JP3065878B2 - Method of forming semiconductor thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor thin film on a substrate by a CVD method.

[0002]

2. Description of the Related Art It is known that when a semiconductor thin film such as an amorphous silicon thin film is manufactured by a method such as a plasma CVD method, defects (dangling bonds) are generated in the thin film. As a method for repairing such a defect, the following method is conventionally known.

(1) A hydrogen annealing method of performing treatment at a high temperature of 800 ° C. or more in a hydrogen gas atmosphere at a relatively high pressure. (2) A hydrogen plasma method in which hydrogen plasma is generated by high frequency (RF) discharge in a hydrogen gas atmosphere, and a semiconductor heated and held in the hydrogen plasma is exposed.

(3) A hydrogen ion implantation method in which hydrogen ions are accelerated and implanted into a semiconductor, followed by heat treatment. (4) A method in which hydrogen is excited by using microwave discharge and the excited hydrogen is exposed to a semiconductor (Japanese Patent Laid-Open No. 1-238112).

[0005]

However, the above-mentioned methods (1) to (3) have a problem that the semiconductor to be processed generally needs to be maintained at a temperature of 500 ° C. or higher. Further, (2) In the method there is a problem that is more thin film surface to a plasma damaged, (3) for the method of hydrogen ions are implanted at a high energy, there is a problem that still cause damage to the thin film surface Was. (4)
Although the above method does not cause the above-mentioned problem, the defect is easily repaired mainly on the surface of the thin film, and as a result, a defect density distribution occurs in the depth direction of the thin film, and it is difficult to form a uniform thin film. was there.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of solving such a conventional problem and forming a semiconductor thin film having less defects uniformly over the entire film without damaging the film surface. It is in.

[0007]

According to a method of forming a semiconductor thin film of the present invention, a semiconductor thin film is formed on a substrate in a chamber by a CVD method.
A method of forming a body thin film that supplies atomic hydrogen.
Supply pipe in the chamber, and the tip of the supply pipe
Is placed in the vicinity of the substrate, and the opening
Semiconductor thin film while supplying atomic hydrogen to the substrate from the mouth
Forming defects such as dangling bonds
Are terminated with hydrogen to form a semiconductor thin film while repairing defects .

[0008] The present invention odor Te, by increasing the pressure of the feed gas for the pressure of the semiconductor thin film forming chamber in the supply pipe, atomic hydrogen is supplied onto the substrate from the supply pipe.

As a method of producing atomic hydrogen, a method of heating hydrogen gas with a filament such as a tungsten filament and thermally dissociating it to produce atomic hydrogen, or a method of decomposing hydrogen gas by microwave discharge to produce atomic hydrogen. A method of generating hydrogen or the like can be employed. Such a filament or microwave source may be provided in the middle of a pipe for supplying the above-mentioned atomic hydrogen or near the pipe outlet.

The supply amount of the atomic hydrogen gas is appropriately selected depending on the supply amount of the thin film source gas, the film formation rate, and the like. When the film formation rate is 10 to 100 ° / min , the supply amount of the hydrogen gas is 10%. About 100 SCCM is preferable.

[0011]

According to the present invention, a semiconductor thin film is formed on a substrate while atomic hydrogen is supplied onto the substrate. For this reason, defects such as dangling bonds are terminated with hydrogen,
A semiconductor thin film is formed while the defect is repaired. Therefore, according to the present invention, a semiconductor thin film having few defects can be uniformly formed in the entire film, particularly in the depth direction (thickness direction) of the thin film.

Further, in the present invention, since the treatment is not performed through the film surface after the film is formed, the film surface is hardly damaged. Further, as a method of terminating with hydrogen while forming a thin film, a method of using a raw material gas in which hydrogen gas is mixed or a reaction gas is a compound of hydrogen is considered, but in this method, it is decomposed by plasma. Since hydrogen radicals collide with the film surface at high speed, the etching may proceed, possibly damaging the film surface. Atomic hydrogen used in the present invention is supplied to the film surface at a lower speed than hydrogen radicals generated by such plasma decomposition, so that such damage is less likely to occur.

[0013]

Embodiment 1 FIG. 1 is a schematic view showing a film forming apparatus used in a forming method according to one embodiment of the present invention. Referring to FIG. 1, parallel plate electrodes 2 and 3 are provided in chamber 1 so as to face each other, and a substrate 4 is provided on electrode 2 to be grounded. A source gas supply pipe 7 for film formation is connected to the electrode 3, and a hole for blowing out the source gas supplied from the source gas supply pipe 7 is formed in the electrode 3. Further, inside the chamber 1, hydrogen supply pipes 5 a and 5 b for supplying atomic hydrogen are provided so that their tips are located near the surface of the substrate 4. The other ends of the hydrogen supply pipes 5a and 5b are connected to the chamber 1
Of tungsten filament 6
a and 6b are provided respectively. The tungsten filaments 6a and 6b serve as heating means for thermally dissociating the supplied hydrogen gas. The raw material gas enters the hydrogen supply pipes 5a, 5b in the chamber 1 and the filaments 6a, 6b
The flow rate of the hydrogen gas is set to about 2 to 10 times the flow rate of the raw material gas so as not to come into contact with the gas. The exhaust port 8 of the chamber 1 is provided on the side opposite to the side on which the filaments 6a and 6b are provided.

