THE INFLUENCE OF POSTEXPOSURE BAKE ON LINEWIDTH CONTROL FOR THE RESIST SYSTEM RAY-PN (AZPN 100) IN X-RAY MASK FABRICATION

Statistically designed experiments for optimization in processing the high sensitive negative tone Hoechst resist RAY-PN (AZ PN 100) were used to establish robust processes for two different applications of the resist: (1) pattern replication on a wafer and (2) during the mask copy process under 40-mbar He environment via x-ray lithography. Minimization of linewidth change with respect to a 1:1 pattern transfer was achieved through manipulation of the following variables: exposure dose, post-exposure bake (PEB) time and temperature, and development time. A two-stage sequential strategy was employed. After specifying the response and the primary variables, the first stage of the sequential approach was based on a full factorial design. In the second stage, the influence of PEB parameters for wafers as well as for x-ray mask blanks were studied using a central composite design. Finally, the response surfaces for the pattern replication on x-ray mask blanks are demonstrated and the optimal process parameter set for a linewidth control within 50 nm for 0.5- to 3.0-mu-m feature size values are given.