JPS627859A - Formation of amorphous silicon film - Google Patents

Abstract

PURPOSE:To obtain the titled film having high photoconductivity, large ratio between the photoconductivity and dark conductivity and excellent photoconductive characteristic in the titled method utilizing electron cyclotron resonance plasma by specifying a gaseous pressure and gaseous components. CONSTITUTION:The region of an electric discharge tube 4 of a vacuum chamber 3 is made larger in the magnetic field intensity than the magnetic field intensity at which electron cyclotron resonance arises. Gases are respectively supplied through an introducing port 6 into such region and through an introducing port 7 into the region where the magnetic field intensity is smaller than the above-mentioned resonance magnetic field intensity. The film forming gas contg. Si atoms is supplied through the port 7. The non-film formable gas to be supplied through the port 6 is any among Ne, Ar, Kr and Xe and is introduced at 0.05-20 times the amt. of the Si-contg. gas. The gaseous pressure during the discharge is maintained under 5X10<-5>-3X10<-2> Torr. The intended amorphous silicon film is thus formed on the substrate 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of forming an amorphous silicon film on a substrate, such as a conductive substrate, and particularly to a method of forming an amorphous silicon film using electron cyclotron resonance plasma.

[Background of the invention]

Regarding the formation of amorphous silicon film using electron cyclotron resonance plasma, see Japanese Patent Application Laid-open No. 1591-1989.
There is a known example described in No. 67. In the above known example, 0.
4 gases or H in the gas pressure range of 2 to 0.5 Torr,
-N, the mixed gas is plasma excited by the resonance of a magnetic field and microwaves and brought into contact with a silicon atom-containing gas.
An amorphous silicon film is formed on a substrate heated to °C, but the film has a dark conductivity of 10-11 S/''l 3 and a conductivity of about 10-13,/-+, so it is not necessarily a good amorphous silicon film. However, the film quality obtained here is equivalent to that of an amorphous silicon film obtained by conventional parallel plate glow discharge plasma (Japanese Unexamined Patent Publication No. 159167/1983).

[Purpose of the invention]

An object of the present invention is to provide a method for forming an amorphous silicon film which has a higher photoconductivity than the amorphous silicon films according to the above-mentioned known examples, and which has excellent photoconductive properties such as a large ratio of photoconductivity to dark conductivity. .

[Summary of the invention]

The first feature of the present invention is that, unlike the above-mentioned known examples, 3×10→
The purpose is to utilize electron cyclotron resonance plasma at a gas pressure of less than Torr. The energy of electrons in plasma in a pressure range of 3×10 Torr or more is about 4 eV or less, but the energy of electrons in the above pressure range increases as the pressure decreases and reaches about 8 eN'. On the other hand, the energy required for the decomposition reaction of the raw material gas, such as SiH, is as follows.

5tH4→St + 2Ht; 4.4 eVS
iH, 4SiH+ He + H; 5.9 eVS
iH4→siH, + H, r 2.1 eVSiH
4-+ SiH, 10H; At 4.1eV-ff, the amorphous silicon film is SiH, fjl Jp SiH.

A film with few SiH-type bonds (i.e., a film in which dangling bonds in the film are effectively terminated by SiH-type bonds) has good photoconductive properties, but obtaining such a film requires a large amount of electron energy, even in terms of the reaction energy mentioned above. It is advantageous to use plasma at low pressure. Such low-pressure debossing is also advantageous in terms of releasing non-film forming gases such as H3. If it is below, it will be difficult to obtain a substantially stable plasma (so this gas pressure will be the lower limit).

The second feature of the present invention is that a gas containing a rare gas with a relatively large atomic weight, such as Ne, Ar, Kr, or Xe, is plasma excited by electron cyclotron resonance in the above gas pressure range, and brought into contact with a gas containing silicon atoms. The purpose is to form an amorphous silicon film using He or H.

