Patterning processes with thermally decomposable polymers

Abstract

Microlithography has traditionally involved a photoinduced solubility change, necessitating a solvent development step. Self-developing resists, in which photolysis results in volatile products, were pioneered in the 1980s but they failed to find commercial traction due in part to fear of contaminating expensive high-resolution projection optics. We have adapted similar chemistry for three applications: high-throughput placement of very large arrays of entire components, such as semiconductor chiplets and microLEDs; direct-write photolithography with thermal development; and a nanoscale-resolution lithography tool based on a modified AFM tip with controlled heating. In the first system, decomposition to small gaseous molecules in a short (of the order of microseconds) time propels the component onto a target substrate. Lithography requires in particular high contrast and stable post-development features. For the third case, decomposition must be endothermic, devoid of residue upon the application of heat, and responsive to both pressure and temperature. Promising results have been obtained for each.