JPS61196528A - Thin film forming apparatus - Google Patents

Abstract

PURPOSE:To avoid any formation of reactive product on windows of armour type sheet in case films are to be formed by photo CVD process by a method wherein reactive gas is fed in the same direction as that of non-productive gas exhausted out of a reaction chamber. CONSTITUTION:A light source chamber 5 and a heating chamber 11 are supplied with non-productive gas and then the gas is led into 14 a reaction chamber through the gaps in a light transmissive shielding sheet 10. Then the gas is exhausted 14' from the armour type light transmissive shielding sheet 10 having a laminar flow on an exhaust port side while reactive gas 31 fed from a nozzle 30 is exhausted 31 having a laminar flow in the same direction as that of the non-productive gas flow 14, 14' in the space between the gas 14, 14' and a substrate 1 with a surface to be formed i.e. the substrate side. Through these procedures, a reactive product may not be formed on the surface of armour type light transmissive shielding sheet 10 at all. Resultantly the reaction chamber may be irradiated with ultraviolet rays with sufficient intensity exciting the reactive gas 31 continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention is a method for forming a thin film by photochemical reaction, in which a film is uniformly formed on a large surface on a transparent shielding plate for light irradiation. The present invention relates to a CVD (vapor phase reaction) device having means for forming a film without coating it with oil or the like.

"Prior Art and its Problems" As a technique for forming thin films through gas phase reactions, a photo-CVD method is known in which a reactive gas is activated by light energy.

This method is superior to the conventional thermal CVD method or plasma CVD method in that it is possible to form a film at a low temperature and does not damage the surface on which it is formed.

When carrying out such a photo-CVD method, an example of the method is shown in FIG.
), heating means (3) for the substrate, and a low-pressure mercury lamp (9) for irradiating light onto the substrate. Doping system (7
) is equipped with a mercury bubbler (13) for excitation of reactive gases and a rotary pump (19) in the exhaust system (8). A reactive gas such as disilane from a doping system is introduced into the reaction chamber (2), and when a reaction product such as amorphous silicon is formed on a substrate (substrate temperature 250°C), ultraviolet light is transmitted through the reaction chamber. light shielding plate (10),
Typically, a large amount of silicon film is also formed on the quartz window at the same time. Therefore, in order to prevent the formation of a film on this window, Fomblin oil (an example of fluorine-based oil) (16
) is thinly coated.

However, although this oil has the effect of preventing the formation of a film on the window (10), it ends up being mixed into the film as an impurity. Furthermore, a reaction product is simultaneously formed little by little on this oil, and the thickness of the film formed is limited due to light absorption there.

In order to solve these problems, the present invention aims to solve the problem in the photo-CVD method by installing a plurality of shielding plates for transmitting ultraviolet light. In order to provide ventilation in the chamber, a plurality of narrow plates are installed at a constant inclination in the form of a device, in which reaction products accumulate on the top surface of the translucent shielding plate and block ultraviolet light. In order to avoid light generation or to block light, remove non-product gases (gases that do not form solids by reaction or decomposition, such as He + A) from the light source chamber side.
r + H2.

Nz, NHz, NzO, O□ or a mixture thereof)
This is a method to derive the following.

Then, a reactive gas is introduced between this gas and the substrate in the same direction as the flow direction of this gas. Then, this reactive gas is efficiently excited onto the surface of the substrate to form a film. This flow of non-product gas can thus constitute a "gas wall" for the reactive gas (the wall action of the gas prevents the excited gas from adhering to the transparent shielding plate).

"Effect" Because of these features, when a film is to be formed by the photo-CVD method according to the method of the present invention, no or very few reaction products are formed on the shroud-like window. As a result, ultraviolet light can fully pass through the "shroud" window,
Sufficiently excite (including decomposition and reaction) reactive gases,
Reaction products may accumulate on the formed surface. At that time, the same reaction product also flies to the top surface of the transparent shielding plate,
This product is inhibited by the "gas wall" created by the non-product gas discharged into the reaction chamber through the gap between the shutter plates, and cannot adhere to the upper surface of the window. Therefore, no reaction products are formed on the surface of the "armor plate-like" light-transmitting shielding plate (also called a window), and as a result, ultraviolet light is emitted with sufficient intensity into the reaction chamber indefinitely to excite the reactive gas. Let's continue. Then, a film can be formed to a sufficient thickness on the surface of the substrate. Then, instead of the conventionally known thickness of 100 to 200 layers (without oil coating) or 1000 to 1,500 layers (with oil coating), a film with a desired thickness of 500 to 5000 layers is repeatedly formed. It can be done.

