Photomask linewidth standards have been fabricated to be used as reference for the calibration of photomasks metrology tools. In order to manufacture these binary masks with submicronic features with good linearity and resolution in a production mode using a MEBESIII type pattern writer, a process was set using the electronbeam negative tone resist SAL6O5 for the imaging layer and transferring the developed patterns via dry etch. To achieve the very tight tolerances required in the specification of the standards, various parameters, which affected the quality of the fmal product, had to be carefully monitored and controlled. The variables to be optimized were the characteristics of the exposure tool, chemically amplified resist system and dry etching tool. We report on the optimization of the exposure current, address size, spot size and feature sizing as well as the effect of post exposure bake (PEB) temperatures, blanks age and humidity levels on resist sensitivity and resolution. Metrology data presented show that a resolution of 300nm with a tolerance of plus or minus 20 nm in both polarity is obtained Keyword : Photomask, SAL6O5, standard
|