PERFORMANCE OF 0.2 MU-M OPTICAL LITHOGRAPHY USING KRF AND ARF EXCIMER-LASER SOURCES

KrF and ArF excimer laser lithography are considered to be candidates for a next lithography tool to achieve a miniaturization below quarter micron. To improve the focus latitude and overlay accuracy, an in-hou se KrF excimer laser stepper with off-axis illumination has been devel oped. This developed system can successfully resolve 0.2 mum features using off-axis illumination combined with an in-house developed positi ve chemically amplified resist and can also attain overlay accuracy of better than 60 nm using heterodyne holographic alignment. Reducing th e optical absorption of the resist and the lens material at 193 nm was a challenge. The newly developed 193 nm resist contains no aromatic g roups, and the designed projection lens has aspherical elements to est ablish ArF excimer laser lithography.