JPH0660405B2 - Coating method by vapor phase method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a photochemical vapor deposition method (Photo Chemical Vapor Depositi
on The first coating is formed by photo CVD or photo CVD, and the plasma vapor phase method (hereinafter
PCVD) or photoplasma vapor phase method (Photo Plasma C)
hemical vapor deposition (hereinafter referred to as "PPCVD"), which relates to an optical CVD method in which a second film is formed by being laminated to enable mass production.

This invention uses a photo-CVD method in which light energy and heat energy are supplied to a reactive gas to directly perform a photochemical reaction without using a mercury sensitization method, and the first surface is formed without spattering (damaging) the surface to be formed. Coatings such as 50 non-single crystal semiconductors
After being formed to a thickness of Å or more, a second film of the same material is further formed on this upper surface by the PPCVD method or the PCVD method with a high film growth rate.
By laminating and forming the coating film of 1), it is possible to prevent the generation of a mixed region at the interface with the surface to be formed, improve the interface characteristics, and further increase the substantial film growth rate. There is.

Conventionally, in the photo CVD method, a substrate having a surface to be formed is heated from below the substrate, while the surface to be formed, which is the upper surface of the substrate, is irradiated with light from the vertical upward direction. A method is known in which the photoexcitation of the above reactive gas by light irradiation is performed to cause a photochemical reaction.

In this conventional method, when the mercury sensitization method is not used,
The film growth rate was only 0.1 to 0.3 Å / sec, which was low, and industrially practically impossible.

Further, for example, when silicon is formed using silane, a part of the photoexcited silicon adheres to the light irradiation window and absorbs the light irradiation. It had the drawback of weakening the strength.

For this reason, the photo CVD method has the feature that it does not damage the substrate surface, but it was completely impossible to apply it to mass production.

On the other hand, in the PCVD method or the PPCVD method, although the film growth rate is extremely fast at 2 to 20 Å / second, the surface of the formation surface is sputtered and one of the components of the substrate forming the formation surface is sputtered. It has a drawback that the part is mixed as an impurity in the film such as a semiconductor film.

The present invention eliminates both of these drawbacks, improves the interfacial properties by the photo CVD method, and improves the film growth rate by the PPCVD method, and proposes a photo CVD device that can be mass-produced industrially for the first time. I am trying.

Therefore, in the present invention, among the semiconductors containing silicon as a main component, silane (Si _n H _{2n + 2} n ≧ 1) is 10
Infrared light having a light energy of ˜15% absorbed by Si—H bonds is photoexcited using a far infrared light source using a carbon dioxide gas laser or nichrome as a light emitting source. 185n
It is also effective to perform photo CVD using ultraviolet light of m, 253 nm.

The features of the present invention will be described below in comparison with a conventional device according to the drawings.

FIG. 1 shows an outline of a conventionally known photo CVD apparatus.

In the drawing, the substrate (1) is arranged in the reaction vessel (2),
It is heated to 200-400 ° C by the heater (53) from below. Furthermore, ultraviolet light (253 nm) is emitted by the low-pressure mercury lamp (9).
The surface of the substrate (1) is vertically irradiated (51) through the quartz plate. Oil (54) is applied to the lower side of the quartz plate to reduce the adhesion of reaction products. The reactive gas is silane (26) from the doping system (20) and the valve from the flow meter (29).
It is supplied in parallel (50) to the substrate surface via (28). Hydrogen or helium as a carrier gas is supplied from (27), a photochemical reaction is performed, and a semiconductor film is formed on the substrate (1). The unnecessary reaction product and the carrier gas are exhausted to the outside from the vacuum pump (18) through the valve (13) for pressure adjustment.

In such conventional equipment, the oil (54) is 200-400 ° C.
If heated to above, oil vapor will be mixed in and is prohibited. Therefore, it is important to heat only the substrate from the back surface of the substrate. However, with such a method, a large number of substrates cannot be arranged at one time, and industrially practically impossible.

