Avoidance/reduction of charging effects in case of partially insufficient substrate conductivity when using ESPACER 300Z

The aim is to apply e-beam lithography for second level imaging of Alternating Phase Shift Masks (altPSM) in the 65 nm node and below. Difficulties due to charging effects arise when exposing areas where the chromium absorber has been cleared away. In order to achieve correct pattern placement, the commercial water-soluble conductive ESPACER 300Z top coat from Showa Denka is applied in combination with chemically amplified resist of type FEP171. The paper describes the method and algorithm to test the efficacy of the material and the technological steps taken to avoid or reduce charge effects. The obtained overlay accuracy proves the ESPACER/FEP171 combination a promising approach for future altPSM manufacturing.