JPH01246364A - Vapor-phase synthesis for hydrofluorinated amorphous silicon carbide thin film and fluorinated amorphous silicon thin film - Google Patents

Abstract

PURPOSE:To obtain the title thin film having a high content of F and having high electric conductivity by producing most capacitive-coupling high-frequency plasma for decomposing a specified gaseous raw material mixture between the counter electrode of a substrate electrode and a reticular electrode arranged between both electrodes and negatively biased with respect to the substrate electrode. CONSTITUTION:The gaseous raw material mixture consisting of hydrogen fluorosilicide, hydrocarbons, and hydrogen is supplied from a gas feeder 3 into a reaction vessel 1 connected to an evacuation system 2 and capable of being kept at a desired vacuum. The raw gas is then decomposed by the capacitive-coupling high-frequency plasma discharge. The plasma discharge in this case is mostly generated between the counter electrode 5 opposed to the substrate electrode 4 and the reticular electrode 8 arranged between both electrodes 4 and 5 and negatively biased with respect to the electrode 4. In addition, the potential of the electrode 8 is controlled by a DC power source 9 connected to the electrode 8. As a result, a hydrofluorinated amorphous silicon carbide thin film contg. crystallitic silicon and having high conductivity can be synthesized in a vapor phase.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has a high fluorine content, which is suitable for the production of solar cells, thin film transistors, temperature sensors, etc. that are highly heat resistant and reliable, and furthermore, The present invention relates to a fluorinated amorphous silicon carbide thin film containing microcrystalline silicon and having high conductivity, and a vapor phase synthesis method of a fluorinated amorphous silicon thin film.

(Prior Art) Conventionally, as this type of vapor phase synthesis method, thermal CVD (chemical vapor deposition) method, plasma CVD method, photoCVD method, etc. are known.

(Problems to be Solved by the Invention) However, in the case of the conventional method, the amount of fluorine incorporated into the thin film during vapor phase synthesis is about several atm%, and there is a disadvantage that a thin film with stable film quality cannot be obtained. have. Further, in particular, in the case of vapor phase synthesis of a fluorinated amorphous silicon carbide thin film, there is a disadvantage that a film containing microcrystalline silicon cannot be obtained.

The present invention solves the disadvantages of the conventional method, and produces a fluorinated amorphous silicon carbide thin film and a fluorinated amorphous silicon thin film that have a high fluorine content and also contain microcrystalline silicon and have high conductivity. Its purpose is to provide a vapor phase synthesis method.

(Means for Solving the Problems) The vapor phase synthesis method of a fluorinated amorphous silicon carbide thin film of the present invention uses a capacitively coupled high-frequency plasma discharge to and a counter electrode disposed opposite to the substrate electrode, and a counter electrode disposed between the substrate electrode and the counter electrode that applies a negative bias to the substrate electrode. It is characterized in that the process is performed between the mesh electrode and the mesh electrode.

In this case, the mixed raw material gas may further contain hydrogen silicide.

Furthermore, the vapor phase synthesis method of the fluorinated amorphous silicon thin film of the present invention is as follows:
A mixed raw material gas consisting of hydrogen fluorosilicide and hydrogen is decomposed by a capacitively coupled high-frequency plasma discharge, and most of the plasma discharge generated at that time is transferred between a counter electrode placed opposite the substrate electrode, and a counter electrode disposed opposite the substrate electrode. It is characterized in that it is carried out between a net-like electrode which is arranged between a counter electrode and a negative bias is applied to the substrate electrode.

In addition, as the hydrogen fluorosilicide, 5IHP3.5IH2
Examples include, but are not limited to, F2, SiH, FSSi□H2F4, and the like.

(Function) In the case of the vapor phase synthesis method for silicon carbide thin films, hydrogen fluorosilicide is used as the mixed raw material gas, so that fluorine-containing radicals generated in the plasma can be used in vapor phase reactions and reactions on the substrate surface. It performs catalytic actions such as gas decomposition and hydrogen extraction, and promotes the arrival of fluorine to the substrate surface. Furthermore, by applying a negative bias to the mesh electrode with respect to the substrate electrode so that most of the plasma discharge occurs between the counter electrode and the mesh electrode, the impact energy of ion species on the substrate surface can be reduced, and the Increases the adhesion rate of fluorine that reaches the
As a result, the fluorine content in the thin film increases.

