Three-dimensional patterning technology for the fabrication of complex micro-components

Virtually all patterning steps in the semiconductor industry make use of resist, a radiation-sensitive film. Masking this film before exposure to the radiation, or alternatively by direct writing with a radiation beam, followed by development, leaves a pattern of resist. This resist pattern is then itself used as a mask for subsequent pattern transfer via, for example, etching, impurity implantation or deposition. In the micro-electronics industry, all transistors and other active components, metallizations, interconnects and dielectrics are defined in this way. Features of sub-micrometre size are readily achieved across wafers of 6'' (0.15m) diameter Ultra-violet (UV) light is the most common radiation used and resists sensitive to UV are termed photoresists. Whilst the technology has developed over the years to provide good two-dimensional control, the third dimension (perpendicular to the surface) is essentially fixed at one value, for example, uniform etch depth, implant depth, or metallization thickness. In recent years, with the advent of micro-optics and micro-engineering, interest in three-dimensional patterning has grown, and effort has been directed towards extending the technology to provide true photo-sculpting. This paper describes the 3-D patterning technology developed at GEC-Marconi Infra-Red Limited over the past six years.