Laser Techniques Make Surfaces Spotless

John Y. Walz

Surface contamination by microscopic particles is currently one of the most serious problems facing the microelectronics industry. As much as 50 percent of yield losses could be attributable to particulates. Furthermore, as the demand for smaller scale technology increases, the minimum critical size of particle that must be removed decreases correspondingly. In today’s submicron integrated circuit technology, particles of 0.1-mm diameter or less are potential sources of circuit failure, while particles as small as 0.015 mm will probably become an issue within the next decade.
The most widespread cleaning techniques in the industry utilize liquid chemicals, which are themselves sources of contamination. Ultrapure, low-particulate-grade chemicals and water are a possibility, but are prohibitively expensive. Moreover, wet cleaning methods are ineffective at removing particles smaller than 0.1 mm in diameter. Researchers have devoted much effort to developing new techniques that reduce or eliminate the amount of liquid required. This article describes two relatively new optical methods for removing submicron particles from surfaces…