JPH04299523A - Method and device for manufacturing non-single crystal silicon - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 method is achieved by a non-single crystal silicon manufacturing method that involves repeatedly depositing non-single crystal silicon, which is characterized by irradiating a film deposited on a substrate with near-infrared light along with visible light or infrared light. Ru.

Further, according to the present invention, the above object includes at least a means for depositing non-single crystal silicon on a substrate;
Production of non-single-crystal silicon, characterized by comprising hydrogen plasma irradiation means for irradiating a film deposited on the substrate with hydrogen plasma, and means for intermittently irradiating near-infrared light together with visible light or infrared light. This is accomplished by a device.

[0008]

[Operation] When non-single crystal silicon deposited on a substrate is irradiated with hydrogen plasma, as mentioned above, the generated atomic hydrogen diffuses to some extent in the deposited film or on the film surface, extracts excess hydrogen, and It is thought that network reorganization is occurring. Furthermore, at the same time, a portion of the extracted excess hydrogen is thought to flow out of the deposited film as a gas depending on the substrate temperature. Therefore, in this process, the non-single-crystal silicon deposited on the substrate is irradiated with highly absorbing visible light to promote the breaking of weak Si-Si bonds, or to break Si-H bonds, SiH2 bonds, etc. Hydrogen plasma irradiation is performed by irradiating infrared light that excites the interatomic bonds of the hydrogen to promote the extraction of excess atomic hydrogen, and by irradiating near infrared rays to provide heat and promote the entire reaction. The object of the present invention is achieved by shortening the time tA of the process and increasing the effective film formation 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 a near-infrared light source, 19' is a visible or infrared light source, 20 is a spectrometer for the light source, 21 is an intermittent controller for the light sources 19 and 19', and V1 and V2 are SiH4 gas, respectively. The valve for controlling the H2 gas is connected to a computer (not shown) to precisely control the opening and closing time. 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 280°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 visible light source 19' and near-infrared light was irradiated from near-infrared light source 19 only during time tB, which took into consideration the temperature rise and fall characteristics of substrate 11. As shown in FIG. 2, the temperature of the substrate 11 is 28
It varied in the range of 0℃ to 340℃ (from 280℃ to 340℃
The time to raise the temperature to 340°C is 5 seconds, and the time to lower the temperature from 340°C to 280°C is 10 seconds). Time tD for depositing a-Si:H
In this case, both valves V1 and V2 were in an open state, and SiH4 gas, Ar gas, and H2 gas were introduced into the reaction chamber 10. SiH4 gas is 4SCC
The M and H2 gases were set at 10 SCCM, and the pressure inside the reaction chamber was adjusted to 0.1 Torr with Ar gas. At this time, the deposition rate was about 1 Å/sec. Also time tD
The thickness of the deposited film 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 a comparison of the amount of hydrogen in the film under the following four conditions: Condition A: Substrate temperature 280°C, tA = tB = 0 seconds (no hydrogen plasma irradiation) Condition B: Substrate temperature 340°C, tA = tB = 0 seconds (no hydrogen plasma irradiation) C conditions: substrate temperature 280°C, tA = 60 seconds, tB =
0 seconds, tD = 7 seconds (conventional method) D conditions: initial substrate temperature 280°C, tA = 60 seconds (near infrared light and visible light irradiation), tB = 50 seconds, tD = 7 seconds The amount of hydrogen in the film is It was measured by infrared spectroscopic absorption method (hereinafter abbreviated as "FTIR"). Note that in FTIR, SiH in the film
, SiH2, etc. It was calculated from 630 cm-1, which shows the total amount of hydrogen. From FIG. 3, it can be seen that the amount of hydrogen in the film decreases in the order of A, B, C, and D. 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 under conditions C and D. However, tD is tA
The time was calculated by subtracting 10 seconds from the temperature drop time. C is a case where near-infrared light and visible light are not irradiated (conventional method), and D is a case where near-infrared light and visible light are irradiated (method of the present invention). It can be seen that in D, hydrogen in the film clearly decreases faster than in C, and the hydrogen content is also slightly lower.

From the above, near-infrared light (for example, wavelength 2.5 μm),
It was also found that by irradiating visible light to promote the breaking of silicon-silicon weak bonds, the hydrogen content in the film was reduced and the hydrogen plasma irradiation time tA was shortened. Additionally, as a result of the FTIR study, 21
The absorption of SiH2 at 00 cm-1 was below the measurement limit (0.1%) regardless of the presence or absence of near-infrared light and visible light irradiation.

