Microplastic Structures
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Abstract
Abstract Thick coatings (5 -15um) of a new dual image, aqueous developable photoresist can be exposed using a light attenuating photomask consisting of clear, opaque and grey areas and then processed to yield thermally stable 3dimensional structures which are potentially useful as mechanical and optical components of devices. In the positive mode, relief and intaglio images are produced by processing similar to positive novolak based resists with 12um resolution and with the added feature that the images can be made thermally stable to temperatures >300° C. Negative mode processing of coated wafers imaged with the special mask produces thermally stable structures with tunnels or hollow chambers as well as cantilever beams. Because these structures are crosslinked at the time of development, processing in the negative mode shows much wider latitude than is the case in the positive mode. Images by negative mode processing are capable of submicron resolution, higher aspect ratio (>3 vs <1.6), and inward sloping wall profiles adjustable by exposu re. The acid hardening resin compositions cover a broad range of compositions so that resins can be tailored to meet specific property requirements. Introduction This paper reports on our continuing investigation of acid hardening resins for microelectronics application.1 Previously, their use as photoresists and the unusual properties of negative images were reported. In this paper the chemistry of acid hardening resins is extended to the formation of micron-scale thermally stable microplastic structures. Dual Image Photoresist from an acid hardening resin To review briefly, when a photoresist containing a photoacid generating sensitizer is exposed to patterned light, an acidic latent image is formed in which the pattern is stored chemically. In an acid hardening photoresist, this acidic pattern can be treated in two ways: