JPS59139927A - Formation of membrane - Google Patents

Abstract

PURPOSE:To form a uniform membrane free from contamination by vapor deposition, in vapor depositing a hydrogen-containing amorphous Si-membrane on the surface of a substrate in a hydrogen atmosphere, by making the acceleration voltage of an electron beam generator negatively larger than the negative voltage of the substrate while directing an electron emitting orifice in parallel to the substrate surface. CONSTITUTION:A substrate 2 to be vapor deposited and an Si-evaporation source 3 are provided in opposed relation to each other within a vapor deposition tank 1 while a pressure reduced hydrogen atmosphere is formed in the tank 1. The substrate 2 is heated to 350-450 deg.C by a heater 6 and negative bias voltage of 0--10kV is applied thereto by a DC power source 7. Electron beam is emitted in parallel to the surface of the substrate 2 from an electron beam generator 8 provided to a position shifted from the region directly under the substrate 2 and Si in the evaporation source 3 is heated and evaporated by an electron beam heater 9 to form a hydrogen-containing amorphous Si-membrane on the surface of the substrate 2. In this case, acceleration voltage applied to the filament of the electron beam generator 8 is made negatively larger than the voltage to be applied to the substrate 2 and, by this method, an Si-membrane free from contamination due to the filament substance of the electron beam generator 8 can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming thin films by vapor deposition.

BACKGROUND ART Recently, amorphous silicon (hereinafter referred to as [a-8iJ)] has been viewed as very useful as a constituent material for solar cells, electrophotographic photoreceptors, and the like.

This a-8i can be formed as a thin film by the vertebral method, but it is necessary to introduce hydrogen atoms into this a-8,i to seal the dangling bonds. For the first time, hydrogen-containing a-8,i (hereinafter referred to as "a-8i:HJ") having large dark resistance and photoconductivity is obtained, making it possible to put it into practical use.

a-8i," Conventionally known methods for forming a thin film of H include a high frequency ion blating method, a direct current ion blating method, and a method of vapor deposition by introducing ionized or activated hydrogen. The formed thin film is easily contaminated, or the thin film forming conditions are unstable and it is difficult to form a stable and homogeneous thin film, or the introduction of hydrogen atoms into the thin film is uneven and a thin film with good characteristics cannot be formed. It has the following disadvantages.

As a method to overcome these drawbacks, hydrogen gas is directly introduced into a tank equipped with a substrate and an evaporation source, and while the hydrogen gas is activated or ionized by irradiating it with an electron beam, the silicon gas is removed from the evaporation source. A method has been developed to deposit it onto a substrate. This method has the advantage that it is easy to uniformly introduce hydrogen atoms into the a-8i thin film that is formed, and that contamination of the thin film can be significantly reduced.

However, it has been found that this method using electron beams has the following problems.

That is, in this method, an electron beam generator usually having a tungsten filament is used to obtain the electron beam,
Thermionic electrons are emitted by energizing the filament to generate heat, and i''L is accelerated by an accelerating electrode and emitted as a beam from the electron beam exit, thereby increasing the effect of the electron beam. In order to achieve this, it is preferable to place the tungsten filament directly under the substrate, which is the electron beam exit port of the electron beam generator. 5. If the membrane is contaminated by contamination.

For this reason, it is necessary to use, for example, a 270-degree deflection electron gun as the electron beam generator, in which the filament cannot be seen through the electron beam exit.

However, in such an electron beam generator, the area in which the emitted electron beam can be scanned is narrow, and therefore the electron beam cannot be scanned uniformly over the entire surface area of the substrate, and as a result, the formed thin film is This results in non-uniformity, and the advantage of using an electron beam is eventually lost.

The present invention was made based on the above circumstances, and
The purpose of this method is to perform deposition while irradiating an electron beam in a deposition tank where at least hydrogen gas is present. The object of the present invention is to provide a method capable of forming a thin film with a high quality.

The present invention is characterized in that at least hydrogen gas is present in a tank provided with a substrate and an evaporation source, and an electron beam is emitted from an electron beam generator provided such that the electron beam exit port is not directly opposed to the substrate. The method consists in depositing an evaporation substance from an evaporation source onto the substrate while irradiating the vicinity of the substrate, thereby forming a thin film.

The present invention will be explained in detail below with reference to the drawings.

In one embodiment of the present invention, as shown in FIG. 1, a vapor deposition substrate 2 and an evaporation source 3 using silicon as an evaporation substance are provided facing each other in a Pelger 1 forming a vapor deposition tank. Hydrogen gas is introduced into the jiber jar 1 through a hydrogen gas introduction pipe 4 connected to the interior of the jiber jar 1, and the inside of the jiber jar 1 is evacuated via an exhaust passage 5 with a vacuum pump (not shown). For example, 1O-
Maintain a reduced pressure of approximately 4 Torr. The substrate 2 is heated to a temperature within the range of 350 to 450° C. by a heater 6, and a negative bias voltage of 0 to −IQI (V) is applied to the substrate 2 by a DC power source 7. At a level position slightly lower than the level of the substrate 2 in an area outside the area directly below the area, an electron beam generator 8 arranged so that its electron beam exit port faces the area directly below the substrate 2 uniformly emits a stain beam. While scanning, the evaporation source 3 is heated by, for example, an electron beam heater 9 to evaporate silicon, which is an evaporation substance, and thereby the surface of the substrate 2 is heated with a-8, .
i: A thin film made of H is formed.

In the above description, it is assumed that the voltage applied to the thermionic emission filament of the electron beam generator 8 is negative and has a larger absolute value than the negative voltage of the substrate 2.

