By Stephen Ormrod, Edwards, West Sussex, United Kingdom
EXECUTIVE OVERVIEW Vacuum technology is not often considered as leading semiconductor manufacturing. However, a look back at the last 50 years reveals that it has played an essential supporting role. Complex interactions between vacuum and manufacturing technologies have inspired the transition to dry pumps and the evolution of turbomolecular pumps. Meanwhile, vacuum processes have increased in number as fabs moved to producing ICs with tighter device geometries.
In the beginning of the semiconductor era, most high-vacuum systems consisted of oil-sealed, positive-displacement, mechanical pumps, and diffusion pumps for those processes that needed lower pressure. Improvements in residual gas analysis revealed that the primary source of contamination was the hydrocarbon oil in the mechanical rough pump. New oils were developed with lower vapor pressures, which led to faster pumping and lower pressures. The earliest integrated circuits needed vacuum only for metal interconnect deposition