Plasma etch challenges for next-generation semiconductor manufacturing

Abstract

Alternative fabrication schemes based on concurrent engineering of plasma etching can overcome the limitations inherent in optical lithography and thus help to achieve ever smaller device dimensions.

High‐Resolution Study of Changes in Morphology and Chemistry of Cylindrical PS‐b‐PMMA Block Copolymer Nanomasks during Mask Development

“…Such initial surface chemistry modification of the PS followed by a constant slow‐paced plasma etching of polymer thin films was also observed and discussed by Rastogi et al. [ 42 ] for PS as well as by the group of von Keudell [ 47,48 ] for other polymers. Possible explanations for this behavior include UV radiation‐induced breaking of CC and CH bonds, cross‐linking, and surface graphitization, which result in the formation of a passivation layer which then retards the etching of PS.…”

“…The wall roughness, determined in a similar way to the interfacial width in non‐PMMA‐removed samples, amounts to (1.6 ± 0.2) nm (Figure 3o) indicating a steep slope of the hole walls. It was argued in literature [ 42 ] that such a small wall roughness might either result from the redeposition of sputtered entities into sharp bumps created during ion bombardment or might stem from a local heating above the glass transition temperature due to energy transfer during ion bombardment and, thus, material reflow and smoothening. The average line edge roughness of the plasma etched holes is (0.5 ± 0.2) nm.…”

“…[ 39,40 ] The major advantages of O 2 /Ar plasmas are a good final surface roughness of the PS masks and a good etch selectivity to most substrates. [ 38,39,42 ] The major disadvantage of dry etching techniques, however, is the limited etch selectivity between PS and PMMA. [ 42 ] A high etching rate of PMMA allows to remove these domains completely, but the etching of PS cannot be avoided.…”

“…[ 38,39,42 ] The major disadvantage of dry etching techniques, however, is the limited etch selectivity between PS and PMMA. [ 42 ] A high etching rate of PMMA allows to remove these domains completely, but the etching of PS cannot be avoided. This not only leads to a reduction of the thickness of the remaining PS mask due to a vertical etching rate, but due to isotropic character also lateral etching takes places, which enlarges the resulting features in size and changes the features in shape.…”