Abstract: This paper reports the initial results on modeling of a positive chemically amplified photoresist for x-ray lithography. A positive tone chemically amplified photoresist, APEX-M from the IBM Corp., was exposed with synchrotron radiation. A kinetic model for exposure and post-exposure bake has been developed. The FTIR spectroscopy measurement data show that the photoacid loss reaction during post-exposure bake is described as a second order reaction. For the mask patterned photoresist, this leads to a nonlinear diffusion - reaction equation. It was shown that the second order photoacid loss mechanism results in different values of the photoacid diffusion range for different exposure doses. A simulation method has been developed to take into account simultaneously photoacid diffusion and photoacid loss for the latent image of the photoresist. The x-ray exposure simulation tool XLITH and the photoresist development simulator SAMPLE-3D have been used for verification of the model for 0.25 $mu@m patterns. The experimental and simulated profiles have shown good agreement. !13
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