Preparation of an
unzipping polyester is reported. The monomer
was prepared from benzoic acid in a four-step sequence. Step growth
polymerization of the monomer provides the target polymer. Efficient
depolymerization upon irradiation at 254 nm was confirmed with a quantum
yield of >0.8. The photolysis mechanism was investigated, and the
results of radical trapping experiments are consistent with an initial
Norrish type I like homolysis followed by a radical mediated depropagation
reaction driven by aromatization.
Pitch division lithography (PDL) with a photobase generator (PBG) allows printing of grating images with twice the pitch of a mask. The proof-of-concept has been published in the previous paper [1,2] and demonstrated by others [1]. Forty five nm half-pitch (HP) patterns were produced using a 90nm HP mask, but the image had line edge roughness (LER) that does not meet requirements. Efforts have been made to understand and improve the LER in this process. Challenges were summarized toward low LER and good performing pitch division. Simulations and analysis showed the necessity for an optical image that is uniform in the z direction in order for pitch division to be successful. Two-stage PBGs were designed for enhancement of resist chemical contrast. New pitch division resists with polymer-bound PAGs and PBGs, and various PBGs were tested. This paper focuses on analysis of the LER problems and efforts to improve patterning performance in pitch division lithography.
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