Applicant:
Dr. Richard Sandstrom, Dr. Bill Partlo, Cymer Inc., USA

Abstract:
An examination of the latest ITRS roadmap highlights the rapid decrease in integrated circuit CD consistent with Moore’s law. The advanced lithography to print such small features is enabled by only one type of laser - a VUV Argon Fluoride (ArF) excimer laser, operating at 193 nm. At the same time, the decrease in price of semiconductor devices has resulted in a microelectronics explosion. Today, all electronic devices - cell phone, IPOD, PDA, digital camera, Playstation, etc. have ICs that have been fabricated using advanced lithography. The concomitant effects of shrinking CD and decreasing price/performance include narrower spectral linewidth and higher laser power from each succeeding generation of ArF lasers.
Although excimer lasers have been around for thirty years, much of industrial excimer development concentrated on high power xenon chloride lasers at 308 nm and lithography lasers at 248 nm. In 2002, when the semiconductor industry decided to shift to the lower VUV wavelength, it experienced unprecedented problems not observed before at UV or DUV wavelengths. They were considered serious enough to either delay the introduction of 193 nm, or worse, delay Moore’s law.
The solution came with the first industrial MOPA laser introduced in 2002 based on the proposition to increase energy by using a master oscillator (MO), power amplifier (PA) configuration and increase pulse duration by using an external optical delay line. A low power, high performance laser produces the required low linewidth at low energy (MO) and a high gain amplifier (PA) boosts the output power to the required levels.