January 20, 1998 (TOKYO) -- Sharp Corp. and Semiconductor Energy Laboratory Co., Ltd. (SEL) said that they have developed a technology called continuous grain silicon (CGS), for growing thin-film single crystals of silicon on a glass substrate.

They have also produced a prototype 2.6-inch color thin-film transistor liquid crystal display (TFT-LCD) panel for projection, which uses the new technology.

With the technology, semiconductor devices, including microprocessors and memory units, can be fabricated on a glass substrate. Such semiconductor devices have been fabricated on a single crystalline silicon wafer.

Use of a glass substrate to produce integrated circuits could reduce costs substantially. A large number of ICs could be fabricated on a 550mm x 650mm substrate designed for an LCD panel.

A sheet-shaped personal digital assistant (PDA) could be produced by fabricating an LCD panel, a microprocessor and memory devices on a glass substrate.

To produce the CGS, amorphous silicon must be grown on a glass substrate. The precise method for producing the CGS has yet to be disclosed. Shumpei Yamazaki, president of SEL, said that it won't be difficult for major companies to produce the glass-substrate silicon once they understand how to do it.

The CGS has a high mobility of 300 cm²V^{- 1}s^-1. The high mobility of a single crystalline silicon is 400 - 500 cm²V^-1s^-1, and that of a polycrystalline silicon used for TFT-LCD is in the range of tens of centimeters to 150 cm²V^{- 1}s^-1.

The two companies produced a nine-cascade ring oscillator using the CGS. The operating frequency of a transistor was about 1GHz and the driving voltage was 5V.

Sharp and SEL also have produced a prototype of a display that integrates driving circuits on a substrate of an LCD panel. The operating frequency of the driving circuits is 13.8MHz. The display, designed for high definition televisions, has a high resolution of 1280 x 1024 pixels, with a numerical aperture of 63 percent.

In addition, the two firms have produced a prototype of a rear- projection display using the LCD panel. The display is 60 inches in size, 900cd/ cm² in luminance and 300:1 in contrast, they said. A 370W metal-halide lamp is used as a light source.

They said they plan to commercialize the product by the end of 1998.

(Nikkei Electronics)