JPS61127122A - Formation of thin film - Google Patents

Abstract

PURPOSE:To obtain the device capable of forming the uniform coating films over a large area by separating an excitation light source chamber from a reaction chamber by a light transmitting screening panel and arranging a pair of electrodes and the heated substrates and effecting the formation of a thin film and etching of disused matters by a photochemical reaction and a plasma chemical reaction. CONSTITUTION:A preparatory chamber 4 is separated from a reaction chamber 2 by a valve 6 and NH3 25 and Si2H6 23 are introduced with the inflow being controlled. The reaction chamber 2 is kept at 3Torr and an Si3N4 film is formed on the substrate 1 which has been heated to 350 deg.C in a heating chamber 11 under the irradiation with a low-pressure Hg lamp 9. Then a high-frequency power 15 is applied, using a reaction gas supply nozzle 1 and a substrate holder as electrodes, and Si3N4 is laminated without damage with the reaction chamber kept at 0.1Torr. After stopping the reaction, the substrates are taken out and the holder is returned to the reaction chamber. NF3 26 is supplied and a high-frequency power is applied under 0.3Torr to etch the Si3N4 on a light transmitting screening panel 10. After that, H2 27 is supplied to remove the residual F. By this device, the uniform coating film of 150Angstrom or over can be formed over a large area with a good reproducibility.

Description

Detailed Description of the Invention: Field of Application of the Invention The present invention is an apparatus for forming a thin film and etching unnecessary materials by photochemical reaction and plasma chemical reaction, which can be mass-produced uniformly over a large surface area. The present invention relates to a CVD (vapor phase reaction) apparatus having means for forming an excellent film on a transparent shielding plate on a light irradiation chamber without coating with oil or the like.

"Prior Art" As a thin film forming technique using a gas phase reaction, a photo-CVD method in which a reactive gas is activated by light energy is known.

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

When carrying out such a photoCVD method, an example of the apparatus 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). 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 ultraviolet light transmitting portion of the reaction chamber is At the same time, a large amount of silicon film is also formed on the shielding plate (10), typically a quartz window. Therefore, in order to prevent the formation of a film on this window, apply Fomblin oil (an example of fluorine-based oil) (16) to this window.
coated with a thin layer of

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.

"Means for Solving the Problems" In order to solve these problems, the present invention provides an apparatus that can perform plasma vapor phase reactions in addition to photo-CVD methods. In the photo-CVD method, it is assumed that the formation of a film on the window and on the substrate at the same time, while reducing the amount of film, is unavoidable and has been rejected. After removing the substrate on which the film has been formed by photo-CVD or plasma CVD, a plasma vapor phase etching reaction is performed to etch away the deposits on the top surface of the window that prevent the transmission of ultraviolet light. The basic idea is to remove it by doing so.

In addition, this etching radical is then introduced with hydrogen,
Plasma/hydrogen cleaning is performed to recreate the reaction chamber in its initial state.

In addition, by providing a metal nozzle through which this reactive gas is introduced into the reaction chamber and electrically insulating it from the reaction chamber, it is possible to connect this nozzle to the substrate (substrate holder) or metal (stainless steel).
Plasma reaction (
etching or debosition).

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 compounds 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.

In addition, vacuum the light source room containing the low-pressure mercury lamp (0°1 to 10t).
orr) to reduce absorption loss of 185 nm ultraviolet light. In addition, by making the pressure between the light source chamber and the reaction chamber approximately the same (the differential pressure is at most 10 torr, generally 1 torr or less), the thickness of the quartz window can be reduced to 2 to 3 mm from the conventional 10 mm. It also has the advantage of low light absorption loss.

``Operation'' Because of these properties, when a new coating is to be formed, the reaction products formed in the previous process on the window are completely removed. 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. (I was able to create a film on the substrate.)

Further, in the present invention, it is possible to fabricate the same or different types of coatings by plasma CVD on this coating in the same batch after CVD using the same reaction chamber.

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 background level vacuum 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 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 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 10 torr 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''). The light source chamber (5) and the reaction chamber (2) are separated by a window (10).
10) A nozzle (14) is provided on the upper side, and this nozzle has a nozzle (14”) for ammonia (NH3) and nitrogen fluoride (NF3) with the spout facing downward (facing the window) (32)
Also, a nozzle (14') for silane (SinHzn-z) + methyl aluminum (81 (CL) 3)
The spout (14') is provided upward (toward the substrate) (33).

