paul@uwvax.ARPA (Paul Haeberli) (08/13/83)
from the "Weekly Bulletin", Lawrence Livermore National Laboratory, Wednesday, May 25, 1983 'Laser pantography' Computer circuit inscribing breakthrough. A revolutionary new process that could give personal computers of the future the power of today's supercomputers was announced last week by Lab scientists at an international meeting of laser researchers. Called "laser pantography", the process uses pulses of laser light, flashing millions of times per second, to "paint" integrated circuits directly onto silicon wafers. According to Lab researchers, it will be possible to inscribe in hours, instead of weeks, the circuits of today's most powerful computers onto a silicon wafer five inches in diameter - more than a 1,000 fold reduction in size. Though similar laser processes have been under study at a number of academic and industrial laboratories, the Lab group claims to be the first to have produced operating circuits. Co-authors of the paper, which was presented at the Conference on Lasers and Electro-Optical Systems in Baltimore, are Bruce McWilliams, Irving Herman, Rod Hyde, Fred Mitlitsky and Lowell Wood, all members of the Lab's Special Studies Group. McWilliams describes laser pantography as "a set of laser paint brushes which we dip into paint pots of various exotic gases in order to paint on a canvas of silicon." The resulting "paintings," however, become the brains of high- powered computers when electricity is applied. "We hope to have a system painting 1,000 transistors a second by the end of the year," McWilliams said. Said Wood, head of the Special Studies group, "New generations of more powerful computers can thus evolve in days rather than in years that currently separate generations." "There are about 60 supercomputers in use in the world today," said Associate Director at Large Carl Haussmann. "I could imagine 10 of these laser pantography units sitting in a single room with each making one supercomputer silicon wafer a day. That could mean more than 1,000 new supercomputers could be built in that one room in just one year." The traditional method for making integrated circuits is slow and expensive and yields a relatively low fraction of usable circuits. Most are irrevocably damaged during the processing. In contrast, the Lab's laser pantography approach shows potential to be fast, direct and reversible. If a design is changed, a new circuit can be made easily from scratch. If a processing mistake is made, it can be erased and corrected. Laser pantography involves rapid reactions using intense green laser light directed onto silicon surfaces with an intensity a billion times greater than noontime sunlight. At times, various gases are introduced into a reaction chamber. The laser is pulsed on and off so fast that reactions occur only in the center of the focused laser spot, about one micron (a millionth of a meter) in diameter. This equals the resolution of current integrated circuit technology. The intense light superheats the silicon surface for such a short time that heating and cooling rates of hundreds of billions of degrees per second are achieved, giving the laser pantography process its great sensitivity and resolution. When the gases are admitted into the chamber, reactions occur on the hot surface that can remove or change the electrical properties of the silicon, or deposit the desired electrical materials.