METROLOGY FOR REPLICATED X-RAY MASKS USING AN ELECTRON-BEAM MACHINE

In this article, electron-beam metrology is applied to the dimensional control of an x-ray mask replication process for a feature size down to 0.15 mum. This task was accomplished by using an e-beam writer in t he metrological mode. Backscattered electrons resulting from the e-bea m scanning on mask gold absorbers are collected by an annular channel plate detector and the metrological information is extracted by means of a custom linewidth algorithm. Statistical samples of data are colle cted for each gold absorber feature, both for master and replicated ma sks. Masks are inspected by taking measurements point by point, in eac h spatial location of the layout. Then, the gold features replicated b y experimental chemically amplified x-ray negative resists, are direct ly compared to the master mask ones. All the relevant statistical para meters for either master or replica masks were obtained by this method . The metrology experiment allowed the study of an x-ray mask replica process for linewidth control within 50 nm in the range of 0. 15-2 mum feature sizes. Moreover, mask absorbers as small as 0.15 mum were ins pected with a precision of 15 nm (3sigma) by this method.