Exposure and Development of Poly (Methyl Methacrylate) Using 254nm Light Source and IPA/Water

Polymethyl methacrylate (PMMA) is a transparent thermoplastic with important applications as a positive resist for various radiation sources. For photo-patterning, PMMA is used with wavelengths shorter than 250 nm, as that is the commonly accepted upper limit of effectiveness. However, we have shown patterning of non-amplified PMMA films at 254 nm. Data for the etch depth as a function of dose (0 to 10 hours), developer temperature (20deg C to 30deg C), and etch time was collected. Developer speeds of up several microns a minute are possible, and the selectivity of exposed over unexposed PMMA can reach nearly 650. This demonstrates the feasibility of PMMA exposure using deep UV at 254 nm.