JPH10177954A - Method for manufacturing polycrystalline silicon thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dehydrogenate an amorphous silicon hydride thin film at a lower temperature. SOLUTION: An amorphous silicon hydride thin film 2 is deposited on an insulating board 1 by plasma CVD, the amorphous silicon hydride thin film 2 on the insulating board 1 is irradiated with carbon monoxide laser beams with a wavelength of approximately 5μm for dehydrogenation. In this case, most of the applied carbon monoxide laser beams are absorbed by the amorphous silicon thin film 2 and the laser beams do not easily reach the insulating board 1. Furthermore, the temperature of the amorphous silicon hydride thin film 2 is relatively low at approximately 300-350 deg.C, and the amorphous silicon hydride thin film 2 can be dehydrogenated at a lower temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a polycrystalline silicon thin film.

[0002]

2. Description of the Related Art In a method of producing a thin film transistor by polycrystallizing an amorphous silicon thin film, for example, a hydrogenated amorphous silicon thin film is deposited on an insulating substrate such as a glass substrate by plasma CVD, and the hydrogenated amorphous silicon thin film is deposited. After performing a dehydrogenation process by performing a heat treatment at a temperature of about 450 ° C. for about 1 hour in a nitrogen atmosphere, the amorphous silicon thin film on the insulating substrate is irradiated with an excimer laser to excite the amorphous silicon thin film. There is a method of manufacturing a thin film transistor using the polycrystalline silicon thin film as a semiconductor layer through a predetermined process after polycrystallization to form a polycrystalline silicon thin film. In this case, the reason why the amorphous silicon thin film is dehydrogenated by performing the heat treatment is to avoid occurrence of defects due to bumping of hydrogen at the time of excimer laser irradiation.

[0003]

However, in such a conventional method of manufacturing a polycrystalline silicon thin film, an insulating substrate having a hydrogenated amorphous silicon thin film is heated at 450 ° C.
Since the dehydrogenation treatment is performed by performing heat treatment at a high temperature, shrinkage or distortion may occur in the insulating substrate, or impurities such as sodium ions may leak from the insulating substrate, which may deteriorate the characteristics of the thin film transistor. There was a problem. An object of the present invention is to enable a hydrogenated amorphous silicon thin film to be dehydrogenated at a lower temperature.

[0004]

According to the present invention, a hydrogenated amorphous silicon thin film is deposited on an insulating substrate by plasma CVD, and the hydrogenated amorphous silicon thin film on the insulating substrate is subjected to a stretching mode of Si-H bond. After dehydrogenation treatment is performed by irradiating a laser having an energy corresponding to the above, the amorphous silicon thin film on the insulating substrate is irradiated with an excimer laser to polycrystallize the amorphous silicon thin film into a polycrystalline silicon thin film. Things.

According to the present invention, the hydrogenated amorphous silicon thin film on the insulating substrate is irradiated with the laser having the energy corresponding to the expansion mode of the Si—H bond to perform the dehydrogenation treatment. Most of the laser is absorbed by the amorphous silicon thin film, the temperature of the insulating substrate does not rise so much, and the temperature of the hydrogenated amorphous silicon thin film at that time is relatively low, about 300 to 350 ° C. The silicon thin film can be dehydrogenated.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a polycrystalline silicon thin film according to an embodiment of the present invention will be described below with reference to FIGS. First, FIG.
As shown in FIG. 1, a hydrogenated amorphous silicon thin film 2 having a thickness of about 500 ° is deposited on the upper surface of an insulating substrate 1 made of a glass substrate or the like by plasma CVD using a mixed gas of SiH ₄ and H ₂ . In this case, the temperature of the insulating substrate 1 is set to 350
It should be below ° C. Next, a dehydrogenation process is performed in order to avoid occurrence of defects due to bumping of hydrogen when high energy is applied by excimer laser irradiation in a later step. That is,
As shown in FIG. 1 (B), the hydrogenated amorphous silicon thin film 2 is irradiated with a laser having an energy corresponding to the stretching mode of the Si—H bond, for example, a carbon monoxide laser having a wavelength of about 5 μm. By vibrating the Si—H bond in the thin film 2 and heating the hydrogenated amorphous silicon thin film 2, the Si—H bond is cut at the same time,
Hydrogen in the hydrogenated amorphous silicon thin film 2 is released, and the hydrogen content is reduced to several atomic% or less. In this case, the temperature of the hydrogenated amorphous silicon thin film 2 is 300
About 350 ° C. In addition, at the time of carbon monoxide laser irradiation, most of the carbon monoxide laser resonates with the Si—H bond and is absorbed by the amorphous silicon thin film 2, so that the temperature of the insulating substrate 1 does not rise so much.
And the impurities hardly leak out from the insulating substrate 1. Next, as shown in FIG. 1C, the amorphous silicon thin film 2 is polycrystallized by irradiating the amorphous silicon thin film 2 with an excimer laser to form a polycrystalline silicon thin film 3.