That is, if another substrate was placed on (1 '), the surface of (1) was irradiated with ultraviolet light by (1') and became shaded. Therefore, the photochemical reaction cannot be performed on the lower substrate (1).

It is not possible to form a large amount of a coating on a substrate at a high growth rate only by the conventional photo CVD method.

Further, in the conventional method shown in FIG. 1, this photochemical reaction is made based on the idea that the photochemical reaction on the surface of the substrate is rate limiting rather than the photochemical reaction in the flying reactive gas. For this reason, a configuration other than that shown in FIG. 1 could not be adopted.

Further, in this method, since the light source is arranged in the atmosphere, in order to prevent the quartz plate (48) from being damaged by pressure or the like,
It cannot be a large area. Therefore, it was whether or not only 2 to 3 3-inch wafers could be simultaneously inserted as substrates. On the other hand, the present invention is based on the experimental finding that a photochemical reaction can be carried out on a reactive gas in flight as a result of thorough examination of this photo CVD method. Furthermore, they found that the coating on the coating surface can be made by using thermal energy rather than irradiation light. That is, it was found that it is not always necessary to irradiate the surface of the silicon film with ultraviolet light at a temperature of 250 ° C. or higher, for example, 300 to 350 ° C.

In addition, even at such temperatures, the photo-CVD method does not use mercury, which is an impurity source, as a sensitizer, so the film growth rate is only 0.1 to 0.3 Å / sec (6 Å / min to 18 Å / min). I couldn't get it. Therefore, in the method of the present invention, even if the surface to be formed is sputtered by PCVD or PPCVD by only light energy (light energy and heat energy), the average thickness (50
The first semiconductor layer is formed on the surface to be formed at ~ 500 Å), and at the same time, while performing this photo-CVD, electric energy is supplied to the reactive gas to promote the activation of the reactive gas. The feature is that the growth rate of the reactive gas coating can be increased to about 6 to 20 Å / sec, which is about 10 times or more.

In the PPCVD method of the present invention, a part of the reactive gas is excited by light irradiation in order to facilitate the start of discharge and prevent the instability in which the discharge is likely to stop even after it has once been discharged. The feature is that the electric energy is added to the reactive gas at the same time as the light energy to facilitate the initiation of the discharge and the sustainability of the discharge.

Example 1 A photo CVD apparatus of the present invention will be described below with reference to the drawings.

FIG. 2 shows an outline of a CVD apparatus which can arbitrarily perform all of photo CVD, PPCVD and PCVD.

FIG. 2 has a reaction system (10) and a doping system (20).

The reaction system (10) is the inner volume of the reaction vessel (2) (width 90 cm, height 60 c
A substrate (1) having a surface to be formed is held by a quartz holder (19) at m, depth 120 cm.

This holder has a size of 65 cm x 65 cm, but has a length of 20 cm in the flow direction (50) of the reactive gas, and allows 20 substrates of 20 cm x 60 cm (total surface area of the formation surface 24000 cm ² ) to be inserted simultaneously. ing.

Further, the surface of the substrate (1) on which the reactive gas is introduced is introduced from above and discharged downward, and is made to stand at regular intervals (2 to 10 cm, eg 5 cm) in the vertical (vertical) direction. .

Further, in the present invention, the pressure in the space in which the halogen heater (7) and the lamp (9) for the photochemical reaction are located is adjusted by opening and closing the valve (49) so as to be equal to the pressure in the reaction vessel (2). Under reduced pressure of 1 atm or less, eg 0.1-10 To
It is held at rr. Therefore, the quartz substrate (48) is not damaged and a large area (80 cm × 80 cm) can be formed. Therefore, it became possible to create a large space with a height of 65 cm × 65 cm (20 to 60 cm) as a reaction space.

The substrate is heated to a halogen heater (7), for example, 200 to 500 ° C.
To be heated. In addition, a photochemical reaction lamp (9) emitting a wavelength of 185 nm, 253 nm or 10.6 μ is provided in the upper light source and the lower light source. As a result, it is possible to perform photo CVD on the heated substrate having a predetermined temperature.