Further, in the present invention, after this photo-CVD, it is possible to produce films of the same type or different types on this film in the same batch by plasma CVD using the same reaction chamber.

Further, according to the present invention, unnecessary products deposited on the window due to an insufficient amount of non-product gas being discharged can be removed by plasma etching without exposing the reaction chamber to the atmosphere. Furthermore, since the apparatus of the present invention is an oil-free reaction system, the background level of vacuum could be kept at 10-'torr or less. A photoCVD film can be formed by photoexcitation of a non-oxide reaction product such as a semiconductor film such as silicon, silicon carbide, silicon nitride, aluminum nitride, or metal aluminum.

``Example j'' The present invention will be described in detail below using an example shown in FIG.

In Fig. 2, a substrate (1) having a surface to be formed is held in a holder (1゛), and is provided in close proximity to a halogen heater (3) (the upper surface of which is water-cooled (32)) above a reaction chamber (2). ing. The reaction chamber (2), the light source chamber (5) in which the ultraviolet light source (9) is disposed, and the heating chamber (11) in which the heater (3) is disposed are kept under approximately the same vacuum at a pressure of 100 torr or less. held at the same time. For this purpose, a non-product gas (nitrogen, argon or ammonia in this case) that does not interfere with the reaction is introduced from (28) into the flowmeter (21), and from the valve (22) into the light source chamber (5) and heating chamber (11). supplied. The gas was then led out (14) into the reaction chamber through the gap in the "armor plate-like" light-transmitting shielding plate (10), thereby preventing unnecessary reaction products from adhering to the upper surface of the shielding plate. Also, this "armor plate shape"
The non-product gas flow (14) is exhausted from the light-transmitting shielding plate (10) to form a laminar flow toward the exhaust port (14"),
(14') and the substrate (1) having the surface to be formed, that is, on the substrate side, there is a reactive gas (31) from the nozzle (30).
The exhaust gas (31') flows in the same direction as (14) and (14') to form a laminar flow. These reactive gases include ammonia (NH3), nitrogen fluoride (NF3), silicide gases such as silane (StnHzn,z), silicon fluoride (Si
Fz, SiF4.5iJi.

H2Sxh) + methyl aluminum (AI (CH
2) 3) or a gas mixture thereof may be used. As the non-product gas, hydrogen, argon or helium was used when a semiconductor such as silicon was produced as a reaction product. When making nitrides (silicon nitride, aluminum nitride), nitrogen or ammonia was used. Hydrogen, argon, or helinium was used to make metallic aluminum.

The doping system (7) includes a valve (22) and a flowmeter (21).
), and the reactive gas to form a solid product after reaction was supplied from (23) to 26). Pressure side of reaction chamber JR c, control valve (17), cock (2)
0), a turbo molecular pump (using Osaka Vacuum PG550) (18), a rotary pump (19),
This was achieved by exhausting the air.

When the preliminary chamber is evacuated using the cock (20), the exhaust system (8) is opened on that side and closed on the reaction chamber side. Furthermore, when the reaction chamber was evacuated or a photochemical reaction was performed, the reaction chamber side was opened and the preliminary chamber side was closed.

The film formation process used a load-lock method in which no pressure difference was created in moving the substrate from the preliminary chamber to the reaction chamber. First, the substrate (1) and holder (1゛) are inserted and arranged in the preliminary chamber (4), and after vacuuming,
Open the gate valve (6) between the reaction chamber (2) which has been evacuated to 10-'torr or lower in advance,
Transfer the substrate (1) and holder (l゛) to the reaction chamber (2), close the gate valve (6), and separate the reaction chamber (2) and the preliminary chamber (
4) and were separated from each other.

After that, to prevent reactive gases from entering the light source chamber due to backflow, first add 100 to 50% of the non-product gas to the light source chamber.
It was introduced into the light source chamber at a flow rate of 0 cc/min, and also into the connected heating chamber at the same time. And they are multiple "armor plate-like"
It is led out (14) into the reaction chamber through the gap between the shielding plates (10) and exhausted (14'). Thereafter, reactive gas (31) was supplied through the nozzle (30).

The light source for the reaction was a low-pressure mercury lamp (9), equipped with water cooling (32"). The ultraviolet light source was a low-pressure mercury lamp (185 nm).

There are 16 lamps (luminous length: 40 cm, irradiation intensity: 20 mW/cm", lamp power: 40 W) that emit light at a wavelength of 254 nm.

This ultraviolet light irradiates the reactive gas (31) in the reaction chamber (2) and the formation surface (1) of the substrate (1) through the "armor plate-like" quartz (10) that is a light-transmitting shielding plate. do.

