Direct patterning of polyimide by pulsed electron beams in soft vacuum

We recently reported on a proximity, flood exposure process using pulsed electron beams.1 We showed replication of 0.5 um feature sizes from an electron transmitting stencil mask on to 3 um PMMA film via 28 KV pulsed electron beams produced in air and helium at 50 mTorr. In this paper, we describe the direct patterning of a commercial polyimide spin coated on a silicon wafer and cured at 100C by exposure to 28 KV pulsed electron beams (current pulse duration 500 nsec, FWHM and 100 pulses) produced in 50 mTorr air and helium. The exposed region of polyimide cross-linked and the region covered by the 7 um line on the electron microscope grid used as stencil mask was unaffected. Patterning was completed by wet development in N-methylpyrolidone at 21C for 15 secs. We present developed thickness vs exposure characteristics and SEM photographs of developed patterns. © 1987 SPIE.