Since the method of the present invention is energized as described above, the electron beam generator 8
Since a good electron beam is irradiated into the space directly below the substrate 2, the hydrogen gas existing in this space is activated or ionized by the action of the electron beam, and on the other hand, this space is a space in which the vapor of the evaporated substance flies. ), therefore, on the substrate 2 is a deposited film in which hydrogen atoms are introduced with high efficiency, that is, a −8,i : H
A thin film is formed.

In the present invention, the electron beam generator 8fc has its electron beam emission port not facing the direction of the substrate 2, so even if the filament for thermionic emission is visible from the electron beam emission port, the filament cannot be seen. Since it does not directly face the substrate 2, there is no risk of contaminants such as tungsten, which is the material of the filament, being mixed into the thin film formed on the substrate 2, and therefore a thin film with the desired good characteristics can be obtained. Can be done.

Furthermore, as described above, since there is no risk of contamination of the electron beam generator 8 by the filament material, it is possible to use an 80° deflection electron gun, which has a wide scanning area, as the electron beam generator 8. Therefore, by uniformly scanning the electron beam over a wide area, it is possible to form a homogeneous thin film over a large area.

As mentioned above, the accelerating voltage applied to the filament HC in the electron beam generator 8 is desirably larger than the negative voltage applied to the substrate 2 by the DC power supply 7, and this is K.
Therefore, even in the region directly under the substrate 2, the electron beam is not bent away from the substrate 2 due to the influence of the negative voltage of the substrate 2, and the above-mentioned effects can be reliably obtained. .

Further, as shown in FIG. 1, a counter electrode 1 connected to a DC power supply 10 and held at a positive potential is arranged so as to face the electron beam generator 8 through an area directly under the substrate 2. Even in this case, the same effect can be achieved.

Further, since the electron beam exit port of the electron beam generator 8 does not face the substrate 2, the substrate 2 is not irradiated with the electron beam, and therefore the substrate 2 is prevented from becoming unexpectedly high temperature. Therefore, crystallization of a-8,i due to high temperature is not caused.

Therefore, it is possible to freely increase the amount of electron beams generated by the electron beam generator 8, thereby increasing the rate of thin film formation.

The substrate for vapor deposition on which a thin film is formed by the method of the present invention is not limited to a substrate, but may also be a drum-shaped or running film.

Various types of electron beam generators can be used as the electron beam generator 8, and it is not limited to a so-called point type, but a linear type that extends in two dimensions as shown in FIG. 2, or a three-dimensional type as shown in FIG. A solid object that extends in dimensions can also be used. In these figures, F is a filament, S is a filament power source, E is an extraction electrode, D is a DC power source for extraction electrode E, W is an electron beam transmission window formed in extraction electrode E, and e is an electron beam.

The uninvented method can form a thin layer M made of a substance that would cause damping bonds if it were simply vapor-deposited, with the gungling bonds sealed, and therefore the evaporation material of the evaporation source 3 can be formed. By changing a-
8:l:Thin films other than H, such as amorphous silicon carbide, amorphous silicon nitride, amorphous silicon germanium, amorphous silicon ditin,
Amorphous germanium and other thin films can be formed entirely.

In order to heat the evaporated substance of the evaporation source 3, K can use not only an electron beam heating means as in the illustrated example but also a resistance heating means.

As described above, according to the present invention, there is no contamination by the filament material of the electron beam generator, a wide scannable area can be obtained, and a homogeneous thin film can be formed.

Next, a specific example of the present invention will be explained.
Silicon was deposited under the following conditions using a vapor deposition apparatus having the configuration shown in FIG. 1 except that the DC power supply 10 was not provided. Note that an 1800 deflection electron gun was used as the electron beam generator.

Hydrogen gas inflow rate: 200SCCM Vacuum degree inside Pelger: lXl0'Torr Substrate voltage
: -4KV board temperature =
3oooC Electron beam heater voltage of evaporation source: -6KV Emission current: 200mA Electron beam generator driving voltage:
-6KV Emission current: 400mA Scanning cycle: 20Hz Film forming rate: 10A/sec Vapor deposition time
: For 1000 seconds, a film thickness of 1 μm was formed.
A thin film of Hl:H was formed. When we conducted a photoresponsive test on this thin film, we found that the dark conductivity was p=lQ-
9 (Ω・cm)-1, wavelength 550 nm, 5 x
The photoconductivity when irradiated with light at 1015 photons/Crn'' seconds was σG = 10-4 (Ω·crn 1), and it was recognized that it had excellent photoresponsiveness.

On the other hand, a thin film of a-8i: When we conducted a responsiveness test, σ, = 1O-6
(Ω・crn)−1, (jc:l: io′(,Q・
It showed no photoresponsiveness in the z-door. This is thought to be caused by contamination by filament material in the electron beam generator.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an apparatus that can be used to implement the thin film forming method of the present invention, and FIGS. 2 and 3 are explanatory diagrams of essential parts in an example of an electron beam generator. 1...Pelger 2--Substrate 3...Evaporation source 4--Hydrogen gas introduction pipe 5--Exhaust path
6... Heater 8... Electron beam generator
9...Electron beam heater 11...Counter electrode F
・・・Filament E・-・Extraction electrode W・・
・Electron beam transmission window $2 figure Reeds 3 figure

Claims (1)

[Scope of Claims] 1) At least hydrogen gas is present in a tank provided with a substrate and an evaporation source, and an electron beam exit port; A method for forming a thin film, characterized in that a thin film is formed by evaporating an evaporated substance from an evaporation source onto a substrate for 11 m while irradiating the vicinity of the substrate with a beam. 2) The thin film forming method according to claim 1, wherein the accelerating voltage of the electron beam generator is more negative than the negative voltage applied to the substrate. 3) The thin film forming method according to claim 1, wherein the electron beam exit aperture ii' of the electron beam generator is oriented in a direction parallel to the surface of the substrate.