DRY DEVELOPMENT OF ION BEAM EXPOSED PMMA RESIST.

THE ETCHING CHARACTERISTICS OF POLYMETHYL METHACRYLATE (PMMA) EXPOSED TO **2**8SI** + IONS AND THEN DRY DEVELOPED BY REACTIVE ION ETCHING IN AN OXYGEN PLASMA HAVE BEEN INVESTIGATED. IT IS SHOWN THAT ETCH RATES OF RESISTS EXPOSED TO DOSES GREATER THAN 1 * 10**1**5 CM** - **2 (1. 6 * 10** - **4 C/CM**2) AT 40 KEV ARE MUCH SMALLER THAN THOSE OF UNEXPOSED RESISTS. A DIFFERENTIAL ETCH RATES AS HIGH AS 11 IS DEMONSTRATED.THIS PROPERTY OF ION BEAM INHIBITED ETCHING (IBIE) HAS BEENUSED TO FABRICATE RESIST STRUCTURES WITH SUBMICROMETER FEATURES USING ″ SEE-THROUGH ″ THIN SILICON FILM MASKS. WITH FURTHER DEVELOPMENTS OF HIGH BRIGHTNESS ION SOURCES, IBIE MAY BE A USEFUL TECHNIQUE TO REALIZE HIGH RESOLUTION NEGATIVE TONE IMAGES IN RESISTS.