JPH04236780A - Formation of film by photo assisted cvd - Google Patents

Abstract

PURPOSE:To continuously form a film by photo assisted CVD or a long time without clouding a light-transmissive window or without cleaning or exchanging the window. CONSTITUTION:A light transmission chamber 38 is partitioned by a gate valve 40 and set on the light-transmissive window 42 side of a reaction chamber 10, the flow rates of the raw gas and purge gas are adjusted so that the purge gas pressure in the chamber 38 is made higher than the raw gas pressure in the reaction chamber 10, and then the valve 40 is opened to form a film on a substrate 18 by photo assisted CVD. The infiltration of the raw gas into the chamber 38 is completely prevented by the pressure difference between the reaction chamber 10 and the chamber 38, hence a thin-film product is not deposited on the inner surface of the window 42, and the window 42 is never clouded while the film is formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a film by photo-CVD.

0002

2. Description of the Related Art PhotoCVD is a method of forming a thin film on a substrate by causing a chemical reaction in a gas material using light energy. Among these methods, the most typical method is to optically excite material molecules and decompose them, and in order to absorb a single photon and cause the decomposition, high-energy ultraviolet light is required. Other methods include using the effect of vibrationally exciting molecules with infrared light, and heating the substrate with a laser to cause thermal decomposition.

As an optical CVD apparatus, one shown in FIG. 3, for example, has conventionally been used. In FIG. 3, the reaction chamber 10 is evacuated by a rotary pump 24 to maintain a vacuum, and a substrate 18 is attached to a holder 16 in which a heater 12 is embedded in the center of the reaction chamber 10. Raw material gas is supplied from the supply pipe 28. Further, a light transmission window 42 made of quartz glass or the like is attached to the surface facing the substrate 18, and light energy is transmitted onto the substrate 18 through the light transmission window 42 from a light source 44 that emits strong ultraviolet light such as a low-pressure mercury lamp. be introduced. Further, the decomposed raw material gas accumulates in the light transmission window 42, clouding the light transmission window 42 and reducing the light transmittance, so a purge gas supply pipe 48 is installed inside the light transmission window 42. The structure is such that a purge gas such as an inert gas is blown from the tank.

0004

[Problems to be Solved by the Invention] However, in the conventional optical CVD apparatus described above, source gas is supplied to the vicinity of the inner surface of the light-transmitting window by blowing a purge gas such as an inert gas onto the inner surface of the light-transmitting window. However, when the valve is operated during gas introduction, a pressure fluctuation occurs momentarily between the raw material gas and the purge gas, and a portion of the raw gas leaks through the light transmitting window. It is impossible to completely prevent fogging of the light-transmitting window by flowing to the inner surface.

[0005] Therefore, it is necessary to frequently interrupt the film-forming operation to clean or replace the light-transmitting window, making it impossible to perform continuous film-forming for a long time, and interfering with the film due to interruption of the film-forming operation. In addition, there is a problem in that replacing the light transmitting window requires expense.

[0006] The present invention solves the problem that when forming a film using a conventional photo-CVD apparatus, decomposition products of the raw material gas accumulate on the light-transmitting window, and the amount of transmitted light is attenuated due to clouding of the light-transmitting window. This was developed to solve the problem, and it prevents the accumulation of thin film products on the inner surface of the light transmitting window, which is the light introducing window, and eliminates the need for cleaning and replacing the light transmitting window. It is an object of the present invention to provide a method for forming a film by photo-CVD, which enables continuous film formation and can form a thick film without an interface.

[0007]

[Means for solving the problem] The inventors have proposed a conventional optical CV
In Method D, the reason why a thin film product is deposited on the inner surface of the light-transmitting window is that the source gas enters the vicinity of the light-transmitting window. We have conducted extensive research on ways to completely prevent this. As a result, by providing a light transmission chamber on the light transmission window side of the reaction chamber and keeping the pressure of the purge gas in the light transmission chamber higher than the pressure of the raw material gas in the reaction chamber, it is possible to prevent the raw material gas from entering near the light transmission window. We have completed the present invention by discovering that this can be completely prevented.

[0008] The method for forming a thin film by photoCVD of the present invention is as follows:
A light transmission chamber 38 having a purge gas supply port 48 and a purge gas discharge port 54 and having a capacity of V2 and a reaction chamber 10 having a capacity of V1 and having a raw material gas supply port 26 and a raw material gas discharge port 20 are partitioned by a gate valve 40. , the light transmission chamber 38 is filled with purge gas at gas pressure P2, the reaction chamber 10 is filled with source gas at gas pressure P1, and after P1<P2, (v1
/V1)<(v2/V2) While supplying the raw material gas at a flow rate v1 and the purge gas at a flow rate v2, the purge gas outlet 54 is closed and the gate valve 40 is opened to reduce the light transmission. The gist is to form a film on the substrate 18 placed in the reaction chamber 10 by irradiating light energy through a light transmission window 42 provided in the chamber 38 .

