With recent improvements in design rule, requirements for CD (Critical Dimension) control have been increasing. Development is one of the critical processes affecting CD control. As a track supplier, we have focused attention on the stage of TMAH puddle formation and investigated various development systems. The behavior of resist dissolution is different between the early stage (when forming the puddle) and the later stages of the develop process (static development). It is already reported that proper control is necessary for the late stage in order to improve the CD control. The most noteworthy phenomenon in the late stage is that the dissolved resist (a develop process by-product) diffuses into the TMAH puddle. During this stage, the by-product and the TMAH are partially mixed in the puddle and cause CD variance within a wafer. Moreover, the amount of by-product on the pattern periphery significantly influences this phenomenon. It’s assumed that the by-product’s behavior contributes to CD fluctuation within a shot.
We attempted to lower the concentration of resist by-product in the later stages of the develop process and confirmed some improvements in CD control. This report summarizes the new process and its effectiveness.