A thin film of hydrogenated amorphous silicon was formed on a substrate 4 by RF plasma CVD using an apparatus as shown in FIG. About 1 filaments 6a and 6b
Heat to 200 ° C and add hydrogen gas 50-100SC here
Introduce at a gas flow rate of CM and supply hydrogen gas to filament 6.
Atomic hydrogen generated by thermal dissociation at a and 6b is supplied onto the substrate 4 by hydrogen supply pipes 5a and 5b. 13.56 MHz high frequency power was applied between the electrodes 2 and 3. Other thin film forming conditions are as shown in Table 1.

[0015]

[Table 1]

Under the above forming conditions, the hydrogen flow rate is 50 SCCM.
To 100 SCCM to form an amorphous silicon thin film and obtain film characteristics (hydrogen content in the film, SiH ₂
/ SiH, defect density). The hydrogen content and SiH ₂ / SiH in the film were determined by the FT-IR method, and the defect density was determined by SP.
It was determined by the M method. These results are shown in FIGS. 2, 3 and 4, respectively. As shown in FIG. 2, it can be seen that as the hydrogen flow rate increases, the amount of hydrogen in the film increases. Further, as shown in FIG. 3, as the flow rate of hydrogen increases, SiH ₂ / SiH, which is an index of the disorder of the film structure, decreases, indicating that a thin film having good film quality is formed. Also, as shown in FIG. 4, it can be seen that the defect density decreases as the hydrogen flow rate increases.

Next, according to the forming method of the present invention, a thin film of the photoelectric conversion layer of the photovoltaic element was formed. Form a transparent electrode film made of tin oxide as a light incident side electrode on a glass substrate,
A p-layer, an i-layer, and an n-layer of an amorphous silicon thin film were sequentially stacked thereon by RF plasma CVD. The thickness of the p-layer is 200 °, the thickness of the i-layer is 5000 °,
The thickness of the n-layer was 300 °. Then, at the time of forming the i-layer, a thin film was formed according to the present invention while supplying atomic hydrogen to the substrate by an apparatus as shown in FIG. After the formation of the amorphous silicon thin film, a silver electrode layer was formed as a back electrode by a normal resistance heating evaporation method. With respect to the obtained photovoltaic element, open-circuit voltage (Voc), short-circuit current (Isc),
The fill factor (FF) and the photoelectric conversion rate (η) were measured and are shown in Table 2.

For comparison, a photovoltaic device was manufactured in the same manner as in the above example, except that atomic hydrogen was not supplied during the formation of the i-layer and a hydrogen plasma treatment was performed after the formation of the i-layer.
The condition of the hydrogen plasma treatment after the i-layer formation is as follows: power: 30
mW / cm ² , temperature: 200 ° C., pressure: 30 Pa, hydrogen flow rate 50 SCCM, processing time: 10 minutes.

The characteristics of the photovoltaic element of the comparative example obtained in this manner were evaluated in the same manner as in the above-described example. Table 2 shows the results.

[0020]

[Table 2]

As is clear from Table 2, according to the present invention, a thin film with less defects can be formed, and as a result, the conversion efficiency (AM1.
5,100 mW / cm ² and irradiation area of 1 cm square) can be improved from 11% to 12%.

Embodiment 2 FIG. 5 is a schematic view showing a film forming apparatus used in a forming method of another embodiment according to the present invention. Referring to FIG. 5, parallel plate electrodes 12 and 13 are provided in chamber 11. A substrate 14 is provided on the grounded electrode 12. A source gas supply pipe 17 is connected to the electrode 13, and a hole for blowing out the source gas is formed in the electrode 13. A hydrogen supply pipe 15 is provided near the surface of the substrate 14. FIG. 6 is a plan view showing such a hydrogen supply pipe 15. As shown in FIGS. 5 and 6, a portion of the hydrogen supply pipe 15 on the substrate 14 has a rectangular ring shape, and the supply pipe is supplied with hydrogen gas to the rectangular portion. 15a is connected. In the rectangular pipe portion, a tungsten filament 16 is provided in an annular shape. In addition, an opening 15b that opens toward the surface of the substrate 14 is provided inside the rectangular pipe. In the present embodiment, three openings 15b are provided on one side, and a total of 12 openings 15b are provided. By supplying the atomic hydrogen from the large number of openings 15b using the pressure difference between the gas pipe and the chamber, the atomic hydrogen can be supplied uniformly on the substrate 14, and the thickness of the thin film can be reduced. The film quality can be made more uniform not only in the direction but also in the plane direction of the thin film. In this embodiment,
Since the filament 16 is provided at a position closer to the substrate 14, atomic hydrogen thermally decomposed by the filament 16 can be supplied onto the substrate 14 in a more active state.

