Environmental stability of 193 nm single layer chemically amplified resists

The principle of chemical amplification was introduced to develop fast and high resolution resist materials, primarily for deep-ultraviolet (UV) lithography. Excellent sensitivity in CA resists emanates from the utilization of a photogenerated species, typically an acid, to cause several catalytic crosslinking or deblocking events' during a postexposure bake (PEB) reaction. Deactivation of the photoacid by airborne basic contaminants or other pathways typically changed the feature width and/or the profile as a function of the delay between exposure and the PEB. Decreasing the photoacid strength, use of low activation energy protecting groups, a decrease in the catalytic turnover rates or a combination of these has helped alleviate this. Today, deep-UV resists that show several hours of postexposure stability are available. We have examined the postexposure delay stability of several 193 nm resists that varied in matrix polymer, photoacid generator, and protecting group chemistry as a function of different concentrations of ammonia and N-methyl pyrrolidone (NMP) at three different relative humidity conditions. In this article we will discuss the experimental setup and describe the environmental contamination stability of these different resists as well as describe in detail the design methodology employed in formulating the resist that showed no significant variation in its linewidth of 0.16 mu m line/space pairs with 13 ppb of ammonia or 14 ppb of NMP. (C) 1999 American Vacuum Society. [S0734-211X(99)04201-8].