Furthermore, by adding hydrogen silicide to the source gas, the amount of microcrystalline silicon increases, thereby increasing the electrical conductivity.

In the case of the vapor phase synthesis method for silicon thin films, hydrogen fluorosilicide is used as the mixed raw material gas, so the fluorine-containing radicals generated in the plasma cause gas decomposition and hydrogen decomposition in the vapor phase reaction and the reaction on the substrate surface. It performs a catalytic action such as drawing and promotes the arrival of fluorine to the substrate surface. Furthermore, by applying a negative bias to the mesh electrode with respect to the substrate electrode so that most of the plasma discharge occurs between the counter electrode and the mesh electrode, the impact energy of ion species on the substrate surface can be reduced, and the This increases the adhesion rate of fluorine that reaches the film, resulting in an increase in the fluorine content in the thin film.

Furthermore, since the impact energy is small, surface diffusion of silicon is promoted and microcrystalization occurs.

(Example) Examples of the gas phase synthesis method of the present invention will be described below with reference to the accompanying drawings.

Figure 1 shows an example of a manufacturing apparatus suitable for use in the gas phase synthesis method of the present invention. In the figure, 1 indicates a reaction vessel that is connected to a vacuum evacuation system 2 and can be maintained at an appropriate degree of vacuum. A gas supply device 3 is connected to the reaction vessel 1 . Although not shown, the gas supply device 3 is configured so that the amount of mixed raw material gas to be supplied can be adjusted to an appropriate amount using a flow rate controller. Inside the reaction vessel 1 is a substrate electrode 4 consisting of a pair of parallel plate electrodes.
and a counter electrode 5 are provided, and a high frequency power source 6 is connected to these electrodes 4.5 to supply energy so that the gas between the electrodes 4.5 can be brought into a plasma state. Note that the substrate electrode 4 is equipped with a heater (not shown), so that the surface temperature of the substrate 7 provided on the substrate electrode 4 can be set to a desired temperature. Further, a mesh electrode 8 is disposed between the substrate electrode 4 and the counter electrode 5, so that most of the plasma discharge occurs between the counter electrode 5 and the mesh electrode 8. .

Incidentally, the potential of the mesh electrode 8 was controlled by a DC type ri, 9 connected to the mesh electrode 8.

Next, specific examples of the vapor phase synthesis method of the present invention carried out using the above-mentioned apparatus will be described together with comparative examples.

Comparative example] N-type with resistivity 10Ω1cffl as a substrate < l OO
>A silicon wafer was used, and the substrate temperature was 350°C.

The mixed raw material gas contains 2cdZ of SiH2F2 and 3cdZ of CH4.
cIi/min, H2 50cri/min, B2H, 0.0
6 cIi/min, which was introduced into a stainless steel reaction vessel and the exhaust volume was adjusted to bring the pressure inside the reaction vessel to I Torr.
maintained. In this state, a high frequency of 13.56 MHz was applied at 100 W to parallel plate electrodes 4.5 having a diameter of 200 mm.

The fluorine content of the obtained silicon carbide thin film was 2 to 3 atm%.

Example 1 Vapor phase synthesis was carried out in the same manner as in Comparative Example 1, except that the mesh electrode 8 made of 100 mesh stainless steel wire mesh and having a potential of 150 V was used. Note that the spacing between electrodes 4 and 8 and the spacing between electrodes 8 and 5 were 30 m+s. In the reflected electron beam diffraction image of the obtained silicon carbide thin film, a ring-shaped diffraction line due to polycrystals was observed within a halo indicating an amorphous state. The fluorine content was 12 ati%.

Example 2 The substrate temperature was 300°C, and the mixed raw material gas was SIH.

2cti/min, 5I82F2 LOcri/min, CH
, was 20 ci/min, H2 was 100 cdZ, and 82H6 was 0.32 caj/min, but vapor phase synthesis was carried out in the same manner as in Example 1.