The irradiation light irradiates the entire reaction space (44). Furthermore, a pair of capacitive coupling type electrodes (5) and (6) are provided in a net shape and are connected to a high frequency oscillator (4) (13.56 MHz, 5 to 500 W). It is possible to perform PCVD by applying electric energy between the electrodes.

Further, PPCVD can be performed by simultaneously applying electric energy and light energy.

The reactive gas reaches the reaction space (44) from the inlet (11) through the quartz nozzle (3), and reaches the exhaust system (12) through the quartz outlet (8).

The exhaust system consists of a pressure adjustment valve (13), a stop valve (14),
Mechanical booster pump (17), rotary pump (1
8) Discharge unnecessary materials to the outside.

The substrate is first placed in the preliminary chamber (16) with a quartz holder,
After evacuation was performed at (23), the gate valve (45) was opened and transferred to the reaction section (44). Reactive gas is added in the doping system (20) with silane from (26) and ammonia from (25) as NH ₃ / SiH ₄ > 50 through the flow meter (29) controlled by the valve (28). .

The reactive gas reaches the reaction system (10) through the flow meter (29). In this reaction system, 100 to 500 ° C, preferably 250 to 350 ° C,
Typically, a substrate having a surface to be formed, which is held at 300 ° C., is arranged, the pressure in the reaction region (44) is 0.1 to 10 Torr, eg, 2 Torr, and the silane flow rate is 1 to 500 cc / min, eg, 50 Torr.
cc / min was supplied. Light irradiation was carried out using a lamp (length 680 cm, diameter 10 mm, maximum output 50 W × 8) that emits infrared light containing light energy of a wavelength of 10 to 15 μm. This was also effective using a carbon dioxide laser.

Thus, the insulating silicon nitride film was formed at a thickness of 50 Å or more on the surface to be formed at 0.1 Å / sec.

Next, in addition to this light energy, electric energy is applied to a pair of (5) and (6) from a high-frequency oscillator (frequency 13.56MHz) (4), plasma glow discharge is applied, PPPP reaction is performed, and photo-CVD is performed. A silicon nitride film of the same material was successively laminated on the above silicon nitride film by PPCVD. The film growth rate in this case was 3Å / sec.

The surface of the substrate is arranged parallel to the irradiation light for the photochemical reaction, and the photochemical reaction is performed not by the surface of the substrate but by a flying halogen lamp at 150 to 350 ° C.
Performed on a reactive gas that was preheated to ° C.

By doing so, it is possible to prevent the irradiation light from being shaded by the substrate and preventing the reactive gas on the opposite side from being irradiated.
We were able to carry out photo CVD that enables mass production.
Further, in the device of the present invention, the reactive gas is preheated to approximately the same temperature as the substrate, and the heated reactive gas is photoexcited, so that sufficient film formation is achieved even if the surface of the substrate is not irradiated with light. It also has the feature that it is possible.

That is, in the photo CVD method, the substrate surface was not damaged by the plasma, so that good film quality could be obtained. However, the growth rate of the coating is extremely low at 0.1 to 0.3 Å / sec, and the optical energy required for the growth is extremely strong.

On the other hand, in PPCVD according to the other invention, some damage due to plasma is observed, but the film growth rate is 6 to 15Å /
We were able to achieve a growth rate of 30 times faster than that of the photo CVD method. In the PPCVD method, thermal energy is applied to a reactive gas in the order of the steps so that light irradiation is performed first, and a part of the reactive gas is photoexcited to make it extremely ionizable, and then electrical energy is applied. It is extremely important that the plasma reaction is generated. By doing so, the plasma shock wave at the start of discharge could be prevented, and the plasma damage on the substrate surface could be substantially prevented.

In addition, in the present invention, since the semiconductor film as the first film is formed in advance to a thickness of 50 Å or more only on the surface to be formed by the photo CVD method to prevent the plasma damage which is still slightly left, Due to this plasma damage, part of the substrate portion forming the formation surface does not mix into the semiconductor, and the boundary area with the formation surface was 100 to 300 Å only in the conventional PCVD method, This is 0
It could be made extremely thin at ~ 100Å, typically 20 ~ 50Å.

