Development of two new positive DUV photoresists for use with direct-write e-beam lithography

Two new positive tone, chemically amplified, DUV resists from Shipley, XP-9525 and XP- 9549Q (UV III) have been investigated for use as direct write e-beam resists. Both of these materials have shown extremely high resolution capabilities while maintaining excellent sensitivity to e-beam exposure. Sub-0.20 micrometers line and space gratings were resolved in UV III, and 0.10 micrometers gratings were resolved in XP-9525. A formal design of experiment was created and used as a framework to develop a process for UV III which would optimize several resultant responses including: exposure latitude, edge roughness, and sensitivity. This paper will discuss the process development of these resists, and detail their performance characteristics. Effects relating to post-exposure bake delay will also be considered due to the susceptibility of many chemically amplified resists to airborne contaminants. UV III exhibited much greater stability than XP-9525, and was able to maintain precise linewidth control after 4 hours of delay, making it acceptable for use in a normal process environment. In contrast, XP-9525 exhibited severe T-topping after post-exposure bake delays of only 15 minutes, a condition which can only be solved using additional processing steps and/or environmental controls.