In the reflected electron beam diffraction image of the obtained silicon carbide thin film, a ring-shaped diffraction line due to polycrystals was observed within a halo indicating an amorphous state. The interplanar spacing of the crystal thus determined was that of silicon. The Raman spectrum had a peak at 508 cm-'m, which coincided with the peak of microcrystalline silicon. The fluorine content by Auger electron analysis was 30 atm%. The electrical conductivity was I x 10"2 S/cm, which was comparable to that of the μc-3i (film) hydrogenated by ECR plasma. The optical band gap was 1.8 eV, which was the same as the highest value of the fluorinated silicon carbide film. It was about.

Comparative Example 2 The substrate temperature was 300°C, and the mixed raw material gas was s+H2F.
Gas phase synthesis was carried out in the same manner as in Comparative Example 1 except for the use of octopus.

The resulting silicon thin film had a fluorine content of 2 att% and an electrical conductivity of 1.6 XIO'-88/c+n.

Example 3 Vapor phase synthesis was performed in the same manner as in Example 1 except that the mixed raw material gases were 5IH2F2 at LOci/min and H2 at 100 cm/min.

In the reflected electron beam diffraction image of the obtained silicon thin film, a ring-shaped diffraction line due to polycrystals was observed within a halo indicating an amorphous state.

The fluorine content is 7 atm% and the conductivity is 7 x 10-
'S/cm.

As is clear from the above examples, according to the vapor phase synthesis method of the present invention, it is possible to relatively easily produce a fluorinated amorphous silicon carbide thin film with a high fluorine content and high conductivity. It can be seen that an amorphous silicon thin film can be obtained.

(Effects of the Invention) As described above, according to the vapor phase synthesis method for a fluorinated amorphous silicon carbide thin film and a fluorinated amorphous silicon thin film of the present invention, a mixed raw material gas containing hydrogen fluorosilicide gas as a raw material gas can be obtained. At the same time, most of the capacitively coupled high-frequency plasma discharge is carried out by a counter electrode disposed opposite to the substrate electrode, and a counter electrode disposed between the substrate electrode and the counter electrode to which a negative bias is applied to the substrate. Since this is done between the mesh electrode and the mesh electrode,
A fluorinated amorphous silicon carbide thin film or a fluorinated amorphous silicon thin film with a high fluorine content can be obtained, and by adding hydrogen silicide to the mixed raw material gas, a fluorinated amorphous silicon carbide film with high conductivity can be obtained. This has effects such as obtaining a silicon carbide thin film.

[Brief explanation of the drawing]

The drawing shows one of the manufacturing equipment for carrying out the vapor phase synthesis method of the present invention.
It is an explanatory diagram of an example. 1...Reaction vessel 2...Evacuation system 3...Gas supply device 4...Substrate electrode 5...Counter electrode 6...High frequency power source 7...Substrate 8...Mesh electrode 9 ...DC power supply

Claims (1)

[Claims] 1. A mixed raw material gas consisting of hydrogen fluorosilicide, hydrocarbon, and hydrogen is decomposed by capacitively coupled high-frequency plasma discharge,
Most of the plasma discharge generated at that time is transferred to a counter electrode disposed opposite to the substrate electrode, and a mesh electrode disposed between the substrate electrode and the counter electrode and negatively biased with respect to the substrate electrode. A method for vapor phase synthesis of a fluorinated amorphous silicon carbide thin film, characterized in that the process is carried out between 2. The method for vapor phase synthesis of a fluorinated amorphous silicon carbide thin film according to claim 1, wherein the mixed raw material gas further contains hydrogen silicide. 3. A mixed raw material gas consisting of hydrogen fluorosilicide and hydrogen is decomposed by capacitively coupled high-frequency plasma discharge, and most of the plasma discharge generated at that time is transferred to a counter electrode disposed opposite to the substrate electrode, and the substrate electrode. vapor phase synthesis of a fluorinated amorphous silicon thin film, characterized in that the process is carried out between a mesh electrode placed between the electrode and the counter electrode and negatively biased with respect to the substrate electrode. Law.