Continuous grain silicon is a next-generation technology developed jointly by
Sharp and Semiconductor Energy Laboratory Co., Ltd. (head office: Atsugi,
Kanagawa Prefecture, Japan; president Shunpei Yamazaki). CG-silicon is a variant
of the LTPS process using laser annealing to get larger domains. In LTPS, the
electron mobility is impaired when moving from domain to domain. The advance of
CG-silicon was the development of ways to make these domain boundaries less of
an impediment through some additional processing steps which triples the carrier
mobility (performance) of CG-silicon relative to LTPS and is 600x the
performance of amorphous silicon.
The result is that high resolution devices can be made in small formats with far fewer layers so that manufacturability and yield far surpass those of the best LTPS processes. CG-silicon has a cost structure much like the n-channel process. These advances allow more system devices on a panel. (Sharp has demonstrated an entire Z80™ processor on the glass to show the ability of system on panel). The future intention is to build the necessary op amps, shift register, interfaces, DC-DC converters, etc. and ultimately to build an entire computer on a single piece of glass. This also will produce systems that are intrinsically more reliable. Probably the weakest element in an ordinary display is the Tape Automated Bonding (TAB) bond, and this process eliminates that bond. This also allows more symmetrical designs when the viewing area is more centered within the outside bezel. Among the many benefits of CG-silicon are far higher transmissivity and contrast ratios.
We have only begun to reap these benefits in Sharp products. While amorphous silicon will remain the dominant technology in the near future, we are seeing an increasing number of mobile LCDs introduced that utilize this new CG-silicon technology.
Z80 is a trademark of ZILOG, Inc.