Laser produced X-rays for high resolution lithography

It has been demonstrated that a relatively small, high repetition rate laser can be a most attractive high average power source of X-rays in the 3/4 to 2 keV range. This X-ray energy range is particularly significant for X-ray microlithography of integrated circuits. Mode locked Nd-YAG lasers focused to several tens of micrometer spot sizes are very efficient X-ray sources for this purpose. Over ten percent of the laser light can be converted to X-rays of energy over 1 keV with a 400 mj 200 psec laser. Mode locked lasers with repetition rates of 10Hz and the above outputs are available now. Applicable laser systems with much higher average power should be available in the near future.