JPS58112045A - Formation of thin film - Google Patents

Abstract

PURPOSE:To mix a modifying element in a ratio controlled in large degree of freedom, by a method wherein a magnetron type gas discharger is provided so as to be connected to a vacuum tank and a thin film is formed while an ion and an active gas are introduced. CONSTITUTION:A magnetron type gas discharger 8 is provided to the external part of a bell jar 1 forming a vacuum tank so as to oppose the outlet thereof to a vapor deposition base plate 4. In this state, when the ion of a modifying element gas and an active gas are formed in said magnetron type gas discharger 8 and an evaporation source is evaporated while said ion and said active gas are introduced into the bell jar 1, a thin film having a modifying element mixed therein can be certainly formed in a high containing ratio.

Description

[Detailed description of the invention] The present invention relates to a thin film forming method.

Generally, the glow discharge method, sputtering method, and vapor deposition method are known as thin film forming methods, but among these, the vapor deposition method has the advantage of being able to obtain a high film forming speed and being relatively easy to form a large area thin film. It is excellent in that it can be

On the other hand, thin films are useful in various fields including semiconductor devices, but they are not limited to thin films whose composition consists only of substances that can be evaporated or sublimated by heating. It is desired to form a compound in such a case that a thin film having the desired properties can be formed by a vapor deposition method.

For example, amorphous silicon, which has recently attracted attention as a solar cell or photoconductive material, has an irregular atomic arrangement structure that is amorphous, so it is necessary to seal the unbonded dangling bonds that inevitably occur with hydrogen atoms, etc. This is the first time that amorphous silicon can be useful as a semiconductor material. Conventionally, satisfactory amorphous silicon could be obtained using a glow discharge method using silane gas, but the same product could not be obtained using a vapor deposition method. If obtained, it would be extremely advantageous in terms of manufacturing costs.

However, in the vapor deposition method, if the gas of the modifying element is simply made to exist in the vapor deposition space, the amount of the modifying element mixed into the deposited film is extremely small, and it is extremely difficult to form a thin film with desired characteristics. .

This is mainly due to the fact that the gas of the modifying element is molecular and stable.

Under these circumstances, it is thought that if the modifying element is activated or ionized and present in the vapor deposition space, the modifying element can be effectively mixed into the deposited film. It has been proposed to introduce the active product obtained by discharging into a vacuum chamber forming a deposition space. This is because if a means of generating electric discharge is used in a vacuum chamber, both the conditions necessary for this electric discharge and the conditions necessary for vapor deposition must be satisfied at the same time, so the setting of conditions is actually limited. This is to avoid the situation where a large degree of freedom cannot be obtained due to a closed system.

This method of mixing a modifying element into a deposited film using a discharge tube is actually effective and has been confirmed in the formation of amorphous silicon containing hydrogen.

However, it has been found that there is a limit to the proportion of the modifying element mixed into the formed thin film in vapor deposition performed by introducing the discharge product of a modifying element gas obtained in a gas discharge tube by direct current glow discharge. . For example, when forming a thin film using the glow discharge method described above, hydrogen is
It is possible to form amorphous silicon containing a high proportion of 0 to 80 atomic percent, but when silicon is deposited in a vacuum chamber into which discharge products from direct current glow discharge of hydrogen gas are introduced, the conditions must be varied. However, the hydrogen content is limited to about 15 at % and cannot be higher than that, so the dark resistance of the amorphous silicon obtained is at most 1010 Ω, which is necessary for example in electrophotographic photoreceptors. It is not possible to obtain sufficient charge retention ability. Incidentally, according to the glow discharge method, 101
Amorphous silicon having a high dark resistance of 2Ω is obtained.

The present invention has been made based on the above-mentioned circumstances, and it is possible to mix a modifying element in a controlled ratio with a large degree of freedom into a thin film formed by a vapor deposition method. It is an object of the present invention to provide a method for forming a thin film that can be made large.

The poem of the present invention includes a vacuum chamber, an evaporation source provided within the vacuum chamber, and a magnetron type gas discharger provided outside the vacuum chamber with its outlet connected to the vacuum chamber. Using a device, the evaporation source material is evaporated from the evaporation source while introducing ions and active gas from the magnetron-type gas discharger into the vacuum chamber, so that the evaporation source material is evaporated onto the substrate placed in the vacuum chamber. The method is to form a thin film of the evaporation source material containing modifying elements by ions and active gas.

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

In this invention, as shown in FIG. A heater 5 that heats the vapor deposition substrate 4
and a DC power supply 6 that applies a negative DC voltage to the vapor deposition substrate 4 or, if the substrate is insulative, a negative DC voltage behind it.
A magnetron type gas discharger 8, which will be described later, is installed outside the Pelger 1 so that its outlet 11 faces the vapor deposition substrate. to configure a thin film forming apparatus,
Using this apparatus, a thin film of amorphous silicon mixed with hydrogen, for example, is formed by the following method.