A film thickness of 1000Å is formed on a silicon single crystal semiconductor substrate,
As a result of examining the C-V characteristics, the interface charge density was 1 as a result.
It was possible to obtain x 10 ¹¹ cm ^-2 or less. Also 2 × 10 ⁶ V /
It was found that the hysteresis phenomenon was not found in the CV characteristics even when the electric field strength of cm was added, and the semiconductor surface was scarcely sputtered (damaged).

Example 2 This example is an example of forming a silicon oxide film by the apparatus of the present invention. The apparatus is the same as in the first embodiment.

With N ₂ O in place of ammonia as reactive gases (25)
Introduced more. Furthermore, silane was added from (26) to N ₂ O / SiH ₄ > 20
Introduced as. The results obtained were similar to those of Example 1. Furthermore, it had a dielectric strength of 1 × 10 ⁷ V / cm.

Experimental Example 1 This experimental example is an example in which a silicon film is formed based on the idea of the present invention.

It carried out using the same apparatus as Example 1.

At that time, as the reactive gas, silane is used in the doping system (20) from the (26) and diborane (B ₂ H ₆ ) or other reactive gas for P type or N type gas such as foshin (PH ₃ ) is used. (2
According to 4), a gas such as ammonia or methane for adding nitrogen or carbon to silicon (25) and hydrogen or helium as a carrier gas from (27) are passed through a flow meter (29) and a valve (28). ) Control and add.

The pressure in the reaction region, the flow rate of silane, and the light energy were determined in Example 1.
Is the same as.

Thus, the first silicon coating was formed on the surface to be formed to a thickness of 50 Å or more.

Next, in addition to light energy, electric energy was applied in the same manner as in Example 1, and a semiconductor, which was a second silicon film made of the same material, was successively laminated on the first silicon film by PPCVD.

The growth rate of this semiconductor film was 0.1 to 0.3 Å / sec, for example, 0.2 Å / sec only in photo CVD. PP
In CVD, a growth rate of 6 to 15Å / sec, for example 12Å / sec, which is 30 times faster, could be obtained.

The surface to be formed is a P-type semiconductor (silicon or Si _x C _1-x 0 <x <
This is 1), and when an I-type silicon semiconductor is to be formed on the upper surface by the method of the present invention, this PI junction interface can be made extremely sharp, and good diode characteristics can be obtained.

If the surface to be formed is a translucent conductive film, when a semiconductor is to be formed on the conductive film, oxygen of ITO and SnO ₂ forming the conductive film should be mixed into the semiconductor due to the interface. It was possible to obtain good semiconductor characteristics.

In the method of the present invention as described above, by setting the oxygen concentration of the non-single-crystal semiconductor containing silicon as the main component to 1 × 10 ¹⁸ cm ⁻³ or less, a better semiconductor can be formed on the formation surface. I was able to.

When the film quality of the silicon film formed on the glass substrate by this method of the present invention is examined, the oxygen concentration is 1 × in SIMS measurement.
10 ¹⁸ atom / cc or less (light output 100 W, discharge output 100 W or less)
I was able to show that.

Furthermore, when the discharge output was set to 50 W, it could be reduced to 2 × 10 ¹⁷ atom / cc, which was 1/5 of that. However, on the other hand, when the film quality of the silicon film formed on the glass substrate was examined only by the PCVD method, it was found that the film contained 4 × 10 ¹⁹ to 2 × 10 ^20.
It had atom / cc and contained 10 to 100 times as much oxygen as the method of the present invention. This is because a part of silicon of the substrate obtained by sputtering the glass substrate by glow discharge plasma is mixed in the semiconductor.

In the device of the present invention, the crystallinity of the film formed by increasing the substrate temperature to 350 ° C. and 400 ° C. further progressed.

