Vinyl ether resist system for UV-cured nanoimprint lithography

Abstract

Cationic curing of vinyl ethers for step-and-flash nanoimprint lithography is described. Photochemical acid generators for use in the vinyl ether formulation were carefully selected on the basis of their solubility in neat lipophilic vinyl ether. Our favorite acid generators include diphenyltolylsulfonium triflate, CGI261, CGI1905, CGI1906, and CGI1907. The CGI1900 series is sensitive to i-line irradiation while the former two can be sensitized to 365 nm radiation by adding 9-anthracenemethanol. Phenothiazine is also an effective i-line sensitizer of the sulfonium salt. A major problem associated with the vinyl ether curing material is poor storage stability and the formulation rapidly solidifies at room temperature. However, it has been found that anthracenemethanol can stabilize the sulfonium salt and CGI formulations against the aging. Phenothiazine extends the shelf life of the sulfonium salt system but violently reacts with the CGI PAGs. Volatility of the vinyl ethers was measured by thermogravimetric analysis at room temperature. Photochemical curing of the formulations was investigated by FT-IR and also by differential scanning calorimetry (DSC) equipped with a UV lamp. The photo-DSC analysis was particularly useful in ascertaining the cure kinetics and the efficacy of the sensitization. Preliminary imprint experiments successfully printed 50 nm dense features.

Ultraviolet curable branched siloxanes as low-k dielectrics for imprint lithography

“…Other UV curable functionality should be explored including epoxides 22 and vinyl ethers, 23,24 which cure through cation mediated polymerization as well as ene-thiol and other radical polymerizations 25 that yield polymers with high ceiling temperatures. A series of pyrolysis GC/MS studies were carried out on a representative methacrylate analog to study the decomposition products from the materials above its stability limit.…”

Photopolymer Materials and Processes for Advanced Technologies

“…Step and flash imprint lithography was invented by Wilson et al , as an alternative to conventional optical lithography. Basically, a pattern is transferred to substrate by impressing an optically transparent template through a liquid reactive monomer and then photopolymerizing the monomer by exposure to UV irradiation.…”

“…Since the first reports of t-BOC chemistry, many research groups have investigated alternative materials chemistries and processes for advanced lithographic applications, and today’s advanced chip fabricators routinely use chemically amplified resists for state-of-the-art manufacturing. ,,− Through the efforts of several research groups, a set of advanced resist design principles began to emerge as outlined in Table .…”

Synthesis and photo-curing behaviors of silicon-containing (vinyl ether)-(allyl ether) hybrid monomers

“…There are several disadvantages associated with the free radical photo‐polymerization process, including it is severely inhibited by oxygen, which normally causes unsatisfactory surface curing, meaning that the reaction needs to be carried out under an inert gas atmosphere that is inconvenient to operate; and it leads to a contraction in the reaction volume. In contrast to the free radical photo‐induced polymerization process, cationic photo‐induced polymerization has several advantages, including it is not inhibited by oxygen; it does not lead to an obvious contraction in the reaction volume; and polymers formed by cationic photo‐polymerization possess stronger levels of adhesion. Another advantage of this process is that the active core of the reaction possesses greater longevity and cannot therefore be easily stopped.…”