JPS61127120A - Formation of thin film - Google Patents

Abstract

PURPOSE:To arrange a thin film over a large area uniformly by separating a light source chamber from a reaction chamber with a light transmitting screening panel and placing the heated substrates and effecting formation of thin films and removal of wastes by a photochemical reaction and a plasma chemical reaction. CONSTITUTION:A light source chamber 5 is separated from a reaction chamber 2 with a crystal plate 10 and a valve 6 is shut to control a flow of NH3 25 and Si2H6 23 which are supplied from a nozzle 14 and the atmosphere is kept at 3Torr. Under irradiation with a low-pressure mercury lamp 9 through the crystal plate 10, Si3N4 is deposited on a substrate 1 which is kept at 350 deg.C by a heating chamber 11. A high- frequency power is applied to the nozzle 14 and a substrate holder, and Si3N4 is deposited to form a film of no less than 0.5mum thick under the internal pressure of 0.1Torr without damage due to a plasma. The substrate 1 is taken out to a preparatory chamber 4 and the holder is returned to the reaction chamber 2. NF3 26 is supplied to make the pressure 0.3Torr and a high-frequency power 15 is supplied thereby removing the disused Si3N4 film on a window 10. H2 27 is supplied and the residual F is removed. By this method, the film of the same thickness can be formed uniformly over a large area with a good reproducibility.

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. The present invention relates to a CVD (vapor phase reaction) method having means for forming a light-transmitting shielding plate without coating it with oil or the like.

``Prior Art j'' As a technique for forming thin films by gas phase reaction, 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.

However, when carrying out such a photo-CVD method, an example of which is shown in FIG.
1), a means for heating the substrate (3), and a low-pressure mercury lamp (9) for irradiating the substrate with light. Doping system (
7) is equipped with a mercury bubbler (13) for excitation of reactive gas, and the exhaust system (8) is equipped with a rotary pump (19). When a reactive gas such as disilane from the doping system is introduced into the reaction chamber (2) and a reaction product such as amorphous silicon is formed on the substrate (substrate temperature 250°C), the reaction chamber is used to transmit ultraviolet light. a 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) (1
6) is thinly coated.

However, although this oil has the effect of preventing the formation of a film on the window, this oil 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.

Also, because low-pressure mercury lamps are held at atmospheric pressure, the quartz must be thicker because of this pressure. The atmosphere between the mercury lamp and the quartz window causes ultraviolet light, especially 185
nm short ultraviolet light is absorbed. When a large window is used to form a large-area substrate, there are drawbacks such as the window being easily damaged by vacuum.

In order to solve these problems, the present invention is based on the premise that the formation of a film on the window and on the substrate at the same time, while reducing the amount, is not accepted as an unavoidable problem. There is. After the substrate on which the coating has been formed is taken out, the window product formed on the window by plasma gas phase reaction that prevents the transmission of ultraviolet light is basically etched away.

In addition, after decomposition of the reactive gases, ammonia, hydrazine, or nitrogen fluoride in a gaseous state was blown out toward the window from a nozzle to prevent the products from adhering to the window. Furthermore, silane (SinH1n*z n
≧1) Aluminum compounds (e.g. Al (CH3)
The liquid is blown out from a nozzle toward the substrate to promote formation of a film. This nozzle is made of metal, and the nozzle and the substrate (substrate holder) or stainless steel reaction chamber are each used as a pair of electrodes for plasma reaction (
etching or deposition).

In this way, a part of the reactive excited gas generated especially by plasma etching also collides with the window, thereby making it possible to remove unnecessary reaction products on the window. Therefore, there is no obstruction to ultraviolet light on the window for the next film formation on the substrate.
The ultraviolet light was able to effectively reach the formation surface of the substrate.

Furthermore, the light source room containing the low-pressure mercury lamp is vacuumed (0.1 to 10 tons).
orr) to reduce absorption loss of 185 nm ultraviolet light. In addition, by making the pressure in the light source chamber and the reaction chamber approximately the same (the differential pressure is at most 10 torr, generally less than 1 torr), the thickness of the quartz window can be reduced from the conventional 10 mm.
Since it can be made as thin as 2 to 3 mm, it also has the advantage of less light absorption loss in quartz.

r Effect j Due to these characteristics, the reaction products formed in the previous process on the window are completely removed when a new coating is to be formed. For this reason, the photovapor phase reaction (photoCVD) can be reproduced to a constant thickness for each formation until the ultraviolet light reaches the substrate surface due to the formation of reaction products on the window. We were able to form a film on the substrate with good performance.