The temperature at which this reaction product is produced is 300 ° C in the PPCVD method.
It was also possible at 150-300 ° C.

In the photo CVD method, when monosilane was used as the reactive gas, it was extremely low and industrial improvement was required.

It is possible to obtain a near-oxygenated polysilane (for example, disilane Si ₂ H ₆ ) synthesized by using a purified monosilane instead of the above-mentioned monosilane and modifying this silane by an apolar discharge method or by irradiation with ultraviolet light. When a semiconductor film is prepared by the above-mentioned photo CVD method using silane containing at least a part (concentration of 5 to 30%) of this disilane, the film growth rate is 0.6 Å / sec, which is three times that of monosilane. I was able to raise it to.

Furthermore, if the concentration of disilane is 75% or more,
I was able to achieve 3Å / sec.

In addition, when the semiconductor film was formed by using disilane following the photo CVD by the PPCVD method, a film growth rate of ~ 100Å / sec could be obtained.

Therefore, it was found that when disilane is used as a raw material in the method of the present invention, ultra-high-speed film growth can be performed without sputtering the surface to be formed.

FIG. 3 shows a 0.5 .mu.m silicon semiconductor layer formed on the glass substrate by the apparatus shown in FIG.

FIG. 3 particularly shows the photo CVD method (light output 0.1 KW,
It is formed to a thickness of 100 Å by 300 ℃), and a silicon semiconductor is formed by the PPCVD method (light output 0.1 KW, (4 mW / cm ² ) discharge output 50 W) to a total film thickness of 0.5 μ. is there.

Electrical properties of silicon semiconductors (56), (64), (65), (66), (68) Electrical properties of semiconductors with a thickness of 0.5 μ made only by the conventional PCVD method (57), (63) ), (58), (67), (69).

In the drawing, in the conventional example, the region (59) is dark electric conductivity.
It shows (57) and has a value of 3 × 10 ⁻⁷ (Ωcm) ⁻¹ . When AM1 (100 mW / cm ² ) is irradiated here in the area (60), it has 1 × 10 ^-4 (Ωcm) ^-1 in the conventional method as shown by the curve (58), and is continuously irradiated for 2 hours. The value was deteriorated by about one digit.

This is because oxygen flows in from the glass of the substrate and combines with a part of hydrogen of the reactive gas to form water (OH group), which induces the photodegradation property.

On the other hand, the semiconductor film produced by the method of the present invention (photo CVD + PPCVD) has a dark conductivity (56) of 1 × 10 ⁻¹⁰ (Ωcm) ^−1.
Has its photoconductivity (64) has a 40 ⁶ at 2 × 10 ^-4 (Ωcm) ^-1 orders and photo Sensitivity tape, is large further irradiation of continuous light of about two orders of magnitude than the conventional example At that time, almost no deterioration of the electric conductivity was observed as shown in the curve (65).

This confirms the importance of coating the semiconductor on the glass plate by photo CVD. The semiconductor produced by this photo CVD method preferably has an average of 50 Å or more (preferably 100 to 1000 Å), and if it is less than that, a part of the semiconductor may not be covered, so the effect was not always sufficient.

Further, in the region (61), the dark conductivity after irradiation was also the same in the error range as compared with (66) and (56) in the present invention.

When heating at 150 ° C, curve (67) becomes (6
9), there is an apparent change in characteristics, and then the area (62)
Deterioration characteristics were observed again when light irradiation was performed again at.

That is, in the conventional example, the electric conductivity is small as shown by (67), and deterioration characteristics are observed by light irradiation.

However, in the present invention, the electrical conductivity is the presence or absence of light irradiation,
Almost no change or deterioration of characteristics was observed with or without thermal annealing, and the photoconductivity and photosensitivity (difference between photoconductivity and dark conductivity) were large, and the dark conductivity was small.

As described above, it was found that the method of the present invention has a synergistic effect that a highly reliable silicon semiconductor layer can be provided.