[0009]

[Operation] The operation of the present invention will be explained based on the schematic diagram of a photo-CVD apparatus used in the method of the present invention shown in FIG. Initially, the reaction chamber 10 with a capacity of V1 cm3 and the light transmission chamber 38 with a capacity of V2 cm3 are separated by a gate valve 40. Next, v1c is supplied to the reaction chamber 10 from the raw material gas supply port 26.
The raw material gas is supplied at a flow rate of m3/min, and is exhausted from the raw material gas outlet 20 by the rotary pump 24.
Purge gas is supplied at a flow rate of m3/min and exhausted from the purge gas outlet 54 by a rotary pump 60.

At this time, since the gate valve 40 is still closed, the source gas is not supplied to the vicinity of the light transmitting window 42. In addition, the number of moles of the raw material gas in the reaction chamber 10 is n1 mole, and the number of moles of the purge gas in the light transmission chamber 38 is n1 mole.
Assuming 2 moles, n1∝v1 n2∝v2, so the pressure P1 of the raw material gas in the reaction chamber 10 and the pressure P2 of the purge gas in the light transmission chamber 38 are each P1=α
(v1/V1)T α: proportional coefficient P2=β(v2/V2)T
β: Proportionality coefficient.

After adjusting the flow rates of the source gas and purge gas so that P1<P2, the valve 5
0, the purge gas outlet 54 is closed, and the gate valve 40 is opened. By doing so, the purge gas is also exhausted together with the raw material gas through the reaction chamber 10 by the rotary pump 24. Therefore, since both the purge gas and the source gas are exhausted by the same rotary pump, P
The proportional coefficients α and β of 1 and P2 are α=β. Therefore, the condition that P1-P2=α(v1/V1-v2/V2)T<0, that is, (v1/V1)<(v2/V2)
If the relationship is satisfied, the raw material gas passes through the light transmission window 42
It is never supplied to

Next, the light transmitting window 4 provided in the light transmitting chamber 38
When light energy is irradiated from the light source 44 through the light transmitting window 2, a film is formed on the substrate 18 installed in the reaction chamber 10 due to the decomposition of the raw material gas, but the supply of the raw material gas to the light transmission window 42 is completely interrupted. Since this is prevented, the light transmission window 42 does not become cloudy, and a long time film forming operation is possible.

[0013]

[Example] An example of the present invention will be explained in comparison with a conventional example,
The effects of the present invention will be clarified. FIG. 1 is a schematic diagram of a photo-CVD apparatus used in the present invention. A holder 16 in which a heater 12 and a thermocouple 14 are embedded is installed in the center of the reaction chamber 10, and a substrate 18 is fixed to the holder 16 at an angle.

A raw material gas exhaust port 20 is provided at the bottom of the reaction chamber 10 below the holder 16, and a rotary pump 24 attached to a raw material gas exhaust pipe 22 connected to this raw material gas discharge port 20 is used to carry out the reaction. The gas in the chamber 10 is exhausted and the reaction chamber 10 is kept in a vacuum.

A raw material gas supply port 26 is provided on the ceiling of the reaction chamber 10 facing above the substrate 18, and a raw material supply pipe 28 connected to this raw material gas supply port 26 has two valves at the front and rear. A reservoir 32 and a mass flow controller 34 are attached. A raw material 36 for CVD is installed in the reservoir 32, and is sublimated by the reduced pressure atmosphere of the reservoir 32 to become a sublimated gas. A carrier gas such as H2 is passed through the mass flow controller 34.
Since the flow rate is adjusted by and supplied to the reservoir 32,
The carrier gas is mixed with the sublimation gas to become a raw material gas, which is supplied to the reaction chamber 10 from the raw material gas supply port 26 .

A light transmitting chamber 38 is provided on the side wall of the reaction chamber 10 facing the substrate 18 from the side, and a gate valve 40 that can be opened and closed is installed between the chamber 38 and the reaction chamber 10 . A light transmitting window 42 is installed at the innermost part of the light transmitting chamber 38, and a light source 4 that emits ultraviolet light is installed outside the light transmitting window 42.
4 is placed so as to irradiate ultraviolet light toward the substrate 18 through the light transmission window 42.

A purge gas supply port 46 is opened toward the light transmission window 42 near the light transmission window 42 of the light transmission chamber 38, and a purge gas supply pipe 48 connected to the purge gas supply port 46 is equipped with a valve 50. Mass flow controller 52
is attached to the mass flow controller 52.
The barge gas such as H2 whose flow rate is adjusted by the light transmitting window 4
2 will be supplied.

A purge gas exhaust port 54 is provided near the gate valve 40 of the light transmission chamber 38, and a valve 58 and a rotary pump 60 are attached to a purge gas exhaust pipe 56 connected to the purge gas exhaust port 54. , the purge gas in the light transmission chamber 38 is exhausted. In addition, 6
2 is a pressure gauge attached to the reaction chamber 10, and 64 is a pressure gauge attached to the light transmission chamber 38.

