SEM micrographs of resist structures formed by catalyzing the cross-link reaction of AZ5214-E resist using liquid HCl. The acid is first spread on the resist surface. The sample is then baked at for . Since AZ5214 is originally a positive photoresist, we need an additional flood exposure to reverse the tone, known in literature as image reversal process. The resist is finally developed after the flood exposure.
Positive process of chemical lithography.
Negative process of chemical lithography.
Comparison of experimental results of positive and negative processes. The left column shows SEM micrographs of resist structures achieved using positive process. The right column shows SEM micrographs of the resist patterns using negative process. Except for the bottom row, these patterns are generated using the same template. Clearly, the structures formed using the positive process are complementary to those formed using the negative process.
Chemical lithography results of using solid acid. The top shows the SEM micrograph of photonic crystal structures patterned using solid acid. The bottom shows an array of lines with different linewidths. Feature size as small as has been realized.
Etch result of silicon substrate patterned using chemical lithography.
SEM micrographs of AFM tips. (a) Solid acid is deposited by physical vapor deposition. (b) Solid acid is synthesized by dip-and-dry method.
Lithography results obtained with different contact forces: (a) firm contact, (b) moderate contact, and (c) gentle contact. The inset in (c) is the AFM tip that is used for the lithography.
linewidth realized by using PVD deposited solid acid.
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