Inter- and intramembrane resist critical dimension uniformity across a SCALPEL mask

The use of chemically amplified (CA) resists in integrated circuit fabrication is accepted in semiconductor manufacturing as a way to achieve high resolution with excellent critical dimension (CD) control and etch selectivity. The use of CA resists for mask fabrication has not had as much favor due to resist storage stability issues and CD variations due to postexposure bake (PEB) sensitivities. One key component to the CD control on SCALPEL membrane masks is the thermal uniformity of the membranes and baking environment during the PEB process. This article discusses the numerical models created to predict temperature gradients within membranes and across membranes on a 200 mm SCALPEL mask. Verifications of the model by comparison of simulation results and actual CD data are also presented.