Robert Kress

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The objective of this project is to characterize Brewer Science EXP97O11 experimental broadband back anti-reflective coating (BARC). This BARC was designed to function at both i-line (365 nm) and g-line (436 urn). The focus of this experiment is to incorporate the BARC process into existing lithography processes at RIT. A “Poor Man’s” DRM was performed on both the BARC as well as Shipley 812 photoresist to determine optimum develop time as well as optimum bake temperature for the BARC. Once the optimum conditions were found, several wafers were processes through 1st level lithography using the BARC on a polysilicon layer and subsequently etched. This was done to observe any effects undercutting of the BARC during develop would have on etched features. SEM analysis will be performed to analyze undercutting as well as standing wave effects in the photoresist caused by reflections off the polysilicon during exposure. The optimum bake temperature for the BARC was found to be 1600 C for 45 seconds with an initial bake of 1000 C for 60 seconds. At this temperature, the develop rate was found to be approximately 30 nm/sec. The optimum development time for approximately 900 angstroms of BARC with 1.2 microns of photoresist was found to be 40 seconds using MF-351 developer. The optimum exposure energy was found to be 105 mJ/cm2. SEM analysis showed a significant undercutting effect with a slight over-development of the BARC. This indications a need to tightly control the development parameters. Standing waves were not observed due to a “pitting” effect on the sidewall resist lines.

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