That is, the inside of the Pelger 1 is evacuated to a vacuum state of 10 to 10 Torr, and the vapor deposition group 64 is heated to a temperature of 2 by the heater 5.
Heating to 50-500℃ and heating with DC power supply 6
While a negative DC voltage of 0 KV or less is applied to the deposition substrate 4, hydrogen gas, which is a modifying element gas, is supplied to the magnetron type gas discharger 8 to drive the magnetron type gas discharger 8. While hydrogen ions and active hydrogen are introduced into the Pelger 1, the evaporation source 7, which uses silicon as an evaporation source material, is heated to evaporate the silicon, thereby forming an amorphous layer on the evaporation substrate 4 with hydrogen mixed therein. Form a thin film of silicon.

As the heating method for the evaporation source, any method such as electron gun heating, resistance heating, induction heating, etc. can be used. It is also preferable to have a structure that can prevent coarse particles from flying away.

An example of the magnetron type gas discharger 8 used in the above is shown in Figure $2. , this gas discharger 8 has an outlet 11
a discharge space surrounding member 12 having an ion outlet 1;
Output power 141115 consisting of a mesh provided in 1
and an anode plate 1 provided to face this extraction electrode 18.
4 and, for example, a through hole 15 provided to divide the discharge space between the extraction electrode 13 and the anode 1114.
A modifying element gas introducing pipe 17 is connected near the anode plate 14, and the outlet 11 is connected to the opening 1 of the Pelger 1.
0 so as to point toward the deposition substrate 4. 18 is a power source for the anode plate 14, and the applied voltage is 200V ~
2KV, 20 is a power source for the electromagnet 16, and its magnet current is 0 to 1 μm. Although the extraction electrode 13 is at ground potential in this example, a potential difference of θ to 8 KV is applied to the electromagnet 16 by a power source 19.

The present invention is a method as described above, in which, in the gas discharger 8, hydrogen gas introduced into the discharge space from the modifying element gas introduction tube 17 is applied to the voltage applied between the anode plate 14 and the electromagnet 16. However, the plasma is confined within the space of the through hole 15 of the electromagnet 16 by magnetic force. Hydrogen ions are extracted from the plasma by the potential difference with the extraction electrode 18, pass through the extraction electrode 13, and are introduced into the Pelger l from the outlet 11, and are applied to the deposition substrate by a bias voltage applied to the deposition group &4 or the electrode behind it. 4, and the active hydrogen also flies in the same direction. At the same time, silicon vapor flies from the evaporation source 7 to the evaporation substrate 4.
As a result, a thin film of amorphous silicon mixed with hydrogen is formed on the deposition substrate 4.

In the present invention, as described above, the ions of the modifying element gas and the active gas are generated in the magnetron type gas discharger 8 and introduced into the Pel jar 1, and in the presence of the ions, the evaporation source material is In order to evaporate the
It is possible to reliably form a thin film mixed with the modifying element, and the gas discharger 8 is functionally independent of the Pelger 1, and its anode plate 14, electromagnet 16, and extraction electrode 1
voltage of 8, magnetic force of electromagnet 16, supply amount of modifying element gas,
In addition, it is also possible to control the evaporation rate of the clay oven source 7, which can individually control the bias voltage and temperature related to the evaporation substrate 4, so it is possible to control the mixing ratio of the modifying element in the thin film over a wide range. can. In particular, the Magnelon type gas discharger B can generate a large amount of ions and active gas compared to a gas discharge tube using glow discharge, and in addition, the Pelger 1 contains accelerated ions with high energy, etc. is introduced, the mixing efficiency into the thin film is high, and therefore the content of modifying elements is high.
A thin film having desired characteristics can be formed, and in the example described above, it is possible to form a thin film of amorphous silicon in which hydrogen is mixed at a high content of 80 atoms.

In addition, since modifying elements can be mixed with high efficiency in this way, the advantage of the vapor deposition method that originally provides a high film formation rate is not diminished, and unless restricted by other conditions, I
The coverage of llIgI can be increased, and for example, a desired thin film can be advantageously formed continuously on the surface of a long evaporation substrate 4 by moving it at a high speed.

In the present invention, as the evaporation source material contained in the evaporation source 7, any material that can be generally evaporated can be used. The number of evaporation sources 7 may also be the number of films, and when forming a thin film of amorphous silicon as described above, co-evaporation can also be performed using an evaporation source of an element belonging to Group 2 or Group V of the periodic table. For example, a p-type or n-type amorphous silicon thin film can be obtained.

