Process for preparing a polycrystalline silicon thin film

Details Process for preparing a polycrystalline silicon thin film Process for preparing a polycrystalline silicon thin film

2000-08-14

2003-03-04

Niebling, John F. (Department: 2812)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

On insulating substrate or layer

C438S486000, C438S487000

Reexamination Certificate

active

06528361

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for preparing a polycrystalline silicon thin film, more specifically, to a process for preparing a polycrystalline thin film comprising a step of microwave annealing and crystallization of an amorphous thin film of silicon semiconductor, silicon semiconductor added with impurities, IV family semiconductor comprising Si alloy such as Si
1
−
x
Ge
x
, III-V family and II-VI family semiconductor.
BACKGROUND OF THE INVENTION
In recent years, a variety of processes for obtaining polycrystalline thin film on amorphous substrate have been suggested in the art, to meet the requirement of polycrystalline thin films to be applied to polycrystalline silicon(poly-Si) thin film transistor(“TFT”) for SRAM, TFT for LCD, solar cell, SOI device, etc. Particularly, attempts to obtain polycrystalline thin film under a low temperature, which is critical factor for the consideration of solar cell or TFT for LCD employing glass as a substrate, have been tried as followings:
Japanese patent laid-open publication (Sho) 4-144122 and (Sho) 3-25633 disclose a process for fabricating polycrystalline thin film by depositing amorphous thin film on a substrate and then crystallizing by way of annealing at a relatively high temperature of about 600° C., in accordance with low-pressure chemical vapor deposition(LPCVD) method.
Inverson et al. also teaches a process for fabricating crystalline thin film with increased grain size by depositing polycrystalline thin film on a substrate, implanting impurities to have amorphous characteristics, and finally annealing at a temperature of about 600° C.(see: R. B. Inverson et al., J. Appl. Phys., 65:1675(1987)).
Furthermore, Nakazawa et al. reports that polycrystalline thin film may be fabricated by depositing amorphous thin film on a substrate employing Si
2
H
6
and then, annealing at a temperature of about 600° C., in accordance with plasma enhanced chemical vapor deposition(PECVD) method(see: Nakazawa et al., J. Appl. Phys., 68:1029(1990)).
The prior art methods are, however, proven less satisfactory in the senses that: low-priced glass cannot be employed as a substrate, since a high temperature of above 600° C. is essentially required to crystallize amorphous thin film; a step of implantation of impurities is also accompanied; and, expensive gas such as Si
2
H
6
is needed, all of which increase the costs for manufacturing process.
As an approach to overcome the problems in the art, an annealing method which employs laser to crystallize through melting, after deposition of thin layer is made in accordance with PECVD or LPCVD method, has been provided. However, this method has also revealed shortcomings that: high cost is required for facilities of manufacturing and films of uniform thickness can be hardly achieved.
On the other hand, a process for obtaining polycrystalline thin film by depositing metals such as copper, gold and platinum as impurities to thin film, has been suggested in the art(see: D. K. Sohn et al., Jpn. J. Appl. Phys., 35:128(1996); S. W. Lee et al., Appl. Phys. Lett., 66:1571(1995)). Although this method permits the use of glass substrate due to the lowered temperature for crystallization, it has also revealed a problem that metals used for crystallization remain inside of polycrystalline thin film as impurities which in turn deteriorates the characteristics of device.
Accordingly, there are strong reasons for exploring and developing an alternative means for preparing a polycrystalline silicon thin film in an economical and simple manner.
SUMMARY OF THE INVENTION
In this regard, the present inventors have made an effort to develop an improved method for fabricating a polycrystalline silicon thin film, and provided a novel process which successfully tides over the said problems by employing a step of microwave annealing for crystallization. In accordance with the process of the invent-ion, efficient and economical fabrication of homogenous polycrystalline thin film can be realized, since it employs microwave annealing of amorphous thin film by which crystallization temperature can be lowered to a degree that allows the use of glass as a substrate.
A primary object of the present invention is, therefore, to provide a process for preparing a polycrystalline silicon thin film employing microwave, which allows crystallization at a low temperature.


REFERENCES:
patent: 4303455 (1981-12-01), Splinter et al.
patent: 4474625 (1984-10-01), Cohen et al.
patent: 5179073 (1993-01-01), Yamazaki
patent: 5529937 (1996-06-01), Zhang et al.
patent: 5543352 (1996-08-01), Ohtani
patent: 5585291 (1996-12-01), Ohtani
patent: 5595944 (1997-01-01), Zhang et al.
patent: 5854096 (1998-12-01), Ohtani et al.
patent: 6172322 (2001-01-01), Shang et al.
Beyers, et al., “Oxygen ordering, phase separation and the 60-K and 90-K plateaus in Yba2Cu3Ox,”Nature,vol. 340, No. 6235, pp. 619-621, Aug. 1989.
Ahn, et al., “Quaternary Phase Relations Near YBa2Cu3O6+xat 850° C in Reduced Oxygen Pressures,”PhysicaC 167 (1990) pp. 529-537.
Lee, et al., “Microwave-induced low-temperature crystallization of amorphous silicon thin films,”J. Appl. Phys.,82 (6), Sep. 15, 1997.
Lee, et al., “Variations of morphology and electrical property of diamond with doping using diborane in a methane-hydrogen gas mixture,”Diamond and Related Materials,8 (1999) 251-256.
Recrystallization of amorphized polycrystalline silicon films on SiO2: Temperature dependence of the crystallization parameters, R.B. Iverson and R. Reif, J. Appl. Phys. 62(5), pp. 1675-1681, Sep. 1, 1987.
Effect of substrate temperature on recrystallization of plasma chemical vapor deposition amorphous silicon films, Kenji Nakazawa and Keiji Tanak, J. Appl. Phys. 68(3), pp. 1029-1032, Aug. 1, 1990.
Pd induced lateral crystallization of amorphous Si thin films, Seok-Woon Lee, et al., Appl. Phys. Lett. 66(13), pp. 1671-1672, Mar. 27, 1995.
Low-Temperature crystallization of Amorphous Si Films by Metal Adsorption and Diffusion, Dong Kyun Sohn, et al., J. Appl. Phys., vol. 35, pp. 1005-1009, Part 1, No. 2B, Feb. 1996.

Affiliated with

Also associated with

Rating

Process for preparing a polycrystalline silicon thin film does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for preparing a polycrystalline silicon thin film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing a polycrystalline silicon thin film will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3031741