JPH04293763A - Production of silicide film - Google Patents

Abstract

PURPOSE:To form a dense silicide film by plasma spraying. CONSTITUTION:A first layer 2 of silicon or a metal is formed on a substrate 1 by plasma spraying. A second layer 3 of the metal or silicon is formed on the first layer 2 by plasma spraying. The silicon and metal of the first and second layers 2, 3 are brought into a reaction under the heat of plasma spraying at the time of forming the second layer 3 to form a silicide film 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a silicide film, and more particularly to a method for manufacturing a silicide film suitable for use in a photovoltaic device in which a polycrystalline silicon thin film is formed on a substrate.

0002

2. Description of the Related Art Amorphous silicon thin films and polycrystalline silicon thin films are widely used as semiconductor thin films used in solar cells, sensors, and the like. Polycrystalline silicon has characteristics that its mobility is one to two orders of magnitude higher than that of amorphous silicon, it is thermally stable, and it has high reliability.

However, polycrystalline silicon requires a higher formation temperature than amorphous silicon. Therefore, for example, the fifth
Proceedings of the 0th Society of Applied Physics, p. 567 (Autumn 1989) article “
As shown in ``Growth of polycrystalline Si thin films for solar cells by liquid phase growth'', monocrystalline silicon and cast polycrystalline silicon are used as substrates, and polycrystalline silicon thin films are formed on the substrates by liquid phase growth. This is the current situation.

As mentioned above, since the formation temperature of polycrystalline silicon is high, the substrate used is also a single crystal silicon or the like which has excellent heat resistance, but the disadvantage is that the substrate is expensive and the cost increases. . Currently, 8-inch wafer single-crystal silicon substrates are being put into practical use in semiconductor integrated circuits, but these substrates are extremely expensive, and when used in solar cells, etc., they become extremely expensive, making it difficult to increase the area. It was becoming an obstacle.

[0005] Therefore, it is possible to use a ceramic substrate or quartz glass as a substrate, but these substrates and a silicon layer formed by liquid phase growth have extremely poor wettability, so it is difficult to form a polycrystalline silicon layer directly on these substrates. I couldn't do that. Here, wettability refers to the rate at which a material adheres to the surface of a substrate, and we define here that wettability is poor when N is 90% or less as shown by the following formula. N=material adhesion area/substrate area×100

[0006] If this wettability is poor, a polycrystalline silicon thin film cannot be formed by liquid phase growth.

Therefore, there is a method of forming polycrystalline silicon on a substrate regardless of the material of the substrate by providing a silicide layer with good wettability on the substrate.

Conventionally, the above-mentioned silicide layer is made of TiSi
2, VSi2, CrSi2, FeSi2, CoSi2,
Or, it is formed on a substrate by plasma spraying using a powder of a silicide material made of NiSi2 and having a particle size of 10 to 44 μm.

[0009]

However, a silicide film formed by plasma spraying using powder of a silicide material has a high porosity. For this reason, it is not possible to obtain a dense film, and the electrical resistance becomes large. When this film is used as a conductive film for a solar cell, there are problems such as a decrease in power generation efficiency.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a method for manufacturing a silicide film that makes it possible to form a dense silicide film.

[0011]

[Means for Solving the Problems] The present invention provides the following features:
The step of forming a first layer made of silicon or metal by plasma spraying, and the step of laminating a second layer made of metal or silicon on this first layer by plasma spraying, It is characterized in that silicon and metal in the first and second layers are reacted with each other by plasma spray heat during formation to form a silicide film.

0012

[Operation] According to the present invention, metal enters the voids of silicon due to plasma spray heat during formation of the second layer and silicidation is performed, so a silicide film can be formed without generating pores, and a dense silicide film can be formed. A membrane is obtained.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic diagram of a reduced pressure plasma spraying apparatus used in the production of this embodiment.

First, the reduced pressure plasma spraying apparatus will be briefly explained. In FIG. 2, 11 is a vacuum container capable of maintaining reduced pressure, 12 is a DC power source for plasma spraying, and this DC power source is connected to the cathode 14a and 1 which constitute the plasma spray gun 13.
4b. 15 is a raw material powder for the semiconductor thin film to be formed, such as silicon (Si) powder, titanium (Ti) powder, tungsten (W) with a particle size of several μm to several tens of μm.
) powder, molybdenum (Mo) powder, tantalum (Ta) powder, etc., are supplied at the powder supply port, where the raw material powder is melted by the heat of the DC plasma generated between the cathode 14a and the anode 14b. Reference numeral 16 denotes a thermal spraying gas inlet into which a thermal spraying gas such as helium, argon, or hydrogen is introduced to inject the melted raw material powder from the plasma spraying gun 13 as a fine particle plasma jet 17, and the plasma jet 17 is a plasma spraying gas. A polycrystalline or microcrystalline silicon thin film based on raw material powder and a metal thin film of titanium, tungsten, molybdenum, tantalum, etc. are formed on the substrate 1 which is placed opposite to the spray gun 13 . 20, 2
Reference numeral 1 denotes an atmospheric gas inlet and an exhaust port for introducing or exhausting atmospheric gas into the vacuum container 11.