The method of the present invention has substantially no spattering (damage) effect and enables mass production. As a result, PN or
The PIN junction can be applied to photoelectric conversion devices, optical sensors, electrostatic copying machines, insulating gate type field effect semiconductors and their integrated devices, and is considered to be extremely effective in industry.

Experimental Example 2 This experimental example is a case of forming ITO (indium tin oxide, indium oxide containing 10% by weight or less of tin oxide, for example, 5% by weight).

The same device as in Experimental Example 1 was used. As a reactive gas (26)
More indium chloride was added, and N ₂ O was added from (25).
Further, tin tetrachloride was added to reduce the sheet resistance of the indium oxide formed from (24), and nitrogen was added as a carrier gas from (27).

After this, photo CVD is performed to form the first film, and then electrical energy is continuously applied to the second film by the PPCVD method.
Was laminated.

Thus, indium oxide or ITO could be obtained at 100-500 ° C, eg 300 ° C.

The film formation rate is 7 tons per second by PPCVD method, 1 torr, 300
I was able to make it at ℃.

The sheet resistance was 20Ω / □ at a film thickness of 500Å, and the transmittance was 87%.

Experimental Example 3 In this experimental example, a transparent conductive film of tin oxide was prepared.

The apparatus was the same as in Example 1.

As reactive gas, tin chloride from (24) and N ₂ O from (25)
Added as N ₂ O / SnCl ₄ > 20.

At the same time, CFBr was added from (26) to reduce the sheet resistance to 50Ω / □ or less (when the thickness is 1000Å).

The formed film is further irradiated with light for photochemical reaction in an N ₂ O atmosphere or a mixed atmosphere of oxygen and nitrogen at 50
It was fired at 0.

Thus, a tin oxide film having acid resistance and plasma resistance could be obtained. This tin oxide film is laminated on the ITO on the glass substrate shown in Example 1 as a coating material even if it is on a translucent insulating substrate such as a glass substrate, and ITO is used as the coating material.
(300-1500 Å), SnO ₂ (200-400 Å) was also effective as a two-layer structure.

In the method of the present invention, the film formed is TMA (trimethylaluminum) as a reactive gas or 0.
It is also applicable to the case of adding 1 to 1% of silane to make a metal aluminum or other metal coating.

As is clear from the above description, the present invention forms a film by a photo-CVD method on a reactive gas first, and further executes the PPCVD continuously in the same reaction furnace to improve the interface characteristics. It was fulfilled. Instead of this PPCVD, PCVD may be used, or any one of them may be repeated for film formation.

However, in PCVD, there is a sputtering effect at the start of discharge and at the time of unstable discharge. Therefore, when using the PCVD method, it is important to perform PPCVD in the middle of photo CVD-PPCVD-PCVD to eliminate the sputtering effect at the start of discharge.

The present invention ensures that one substrate does not shade another.
It is characterized by irradiating light parallel to the surface of this substrate to photoexcite the reactive gas during flight, and as a result,
As shown in the examples of the present invention, it becomes possible to carry out photo CVD, PCVD, and PPCVD in the same reaction furnace. In addition 20
20 cm × 60 cm substrates or 100 5 inch size silicon substrates can be similarly inserted, and mass production of 10 to 30 times that of the conventional method can be achieved by the high-speed film manufacturing method. Believe that the effect of is extremely great.

Of course, the apparatus using the method of the present invention is not limited to the structure shown in FIG. 2, and it is possible to make the structural shape and size other than those described in the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an outline of a conventional photo CVD apparatus. FIG. 2 shows an outline of a photo CVD apparatus using the method of the present invention. FIG. 3 shows the electric conductivity characteristics obtained by the method of the present invention and the conventional example.

Claims (1)

[Claims] 1. A step of forming a film of silicon nitride or silicon oxide on a surface to be formed on a substrate by a photo-vapor phase reaction method, and a step of forming a film of the same main component material on the film by a photo-plasma vapor-phase method. 2. A method of forming a film by a vapor phase method, which comprises forming the silicon nitride or silicon oxide film of No. 2 by laminating.