Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Amorphous semiconductor
Utility Patent
1999-08-23
2001-01-02
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Amorphous semiconductor
C438S166000, C438S487000, C438S486000, C438S482000, C257S070000
Utility Patent
active
06169014
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to laser crystallization of thin films. Crystallization of silicon films has been used extensively in order to produce high performance active matrix liquid crystal displays and other devices. A particular advantage of the use of laser crystallization is that polysilicon thin film transistors can be fabricated on glass substrates, without introducing thermal damage to the glass substrate.
Various measures have been proposed in order to increase the grain size of laser crystallized silicon films, so as to reduce the number of grain boundaries occurring in devices formed from the silicon film. The article “Single-Crystal Si Films Via A Low-Substrate-Temperature Excimer-Laser Crystallization Method” in Mat. Res. Soc. Symp. Proc. Vol. 452 pp.953-958 by R. S. Sposili, et. al. describes the use of a chevron-shaped laser beam profile for the crystallization of silicon to form single-crystal regions at predetermined locations on thin silicon films. The contents of this article are incorporated herein as reference material. The described method is applied to a film of silicon having a thickness of 200 nm, and the method may practically be applied for film thicknesses down to approximately 100 nm. For thicknesses below this level self-nucleation within the film results in reduction in the grain size.
It is desirable to reduce the film thickness of the semiconductor layer for various reasons. A lower thickness results in a more rapid laser crystallization process, because a thicker semiconductor film requires more energy to melt the film. As a result, for a given energy of laser source, a smaller area of the film can be treated using the laser source. Furthermore, a thinner semiconductor film has reduced light sensitivity, which may be desirable for certain semiconductor devices.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a method of manufacturing an electronic device comprising a semiconductor component having a thin film semiconductor layer provided on an insulating substrate, wherein the semiconductor layer is crystallized by scanning a pulsed laser beam over the film, the laser beam being shaped to define a chevron, each pulse of the laser beam comprising at least a first pulse portion of a first energy and a second subsequent pulse portion of a second energy, at least the first and second pulse portions of each pulse being applied at substantially the same position over the film. Each pulse of the chevron-shaped beam may comprise more than two pulse portions. Thus, each pulse may comprise successive pulse portions of different energies which are applied at substantially the same position over the film.
The use of a chevron-shaped crystallization beam enables the grain size of single crystal regions in the semiconductor film to be increased. Furthermore, the use of the multiple-pulse laser reduces the tendency to self-nucleation within the semiconductor film. This enables the crystallization method to be employed for film thicknesses below 100 nm, and preferably for film thicknesses of approximately 40 nm.
The invention also provides a laser crystallization method for crystallizing a thin film semiconductor layer, comprising the steps of:
providing a film of semiconductor material on an insulating substrate;
scanning a pulsed laser beam over the film, the laser beam being shaped to define a chevron, each pulse of the laser beam comprising at least a first pulse portion of a first energy and a second subsequent pulse portion of a second energy, at least the first and second pulse portions of each pulse being applied at substantially the same position over the film.
A double-pulse laser crystallization method is known from the article “A Novel Double-Pulse Excimer-Laser Crystallization Method of Silicon Thin-Films” in Jpn. J. Appl. Phys. Vol 34 (1995) pp 3976-3981 by R. Ishihara et. al., and the method is described as increasing the grain size of excimer-laser crystallized silicon films, particularly so that a single split pulse can produce crystallization of a 1 micrometer region of film material. The contents of this article are also incorporated herein as reference material.
The invention also provides a laser crystallization apparatus comprising:
a pulsed laser source providing laser beam pulses;
an optical processing system for splitting the laser beam pulses to provide output pulses having an intensity profile defining at least a first pulse portion of a first energy and a second subsequent pulse portion of a second energy;
means for shaping the output pulses to form chevron-shaped pulses; and
a projection system for projecting the chevron-shaped pulses onto a sample for crystallization.
REFERENCES:
patent: 3585088 (1971-06-01), Schwuttke et al.
patent: 3600237 (1971-08-01), Davis et al.
patent: 4309225 (1982-01-01), Fan et al.
patent: 4330363 (1982-05-01), Biegelsen et al.
patent: 4400715 (1983-08-01), Barbee et al.
patent: 4604791 (1986-08-01), Todorof
patent: 6014944 (2000-01-01), Aklufi et al.
patent: 9745827 (1997-12-01), None
A Novel Double-Puse Excimer-Laser Crystallization Method of Silicon Thin-Filsm, Ishihara et al, Japanese Journal of Applied Physics, Part 1, vol. 34, No. 8a, Aug. 1995 pp. 3976-3981.
“Single-crystal Si Films Via a Low-Substrate-Temperature Excimer-Laser Crystallization Method” by Robert S. Sposili, M.A. Crowder and James S. Im in Mat. Res. Soc. Symp. Proc. vol. 452, pp. 953-958, 1997 Materials Research Society.
“A Novel Double-Pulse Excimer-Laser Crystallization Method of Silicon Thin-Films” by Ryoichi Ishihara and Masakiyo Matsumura, in Jpn. J. Appl. Phys. vol. 34 (1995) pp. 3976-3981,, Part 1, No. 81, Aug. 1995.
Fox John C.
Lee, Jr. Granvill D.
Smith Matthew
U.S. Philips Corporation
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