It becomes possible to obtain an amorphous silicon film with better film quality than when the film is formed using electron cyclotron resonance plasma using only a light gas such as. The amount of Ne, Ar, or Xe introduced needs to be α05 or more relative to the amount of silicon atom-containing gas introduced, and although there is no practical upper limit, from the viewpoint of low-pressure film formation mentioned above, it is 20 The limit is about double that. The above-mentioned rare gas having a relatively high atomic weight contains 102 to 104 times as many ionized ions under the above-mentioned film-forming pressure conditions as in the case of a normal parallel plate glow discharge plasma or the above-mentioned example. It is believed that the ionized ions are accelerated to 1 to 20 eV and incident on the film forming surface, thereby contributing to improving the film quality. The film quality improvement effect of the rare gas is more effective when the atomic weight of the rare gas is larger, but from a cost standpoint, it is desirable to use Ar gas.

In order to obtain a good amorphous silicon film, the substrate should be
Although it is necessary to heat the plasma to 00°C or higher, the temperature is 5°C compared to the normal parallel plate type glow discharge plasma or the above-mentioned known example.
An amorphous film with equivalent film quality can be obtained at a temperature 0 to 100°C lower, and particularly when the substrate is heated to 200°C or higher, a good film quality that is difficult to obtain with conventional methods can be obtained.

Note that by including the gas KHe or H gas containing Ne, Ar, Kr, or Xe, it is possible to maintain the film quality and increase the deposition rate of analysilicon. In order to obtain the effect of increasing the deposition rate of amorphous silicon, it is necessary to introduce 0.05 or more of He or H gas to the amount of silicon atom-containing gas introduced into the vacuum chamber. However, if too much light gas is included, the film quality will deteriorate, so the limit is about 10 times the amount of silicon atom-containing gas introduced. In order to obtain the above-mentioned effect of increasing the film formation rate, it is necessary to efficiently excite the plasma of He, H, gas, or gas. However, when mixed with a gas containing silicon atoms, the effect is small.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples.

FIG. 1 is an explanatory diagram of the configuration of an electron cyclotron plasma film forming apparatus used in an embodiment of forming an amorphous silicon film of the present invention. In the figure -1 is the magnetron,
Typically, microwaves of 0.1 to 10 GHz are generated. The generated microwaves are guided into the vacuum chamber 3 through the circular waveguide 2. 4 is a discharge tube made of an insulating material (for example, quartz glass, alumina, etc.) to transmit microwaves. 5 is a solenoid coil for forming a magnetic field within the vacuum chamber. 6.7 is a gas inlet of a different system, the gas inlet 6 is arranged to supply gas to the high magnetic field area in the vacuum chamber 3, and the gas inlet lower is arranged to supply gas to the low hot water output area in the vacuum chamber 3. It is arranged to supply. Reference numeral 8 denotes a substrate to be film-formed, which is installed so that the gas supplied from the gas introduction lower is incident on the surface. 9 is a sample stage equipped with a heating mechanism. Reference numeral 10 denotes an exhaust boat to which a decompression pump (not shown) having a high exhaust speed, such as a turbo molecular pump or an oil diffusion pump, is connected.

When a discharge gas is introduced into a vacuum chamber at a predetermined pressure and microwave power is supplied, a microwave discharge is generated due to the interaction between the microwave electric field and the magnetic field. I will explain about it. Electrons in a magnetic field move in a cyclotron around magnetic field lines,
The cyclotron frequency fce of the electron is determined by the magnetic field strength as fce = a ''L (Hz) 2πm where B: @flux density [T] m: electron mass (Kg) e: electron charge (Coulomb). fce is the incident micro Electron cyclotron resonance excitation occurs at a position where the magnetic field strength coincides with the wave frequency.In Fig. 1, the area of the discharge tube 4 in the vacuum chamber 3 is set to be below the magnetic field strength where the electron cyclotron resonance occurs;
The configuration is such that gas is supplied from the gas introduction port 6 to this region, and another system of gas is supplied from the gas introduction lower to the region where the magnetic field strength is smaller than the electron cyclotron resonance magnetic field. In such a configuration, a non-film-forming gas is introduced from the gas inlet 6. The gas introduced here is Ne, Ar, or K.
When containing r or
The light is accelerated to 20 eV and enters the film-forming surface of the base 8. A film-forming gas containing silicon atoms is supplied from the gas introduction lower, and is decomposed by high-energy ionized electrons due to low-pressure electron cyclotron resonance to form an amorphous silicon film on the surface of the substrate 8. B in the amorphous silicon film,
P.C.

