AN OVERVIEW OF RESIST PROCESSING FOR DEEP-UV LITHOGRAPHY

Continued advances in microelectronic fabrication are trying the limits of conventional lithographic technologies [1]. The traditional diazonaphthoquinone/novolac resist materials are not suitable for use with the deep-UV exposure tools both from the absorption and sensitivity considerations [2]. New resist materials and processes are necessary to fully utilize the potential of deep-UV microlithography, a more promising technology for the production of sub-0.5μm geometries. The advent of resist materials based on chemical amplification principle [3, 4], where one photochemical event leads to a cascade of subsequent events causing a solubility differential, exhibit high resolution, excellent sensitivity and good etch selectivity required for deep-UV lithography. While process sequence for chemically amplified materials is similar to conventional positive resist process sequence, post-exposure bake (PEB) assumes the role of effecting a solubility differential by means of thermally activating the acid catalyzed crosslinking or deblocking reaction. The PEB parameters, the delay time between exposure and post exposure bake (post exposure delay time, PED) and the inherent chemistry of the resist system greatly effect the process performance. This paper summarizes the process characteristics of select positive and negative deep-UV resists, and attempts to correlate the results to the chemical design of the individual resists.