Measuring system for simulation parameters of chemical amplification resist systems

The resolution of a chemically amplified resist tends to be degraded due to postexposure delay (PED). To elucidate the characteristics of the degradat ion, we conducted studies employing simulations of lithographic processes. In performing such studies, simulation parameters (diffusion length of the photoactive compound, surface inhibition parameters) are normally estimated by calculating the distribution of the photoactive compound concentration in the resist film using Dill's ABC parameters for a conventional resist. H owever, bleaching in many chemically amplified resists does not occur (para meter A = 0), making it difficult to compute the ABC parameters. Therefore, we studied a method of estimating simulation parameters that uses the accu mulated exposure energy instead of the concentration distribution of the ph otoactive compound in the resist film. Simulation parameters were estimated for a t-BOC chemically amplified resist for use with KrF excimer lasers. T he values obtained were input to the PROLITH/2 photoresist profile simulato r, and profiles were calculated. Pattern calculations assumed a wavelength of 248 nm, with NA = 0.5 and a coherence factor of 0.6, and line and space of 0.25 mu m and 0.30 mu m. The results were compared with SEM observations to confirm the validity of the method of estimation. Good agreement was fo und between the simulated results and the SEM observations, confirming the soundness of the estimation method. In addition, simulations confirmed that the cause of resolution deterioration, as FED progresses, is the formation of a surface-inhibiting layer extending deep into the resist film. (C) 199 9 Scripta Technica.