When you want to dope a foreign atom such as N*Ge?
.

Doping can be performed efficiently by supplying a gas containing foreign atoms to the gas introduction lower part.

Next, a method for forming an amorphous silicon film according to the present invention using the above-mentioned plasma film forming apparatus will be described with reference to a typical example.

SiH4 was used as the 8i atom-containing gas and was supplied from the gas introduction lower. Ar gas is supplied from gas inlet 6.
The same amount of iH gas was supplied. Microwave frequency -2,45
GHz? Microwave input car 3oow', discharge gas pressure = 6 x 10-'Torr 1 base temperature ■200
℃. The maximum a-field distribution is 1750G in the discharge tube 4 part.
・The discharge tube 4 was set to have a force of 875 G (resonant tapping strength of the child cyclotron) at the exhaust side end.

A turbo molecular pump with an exhaust speed of 500 t/sec was used for the exhaust system. The amorphous silicon film formed under these conditions has a photoconductivity of 1.5. /)x It was a good quality film with a ratio of primary conductivity to dark conductivity of 101.

In addition, when Ne e Kr #
A film with a good quality of 106 and the above ratio of about 104 can be formed by heating the substrate at 100°C.
Good results are obtained even when Ar, Kr+ was obtained at about 15 times faster film formation rate.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to form amorphous silicon with better photoconductive properties than before, or it is possible to form a relatively good amorphous silicon film at a low temperature, making use of photoconductive properties. It becomes possible to apply it to various devices.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of an electron cyclotron resonance plasma deposition apparatus used for forming an amorphous silicon film according to the present invention. 1... Magnetron, 2... Waveguide, 3...
Vacuum chamber, 4...Discharge tube, 5...Solenoid coil, 6.7...Gas inlet, 8...Base body,
9... Sample stand, 10... Exhaust boat. (Figure 1) Indication of the case Patent Application No. 146528 of 1985 Title of the invention Method for forming an amorphous silicon film Shoes with a person who makes corrections Patent applicant name Name L5+o+Hitachi Co., Ltd. Manufacturer's agent

Claims (1)

[Claims] 1. A magnetic field is formed in at least a part of the vacuum chamber, microwaves are introduced into the vacuum chamber, and the gas introduced into the vacuum chamber is subjected to electron cyclotron resonance due to the magnetic field and the microwaves. Accordingly, in the method for forming an amorphous silicon film in which plasma is excited to decompose a silicon atom-containing gas introduced into the vacuum chamber and an amorphous silicon film is formed on a substrate placed in the vacuum chamber, the discharge gas is Ne. Alternatively, the gas contains 0.05 to 20% of Ar, Kr, or
A method for forming an amorphous silicon film characterized by a pressure of 10^-^2 Torr. 2. The magnetic field intensity formed in the vacuum chamber decreases from being larger than the electron cyclotron resonance magnetic field along the microwave introduction path, and becomes smaller than the resonance magnetic field after passing through the resonance magnetic field, and the magnetic field intensity is larger than the electron cyclotron resonance magnetic field. N in the area of
A non-film-forming gas containing e, Ar, Kr, or Xe at a ratio of 0.05 to 20% relative to the silicon atom-containing gas introduced into the vacuum chamber is introduced into a region where the magnetic field strength is smaller than the electron cyclotron resonance magnetic field. 2. The method of forming an amorphous silicon film according to claim 1, wherein the film is formed on a substrate placed in a region where a silicon atom-containing gas is introduced and the magnetic field strength is smaller than an electron cyclotron resonance magnetic field. 3. The gas containing Ne, Ar, Kr, or Xe is a gas containing He or Hz of 0.05 to 10 Hz relative to the silicon atom-containing gas introduced into the vacuum chamber. A method for forming an amorphous silicon film according to item 1 or 2. 4. The method for forming an amorphous silicon film according to claim 1, 2, or 3, wherein the film is formed under the condition that the substrate is heated to 100° C. to 400° C.