Laser Cleaning of Model Sub-Micrometer Particulate Contaminants From Si Surfaces

The removal of particles less than or equal to 1 J.lm in diameter adhered to surfaces poses a challenge to IC fabrication, space optics, high-resolution and highpower optics, large area displays, magnetic storage devices and other critical surfaces. If we consider, as example, the IC fabrication industry's current trends, the chip feature size is shrinking rapidly. In the modern very-large-scale integration (VLSI) fabrication industry 75% of yield loss is due to particle contamination. As chip feature size decreases, smaller particles can mask a larger portion of the pattern element. This will mean that part of the chip will not be produced to specification and will lead to the rejection of the whole chip. Since Moore's law projects that the number of transistors on an IC chip will be double every two years, the problem will only become more significant. Various cleaning techniques (wet chemical cleaning, scrubbing, pressurized jets and ultrasonic processes) are currently used to clean critical surfaces. Most of these techniques are limited to the removal of micrometer-sized particles and some of them can even damage the wafer. Thus, a highly efficient technique is needed to remove sub-micrometer or even smaller, sub-100-nm (nanometer-scale) particles, without damaging critical surfaces of interest.