Pattern-etching process profile control

The spacer technique is unique in that with one lithographic exposure, the pitch can be reduced by a factor of two indefinitely, just with the application of a succession of spacer-formation and pattern-transfer processes. Furthermore, because spacer materials are mostly drawn from HM materials, their postetch pattern quality tends to be superior, especially in terms of line edge roughness and CD control, when compared to corresponding resist profiles after etch. It is also not sensitive to interlayer alignment. 

The spacer double-patterning approach has some issues, the main one of which concerns placement accuracy of the features, which requires excellent dose and etch uniformity control. Equally problematic is the fact that the spacers may not stay in place at the proper location after the material to which they are attached (the HM pattern) is removed. Forming acceptable uniform spacer profiles that will yield uniform CDs is not a trivial exercise. In addition, the etch pattern transfer steps, often involving delicate removal of materials adjacent to the spacers, place unusually tight etch process tolerance on this technique, in order to have a successful outcome. 

ICP is an important technology for micro- and nanoscale patterning process. High etch rate, high aspect ratio and anisotropic, good profile control, high uniformity, and RIE lag elimination are important issues in the development of MEMS... 

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