the source gas.

〔Effect of the invention〕

According to the present invention, it is possible to prevent the formation of an undesired film and the adhesion of fine particles on the inner surface of the light entrance window of the C reaction vessel in the photo-CVD method, and it is possible to form a thick film with a high film deposition rate.

For this reason, we were able to develop a photo-CVD device with good workability and mass productivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional photo-CVD apparatus, and FIG. 2 is a schematic diagram of a photo-CVD apparatus according to the present invention.

Claims (1)

[Claims] 1. A thin film forming apparatus using a photo-excited gas phase chemical reaction, including: (a) a reaction vessel having a window through which light of nine selected wavelengths enters; (b) a thin film placed in the reaction vessel; (c) means placed outside the reaction vessel for heating the substrate; (d) means for introducing light of a selected wavelength through a light entrance window of the reaction vessel; ,' (e) a means for introducing raw material gas for the reaction into the reaction vessel and a means for exhausting exhaust gas and adjusting the pressure within the reaction vessel; (f) forming a deposit toward the inner surface of the light entrance window of the reaction vessel; 1. A thin film forming apparatus comprising: means for spraying a non-reactive inert gas. 2. According to claim 1, a louver is provided between the light entrance window and the substrate in the reaction vessel to reduce mixing of the raw material gas for the reaction and the inert gas sprayed onto the light entrance window. A device for forming thin films using photo-excited gas phase reactions.