A hydrogenated amorphous silicon thin film was formed on the substrate 14 by using the apparatus shown in FIGS. 5 and 6 while varying the supply amount of hydrogen gas from 50 SCCM to 100 SCCM. Other film forming conditions were the same as in Example 1 above.

FIGS. 7 to 9 show the film properties (hydrogen content in the film, SiH ₂ / SiH, defect density) of the hydrogenated amorphous silicon thin film obtained as described above.
The hydrogen content and SiH ₂ / SiH in the film were determined by the FT-IR method, and the defect density was determined by the SPM method. As in the first embodiment, as the hydrogen flow rate increases, the amount of hydrogen in the film increases, SiH ₂ / SiH decreases, and the defect density decreases.

Embodiment 3 FIG. 10 is a schematic view showing a film forming apparatus used in a forming method of still another embodiment according to the present invention. FIG.
With reference to FIG.
2, 23 are provided. A substrate 24 is provided on the grounded electrode 22. The source gas supply pipe 27 to which the source gas is supplied is connected to the electrode 23. The electrode 23 is provided with a hole for discharging the gas supplied from the source gas supply pipe 27. The chamber 21
Is provided with a hydrogen supply pipe 25 to which a microwave source 26 is attached. The tip of the hydrogen supply pipe 25 is provided near the surface of the substrate 24. In this embodiment, hydrogen gas is excited by microwave discharge, decomposed into atomic hydrogen, and supplied onto the surface of the substrate 24. The hydrogen gas is supplied at a flow rate of, for example, 10 to 100 SCCM, and the microwave source 26 has a power of 2.45 GHz and an output of 20 SCCM.
Microwave energy of 0-500 W is provided, and hydrogen gas is decomposed into atomic hydrogen. As described above, a hydrogenated amorphous silicon thin film can be formed in the same manner as in the first and second embodiments while supplying atomic hydrogen onto the substrate 24.

In the above embodiment, heating by a filament and excitation by microwave discharge have been described as examples of the method of generating atomic hydrogen. However, the present invention is not limited to these, and other methods are used. Atomic hydrogen can be generated and provided on the substrate.

In the above embodiment, the amorphous silicon thin film is formed by the RF plasma CVD method. However, the present invention can be applied to other CVD methods and to the formation of other semiconductor thin films. Can be.

[0028]

According to the present invention, a semiconductor thin film is formed on a substrate while supplying atomic hydrogen. Since atomic hydrogen is supplied during the formation of the thin film, a semiconductor thin film having few defects can be formed uniformly in the thickness direction of the thin film. In addition, since atomic hydrogen is supplied at the time of thin film formation, there is little damage to the film surface, etc.
A semiconductor thin film having good film quality can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a film forming apparatus in one embodiment according to the present invention.

FIG. 2 is a diagram showing a relationship between a hydrogen flow rate and a hydrogen amount in a film in an example using the apparatus shown in FIG.

FIG. 3 is a diagram showing the relationship between the amount of hydrogen and SiH ₂ / SiH in an example using the apparatus shown in FIG. 1;

FIG. 4 is a diagram showing a relationship between a hydrogen flow rate and a defect density in a film in an example using the apparatus shown in FIG.

FIG. 5 is a schematic view showing a film forming apparatus in another embodiment according to the present invention.

FIG. 6 is a plan view showing a hydrogen supply pipe used in the apparatus shown in FIG.

FIG. 7 is a view showing a relationship between a hydrogen flow rate and a hydrogen amount in a film in an example using the apparatus shown in FIG. 5;

FIG. 8 is a diagram showing a relationship between the amount of hydrogen and SiH ₂ / SiH in an example using the apparatus shown in FIG. 5;

9 is a diagram showing a relationship between a hydrogen flow rate and a defect density in a film in an example using the apparatus shown in FIG.

FIG. 10 is a schematic view showing a film forming apparatus in still another embodiment according to the present invention.

[Explanation of symbols]

 1,11,21 ... chamber 2,3,12,13,22,23 ... parallel plate electrode 4,14,24 ... substrate 5a, 5b, 15,25 ... hydrogen supply pipe 6a, 6b, 16 ... filament 7,17 , 27 ... Source gas supply pipe 26 ... Microwave source

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-131511 (JP, A) JP-A-61-247018 (JP, A) JP-A-1-234314 (JP, A) JP-A 62-1987 213118 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 H01L 21/31 C30B 25/00 C23C 16/00

Claims (2)

(57) [Claims] In a method of forming a semiconductor thin film on a substrate in a chamber by a CVD method, a supply pipe for supplying atomic hydrogen is provided in the chamber.
Provided, the tip of the supply pipe is arranged near the substrate,
Atomic hydrogen is deposited on the substrate from the opening facing the surface
By forming a semiconductor thin film while supplying, dangling
Terminate defects such as ring bonds with hydrogen, repair defects
A method of forming a semiconductor thin film while forming a semiconductor thin film. By wherein to be higher than the pressure of the source gas for a semiconductor thin film type formed in the pressure before Campanulaceae supply in the pipe chamber, to supply atomic hydrogen on a substrate from said supply pipe The method for forming a semiconductor thin film according to claim 1, wherein: