The consumer electronics industry has a new contender pursuing small products with high performance. A family of transflective TFT-LCDs, introduced by Sharp Microelectronics of the Americas, seeks to improve high-resolution formats in small space.
While its competitors focus on larger display products or CMOS-based mobile products, Sharp uses its proprietary Continuous Grain Silicon (CG-Silicon) technology, developed in conjunction with Semiconductor Energy Laboratory Co., Ltd. (Atsugi, Japan), in order to achieve a crisper image with better color and clarity. As opposed to conventional amorphous silicon, CG-Silicon achieves these improvements with silicon grains aligned having atomic-level continuity at the grain boundary, which boosts the speed of electrons moving through the semiconductor at a carrier mobility of 300 cm2/Vs—about 600 times faster than a conventional amorphous silicon TFT device. "Think of it like a cornfield," says Joel Pollack, Vice President of the Display Business Unit at Sharp. Silicon atoms line up like rows of corn, allowing electrons to travel across the semiconductor, but the silicon grain boundary is like a stone wall between adjacent cornfields. "We've reduced the height of that stone wall, ultimately improving movement from domain to domain," he says.
Also important, the technology provides the basis for System LCDs, or System-on-Glass, in which fully digital circuits—including drivers, shift panels, and I/O interfaces—may be incorporated into the LCD display itself. By reducing the number of external parts and integrating more functionality, the overall package size and weight of the display is reduced. Pollack says that the CG-Silicon technology has helped Sharp to achieve high resolution in a small 4-inch diagonal display and improve reliability with internal parts by building memory into the display itself. Compared to an amorphous TFT device, an improved aperture ratio of CG-Silicon, Pollack claims, reduces the power needed to run the backlight of the display—a significant source of power consumption.
"CG-Silicon technology image improvements, combined with Advanced TFT technology's improved light transmission, allow the display modules to be used with a relatively small amount of backlight for use indoors and outdoors," Pollack adds. Currently, CG-Silicon LCDs have been used in mobile phones, next-generation PDAs, portable PCs and TVs, and handheld gaming devices.
Sharp Microelectronics of the Americas, www.sharpsma.com Enter 576