The heater (3) is a "deposition amplifier" type heater located above the reaction chamber (2) to prevent flakes from adhering to the surface to be formed and causing pinholes, and to prevent the flakes from adhering to the substrate (
1) was heated from the back side to a predetermined temperature (chamber/ML to 500°C) using a halogen heater.

Furthermore, even if flakes fall onto the armor plate window, the non-product gas (14) spewing out from the gap will cause the exhaust system (16') to
blew it away.

The reaction chamber was made of stainless steel, and the ultraviolet light source was also kept in a reduced pressure atmosphere in a stainless steel container surrounding the light source chamber and the reaction chamber, which were kept under vacuum. Therefore, a film can be formed on a substrate with a size of 30 cm x 30 cm instead of a small film formation area of 5 cm x 5 cm without any industrial problems.

In this example, the "armor plate-like" light-transmitting shielding plate is 3 cm long.
(width) x 34 cm (length) x 21 II m (thickness), and each was overlapped by 3 mm. Twelve such armor plates were arranged with a gap of 50 μm between them. The average wind speed is 3 torr, and the pressure in the reaction chamber is 3 torr.
If the gas is discharged at 20 cc/min, the flow rate will be 1 m/min. As a result, a sufficient wind speed (50 cm/min to 5 m/min) can be obtained to deposit the excited reactive gas in a 3 cm wide area.

Further, specific examples according to the present invention are shown in Experimental Examples 1 to 4 below.

Experimental Example 1...Ammonia was supplied from (25) at a rate of 50 cc/min and disilane was supplied from (23) at a rate of 8 cc/min as reactive gases on the silicon nitride film formation side, and the substrate temperature was 350.
℃. The substrates were four 5-inch diameter wafers. The internal pressure of the reaction chamber (2) was 3.0 torr.

Nitrogen was flowed as a non-product gas at a flow rate of 200 cc/min (average wind speed of 1 m/min) to prevent silicon nitride from adhering to the upper surface of the armor plate-like shielding plate.

A film thickness of 1,500 wafers was formed on the substrate in a 30-minute reaction. The film formation rate was 50 people/min. The present invention uses direct optical excitation without using mercury vapor or the like.

The variation in the five points of the coating was within ±10%.

In order to obtain a film thickness of 1500 Å or more, the film formation time may be increased to 1 hour or more.

For example, a film of 0.5μ can be obtained.

Furthermore, in order to stop the reaction after this, a reactive gas (3
Stop the introduction of 1), evacuate the inside of the reaction chamber (2),
Furthermore, after stopping the introduction of the non-product gas (14) using the valve (22), the gate valve was opened and the substrate on which the film was formed was transferred to the preliminary chamber.

In this example, after the film was formed, the reaction chamber was opened and the state of the silicon nitride biofilm on the upper surface of the "armor plate-like" shielding plate was examined. However, there was almost no biofilm. Of course “armor plate”
When the non-product gas was not led out from the gap in the shielding plate, a silicon nitride film of about 200 layers was formed on the shielding plate, completely blocking ultraviolet light. As a result, only a silicon nitride film with a thickness of 200 mm could be obtained on the surface of the substrate.

Experimental Example 2 A silicon nitride film was formed under the same conditions as Experimental Example 1. However, the nitrogen gas discharged from the light source chamber was 20 cc/min, which was 1710 cc/min as in Example 1. As a result of 2 hours of coating, it is possible to coat 700 people. However, it was almost impossible to form a further film even if a film-forming process was performed.

As a result of examining the silicon nitride film on the "armor plate-shaped" shielding film in the same manner as in Example 1, it was found that the silicon nitride film on the upper surface of the shielding plate was approximately 2.
It was formed with a thickness of 0.00 people. It is presumed that this made it difficult to form a silicon nitride film on a larger substrate.

In order to remove this unnecessary product, the inner wall of the reaction chamber,
In order to simultaneously remove unnecessary reaction products that become flakes on the holder, the apparatus of the present invention applies electrical energy to a pair of electrodes, the holder (1°) and the electrode (29), from a high frequency power source to perform plasma etching. . That is, after returning the holder to the original reaction chamber and closing the gate, (26)
NF was supplied.

At this time, the non-product gas (14) was set at Occ/min. Then, the pressure in the reaction chamber was set to 0.1 torr, and the pressure was 13.56M.
)lz high frequency wave was applied at an output of 80 cm to perform plasma etching on the inside of the reaction chamber (2) and the upper surface and inner surface (light source chamber side) of the window (10).

