CF4-RIE development characteristics of columnar-SeGe ion resists with focused-ion-beam lithography

In the very near future, focused-ion-beam lithography (FIBL) may play an important role for the microelectronic device fabrication. In particular, FIBL is evaluated as a novel vacuum technique available to generate original pattern (or masks), with the sub-0.1 μm linewidth for X-ray lithography (or ion-projection lithography). In order to delineate a fine pattern, it is essential to develop a lithographic tool with high resolution and a resist with high sensitivity. In this work, the sub-0.1 μm patterning characteristics of the columnar structural Se-Ge resists have been studied using low-energy Ga⁺-FIB exposure and CF₄ reactive-ion-etching (RIE) development. The Se-Ge ion resists were normally (0°) and obliquely (60° and 80°) deposited on Si substrate and parts of resists were annealed for several minutes at glass transition temperature (T_g~220°C). After annealing, FIB exposure and CF₄ -RIE development were performed. For 80°-obliquely deposited and T_g-annealed resist, the threshold dose (D₁) is evaluated to be approximately 7×10¹⁴ [ions/cm² ], which corresponds to half of that for non-annealed 0°-resist. The fine patterns with about 0.06~0.09 μm linewidths were obtained successfully for an exposure just above D₁