JP2706182B2 - Manufacturing method of silicide film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 having a polycrystalline silicon thin film 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 of higher mobility than amorphous silicon by about one to two digits, thermal stability, and high reliability.

[0003] However, polycrystalline silicon has a higher forming temperature than amorphous silicon. Therefore, for example, the fifth
Proceedings of the 0th Annual Meeting of the Society for Materials Science p. As shown in the article “Growth of polycrystalline Si thin film for solar cell by liquid phase method” in 567 (Autumn 1989), monocrystalline silicon and cast polycrystalline silicon are used as substrates, and polycrystalline silicon is formed on the substrate. At present, thin films are formed by a liquid phase growth method.

As described above, since polycrystalline silicon has a high formation temperature, a substrate to be used is single-crystal silicon or the like having excellent heat resistance, and the substrate is expensive and costly. . At present, a single-crystal silicon substrate of an 8-inch wafer is put to practical use for a semiconductor integrated circuit. However, this substrate is very expensive, and becomes extremely expensive when used for a solar cell or the like. Had been an obstacle.

Therefore, it is conceivable to use a ceramic substrate, quartz glass or the like as a substrate. However, these substrates have extremely poor wettability with a silicon layer formed by liquid phase growth, and a polycrystalline silicon layer is formed directly on these substrates. I couldn't do that. Here, the wettability refers to the rate at which the material adheres to the substrate surface, and a material having an N of 90% or less represented by the following equation is defined as poor wettability. N = material adhesion area / substrate area × 100

If the wettability is poor, a polycrystalline silicon thin film cannot be formed by the liquid phase growth method.

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

Conventionally, the above-mentioned silicide layer is made of TiSi
₂ , and formed on the substrate by plasma spraying using a powder of a silicide material having a particle size of 10 to 44 μm made of VSi ₂ , CrSi ₂ , FeSi ₂ , CoSi ₂ , or NiSi ₂ .

[0009]

However, a silicide film formed by plasma spraying using a powder of a silicide material has a large porosity. For this reason, a dense film cannot be obtained, and the electric resistance becomes large. When this film is used as a conductive film of a solar cell, there is a problem that the power generation efficiency is reduced.

An object of the present invention is to provide a method of manufacturing a silicide film which enables formation of a dense silicide film in view of the above-mentioned conventional problems.

[0011]

According to the present invention, there is provided a semiconductor device comprising:
Forming a first layer made of silicon or metal by plasma spraying, and laminating a second layer made of metal or silicon by plasma spraying on the first layer formed by plasma spraying. The method is characterized in that the silicide film is formed by reacting silicon and metal of the first layer and the second layer by plasma spraying heat at the time of forming the second layer.

[0012]

According to the present invention, the metal or silicon constituting the second layer enters the gap of the first layer made of silicon or metal formed by plasma spraying by the plasma spraying heat at the time of forming the second layer, and the silicide is formed. Therefore, a silicide film can be formed without generating pores, and a dense silicide film can be obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram of a reduced pressure plasma spraying apparatus used for manufacturing the present embodiment.

First, the reduced pressure plasma spraying apparatus will be briefly described. In FIG. 2, reference numeral 11 denotes a vacuum vessel capable of maintaining a reduced pressure, and reference numeral 12 denotes a DC power supply for plasma spraying. This DC power supply is connected to a cathode 14a and an anode 14b constituting the plasma spray gun 13. Reference numeral 15 denotes a raw material powder of a semiconductor thin film to be formed, for example, silicon (Si) powder, titanium (Ti) powder, tungsten (W) powder, molybdenum (Mo) powder, tantalum (T) having a particle size of several μm to several tens μm.
a) At the powder supply port to which the powder or the like is supplied, the cathode 1
The raw material powder is melted by the heat of the DC plasma generated between 4a and the anode 14b. Reference numeral 16 denotes a spray gas inlet for introducing a spray gas, such as helium, argon, or hydrogen, for injecting a melt of the raw material powder from the plasma spray gun 13 as a fine-particle plasma jet 17. Gun 1
A polycrystalline or microcrystalline silicon thin film based on a raw material powder and a metal thin film of titanium, tungsten, molybdenum, tantalum or the like are formed on the substrate 1 opposed to the substrate 3. Reference numerals 20 and 21 denote an atmospheric gas inlet and an exhaust port for introducing or exhausting an atmospheric gas into the vacuum chamber 11.

The present invention provides a step of forming a first layer made of silicon or metal on a substrate 1 by plasma spraying using the above-described low-pressure plasma spraying apparatus, and a step of forming a first layer on the first layer formed by plasma spraying. Then, a second layer made of metal or silicon is formed by plasma spraying. The silicide film is formed by reacting silicon and metal of the first and second layers by the plasma spray heat at the time of forming the second layer.

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

[0018]

[Table 1]

Table 2 shows the melting point and forming temperature of silicide. Note that the 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 of silicon and metal is much lower than the melting point and about one third of the melting point.
Therefore, when heat of about the reaction start temperature is applied, silicon and metal react and silicidation proceeds. Since the layer on which silicide is formed has a much higher melting point, there is no possibility of melting, and the layer is formed as it is as a silicide film.

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

First, quartz glass or alumina (Al
₂ O ₃ ), aluminum nitride (AlN), yttria (Y
_A heat-resistant substrate 1 made of a ceramic such as ₂ O ₃ ), magnesia (MgO), or zirconia (ZrO ₂ ) is placed in a plasma spraying apparatus. After evacuating the vacuum chamber 11 of the plasma spraying apparatus to about 100 to 400 Torr, 5 to 30 slm of argon gas is introduced from the spraying gas inlet 16, and 1 to 20 g of silicon powder having a particle diameter of 10 μm or less from the powder supply port 15. / Min to introduce.