Furthermore, after this photoCvD, it is possible to produce the same or a different type of coating on this coating by plasma vapor phase reaction in the same batch.

Further, in the present invention, the reaction system can be of a load-lock type in order to remove unnecessary substances on the window by plasma etching without exposing the reaction chamber to the atmosphere. Furthermore, since it is an oil-free reaction system, the degree of vacuum at the bank ground level can be reduced to 10
−' torr or less. Films could be formed by optical excitation of non-oxide products such as semiconductor films such as silicon, silicon carbide, silicon nitride, aluminum nitride, and metal aluminum.

``Example'' 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 installed in the reaction chamber (2) in close proximity to a halogen heater (3) (the top surface of which is water-cooled (31)). ing. Reaction chamber (2), light source chamber (5) equipped with an ultraviolet light source
The heating chamber (11) in which the heater (3) and the heater (3) were provided were maintained at approximately the same degree of vacuum, with each pressure being 1 Qtorr or less. This was accomplished by supplying a gas (nitrogen, argon, or ammonia) that does not interfere with the reaction to (12) from (28) or exhausting from (12°). Further, the light source chamber (5) and the reaction chamber (2) are separated by a quartz window (10) which is a light-transmitting shielding plate. A nozzle (14) is provided above this window (10), and this nozzle has a nozzle (14") for ammonia (NH3) and nitrogen fluoride (NF3) with the spout facing downward (facing the window) (3
2), and a nozzle (1) for silane (SinHzn-z) + methyl aluminum (AI (CH3) 3).
4") with the spout (14") facing upward (toward the substrate) (3
3).

This nozzle (14) serves as one electrode of a high frequency power source (15) in plasma CVD and plasma etching.

A heater (29) was provided to prevent reactive gas from entering the light source chamber due to backflow when the light source chamber was evacuated.

This traps the components of the reactive gas that become solid after decomposition, resulting in flashback of only the gas.

Regarding movement, a load-lock system was used to prevent pressure differences from occurring. First, in the preliminary room (4), the board (1),
Holder (1°), board and board holding (1”’)
After inserting and arranging the chamber (to efficiently conduct heat to the substrate) and drawing a vacuum, open the gate valve (6) and open the reaction chamber (2
), and with the gate valve (6) closed, the reaction chamber (2
), the preliminary room (4) was partitioned off from each other.

The doping system (7) includes a valve (22) and a flow meter (2).
1), the reactive gas that forms the solid product after the reaction was supplied from (23) and (24), and the gaseous product after the reaction was supplied from (25) and (26) to the reaction chamber (2). . The pressure in the reaction chamber is controlled using control pulp (17
), turbo molecular pump (using Osaka Vacuum PG550) (18), rotary pump (
19) and then evacuated.

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 evacuating the reaction chamber, the reaction chamber was opened and the preliminary chamber side was closed.

The substrate was thus inserted into the reaction chamber as shown.

The degree of vacuum in this reaction chamber was set to 10-' torr or less. Thereafter, nitrogen was introduced from (28) and a reactive gas was further introduced into the reaction chamber from (7) to form a film.

The light source for the reaction was a low pressure mercury lamp (9), and water cooling (31') was provided. The ultraviolet light source is a low-pressure mercury lamp (185 nm).

Emit light with a wavelength of 254 nm, emission length 40 cm, and irradiation intensity 20 mW/cm2. Lamp power: 40W) Number of lamps: 16.

This ultraviolet light passes through quartz (10), which is a transparent shielding plate, and irradiates onto the formation surface (1) of the substrate (1) in the reaction chamber (2).

The heater (3) was located above the reaction chamber (deposition amplifier type) to avoid flakes from adhering to the surface to be formed and causing pinholes.

The reaction chamber is made of stainless steel, and both the light source chamber and heating chamber (11) are evacuated to maintain a pressure difference of 10 torr.
The following was made. As a result, the present invention does not have the disadvantage of not being able to withstand pressure when the area of the quartz plate is increased for irradiation of a large area, as shown in the conventional example. That is, the ultraviolet light source is also kept under vacuum in a stainless steel container surrounding a light source chamber and a reaction chamber that are kept under vacuum. For this reason, 5
The size is 30cm x 30cm instead of cm x 5cm.
A substrate having a size of m can also be produced without any industrial problems.

In the case of the drawing, the effective area to be formed is 30cm x 30ct
RL, and five boards (1) with a diameter of 5 inches are placed in a holder (
The substrate was heated by a halogen heater (3) to a predetermined temperature ranging from room temperature to 500°C.

Further, specific examples according to the present invention are shown in Experimental Examples 1 to 3 below.

