Applications of 2D etch transfer are, for example, semiconductors, as high resolution (< 20 nm half-pitch possible), high aspect-ratio (amplification in depth up to 50x) and low line edge roughness (< 3 nm, 3σ) are required.
The etch process involves multiple steps of RIE (e.g. oxygen and fluorine) steps using a 3-layer stack (e.g. PPA, SiO2, JSR HM8006). In a single RIE step, patterns can be transferred into silicon with a subsequent depth amplification. A tri-layer stack is recommended to achieve even better depth amplification, vertical walls or undercuts. A SiO2 hardmask and a cross-linked polymer below the PPA resist have proven to allow a depth amplification by 50x. High-resolution structures in PPA have been transferred by RIE and achieved an exceptionally low 1σ-line edge roughness below 1 nm.
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