To form a film by photo-CVD according to the method of the present invention using the apparatus of this embodiment, the flow rate was controlled to v1 by the mass flow controller 34 into the reaction chamber 10 having a capacity of V1 with the gate valve 40 closed. The raw material gas is supplied from the raw material gas supply port 26, and the gas in the reaction chamber 10 is exhausted by the rotary pump 24. On the other hand, capacity V2
v to the light transmission chamber 38 by the mass flow controller 52
2, the purge gas with a controlled flow rate is supplied to the purge gas supply port 46.
The purge gas in the light transmission chamber 42 is exhausted from the purge gas outlet 54 by the rotary pump 60.

Here, the reaction chamber 10 indicated by the pressure gauge 62
After adjusting the flow rate v1 of the source gas and the flow rate v2 of the purge gas so that the pressure P2 in the light transmission chamber 38 indicated by the pressure gauge 64 is higher than the pressure P1 in the pressure gauge 64, the valve 58 is closed and the gate valve 40 is Open. By doing so, the purge gas is also exhausted together with the raw material gas through the reaction chamber 10 by the rotary pump 24. Therefore, the proportional coefficients α and β of P1 and P2 are α=β. Therefore, the condition that P1-P2=α(v1/V1-v2/V2)T<0, that is, (v1/V1)<(v2/V2)
The following relationship is satisfied, and the raw material gas is not supplied toward the light transmission window 42.

Next, the light transmitting window 4 provided in the light transmitting chamber 38
When the substrate 18 is irradiated with ultraviolet light from the light source 44 through 2, the substrate 18 placed in the reaction chamber 10 decomposes the raw material gas.
Although a film is formed on the surface of the light-transmitting window 42, the supply of raw material gas to the light-transmitting window 42 is completely prevented, so the light-transmitting window 42 does not become cloudy, and a long time film-forming operation is possible. .

Next, as an example of the present invention, the capacity V1 of the reaction chamber 10 is 5000 cm3, the inner diameter of the light transmission chamber 38 is 50 mm,
Using a device with a length of 200 mm and a capacity V2 of 500 cm3, W(CO)6 is installed as a raw material in the reservoir 32, H2 is used as a carrier gas, and the raw material gas flow rate v1 is set to 5.
0 cc/min, using H2 as the purge gas and setting the flow rate v2 to 50 cc/min, following the above procedure.
The film-forming process was repeated 10 times to form a W film on the substrate 18.

Note that v1/V1=0 in the above embodiment
．． 01, v2/V2=0.1, (v1/V1)
<(v2/V2). For comparison, a W film was formed on the substrate 18 using the conventional apparatus shown in FIG. 3 and using the same raw material gas and purge gas as in the conventional example, and repeating the same one-hour film forming operation 10 times. After forming the W film on the substrate 18, the film thickness of the W film deposited on the light transmission window 42 of the present invention example and the conventional example was measured, and the obtained results are summarized in FIG. 2.

As shown in FIG. 2, when the W film was formed using the conventional method, the W film thickness on the light transmission window was approximately 1200 Å, whereas in the method of the present invention, the W film on the light transmission window was approximately 1200 Å thick. No deposition was observed at all, confirming the effectiveness of the present invention.

[0025]

Effects of the Invention As described in detail above, the film forming method using the photoCVD method of the present invention includes a light transmitting chamber partitioned off by a gate valve on the light transmitting window side of the reaction chamber, and the material gas pressure in the reaction chamber is lower than the After adjusting the raw material gas flow rate and purge gas flow rate so that the purge gas pressure in the light transmission chamber is high, the gate valve is opened and a film is formed on the substrate by the photoCVD method, and the pressure between the reaction chamber and the light transmission chamber is The difference completely blocks the raw material gas from entering the light transmission chamber, which prevents thin film products from accumulating on the inner surface of the light transmission window and completely prevents the light transmission window from fogging during film formation. be done. Therefore, there is no need to clean or replace the transmission window, and it is possible to form a thick film without an interface by continuous film formation over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a photo-CVD apparatus used in the method of the present invention.

FIG. 2 is a diagram showing the thickness of a light transmission window formed after film formation by a conventional method and a method of the present invention.

FIG. 3 is a schematic diagram of a photo-CVD apparatus used in a conventional method.

[Explanation of symbols]

10 Reaction chamber 18 Board 20 Raw material gas outlet 26 Raw material gas supply port 38 Light transmission chamber 40 Gate valve 42 Light transmission window 44 Light source 46 Purge gas supply port 54 Purge gas outlet

Claims (1)

[Claims] 1. A light transmission chamber 38 having a capacity of V2 and having a purge gas supply port 48 and a purge gas discharge port 54, and a reaction chamber 10 having a capacity of V1 and having a raw material gas supply port 26 and a raw material gas discharge port 20. Partitioned by a gate valve 40, the light transmission chamber 38 is filled with purge gas at a gas pressure P2, the reaction chamber 10 is filled with source gas at a gas pressure P1, and P1<P2.
After that, the purge gas outlet 54 is supplied while supplying the raw material gas at a flow rate v1 and the purge gas at a flow rate v2 so as to satisfy the relationship (v1/V1)<(v2/V2).
is closed, the gate valve 40 is opened, and a film is formed on the substrate 18 installed in the reaction chamber 10 by irradiating light energy through the light transmission window 42 provided in the light transmission chamber 38. Characteristic film forming method using photo-CVD.