JPH04299521A - Method and device for manufacturing non-single crystal silicon - Google Patents

Abstract

PURPOSE:To improve the substantial film-forming rate at the time of deposition of a non-single crystal silicon film while a process for depositing the silicon film and a process for applying hydrogen plasma to the deposited silicon film are alternately repeated. CONSTITUTION:Visible light is applied to a film deposited on a substrate 11. 10 is a chamber, 14 is a high-frequency power supply, 16 is a raw gas introducing port, 17 is a hydrogen gas introducing port and 18 is a microwave generation source. The visible light is applied from a visible light source 19 through the film through a window 22 in a hydrogen plasma irradiation process. As dissociation of an Si-Si weak bond is promoted in a structural relaxation process, a hydrogen plasma irradiation time is shortened and the improvement of the substantial film-forming rate of the non-single crystal silicon film is made.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for manufacturing thin film semiconductors suitable for solar cells, active matrix displays, and photoelectric conversion elements. In particular, the present invention relates to a method and apparatus for manufacturing non-single crystal silicon, and particularly to improving processing efficiency of thin film semiconductors.

0002

2. Description of the Related Art In recent years, semiconductor devices using non-single crystal silicon have been actively developed. Non-monocrystalline silicon refers to polysilicon, microcrystalline silicon, amorphous silicon, and a mixture mainly composed of at least one of these. In particular, the development of solar cells that can be produced over a large area and at low cost, and the development of facsimile reading sensors that can be made lightweight and compact, are actively being developed. The deposition method for amorphous silicon (hereinafter abbreviated as "a-Si:H") used in these semiconductor devices is R, which uses SiH4 or Si2H6 as a film-forming gas.
The F plasma CVD method, the microwave plasma CVD method, or the reactive sputtering method in which a Si target is sputtered in Ar plasma in the presence of hydrogen gas have been used. Experimentally, in addition to this, photo-CVD method, ECR
There have been reports of CVD methods, vacuum evaporation methods of Si in the presence of hydrogen atoms, etc., and there are also success stories of thermal CVD methods using Si2 H6 and the like. a-Si obtained by these methods
:H film is a film containing almost 10% or more hydrogen. The most popular method for depositing such a-Si:H films is the plasma CVD method, in which Si
Using H4, Si2 H6 gas, diluting with hydrogen gas as necessary, 13.56MHz or 2.45G
Plasma is generated using a high frequency of Hz, the film-forming gas is decomposed by the plasma, reactive active species are created, and an a-Si:H film is deposited on the substrate. Furthermore, in order to increase the deposition efficiency of a-Si:H, ultraviolet light is irradiated during deposition to further decompose unreacted gas in the plasma (Japanese Patent Application Laid-open No. 172237/1982), and interatomic bonds are (Japanese Unexamined Patent Publication No. 2-207525), or near-infrared rays are applied to a film being deposited to heat it (Japanese Unexamined Patent Publication No. 1983-207525).
172237)).

[0003] Such non-single crystal silicon, especially a-Si
:As a new method for depositing an H film, a method has been proposed in which the process of depositing non-single crystal silicon on a substrate and the process of irradiating hydrogen plasma onto the non-single crystal silicon deposited on the substrate are repeated alternately. (Autumn 1990 No. 51)
Japan Society of Applied Physics Academic Conference No. 28 p-MD-1, etc.). The procedure of this method, including the study by the present inventors, will be explained using FIG. 7. During time tD, capacitively coupled high-frequency glow discharge decomposes the raw material gas into a-Si:H
After the layer is deposited, the deposited film is formed by repeating a set of steps in which hydrogen gas is decomposed by microwave plasma provided separately from the deposition space and hydrogen plasma is irradiated for a time tA. During tA, the surface of the deposited film is exposed to hydrogen plasma irradiation. The effects of hydrogen plasma irradiation will be explained. During this time, it is thought that atomic hydrogen in the hydrogen plasma diffuses to some extent into the deposited film or on the surface of the deposited film, extracts excess hydrogen, and at the same time rearranges the Si network (structural relaxation). Further, the thickness of the a-Si:H film deposited during tD is preferably 10 Å or more. If the newly deposited layer is only one atomic layer, the amorphous structure cannot be maintained stably, and crystallization will proceed due to hydrogen plasma irradiation. The cause of this is thought to be excessive extraction of hydrogen by atomic hydrogen. If the deposited layer is thin and too much hydrogen is extracted, crystallization will easily occur. Therefore, in order to prevent crystallization due to hydrogen plasma irradiation and promote structural relaxation with good controllability to create a-Si:H, the thickness of the a-Si:H layer deposited during tD must be 10 Å or more. is necessary.