Now, the present invention involves the steps of forming a first layer made of silicon or metal by plasma spraying on the substrate 1 using the above-mentioned low pressure plasma spraying apparatus, and forming a first layer made of silicon or metal by plasma spraying on the first layer. Alternatively, a second layer made of silicon is laminated. The plasma spray heat during the formation of the second layer causes the silicon and metal of the first and second layers to react to form a silicide film.

First, Table 1 shows the metals used in the present invention.

[0018]

[Table 1]

Table 2 shows the melting point and formation temperature of silicide. Note that the film thickness of silicon and metal is 2:1.

[0020]

[Table 2]

As can be seen from Table 2, by employing plasma spraying as in the present invention, the reaction initiation temperature between silicon and metal is much lower than the melting point, and is about 1/3 of the melting point. Therefore, when heat approximately equal to the reaction initiation temperature is applied, silicon and metal react and silicide formation progresses. Since the layer in which silicide is formed has a much higher melting point, there is no risk of melting and the layer is formed as a silicide layer as it is.

FIG. 1 is a sectional view showing an embodiment of the present invention. Next, the embodiment of the present invention shown in FIG. 1 will be explained.

First, quartz glass or alumina (Al2O
3), aluminum nitride (AlN), yttria (Y2
O3), magnesia (MgO), zirconia (ZrO2
A heat-resistant substrate 1 made of ceramic such as ) is placed in a plasma spraying apparatus. After evacuating the inside of the vacuum chamber 11 of the plasma spraying device to about 100 to 400 Torr,
Argon gas is supplied from the thermal spray gas inlet 16 at 5 to 30 slm.
Silicon powder with a particle size of 10 μm or less is introduced from the powder supply port 15 at a rate of 1 to 20 g/min.

Then, as shown in FIG. 1(A), a power of 10 to 50 KW is applied from the DC power supply 12 to generate a plasma jet 17, thereby depositing a first layer of polycrystalline silicon thin film on the substrate 1. Deposit 2.

Next, from the powder supply port 15, a particle size of 10
Powder of titanium, tungsten, molybdenum, tantalum, etc. with a particle diameter of 1 to 20 g/min is introduced.

Then, as shown in FIG. 1(B), a power of 10 to 50 KW is applied from the DC power source 12 to generate a plasma jet 17, thereby forming a second layer made of a metal thin film on the first layer 2. Deposit 3. Simultaneously with the formation of this metal thin film, silicidation progresses, as shown in Figure 1 (c).
A silicide film 4 is formed. Note that the silicon film thickness and the metal film thickness are controlled to have a ratio of 2:1.

[0027] The total thickness of the first layer and the second layer is 5
If the thickness is about μm, the silicide film 4 can be obtained by performing the above process once. Further, if a silicide film 4 with a thickness of 5 μm or more is required, the above process may be repeated.

Furthermore, in the above embodiment, silicon is formed in the first layer 2 and a metal thin film is formed in the second layer 3.
Even if metal is formed on the second layer 3 and silicon is formed on the second layer 3, silicidation proceeds in the same way, and a silicide film 4 can be formed.

Table 3 shows manufacturing conditions for specific examples of the present invention.

[0030]

[Table 3]

The porosity of the silicide film 4 formed according to the present invention as described above was investigated and found to be zero, whereas the porosity of the silicide film 4 formed by the conventional method, that is, using silicide powder as powder, was investigated. A few percent
Met. Thus, according to the present invention, a dense silicide film can be formed.

Table 4 shows the resistivity of the silicide film 4 formed according to the present invention.

[0033]

[Table 4]

Although each of the above embodiments describes the formation of silicide in which one type of metal is involved, silicide in which two or more types of metal are involved can be similarly formed. For example group VIII metal combinations, e.g. Ni/Pt
, combinations of refractory metals and group VIII metals, e.g. Ni/C
A silicide film can be formed in the same manner using a combination of R, a combination of high melting point metals, Mo/W, and the like.

Next, an example of manufacturing a photovoltaic device using a silicide film formed according to the present invention will be described.

FIG. 3 is a schematic diagram showing the structure of a liquid phase growth apparatus used for manufacturing a photovoltaic device. The structure of the liquid phase growth apparatus will be briefly explained with reference to FIG.

In FIG. 3, 30 is a tray made of high-purity carbon, and on this tray 30 made of high-purity carbon,
A substrate 1 to be subjected to liquid phase growth is held.

