JP3205037B2 - Substrate for forming polysilicon thin film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for forming a polysilicon thin film applicable to a thin film transistor or a thin film solar cell, and a method for producing the same. More particularly, to a polysilicon thin film forming substrate and its manufacturing method that obtained by controlling the grain size of the polysilicon thin film.

[0002]

2. Description of the Related Art Conventionally, a polysilicon thin film has been used in order to simplify a manufacturing process of a thin film transistor and a thin film solar cell and to reduce a manufacturing cost. In order to minimize the recombination of carriers in the polysilicon thin film, it is necessary to increase the crystal grain size (hereinafter, also referred to as grain size). The grain size of the polysilicon film is affected by the substrate temperature, and it is necessary to raise the substrate temperature to 900 ° C. or higher in order to obtain polysilicon having a large grain size. Therefore, it is difficult to form a large grain size polysilicon film on an inexpensive glass substrate or metal substrate.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is directed to a polysilicon thin film forming substrate capable of forming a polysilicon thin film having a large grain size. It aims to provide a manufacturing method.

[0004]

The substrate for forming a polysilicon thin film of the present invention has a crystallization promoting surface layer on a supporting substrate.
The crystallization promoting surface layer has a thickness of 200 mm or less .
The amorphous silicon film is the excimer laser beam irradiation
Thus while being partially crystallized, hydrogen radical irradiation silicon crystal particles I'm especially etched are exposed on the surface, the port on the crystallization promoting surface layer
It is characterized in that a silicon thin film is to be grown .

[0005] In the substrate for forming a polysilicon thin film according to the present invention, the excimer laser is ArF, KrF or Fr.
It is preferably an excimer laser _2, and its energy is even more preferably at 20 mJ / cm ² or more.

Further, in the substrate for forming a polysilicon thin film of the present invention, it is preferable that the flux of the hydrogen radicals is 1 × 10 ¹⁵ atoms / cm ² · sec or more near the substrate.

Furthermore, in the substrate for forming a polysilicon thin film of the present invention, it is preferable that the amorphous silicon film is formed by a plasma CVD method.

In the method of manufacturing a substrate for forming a polysilicon thin film according to the present invention, an amorphous silicon film having a thickness of 200 ° or less is deposited on a supporting substrate.
Irradiation of excimer laser light on the film produced partial crystallization.
And silicon by etching with hydrogen radicals
Exposure of crystallization by exposing fine crystal particles to the surface
A surface layer is formed, and the polysilicon thin film is
It is characterized by being grown on a surface layer .

In the method of manufacturing a substrate for forming a polysilicon thin film according to the present invention, the excimer laser is formed of ArF, KrF
Alternatively, it is preferably an excimer laser of F ₂ , and more preferably, its energy is 20 mJ / cm ² or more.

Further, in the method of manufacturing a substrate for forming a polysilicon thin film according to the present invention, the flux of the hydrogen radical is reduced to 1 × 10 ¹⁵ atoms / cm ² · sec near the substrate.
It is preferable that this is the case.

Further, in the method of manufacturing a substrate for forming a polysilicon thin film according to the present invention, it is preferable that the amorphous silicon film is formed by a plasma CVD method.

[0012]

According to the present invention, an amorphous silicon film formed as the substrate surface layer, with silicon in the <br/> film by an excimer laser is partially crystallized,
By etching with hydrogen radicals, the size and occur density of silicon crystal nuclei is controlled. Therefore, if a silicon film is formed using the substrate of the present invention,
A polysilicon film having a desired particle size can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments with reference to the attached drawings, but the present invention is not limited to only such embodiments.

FIG. 1 is a schematic view of an apparatus used for manufacturing a substrate for forming a polysilicon thin film of the present invention. In FIG.
1 is a reaction chamber, 2 is a substrate, 3 is a heater, 4 is an ECR plasma generator, 5 is an excimer laser light source, and 6 is a plasma C.
The VD device 7 indicates a laser beam entrance window.

As the substrate 2, a glass substrate, a glass substrate on which a transparent electrode or a metal electrode is formed, a metal substrate of stainless steel, tungsten, molybdenum, nickel, titanium or the like is used.