The hydrogen concentration in the film can be controlled by controlling the thickness and quality of the film deposited during tD, the hydrogen plasma irradiation time tA, the substrate temperature, etc.
When the temperature is 00° C. or higher, the hydrogen concentration in the film can be 3 to 4%. Furthermore, the electrical properties of this film are almost free from the photodeterioration seen in conventional a-Si:H, and the photoelectric properties are improved by about an order of magnitude.

[0005]

[Problem to be solved by the invention] Among the above conventional techniques,
In a method for producing non-single crystal silicon in which a step of depositing non-single-crystal silicon on a substrate and a step of irradiating the film deposited on the substrate with hydrogen plasma are alternately repeated, hydrogen plasma irradiation treatment is performed. Process time tA
Therefore, there was a disadvantage that the actual film formation rate was significantly reduced to a fraction of a fraction. An object of the present invention is to improve such disadvantages of the prior art.

[0006]

[Means for Solving the Problems] According to the present invention, the above object is achieved by alternately performing a step of depositing non-single crystal silicon on a substrate and a step of irradiating the film deposited on the substrate with hydrogen plasma. This is achieved by a non-single-crystal silicon manufacturing method in which a film deposited on a substrate is irradiated with visible light in a method of manufacturing non-single-crystal silicon that is repeatedly deposited.

Further, according to the present invention, the above object includes at least a means for depositing non-single crystal silicon on a substrate;
An apparatus for producing non-single crystal silicon, comprising: hydrogen plasma irradiation means for irradiating a film deposited on the substrate with hydrogen plasma; and means for intermittently irradiating visible light.
This is achieved by

[0008]

[Operation] As is well known, non-single crystal silicon deposited on a substrate absorbs visible light throughout the film. Non-single-crystal silicon, especially a-Si:H, absorbs light over a wide visible light range, resulting in deterioration of photoelectric properties. a-S
As for this photodegradation in i:H, recent research results have proposed the idea that Si-Si weak bonds are cut due to photodegradation and dangling bonds are formed. On the other hand, in the step of hydrogen plasma irradiation treatment, as explained in relation to the prior art, the generated atomic hydrogen is assumed to relax the structure while extracting hydrogen from the deposited non-single crystal silicon. Particularly, in this process, the visible light irradiation promotes the dissociation of Si-Si weak bonds, and the time t of the hydrogen plasma irradiation step
The objectives of the present invention are achieved by reducing A and increasing the effective deposition rate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an example of the apparatus of the present invention used to carry out the method of the present invention. In the figure, 10 is a reaction chamber, 11 is a substrate on which non-single crystal silicon is deposited, and 12 is a reaction chamber.
1 is an anode electrode having a heater (not shown); 13 is a cathode electrode; 14 is a 13.56 MHz high-frequency power source;
5 is an exhaust pump, 16 is a SiH4 gas (sometimes containing diluted hydrogen) introduction pipe, 17 is an H2 gas (including Ar gas as a carrier gas) introduction pipe, and 18 is a 2.45 GHz for generating atomic hydrogen. 19 is an AM1 light source for solar cell photodegradation evaluation with an infrared cut filter, 21 is an intermittent controller for light source 19, V1
, V2 are valves that control SiH4 gas and H2 gas, respectively, and are connected to a computer (not shown) to precisely control opening and closing times. This computer is also connected to the light source controller 21. 22 is a window of the chamber 10.