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

Subsequently, a particle size of 10
Powder of titanium, tungsten, molybdenum, tantalum or the like having a size of μm or less is introduced at 1 to 20 g / min.

Then, as shown in FIG. 1 (b), a power of 10 to 50 kW is applied from the DC power supply 12 to generate a plasma jet 17, and a second layer made of a metal thin film is formed on the first layer 2. 3 is deposited. The silicidation proceeds simultaneously with the formation of the metal thin film, and as shown in FIG.
A silicide film 4 is formed. The thickness of the silicon and the thickness of the metal are controlled so as to have a ratio of 2: 1.

The total thickness of the first and second layers is 5
If it is about μm, the silicide film 4 can be obtained by performing the above process once. When the silicide film 4 having a thickness of 5 μm or more is required, the above process may be repeated.

In the above embodiment, the first layer 2 is formed of silicon and the second layer 3 is formed of a metal thin film.
Even if metal is formed on the second layer 3 and silicon is formed on the second layer 3, silicidation proceeds similarly, and a silicide film 4 can be formed.

Table 3 shows specific manufacturing conditions of the present embodiment .

[0030]

[Table 3]

The porosity of the silicide film 4 formed according to the present invention described above was found to be zero, whereas the porosity of the conventional method, that is, the porosity of the silicide film 4 formed using silicide powder as the powder, was examined. A few percent. 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]

In each of the embodiments described above, the formation of silicide involving one kind of metal has been described. However, silicide involving two or more kinds of metals can be similarly formed. For example, a silicide film is similarly formed on a combination of Group VIII metals, for example, Ni / Pt, a combination of a refractory metal and a Group VIII metal, for example, a combination of Ni / Cr, a combination of refractory metals, and Mo / W. Can be.

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 view showing the structure of a liquid phase growth apparatus used for manufacturing a photovoltaic device. The configuration of the liquid phase growth apparatus will be briefly described with reference to FIG.

In FIG. 3, reference numeral 30 denotes a high-purity carbon tray.
A substrate 1 for liquid phase growth is held.

Numeral 31 denotes a high-purity carbon boat, which is made of silicon tin (Si) in a crucible 32 in the boat 31.
Sn) is dissolved . Its to the substrate 1 held on the tray 30 on the high-purity carbon-made boat 31 crucible 3
2 so as to be in contact with the surface of the SiSn solution 33 dissolved therein.

Subsequently, the temperature of the crucible was set to, for example, 1000 ° C. in an atmosphere of hydrogen atmosphere and the substrate 1 was set.
By lowering the temperature at a rate of 1 to 2 ° C. per minute and lowering the crucible temperature to 950 ° C., a polycrystalline silicon thin film of about 50 μm is formed on the substrate 1.

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

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

When the temperature of the substrate 1 was lowered from 1000 ° C. to 1 to 2 ° C./minute in an atmosphere of hydrogen atmosphere and the substrate 1 was separated from the SiSn solution 33 at 950 ° C., the substrate 1 was deposited on the substrate 1. A p ⁺ -type polycrystalline silicon layer 5 having a thickness of 50 μm is formed on the silicide film 4 by liquid phase growth.

Thereafter, the substrate 1 on which the polycrystalline silicon layer 5 has been formed is similarly supported on a high-purity carbon tray 30, and the surface of the SiSn solution 33 dissolved in the crucible 32 of the high-purity carbon boat 31 is The tray 30 is stopped so that the surface of the substrate 1 contacts. At this time, the SiSn solution 3
3 is mostly Sn based on the phase diagram. 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 is lowered from 1000 ° C. to 1 to 2 ° C./min in an atmosphere of hydrogen at atmospheric pressure.
When the substrate 1 is separated from the SiSn solution 33 at 900 ° C., a film thickness of 100 μm is formed on the p ⁺ -type polycrystalline silicon 5 deposited on the substrate 1.
An m-p-type polycrystalline silicon layer 6 is formed by liquid phase growth.

Thereafter, similarly, an n ⁺ -type polycrystalline silicon layer 7 is formed by a liquid phase growth method. 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 is lowered from 1000 ° C. to 1 to 2 ° C./min in an atmosphere of hydrogen at atmospheric pressure.
When the substrate 1 is separated from the SiSn solution 33 at 995 ° C., a thickness of 5 μm is formed on the p − type polycrystalline silicon layer 6 deposited on the substrate 1.
A μm n ⁺ -type polycrystalline silicon layer 7 is formed by liquid phase growth.

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

[0048]

As described above, according to the present invention, the metal enters the voids of silicon due to the plasma spraying heat at the time of forming the second layer and is silicided, so that silicide is formed without generating pores. A film can be formed, and a dense silicide film can be obtained. Therefore, the electric resistance can be reduced, and when this film is used as a conductive film of a solar cell, power generation efficiency is improved.

[Brief description of the drawings]

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

FIG. 2 is a schematic view 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 sectional view showing a photovoltaic device using a silicide film formed according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st layer 3 2nd layer 4 Silicide film

Claims (1)

(57) [Claims] 1. A step of forming a first layer made of silicon or metal on a substrate by plasma spraying, and a second layer made of metal or silicon by plasma spraying on the first layer formed by plasma spraying. Forming a silicide film by reacting silicon and metal in the first and second layers by plasma spraying heat during the formation of the second layer. Manufacturing method.