31 is a boat also made of high purity carbon, and a crucible 32 inside this boat 31 is made of silicon tin (Si).
Sn) is dissolved. Then, the substrate 1 held on the tray 30 is placed in contact with the surface of the SiSn solution 33 being dissolved in the crucible 32 of the boat 31 made of high-purity carbon.

Next, in a hydrogen atmospheric pressure atmosphere, the crucible temperature is set to, for example, 1000°C, and after setting the substrate 1, the temperature is lowered at a rate of 1 to 2°C per minute until the crucible temperature reaches 95°C.
By lowering the temperature to 0°C, a thickness of approximately 50 μm is formed on the substrate 1.
A polycrystalline silicon thin film is formed.

Next, an example of manufacturing a photovoltaic device shown in FIG. 4 using a silicide film formed according to the present invention will be described.

In a hydrogen atmospheric pressure atmosphere, the substrate 1 on which the silicide layer 4 has been deposited is supported on a tray 30 made of high-purity carbon, and the surface of the SiSn solution 33 dissolved in the crucible 32 of the boat 31 made of high-purity carbon is The tray 30 is stopped so that the surface of the silicide layer 4 of the substrate 1 is in contact with the surface of the silicide layer 4 of the substrate 1. At this time, the SiSn solution 33 contains mostly tin (Sn) based on the phase diagram.
). Further, the silicon (Si) source is p-type single crystal silicon, and its specific resistance is 1 Ωcm or less.

[0042] When the temperature of the substrate 1 is lowered from 1000°C at a rate of 1 to 2°C per minute in a hydrogen atmospheric pressure atmosphere and the substrate 1 is removed from the SiSn solution 33 at 950°C, the SiSn solution 33 is deposited on the substrate 1. A p+ type polycrystalline silicon layer 5 having a thickness of 50 μm is formed on the silicide layer 4 by liquid phase growth.

Thereafter, the substrate 1 on which the polycrystalline silicon layer 5 has been formed is similarly supported on a tray 30 made of high-purity carbon, and the surface of the SiSn solution 33 dissolved in the crucible 32 of the boat 31 made of high-purity carbon is exposed. The tray 30 is stopped so that the surface of the substrate 1 is in contact with the surface. At this time, SiSn solution 33
is mostly Sn based on the phase diagram. Further, the silicon (Si) source is p-type single crystal silicon, and its specific resistance is 5 Ωcm or less.

In the same manner as described above, the temperature of the substrate 1 was lowered from 1000° C. at a rate of 1 to 2° C. per minute in a hydrogen atmosphere, and
When the substrate 1 is separated from the SiSn solution 33 at 00°C, the substrate 1
A film with a thickness of 100 mm is deposited on the p+ type polycrystalline silicon 5 deposited on top.
A p-type polycrystalline silicon layer 6 of .mu.m is formed by liquid phase growth.

Thereafter, an n+ type polycrystalline silicon layer 7 is formed in the same manner by liquid phase growth. At this time SiS
The silicon (Si) source of the n-solution 33 is n-type single crystal silicon, and its specific resistance is 1 Ωcm or less.

In the same manner as described above, the temperature of the substrate 1 was lowered from 1000° C. at a rate of 1 to 2° C. per minute in a hydrogen atmospheric pressure atmosphere.
When the substrate 1 is separated from the SiSn solution 33 at 95°C, the substrate 1
A film thickness of 5μ is deposited on the p-type polycrystalline silicon layer 4 deposited on top.
n+ type polycrystalline silicon layer 7 of m is formed by liquid phase growth.

Thereafter, electrode layers in ohmic contact with the n + -type polycrystalline silicon layer 7 and the p + -type polycrystalline silicon layer 5 are provided by vapor deposition of aluminum, respectively, and patterned to form a comb-shaped front electrode 8 and a back surface. A photovoltaic device is formed by forming an electrode extraction electrode 9.

[0048]

As explained above, according to the present invention, metal enters the voids of silicon due to plasma spray heat during formation of the second layer and silicidation is performed.
A silicide film can be formed without generating pores, and a dense silicide film can be obtained. Therefore, electrical resistance can be reduced, and when this film is used as a conductive film in a solar cell, power generation efficiency is improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining an embodiment of the present invention.

FIG. 2 is a schematic diagram of a plasma spraying apparatus used in the present invention.

FIG. 3 is a schematic diagram of a liquid phase growth apparatus.

FIG. 4 is a cross-sectional view showing a photovoltaic device using a silicide film formed according to the present invention.

[Explanation of symbols]

1 Board 2 First layer 3 Second layer 4 Silicide layer

Claims (1)

[Claims] 1. A step of forming a first layer made of silicon or metal on a substrate by plasma spraying;
forming a second layer made of metal or silicon on the layer by plasma spraying, the silicon and metal of the first layer and the second layer being stacked by plasma spraying heat during formation of the second layer. A method for producing a silicide film, characterized by forming a silicide film through reaction.