Since the configurations of the heater 3, the ECR plasma generator 4, the excimer laser light source 5, the plasma CVD device 6, and the laser beam entrance window 7 are the same as those of the prior art, detailed description of the configuration is omitted. .

In order to form a large grain size polysilicon film on the substrate 2 using the apparatus shown in FIG. 1, it is important how to control the size and density of silicon crystal nuclei. The size of silicon crystal nuclei formed on the substrate 2 need only be a 10Å~200Å but preferably there is a particle size of 20A～100A. Here, the size of the silicon crystal nucleus is
Is controlled by the thickness of the amorphous silicon film formed as the surface layer of the above .

The amorphous silicon film is usually formed by plasma CVD at a substrate temperature of 250 ° C. to 350 ° C.
Reaction chamber pressure: 0.1Torr~1Torr, RF power density is deposited under the 0.01W / cm ² ~1W / cm ² conditions.

The thickness of the amorphous silicon film is
15 to 250 degrees. By an excimer laser to the amorphous silicon film, although the particle size of silicon crystal nuclei formed by laser annealing is substantially equal to the thickness tends to be smaller than a little thickness. As the excimer laser used at this time, a laser having a shorter wavelength is preferable in view of the absorption coefficient of amorphous silicon.
rF, ArF, lasers such as F ₂ is preferred. Energy during the laser annealing, the optimum value differs depending on its wavelength, need only be a ^{20mJ / cm 2 ~400mJ / cm 2} , that what is 50mJ / cm ² ~300mJ / cm ² preferably. The density of silicon crystal nuclei is
It is mainly determined by the amount of hydrogen radical flux and the substrate temperature.

The flux amount of hydrogen radical is 1 × 10
¹⁵ atom / cm ² · sec to 1 × 10 ¹⁸ atom / c
m ² · sec, but 1 × 10 ¹⁶ ato
^{m / cm 2 · sec~1 × 10} 18 atom / cm 2 · se
It is preferably set to c. 1 × 10 ¹⁵ atom / c
If it is less than m ² · sec, the etching reaction of the amorphous silicon film does not proceed, and there is a disadvantage that the density of silicon crystal nuclei cannot be controlled. Conversely, 1 × 10 ¹⁸ a
The tom / cm ² · sec or more, the amorphous silicon film is all etched want Unode undesirable.

The substrate temperature is preferably higher as the higher the temperature, the higher the etching rate. However, considering that glass may be used as the substrate 2, the temperature is preferably 200 to 500 ° C., and more preferably 300 to 500 ° C. Is preferred.

Hereinafter, the present invention will be described in detail with reference to more specific examples. Example 1 A substrate for forming a polysilicon thin film was manufactured by the apparatus shown in FIG. 1 in the following manner.

First, SiH ₄ gas: 50 SCCM is introduced near the substrate, and the substrate temperature: 400 ° C., the reaction chamber pressure: 0.1 Torr, and RF by the plasma CVD apparatus 6 shown in FIG.
An amorphous silicon film having a thickness of 100 ° was formed on the glass substrate 2 under the conditions of a power density of 0.1 W / cm ² . In FIG. 1, reference numeral 61 denotes an RF power source;
Denotes a matching box, and 63 denotes a power supply.

Next, plasma CVD is performed using the apparatus shown in FIG.
Using the excimer laser light source 5 and the ECR plasma device 4 without using the device 6, the substrate 2 on which an amorphous silicon film was formed as a surface layer with a thickness of 100 ° by the above-described process was processed. In FIG. 1, reference numeral 41 denotes an ECR plasma source, and reference numeral 42 denotes a microwave power supply.

ArF (193) is used as the excimer laser light.
nm) and the energy was 70 mJ / cm ² . The laser beam irradiation was performed through the laser beam incident window 7 at a frequency of 5 Hz for 2 minutes.

At the same time, hydrogen gas: 100 SCCM
R plasma source 41, ECR power: 40
A hydrogen plasma was generated at 0 W and a reaction chamber pressure of 5 mTorr, and the plasma was applied to the substrate 2 for 2 minutes.
At this time, the flux of the hydrogen plasma was 4 × 10 ¹⁶ at.
om / cm ² · sec, and the substrate temperature was 400 ° C.