(Example 1) Using the apparatus shown in FIG. 1, non-single crystal silicon was deposited according to the method of the present invention in the following steps:
■First, the silicon wafer substrate 11 was set, and the inside of the chamber 10 was evacuated to a predetermined pressure using the exhaust pump 15, and at the same time, the temperature of the substrate 11 was raised to 340°C using a heater (not shown); ■Next, SiH4 gas and H2 The timing of gas introduction was controlled as shown in FIG. That is, the time tD for depositing a-Si:H and the time t for irradiating H2 plasma.
The steps with A and (tD + tA) were repeated. At time tA, visible light was irradiated from the visible light source 19 at the same time. At the time tD of depositing a-Si:H, both valves V1 and V2 are in the open state,
SiH4 gas, Ar gas and H2 gas were introduced into the reaction chamber 10. SiH4 gas is 10SCCM, H2 gas is 10SCCM
CM, and the pressure inside the reaction chamber was set to 0.1T using Ar gas.
Adjusted to orr. At this time, the deposition rate is about 3 Å/se
It was c. Further, the film thickness deposited at time tD was approximately 20 Å. During the H2 plasma irradiation time tA, H2 plasma was irradiated with the valve V1 closed and the valve V2 opened.

Depending on the H2 plasma irradiation time tA, the film quality of a-Si:H deposited at time tD changes,
The amount of H contained changed. Figure 3 shows the relationship between changes in the amount of hydrogen in the film and changes in visible light intensity when the power of the high-frequency power source 14 is maintained at a constant value of 10 W and the hydrogen plasma irradiation time tA is maintained at a constant value of 20 seconds. . The amount of hydrogen in the film was measured by infrared spectroscopy (hereinafter abbreviated as "FTIR"). Note that in FTIR, SiH in the film, SiH
Calculated from 630 cm-1, which shows the total amount of hydrogen such as 2. From FIG. 3, it can be seen that when visible light is irradiated, the amount of hydrogen in the film decreases depending on the power of visible light. FIG. 4 shows the relationship between the change in the amount of hydrogen in the film and the change in the hydrogen plasma irradiation time tA when the power of the high frequency power source 14 is kept constant and the power of visible light irradiated is kept constant. A is the case where visible light was not irradiated (conventional method), and B is the case where visible light was irradiated (method of the present invention). It can be seen that in film B, hydrogen in the film clearly decreases faster than in film A, and the hydrogen content is also slightly lower.

From the above, it has been found that the hydrogen plasma irradiation time tA can be shortened by performing hydrogen plasma irradiation while performing visible light irradiation that promotes Si--Si weak bond cutting. Additionally, as a result of the FTIR study, 210
The absorption of SiH2 at 0 cm-1 was below the measurement limit (0.1%) regardless of the presence or absence of visible light irradiation.

(Example 2) Next, in order to understand the photoelectric properties of non-single crystal silicon obtained by the method of the present invention, a coplanar type sensor was fabricated. That is, the above Example 1
Under the same film forming conditions as above, the film thickness deposited at time tD was set to 25
The hydrogen plasma irradiation time tA was set as 40 seconds for A without visible light irradiation and 20 seconds for B with visible light irradiation. This step was repeated 5000 times, and the substrate (Corning #7059) Non-single-crystal silicon with a thickness of approximately 1 μm was deposited on top, and aluminum electrodes were further applied to predetermined areas on the surface of the non-single-crystal silicon to form sample A without visible light irradiation and sample B with visible light irradiation. and was created. A structural diagram of the sensor is shown in Figure 5. 50
is a substrate, 51 is non-single crystal silicon, and 52 is an electrode.

[0015] Light was irradiated from the electrode 52 side to measure photoelectric characteristics and photodeterioration over time. Note that a 630 nm He--Ne laser with an output of 100 μW/cm 2 or less was used as the light for measuring photoelectric characteristics, and AM1 light was used as the light for measuring photodeterioration. The photoelectric properties of both A and B were almost the same and were very excellent. The photodegradation characteristics are shown in FIG. Here, the initial photocurrent before photoirradiation for deterioration is shown as 100. As shown in FIG. 6, there was almost no deterioration in both A and B for about 100 hours.