(Example 2) Example 1 except that infrared light irradiation was performed instead of visible light irradiation in Example 1.
Non-single crystal silicon was produced under the same conditions as D. That is, the infrared light from the light source 19' is separated by the spectroscope 20, and the infrared light is separated from the Si-H bonds and S of the deposited non-single crystal silicon.
2100cm- which excites interatomic bonds such as iH2 bonds.
The infrared light of No. 1 was irradiated at the timing shown in FIG. The hydrogen content in the obtained film was the same as that under Condition D of Example 1. Furthermore, the dependence of the hydrogen content in the film on the hydrogen plasma irradiation time tA was slightly better than in the case of the D condition of Example 1.

From the above, near-infrared rays are used to provide heat to the deposited film during hydrogen plasma irradiation to promote the diffusion of atomic hydrogen, the extraction of excess hydrogen, the outflow of the extracted excess hydrogen gas, and the reorganization of the network. Irradiate light and S
By irradiating with 2100 cm-1 infrared light that excites interatomic bonds such as i-H bonds and SiH2 bonds, the hydrogen content in the film can be reduced and the hydrogen plasma irradiation time tA can be shortened. Understood. Additionally, as a result of FTIR studies, the absorption of SiH2 at 2100 cm-1 is at the measurement limit (0.1%) regardless of the presence or absence of near-infrared light and infrared light irradiation.
It was below.

(Example 3) Next, in order to ascertain 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
Å, and the hydrogen plasma irradiation time tA is 40 seconds for both C without near-infrared light and visible light irradiation and D with near-infrared light and visible light irradiation, and in D with near-infrared light and visible light irradiation. If the time tB is 25 seconds, this step is repeated for 40 seconds.
00 times, non-single crystal silicon with a thickness of approximately 1 μm was deposited on a substrate (#7059 manufactured by Corning), and aluminum electrodes were added to predetermined areas on the surface of the non-single crystal silicon to emit near-infrared light. Sample C was prepared without irradiation with light or visible light, and sample D was irradiated with near-infrared light and visible light. 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.

Light was irradiated from the electrode 52 side to measure photoelectric characteristics and photodeterioration over time. As the light for measuring photoelectric characteristics, a 630 nm He-Ne laser with an output of 100 μW/cm 2 or less was used, and as the light for measuring photodeterioration, AM1 light for evaluating photodeterioration of solar cells was used. Regarding the photoelectric properties, D was slightly superior to C and was 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, D produced by the method of the present invention showed less photodeterioration than C produced by the conventional method.

From the above, it is possible to deposit non-single-crystal silicon by alternately repeating the steps of depositing non-single-crystal silicon and irradiating hydrogen plasma while irradiating the deposited non-single-crystal silicon with near-infrared light and visible light. By depositing , the hydrogen content is lower than that without near-infrared light and visible light irradiation, and the photoelectric properties and photodegradation properties are better, and the hydrogen plasma irradiation time is almost halved. The actual film formation rate was approximately 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 visible light or infrared light to be absorbed changes and is selected from an appropriate wavelength (for example, 2.5 μm or more in the case of infrared light). 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. Also,
The source gas and hydrogen gas may be decomposed using heat, light, or plasma.

[0020]

Effects of the Invention According to the present invention, the step of depositing non-single crystal silicon and the step of depositing Si-S on the deposited non-single crystal silicon
Visible light and S that promote the breaking of i-bond weak bonds
By depositing non-single crystal silicon by alternately repeating the process of irradiating hydrogen plasma while irradiating near-infrared light with infrared light that excites interatomic bonds such as i-H bonds and SiH2 bonds. , SiH, and SiH2, and the reaction in the process considered to be structurally relaxed is promoted, the hydrogen plasma irradiation time is shortened, and the film formation rate is substantially improved. 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, near-infrared light irradiation, visible light or infrared light irradiation, and substrate temperature.

FIG. 3 is a comparison diagram of the amount of hydrogen in the film.

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 Near-infrared light source 19’ Visible light source or infrared light source 20 Spectrometer 21 Light source controller 22 Window 50　　　　Substrate 51 Non-single crystal silicon film 52 Electrode

Claims (7)

[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, which is characterized by irradiating a film deposited on it with near-infrared light in addition to visible light or infrared light. 2. The method 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 near-infrared light together with visible light or infrared light. 1. The method for producing non-single crystal silicon according to 1. 3. 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 near-infrared light as well as visible light or infrared light. 1. An apparatus for manufacturing non-single crystal silicon, comprising means for intermittently irradiating with. 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. 6. The non-single crystal silicon manufacturing apparatus according to claim 3, wherein the near-infrared light has a wavelength of less than 2.5 μm. 7. The non-single crystal silicon manufacturing apparatus according to claim 3, wherein the wavelength of the infrared light is 2.5 μm or more.