0.35-MU-M RULE DEVICE PATTERN FABRICATION USING HIGH ABSORPTION-TYPE NOVOLAC PHOTORESIST IN SINGLE LAYER DEEP ULTRAVIOLET LITHOGRAPHY - SURFACE IMAGE TRANSFER FOR CONTACT HOLE FABRICATION

0.35 mum design rule device patterns were fabricated using high absorption-type positive and negative photoresist with a KrF excimer laser stepper. The main reason for using high absorption-type photoresist was to minimize the thin film interference effect caused by high reflectivity of the substrate in the deep ultraviolet region. The positive photoresist was FH-EX1 (Fuji-Hunt) and negative photoresist was SAL601. Both contain novolac resin as the base polymer. The positive photoresist was mainly used for poly-Si and W-Si layer pattern fabrication and the negative photoresist was used for the contact hole pattern fabrication. In the contact hole fabrication a surface image transfer technique was used. This technique relies on the direct transfer of the surface negative photoresist image to the insulating layer with highly anisotropic etching and is completely different from the so-called ''surface imaging technique'' using gas phase silylation and successive dry resist development (O2 reactive ion etching). Although the process was a tentative one, critical dimension controllability of this approach satisfied research and development level device fabrication requirements.