Experimental example 1...Ammonia was supplied from (25) at 30 cc/min and disilane was supplied from (23) at 8 cc/min as reactive gases on the silicon nitride film formation side, and the substrate temperature was 350.
℃. The substrates were five wafers each having a diameter of 5 inches. The pressure inside the reaction chamber (2) is 3. I set it to Qtorr.

A film with a thickness of 1,500 people was formed in a 30-minute reaction. The film formation speed was that of 65 people. The present invention uses direct optical excitation without using mercury vapor or the like. The variation of the 5 points of the coating was within ±5%. However, it is extremely difficult to form a silicon nitride film on the window to a thickness greater than this thickness.

To obtain a film thickness of 1500 Å or more, a plasma etching method may be performed after this. That is, from (15), 13.56MHz
frequency (40W) was applied. Then, 2.3 A/sec was obtained using the same reactive gas (but at a pressure of 0.1 torr). Thus, with this method, a film of 0.5 μm can be obtained without causing plasma damage to the surface on which it is formed.

Furthermore, after this, the reaction was stopped, the reaction chamber was evacuated, and the substrate on which the film was formed was removed to the preliminary chamber.

Thereafter, the substrate was further taken out, the holder was returned to the original reaction chamber, and after closing the gate, Nh was supplied to the reaction chamber from (26). Then, the pressure in the reaction chamber was set to 0.3 torr, and a high frequency wave (15) of 13.56 MHz was applied at an output of 80 - to perform plasma etching on the upper surface 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 removing this NF3, hydrogen was added from (27), 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 2. ... Formation example of amorphous silicon film Disilane (SizL) was supplied from (23). Also, (27
) was supplied with hydrogen. A film thickness of 1,000 layers could be formed on the surface to be formed in 60 minutes of deposition.

After removing the substrate to the preliminary chamber, the silicon film adhering to the inner wall of the reaction chamber (2) and the top surface of the window (10) was etched using the same plasma etching method with NF added as in Example 1. Removed. Adhering silicon on the windows and inside the reaction chamber could be removed in just 15 minutes.

The substrate temperature was 250° C. and the pressure was 2.5 torr.

Experimental example 3... Formation example of aluminum nitride AI (CH
z) Methyl aluminum with i as a representative example (23)
It was supplied at a rate of 8 cc/min. Ammonia was supplied from (25) at a rate of 30 cc/min. As a result, methyl aluminum was decomposed without using mercury in the light source chamber, and an aluminum nitride film with a thickness of 1,300 mm could be made. The film formation rate was 330 mm/min (pressure: 3 torr + temperature: 35 mm)
0°C). Ethyl aluminum AI
Other alkyl compounds such as (C2H5):1 may also be used.

For plasma etching of the window, CC1a was supplied from (26) to perform a plasma reaction. In addition, hydrogen was supplied from (24). In this way, aluminum nitride could be removed.

Even if this film formation was repeated 10 times, the same film thickness could be obtained under the same conditions.

r Effect j As is clear from the above description, in the present invention, when forming a film on a large-area substrate, an unnecessary reaction-generated film on a window can be completely removed by plasma etching. 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, in addition to forming a film by this photo-CVD method, it is possible to form the same or a different film overlying this film by a plasma etching method. In such cases, optical CV
It is also possible to form a film by the D method without sputtering the surface on which it is formed, and then to superimpose the same film or another similar film thereon by a plasma vapor phase method. That is, it was possible to form a film with good reproducibility without slowing down the film formation rate.

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, and aluminum nitride, it is also possible to use M(CH
ff) fi, that is, M as In+ Cr, Sn, Mo
, Ga, and W may be used to fabricate a metal M or a silicide thereof. 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)).
, argon laser, nitrogen laser, etc. may also be used.

[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 thin film forming method using a photochemical reaction, comprising: a light source chamber in which a light emitting source is disposed; a light-transmitting shielding plate that partitions the light source chamber and a reaction chamber; and a light-transmitting shielding plate disposed in the reaction chamber. A heated substrate having a surface to be formed is formed, and a thin film is formed on the surface to be formed by the photochemical reaction, and the thin film formed on the surface of the light-transmitting shielding plate is Complete the formation,
A method for forming a thin film, comprising removing the substrate by performing a plasma vapor phase etching reaction after removing the substrate from a reaction chamber. 2. A thin film according to claim 1, characterized in that the plasma vapor phase etching reaction is carried out by supplying high frequency electrical energy between a nozzle for supplying a reactive gas and a substrate holder or a reaction chamber. Formation method. 3. A method for forming a thin film according to claim 1, wherein the thin film is formed by performing a plasma gas phase reaction after a photochemical reaction.