As described above, the hydrogenated amorphous silicon thin film 2 on the insulating substrate 1 is irradiated with a laser having an energy corresponding to the stretching mode of the Si—H bond, for example, a carbon monoxide laser having a wavelength of about 5 μm to dehydrogenate. Since the treatment is performed, most of the irradiated carbon monoxide laser is absorbed by the amorphous silicon thin film 2, the temperature of the insulating substrate 1 does not rise so much, and the temperature of the hydrogenated amorphous silicon thin film 2 at that time is 300 to A relatively low temperature of about 350 ° C., and at a lower temperature, hydrogenated amorphous silicon thin film 2
Can be dehydrogenated. Therefore, shrinkage and distortion hardly occur in the insulating substrate 1, impurities hardly leak from the insulating substrate 1, and characteristics of the thin film transistor are hardly deteriorated.

Here, an example of a structure of a thin film transistor formed using the polycrystalline silicon thin film shown in FIG. 1C will be described with reference to FIG. First, after the polycrystalline silicon thin film 3 is subjected to element isolation as is well known, a gate insulating film 11 and a gate electrode 12 are formed, and impurities are diffused into the polycrystalline silicon thin film 3 using the gate electrode 12 as a mask.
When a source / drain electrode 15 connected to the impurity diffusion layer via the interlayer insulating film 13 and the contact hole 14 formed in the interlayer insulating film 13 is formed, a thin film transistor is completed. In this thin film transistor, characteristics can be hardly deteriorated.

In the above embodiment, the dehydrogenation treatment is performed by irradiating the hydrogenated amorphous silicon thin film 2 on the insulating substrate 1 with a carbon monoxide laser having a wavelength of about 5 μm. While heating the hydrogenated amorphous silicon thin film 2 with a wavelength of 5 μm.
Irradiation with a carbon monoxide laser of about m may be performed. In this case, dehydrogenation can be performed more efficiently. Further, a carbon monoxide laser having a wavelength of about 5 μm may be irradiated while heating the insulating substrate 1 using a heater.

[0010]

As described above, according to the present invention, the hydrogenated amorphous silicon thin film on the insulating substrate is irradiated with a laser having an energy corresponding to the stretching mode of the Si-H bond to perform the dehydrogenation treatment. Most of the irradiated laser is absorbed by the amorphous silicon thin film, the temperature of the insulating substrate does not rise so much, and the temperature of the hydrogenated amorphous silicon thin film at that time is 300 to 35.
The temperature is relatively low at about 0 ° C., and the hydrogenated amorphous silicon thin film can be dehydrogenated at a lower temperature.

[Brief description of the drawings]

1A and 1B are views for explaining a method of manufacturing a polycrystalline silicon thin film according to an embodiment of the present invention, in which FIG. 1A is a cross-sectional view showing a state in which a hydrogenated amorphous silicon thin film is deposited on an insulating substrate, and FIG. ) Is a cross-sectional view showing a state in which a hydrogenated amorphous silicon thin film is dehydrogenated by irradiating a carbon monoxide laser, and (C) is a polycrystalline silicon thin film obtained by irradiating an excimer laser to polycrystallize the amorphous silicon thin film. FIG.

FIG. 2 is a cross-sectional view illustrating an example of a structure of a thin film transistor including the polycrystalline silicon thin film illustrated in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Amorphous silicon thin film 3 Polycrystalline silicon thin film

Claims (3)

[Claims] A hydrogenated amorphous silicon thin film is deposited on an insulating substrate by plasma CVD, and the hydrogenated amorphous silicon thin film on the insulating substrate is
After dehydrogenation treatment is performed by irradiating a laser having an energy corresponding to the stretching mode of the H bond, the amorphous silicon thin film on the insulating substrate is irradiated with an excimer laser to polycrystallize the amorphous silicon thin film. A method for producing a polycrystalline silicon thin film, wherein the method is a crystalline silicon thin film. 2. The method for producing a polycrystalline silicon thin film according to claim 1, wherein the laser having an energy corresponding to the stretching mode of the Si—H bond is a laser having a wavelength of about 5 μm. 3. The method according to claim 1, wherein the temperature of the hydrogenated amorphous silicon thin film when the hydrogenated amorphous silicon thin film is dehydrogenated is about 350 ° C. or less. .