After about 20 minutes, the silicon nitride film on the quartz (10), which was an unnecessary reaction product, could be completely removed. After this NF was removed in vacuo, hydrogen was added from step (25), and residual fluorine in the reaction chamber was removed by plasma cleaning. After this, a second coating was produced, and a coating with good reproducibility was also produced.

Experimental Example 3 Formation example of amorphous silicon film Disilane (SizHb) was supplied from (23) at a flow rate of 100 cc/min. Further, hydrogen was supplied from (28) at a flow rate of 500 cc/min to prevent it from adhering to the upper surface of the "armor plate-like" shielding plate. The temperature was 210° C. and the reaction chamber pressure was 3 torr. A film thickness of 1,200 layers could be formed on the surface to be formed in 60 minutes of deposition.

Even if the same process is repeated, the same film thickness of 1000~1
We were able to get 200 people.

Experimental example 3... Formation example AI of aluminum nitride (C
H3) methylaluminum with x as a representative example (2
3) at a rate of 30 cc/min. (24), hydrogen was diluted at 30 cc/min. Additionally, ammonia was supplied from (28) at a rate of 300 cc/min. As a result, the methyl aluminum decomposed without introducing mercury vapor into the light source chamber, and it was possible to create an aluminum nitride film 1,300 times thick. Film formation speed: 30 people, 7 minutes (pressure: 3 torr).

The temperature was 350°C). Other alkyl compounds such as ethylaluminum diimium (CzHs) 3 may also be used.

Experimental Example 4: Formation of metallic aluminum In Experimental Example 3, hydrogen was added from (28) at a flow rate of 300 cc/min. After 3 hours of deposition, a metal aluminum layer with a thickness of about 500 people was obtained on the surface to be formed. The rest was the same as in Experimental Example 3.

"Effects" As is clear from the above description, the present invention, when forming a film on a large-area substrate, removes the unnecessary reaction-generated film on the light-transmitting shielding plate by using a plurality of "armor plate-like" By using a shielding plate, it can be removed more completely.

Therefore, there is no need to use any oil on the top surface of the window.

Therefore, it is difficult for impurities such as carbon to enter the coating, and the exhaust pressure can be set to a high vacuum of 10'' torr, making it possible to produce an oil-free coating with high purity.

Furthermore, by removing flakes and the like that had fallen onto the top surface of the window, we created a completely oil-free environment in the reaction chamber, making continuous formation possible for the first time.

Although the present invention has shown experimental examples using silicon, silicon nitride, aluminum nitride, and metal aluminum, M(CI(:l), that is, M as In+
Using Sn, Cr, Sn + Mo, Ga + H, introducing M metal or oxide gas into it, MSi2
You may also produce a silicide such as. It is also effective to use a carbonylated product of iron, nickel, or cobalt as a reactive gas to form a film of iron, nickel, cobalt, or a compound thereof, or a compound of silicide and these.

In the experimental examples described above, dopants can be added at the same time when forming a silicon semiconductor. Also, do not use a low-pressure mercury lamp as a light source (excimer laser (wavelength 100-400 nm)).
It goes without saying that , argon laser, nitrogen laser, etc. may be used in place of or in combination with the low-pressure mercury lamp.

In the present invention, the film growth rate may be improved by passing the film through a mercury bubbler.

In an experimental example of the present invention, a shielding plate in the form of an armor plate was arranged to be tilted from one side, in FIG. 2, from the lower right side to the upper left side. However, this may be an armor plate in which the nozzle is disposed in the center and a shielding plate is disposed tilted upward from the center to the left and right. Further, when the gas flow is supplied from the center toward the outer periphery, if the center is located concentrically from the center, the gas flow may be arranged concentrically from the outside toward the center in the form of a shroud.

[Brief explanation of drawings]

FIG. 1 shows a conventionally known optically pumped CVO device. FIG. 2 shows a CVO device of the present invention.

Claims (1)

[Claims] 1. A light source for excitation of a reactive gas and a reaction chamber in which a substrate having a surface to be formed is disposed, and a light-transmitting shield is provided between the light source and the reaction chamber. In a thin film forming apparatus having a plate, the shielding plate being divided into a plurality of armor plate-like parts, the non-product gas is led out to the reaction chamber side through the gap between the armor plate-shaped light-transmitting shielding plates, and By introducing the reactive gas into the reaction chamber in the same direction as the direction in which the non-product gas is exhausted and closer to the substrate than the non-product gas, the reactive gas is introduced into the armor plate-like translucent surface. A method for forming a thin film, characterized in that it does not accumulate or is difficult to accumulate on a shielding plate. 2. A thin film forming method according to claim 1, characterized in that a gas wall is formed in a boundary region between a non-product gas and a reactive gas.