By the above process , the surface of the glass substrate 2
Silicon crystal nuclei were formed in the layer . A polysilicon film was formed by a plasma CVD method on the surface layer of the substrate 2 on which the above-described processing was performed. The film forming conditions were as follows: SiH ₄ gas: 2SC
CM, H ₂ gas: 400 SCCM, reaction chamber pressure: 1 To
rr, RF power density: 1 W / cm ² , substrate temperature: 40
0 ° C.

The grain size of the obtained polysilicon thin film is SE
From M observation, it was 4000 to 5000 °.

Production Examples 1 to 7 Using the substrate 2 having been subjected to the surface treatment by the above-described method,
The substrate temperature is constant at 400 ° C., the reaction chamber pressure is constant at 5 mTorr, the hydrogen gas flow rate is constant at 100 SCCM, the hydrogen plasma and laser light irradiation time are constant, and the laser irradiation frequency is 5
By changing the energy density of the ArF excimer laser and the ECR power for hydrogen plasma generation as Hz, a polysilicon thin film was formed (Production Examples 1 to 7), and the particle size was measured based on SEM photographs. The results are shown in Table 1.

[0030]

[Table 1]

[0031]

As described above, a polysilicon thin film having a large grain size can be obtained by using the substrate for forming a polysilicon thin film of the present invention.

Further, according to the manufacturing method of the present invention, a substrate on which a polysilicon thin film having a large grain size can be formed can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used for producing a substrate for forming a polysilicon thin film of the present invention.

[Explanation of symbols]

1 reaction chamber, 2 substrates, 3 heaters, 4 ECR plasma generator, 5 excimer laser light source, 6 plasma C
VD device, 7 Laser light entrance window.

Claims (10)

(57) [Claims] 1. A <br/> polysilicon thin film forming substrate having a crystallization promoting surface layer on a support substrate, wherein the crystallization promoter
The surface layer, with the following thicknesses of the amorphous silicon film 200Å is thus partly crystallized excimer laser beam irradiation, it is etched with hydrogen radical irradiation
In particular silicon crystal fine it'll have been exposed to the surface
Cage, polysilicon thin film is grown on the crystallization promoting surface layer
A substrate for forming a polysilicon thin film, which is to be formed. _2. The polysilicon thin film forming substrate according to claim 1, wherein said excimer laser is an ArF, KrF or F ₂ excimer laser. 3. The substrate for forming a polysilicon thin film according to claim 1, wherein the flux of the hydrogen radical is 1 × 10 ¹⁵ atom / cm ² · sec or more near the substrate. 4. An excimer laser having an energy of 20
3. The substrate for forming a polysilicon thin film according to claim 1, wherein the substrate is at least mJ / cm ² . 5. The polysilicon thin film forming substrate according to claim 1, wherein said amorphous silicon film is formed by a plasma CVD method. 6. A crystallization promoting surface layer on a supporting substrate
A method of polysilicon thin film forming substrate, the the supporting substrate is deposited a thickness of the amorphous silicon film 2 Å, and irradiating the excimer laser beam to the amorphous silicon film
With resulting partial crystallization Te, to expose the silicon crystal particles on the surface and <br/> etched with hydrogen radical
Thereby forming the crystallization promoting surface layer, and growing a polysilicon thin film on the crystallization promoting surface layer.
A method for manufacturing a substrate for forming a polysilicon thin film, which is to be performed . 7. The excimer laser according to claim 1, wherein said excimer laser is ArF, KrF.
Or preparation of polysilicon thin film forming substrate according to claim 6, characterized in that the excimer laser of the F _2. 8. The method for producing a substrate for forming a polysilicon thin film according to claim 6, wherein the flux of the hydrogen radical is 1 × 10 ¹⁵ atom / cm ² · sec or more near the substrate. 9. An excimer laser having an energy of 20
8. The method for producing a substrate for forming a polysilicon thin film according to claim 6, wherein the substrate is at least mJ / cm ² . 10. The method according to claim 6, wherein the amorphous silicon film is formed by a plasma CVD method.