Novel two-step baking process for high-aspect-ratio photolithography with conventional positive thick photoresist

Jun Bo Yoon, Chul Hi Han, Euisik Yoon, Choong Ki Kim

Research output: Contribution to journalConference articlepeer-review

18 Citations (Scopus)


We have developed a novel two-step baking process to achieve high-aspect-ratios in UV photolithography with a conventional positive thick photoresist. We newly report high-aspect-ratio (>10:1) results in a single coated 91 μm-thick photoresist AZ9262, which was introduced Hoechst at SPIE in 1996. From extensive experiments, we improved the aspect ratio by minimum exposure, diluted development, reabsorption of sufficient water before exposure, and especially by extended and effective soft bake in two steps. In the optimum two-step baking, first the baking is performed at an intermediate temperature in a forced convection oven for hours to evaporate large amounts of solvent. Second, the photoresist is heat-treated at an elevated temperature on an air-gapped hotplate with cover for minutes to enhance aspect ratios. The reason for this improvement has been studied based on the photochemical process of the DNQ/novolac-type positive photoresist. Using this two-step baking, we have obtained lines of 4.4 μm-wide bottom in a single coated 91 μm-thick photoresist. (aspect ratio:20) The line width in the mask was 8.9 μm, and hence 2.2 μm undercut was observed.

Original languageEnglish
Pages (from-to)316-325
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 1998
EventProceedings of the 1998 Conference on Materials and Device Characterization in Micromachining - Santa Clara, CA, USA
Duration: 1998 Sept 211998 Sept 22

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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