From the above, it is possible to deposit non-single crystal silicon by alternately repeating the step of depositing non-single crystal silicon and the step of irradiating hydrogen plasma while irradiating the deposited non-single crystal silicon with visible light. Compared to the case without visible light irradiation, the hydrogen plasma irradiation time can be halved while maintaining the photoelectric properties and photodegradation characteristics almost the same, and the actual film formation rate is approximately 1.5%. It has doubled.

According to the idea of the present invention, the method and apparatus for producing non-single crystal silicon of the present invention can be applied not only to the intrinsic semiconductor mentioned in the embodiment, but also to the method for producing an impurity layer and an alloy of Si, Ge, C, etc. But it goes without saying that it has the same effect. however,
In this case, the wavelength of the visible light to be absorbed changes and is selected from appropriate wavelengths. Furthermore, in the examples of the present invention, visible light was irradiated only during the hydrogen plasma irradiation time, but it may also be irradiated during deposition. Furthermore, the film-forming raw material gas is not limited to that used in the examples, and may be, for example, disilane gas or the like, or may contain F or the like. Furthermore, the source gas and hydrogen gas may be decomposed using any of heat, light, and plasma.

[0018]

According to the present invention, the process of depositing non-single crystal silicon and the process of irradiating the deposited non-single crystal silicon with hydrogen plasma while irradiating it with visible light are alternately repeated. By performing the deposition, SiH
, the dissociation of Si--Si weak bonds is promoted in the process considered to extract hydrogen from SiH2 and relax the structure, shortening the hydrogen plasma irradiation time and substantially improving the film formation rate. In addition, high quality non-single crystal silicon with less photodegradation is produced.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of the device of the present invention.

FIG. 2 is a timing diagram of deposition, hydrogen plasma irradiation, and visible light irradiation.

FIG. 3 is a diagram showing the dependence of the amount of hydrogen in the film on the intensity of irradiated visible light.

FIG. 4 is a diagram of the dependence of the amount of hydrogen in the film on time tA.

FIG. 5 is a structural diagram of a device for measuring photoelectric properties of non-single crystal silicon produced according to the present invention.

FIG. 6 is a photodegradation characteristic diagram of non-single crystal silicon.

FIG. 7 is a diagram for explaining a conventional manufacturing method.

[Explanation of symbols]

10 Chamber 11　　　　Substrate 12 Anode electrode 13 Cathode electrode 14 High frequency power supply 15 Exhaust pump 16 Raw material gas inlet 17 Hydrogen gas inlet 18 Microwave source 19 Visible light source 21 Visible light source controller 22 Window 50 Board 51 Non-single crystal silicon film 52 Electrode

Claims (5)

[Claims] 1. A method for manufacturing non-single-crystal silicon in which a step of depositing non-single-crystal silicon on a substrate and a step of irradiating the film deposited on the substrate with hydrogen plasma are alternately repeated. A method for producing non-single crystal silicon, characterized by irradiating a film deposited on it with visible light. 2. The method of manufacturing non-single crystal silicon according to claim 1, wherein in the step of irradiating the film deposited on the substrate with hydrogen plasma, the film deposited on the substrate is irradiated with visible light. Manufacturing method. 3. The method comprises at least means for depositing non-single crystal silicon on a substrate, hydrogen plasma irradiation means for irradiating the film deposited on the substrate with hydrogen plasma, and means for intermittently irradiating visible light. A manufacturing device for non-single crystal silicon, which is characterized by: 4. The means for depositing non-single-crystal silicon on the substrate includes decomposition of a raw material gas for non-single-crystal silicon by heating,
4. The non-single-crystal silicon manufacturing apparatus according to claim 3, characterized in that the manufacturing apparatus uses plasma and/or light. 5. The hydrogen plasma irradiation means for irradiating the film deposited on the substrate with hydrogen plasma uses heat, plasma and/or light,
The non-single crystal silicon manufacturing apparatus according to claim 3.