Building a Computer the Size of a Credit Card

TOKYO -- Sharp and its partner Semiconductor Energy Laboratory unveiled Tuesday what the companies claim to be a world-first prototype of an LCD with an 8-bit CPU on its glass substrate.

Putting a CPU directly on the glass substrate of an LCD allows the display to function as a computer and makes possible the development of computers and televisions that can be thinner than 2 millimeters, they said.

Display makers, including Sharp, have been putting integrated circuits onto glass substrates for some time. Until now, that has meant putting driver ICs, which control the display, on the substrate. The advance announced by Sharp and SEL opens the possibility of putting an entire computer on a glass substrate, including a CPU, memory, and other chips.

Long-Term Project

The prototype announced Tuesday was produced using Sharp's continuous grain silicon technology. Sharp has been working on the development of LCDs that incorporate ICs and CGS since 1998.

CGS maintains atomic-level continuity at the crystal grain boundaries. This allows electrons to travel through the semiconductor 600 times faster than with conventional amorphous silicon, which is currently used to produce most LCDs, and approximately three times faster than low-temperature polysilicon, which is an emerging technology in the field.

The CPU used in the prototype screen produced by Sharp is a Zilog Z80 processor that contains 13,000 transistors and was manufactured using a 3-micron process. Zilog first produced the chip in 1976, Sharp said.

By 2005, Sharp hopes to develop a new breed of mobile display devices based on CGS, such as information terminals that are as thin as a credit card, said Mikio Katayama, general manager of Sharp's mobile-LCD group.