Control of inclination angle of glass-like carbon mold by defocus UV exposure on Si-containing photoresist

Abstract

The authors fabricated micropatterns with inclined sidewalls in a glass-like carbon (GC) mold to thermal imprint on a glass substrate, and succeeded in controlling its inclination angle. The technology comprised three features: (1) A Si-containing photoresist was used with its etching resistance higher than that of the conventional photoresist; (2) the inclination angle of pattern's sidewalls was controlled by a defocus UV exposure technique; and (3) a GC substrate was etched to form a mold by using a Si-containing photoresist structure with inclined sidewalls as a masking layer; the technique was also used to control the inclination angle of the trench's sidewalls in the GC mold. The authors input different focus offset values to defocus the image in order to control the intensity distribution of UV lights within a film of Si-containing photoresist that was spin-coated on a polished GC wafer. In the next step, GC was etched by a 19:1 mixture of O2 and CHF3 which then created a trench structure with inclined sidewalls according to the variations in local masking thicknesses. By changing the focus offset in the UV exposure system from 0 to −12 μm, the inclination angle of the Si-containing photoresist microstructures was varied from 17° to 40°. With these changes, the range of the angles of GC molds became 6° to 17°. Then by thermal imprinting on Pyrex glass and quartz, these numbers expanded from 10° to 32°.