Characterization And Modeling Of High Resolution Positive Photoresists

In this paper, dissolution rate characteristics for high resolution positive photoresists are studied. The dissolution mechanism investigated by changing the concentration of photoactive compound, PAC, in the photoresist is also presented. Based on these dissolution rate characteristics, a new dissolution model and an analytic rate function are proposed. Dissolution rate, R, was measured as a function of relative PAC concentration, M, by changing exposure dose. It is found that R(M) is divided into three regions, depending on M values. These characteristics are commonly observed in high resolution positive photoresists which can resolve 0.5μm L/S with a high NA (0.45) g-line steppiere These behaviors cannot be explained by conventional dissolution model proposed so far.I To investigate this dissolution mechanism, dissolution rates, RI(M), of non-exposed resist (PAC+novolak) and ,RE(P), of fully-exposed resist (PPA+novolak) were measured. Log RE is almost proportional to PPA concentration, P. On the other hand , log RI shows a drastic change at the medium PAC concentration. R(M) expressed as a product of RI(M) and RE(P), agreed with measured dissolution rate. From these results,it is considered that the distinctive dissolution behavior of high resolution positive photoresist is mainly attributed to the PAC inhibitation effect. Based on these dissolultion rate behaviors, a new analytic dissolution rate function is proposed. SAMPLE simulation results show good agreement with the experimental pattern profiles.