The design of a cost effective multi wavelength development rate monitoring tool

Understanding the development rate of resists is critical for the characterization of photoresist formulations and accurate modeling of the photolithographic process. Most commercial development rate monitors (DRMs) are based on the optical interference of a single wavelength of light. (Perkin-Elmer DRM5800; Litho-tech Japan RDA-790). DRMs based on the interference across a broad spectrum of wavelengths, known as multi wavelength DRMs (MW-DRM), were first reported by Konnerth 1,2 and have also been used for photolithographic research 3,4 , This technique has been applied to commercial DRMs (SC Technology Inspector), but the high cost of these tools has made them inaccessible to most research and development facilities. This paper describes the development of a new cost-effective, scaleable, multi-channel DRM that allows collection and calculation of multiple development rate curves using MW-DRM technology. Techniques are presented for collection of multi wavelength data at rates exceeding 80 Hz, which in turn allows the study of photoresists that develop at rates in excess of 5 microns per secand. The algorithms necessary to analyze this data are presented. The use of these algorithms for the extraction of development rate curves is demonstrated with resists that exhibit surface inhibition and standing waves. The use of multi-layer algorithms to collect development rate infomation in films between 0 and 200 nm thick is also shown. Finally, the use of these techniques for characterization of deprotection in chemically amplified photoresists, is presented.