The modifying element gas may be any gas that provides ions and activated products of the element that can be mixed into the substance formed by evaporation from the evaporation source, and may include not only a gas consisting only of the element, but also a compound gas thereof. You can also use For example, in the example described above, if part of the hydrogen gas is replaced by hydrocarbon gas, a thin film of amorphous silicon carbide mixed with hydrogen can be obtained.

As described above, according to the present invention, it is possible to mix a modifying element in a controlled ratio with a large degree of freedom into a thin film formed by a vapor deposition method, and in particular, it is possible to increase the content ratio. .

The present invention will be explained in detail below.

Example 1 Using an apparatus having the configuration shown in the figure, 1. A thin film of amorphous silicon mixed with hydrogen was formed under the following conditions.

Condition vacuum degree in Pelger 5 X 1O-5 Torr (hydrogen pressure) Evaporation source material Silicon evaporation substrate Type Aluminum temperature 400℃ Applied voltage -2KV Condition vacuum degree of magnetron type gas discharger I X 1O-2 Torr (hydrogen pressure) Modifying element Gas type Hydrogen gas flow rate 50CC/min Anode plate voltage 1 from earth, 700V Electromagnet voltage 50V from earth Extracting electrode Position the earth Conditioned film forming speed 40A/sec Time
The amorphous silicon thin film with a thickness of 1 μm obtained for 250 seconds had a hydrogen content of 30%, a dark resistance of 1×10 12 Ω·CII+, and had good semiconductor properties.

Example 2 A transparent conductive film made of indium oxide was formed using an apparatus having the configuration shown in the figure under the following conditions.

Condition vacuum degree in Pelger 4 x 10 'I'orr (oxygen pressure) Evaporation source material Indium evaporation substrate Type Glass temperature 200℃ Applied voltage -2KV Condition vacuum degree of magnetron type gas discharger 2 x 1 o 'rorr
(Oxygen pressure) Modifying element gas Type Oxygen gas flow rate 50CC/min Voltage of anode plate 700 V from earth Voltage of electromagnet 50 V from earth Extracting electrode Conditioned speed for film formation at earth potential 2λ/sec Time
Thickness 2 obtained here for 120 seconds
The transmittance of light with a wavelength of 550 n111 in the transparent conductive film of 40 people was 86%, and the conductivity was 1O-3 (Ω cm
)-' and had good conductive properties.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view showing the structure of an example of an apparatus used in the thin film forming method of the present invention, and FIG. 2 is an explanatory sectional view showing the structure of an example of a magnetron type gas discharger. 1...Helscher 2..., butterfly valve 8...exhaust path 4...evaporation substrate 7...
Evaporation source 8... Magnetron type gas discharger 11... Outlet 12... Discharge space surrounding member 18... Drawer t birch 14... Anode plate
16...Electromagnet 1...Modifying element gas introduction tube procedure amendment (voluntary) February 141, 1981'' Commissioner of the Japan Patent Office Kazuo Wakasugi 1, Indication of the case 1982 Patent 192732 'Application No. 2 Invention Name of Thin Film Forming Method 3, Relationship with the Amendment Case Patent Applicant Furigabu Address: No. 2, 1-26 Nishi-Shinjuku, Shinjuku-ku, Tokyo
Place 4, Attorney 5, Date of amendment order 6, Number of inventions increased by the amendment 7, Addition of detailed explanation of the invention in the specification subject to amendment. "In the above, the degree of vacuum inside Pelger 1 is 10-
3~lO-! Torr, but it is actually difficult to obtain a degree of vacuum higher than 4.10"Trr using a diffusion pump as a vacuum pump, and the degree of vacuum is 10"Torr.
If it is lower than rr, the K will become so high that spark discharge will occur in the gas discharge tube 8, and the efficiency of ionization or activation of the modifying element gas will decrease, and evaporation from the evaporation source will be suppressed, and furthermore, the gas discharge tube The mean free path of active species such as hydrogen ions generated in step 8 is short (because of its II
To I) Introduction efficiency becomes smaller. By the way, 10”T
The mean free path of hydrogen ions in the vacuum space of orr is about 10 cm. ”

Claims (1)

[Claims] 1) A device comprising a vacuum chamber, an evaporation source provided within the vacuum chamber, and a magnetron-type gas discharger provided outside the vacuum chamber with its outlet connected to the vacuum chamber. using
While introducing ions and active gas from the magnetron type gas discharger into the vacuum chamber, the evaporation source material is evaporated from the evaporation source, so that the ions and active gas are deposited on the substrate placed in the vacuum chamber. A method for forming a thin film, comprising forming a thin film using the evaporation source substance containing a modifying element according to the method. 2) The thin film forming method according to claim 1, wherein a negative DC voltage is applied to the #1 substrate or its rear electrode.