JPS6346719A - Manufacture of thin-film - Google Patents

Abstract

PURPOSE:To equalize the photochemical reaction of a raw material gas, to decrease internal defects in a thin-film acquired and to improve film quality by irradiating the raw material gas containing mercury with continuous beams having substantially constant light intensity. CONSTITUTION:A raw material gas containing mercury is irradiated with continuous beams having substantially constant light intensity. That is, a quartz glass window 2 is mounted to the upper wall of a reaction chamber 1, and a light source 5 generating continuous beams such as a low-pressure mercury lamp using DC discharge or high-frequency discharge is arranged to the upper section of the window 2. A substrate 3 is disposed horizontally onto a heater 4 on the reaction 1 chamber 1, and the inside of the reaction chamber 1 is supplied with a gas, in which mercury vapor is mixed to a raw material gas (including a doping gas such as B2H6, PH3, etc. if necessary) as a thin-film substance source such as silanes such as SiH4 or GeH4, Ge2H6, etc. or these fluorides or chlorides, in response to a thin-film to be manufactured through a supply nozzle 6 and an exhaust port 7, heating the substrate 3 by the heater 4. Mercury is excited continuously by continuous beams from the light source 5, and generates a photochemical reaction with the raw material gas, thus shaping the thin- film consisting of Si, Ge, etc. on the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thin film manufacturing method for manufacturing a thin film of silicon or the like used in a thin film device on a substrate by a mercury-sensitized photo-CVD method.

[Conventional technology]

Semiconductors such as amorphous silicon (hereinafter abbreviated as a-8i) and amorphous dalmanium (hereinafter abbreviated as a-Ge) are used as thin films for solar cells, electrophotographic photoreceptors, optical sensors, thin film transistors, etc. Widely used for Debye pages.

Methods for producing these thin films include ion silating method, sintering method, vacuum evaporation method, and CVD (C
chemical vapor deposition
) law etc. are well known. The plasma CVD method involves depositing a thin film on a substrate from plasma generated by glow discharge of a raw material gas.The CVD method involves irradiating the raw material gas with light such as ultraviolet rays to form a thin film on the substrate from the raw material gas through a photoexcitation reaction. There is a photo-CVD method that does this.

Photo-CVD methods include direct excitation method and mercury sensitized excitation method, but since both are plasma-free systems, there is no damage or contamination of thin films due to high-energy ions, and it is possible to form high-quality thin films. You can expect it. In particular, in the mercury-sensitized excitation method, the raw material gas is doped with a trace amount of mercury vapor.
Since mercury is excited by light irradiation and reacts with the raw material gas, efficient decomposition of the raw material gas is possible due to the catalytic action of the excited mercury.

However, the irradiation light used in the conventional photo-CVD method using mercury sensitization was light from an ultraviolet lamp using a commercial frequency voltage, and was so-called AC discharge light. Therefore, as shown in Figure 3, the light is 100H synchronized with the commercial frequency.
Repeat ON and OFF periodically at z or 120Hz,
The light intensity changed periodically. As a result, the photochemical reaction of the raw material gas is non-uniform, the quality of the obtained thin film is poor, and the characteristics of the thin film Z-chair using this are also unsatisfactory.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for producing a thin film that can uniformize the photochemical reaction of a raw material gas in a mercury-sensitized photoCVD method and form a thin film with good film quality.

[Means for solving problems]

The method of producing a mercury-sensitized thin film by photoCVD according to the present invention is characterized in that a raw material gas containing mercury is irradiated with continuous light having a substantially constant light intensity.

The continuous light used in the present invention only needs to have a substantially constant light intensity, and includes light from ultraviolet lamps such as deuterium lamps and low-pressure mercury lamps using direct current discharge, as well as light from ultraviolet lamps using high-frequency discharge. Since the repetition frequency of ON and OFF is high, the light intensity becomes continuous light that is substantially constant, so other laser lights can also be used if they are effective.

The thin film manufacturing method of the present invention will be explained with reference to FIG. 1, which shows a specific example of a manufacturing apparatus.

A quartz glass window 2 is provided on the earthen wall of the reaction chamber 1, and a light source 6 that generates continuous light, such as a low-pressure mercury lamp using direct current discharge or high-frequency discharge, is arranged above the window. The substrate 3 is placed horizontally on the heater 4 in the reaction chamber 1, and while the substrate 3 is heated by the heater 4, the supply nozzle 6 and the exhaust lower are passed through the entire supply nozzle 6 and the exhaust lower to produce a thin film such as S i 84. silanes or Qei (4.