This nozzle (14) serves as one electrode supplied from 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 method was used to prevent pressure differences from occurring. First, in the preliminary room (4), the board (1),
Holder (1゛), board and board holder (1゛) (
After inserting and arranging the device (to efficiently conduct heat to the substrate) and drawing a vacuum, open the gate valve (6) and open the reaction chamber (2).
and close the gate valve (6) to open 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 a control valve (17
), a turbo molecular pump (PG550 manufactured by Osaka Vacuum Co., Ltd. was used) (18) and a rotary pump (19) for exhaustion.

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 the 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), equipped with water cooling (31'').The ultraviolet light source was a low-pressure mercury lamp (185 nm).

The number of lamps is 16, emitting light with a wavelength of 254 nm, emitting length of 40 cm, irradiation intensity of 20 m W/Cm'' + lamp power of 40 W).

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 a "deposition up" type heater located above the reaction chamber 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.

The temperature of the substrate is heated by a halogen heater (3) to a temperature between room temperature and
The predetermined temperature was up 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 internal pressure of the reaction chamber (2) was 3.0 torr.

A film with a thickness of 1,500 people was formed in a 30-minute reaction. The film formation rate was 65 people/min. 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, plasma CV
Just use method D. That is, from (15), 13.56MHz
high frequency (40W) was applied. Then the same reactive gas (
However, a speed of 2.3 to/sec was obtained 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.

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

After that, further substrates were taken out, the holder was returned to the original reaction chamber, and after closing the gate, NF was added to the reaction chamber from (26).
was supplied. 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 H 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 NP, 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 (SizH6) was supplied from (23). Also, (27
) was supplied with hydrogen. A film with a 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 upper surface of the window (10) was etched using the same plasma etching method with NFI 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 ((:
Methyl aluminum with H+)i as a representative example (23
) at a rate of 8 cc/min. Ammonia was supplied from (25) at a rate of 30 cc/min. As a result, methylaluminum was decomposed without using mercury in the light source chamber, and an aluminum nitride film with a thickness of 1,300 mm was created.

Film formation rate: 330 persons/min, pressure: 3 torr, temperature: 3
50°C). Ethyl aluminum A
Other alkyl compounds such as l(C2H5):1 may also be used.

For plasma etching of the window, CC1 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.

"Effects" As is clear from the above description, the present invention can completely remove unnecessary reaction-generated films on windows by plasma etching when forming a film on a large-area substrate. 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 1f17 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 on top of it by a plasma CVD 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
3), immediately (M as I n + Cr + S n +
M o + Ga + W may be used to produce the metal M or its silicide. It is 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 these with a silicide.

In the experimental examples described above, dopants can be added at the same time when forming a silicon semiconductor. Also, the light source is not a low-pressure mercury lamp but an excimer laser (wavelength: 100 to 400 nm).
), argon laser, nitrogen laser, etc. may of course be used.

[Brief explanation of drawings]

FIG. 1 shows a conventionally known photoexcited CVD apparatus. FIG. 2 shows a CVO device of the present invention.

Claims (1)

[Scope of Claims] 1. A light source chamber in which a light source for excitation of a reactive gas is disposed, a light-transmitting shielding plate that partitions the light source chamber and the reaction chamber, and a light-transmitting shielding plate disposed in the reaction chamber. A heated substrate having a surface to be formed, a holder for holding the substrate, a pair of electrodes in the reaction chamber, and a power source for supplying electrical energy to the electrodes, and the surface to be formed by the photochemical reaction. A thin film characterized by forming a thin film on a surface, generating a plasma glow discharge using the pair of electrodes, forming a film by a plasma vapor phase method, or removing unnecessary deposits by a plasma etching reaction. Forming device. 2. In claim 1, the plasma vapor phase etching reaction or the plasma vapor phase film forming reaction has a nozzle for supplying a reactive gas as a pair of electrodes and a substrate holder or a reaction chamber, and a substrate holder or a reaction chamber is provided between these. A thin film forming apparatus characterized by having means for supplying high frequency electrical energy.