Raw material gas for thin film material such as Qe2H6, etc., or their fluorides and chlorides (B2H6+PH if desired)
A mixture of mercury vapor and a doping gas (containing a doping gas such as No. 3) is supplied into the reaction chamber 1. Continuous light from the light source 6 continuously excites mercury and causes a photochemical reaction with the source gas, forming a thin film of Sl, Ge, or the like on the substrate 1.

[Effect]

The photochemical reaction by the photoCVD method in mercury sensitization is thought to include a primary reaction and a secondary reaction. For example, S
Taking iH4 as an example, the -order reaction is thought to be based on the following reaction formula: 1-1g+hν →Hg* Hg* + 5i) (4→ SiH3*+ H
* + Hg"Hg* + H2→ 2H*
+Hg*SiH4+ H* →SiH3*+ H3(
In the formula, Hg*, I-1", and SiH3* represent mercury, hydrogen, and silane radicals, respectively.) SiH3" produced in this -order reaction has low reactivity, long life, and forms a high-quality thin film. It is considered to be.

On the other hand, although the process of the secondary reaction has not yet been clarified,
It is thought that highly reactive and short-lived radicals such as SiH* and SiH2* are generated, and these radicals deteriorate the film quality.

Under discontinuous light such as a low-pressure mercury lamp using AC discharge at a commercial frequency as shown in Figure 3, when the light is irradiated, the -order reaction and the second-order reaction occur continuously in (a). It is presumed that when no light is irradiated (b), only secondary reactions occur and the desired SiH3* is not produced, resulting in poor film quality.

In the present invention, as shown in FIG. 2, since continuous light with almost constant light intensity is used, it is possible to maintain a state where the primary reaction is always occurring, and because only the secondary reaction does not occur, Good film quality can be obtained.

Further, by lowering the pressure in the reaction chamber and/or increasing the gas flow rate than in the usual mercury-sensitized photoCVD method, undesired substances produced in the above-mentioned secondary reaction can be quickly discharged, which is more preferable.

〔Example〕

Using the apparatus shown in FIG. 1 equipped with a high-frequency, low-pressure mercury lamp as a light source, a photoconductive layer with a pin structure was formed on a transparent electrode on a glass substrate by mercury-sensitized photochemical CVD, and an aluminum electrode was formed on top of the photoconductive layer. A solar cell was constructed. still,
The high frequency voltage used was 10V, the power was 35W, and the frequency was 2kHz.

The raw material gases, flow rates, and film-forming times used to form the p-layer, i-layer, and n-layer of the photoconductive layer are as shown in Table 1 below, and the other conditions are a pressure of 5 Torr, a substrate temperature of 180 tons, and mercury. The temperature was 60C.

Table 1 (Note) Hydrogen dilution gas was used for GeH4, B2H6, and PH3.

Comparing the characteristics of the solar cells manufactured as described above with those of solar cells of the same structure manufactured using the conventional mercury-sensitized photoCVD method using discontinuous light, AMl, 5 and 100
Under sunlight of mW/cm2, the results were as shown in Table 2 below.

Table 2 Characteristics Present invention Conventional Short circuit current (m!VCrn”) 19 1
5 Open circuit voltage (V) 0.62 0.6
1 Flexibility factor (%) 60 54 Conversion efficiency (ch) 7.1 4.9 [Effects of the invention] According to the present invention, by using continuous light in the mercury-sensitized photoCVD method, the The photochemical reaction is made more uniform, and the film quality can be improved by reducing internal defects in the obtained thin film.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a specific example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a graph showing the light intensity of continuous light from an ultraviolet lamp using direct current discharge. Third
The figure is a graph showing the light intensity of discontinuous light from an ultraviolet lamp using AC discharge using a commercial frequency current. ■... Reaction chamber, 2... Quartz glass window, 3... Substrate, 4... Heater, 5... Light source, 6... Supply, l'/l/, 7... ·exhaust port. Figure 1 Figure 2 Illustration room

Claims (2)

[Claims] (1) A method for producing a thin film on a substrate by a mercury-sensitized photo-CVD method, which comprises irradiating a raw material gas containing mercury with continuous light having a substantially constant light intensity. (2) The method for producing a thin film according to claim (1), wherein the continuous light is light from an ultraviolet lamp using direct current discharge or high frequency discharge.