Experimental analysis of image placement accuracy of single-membrane masks for LEEPL

Abstract

We have fabricated seven masks with different patterns on a 27 mm x 34 mm single-membrane for Low Energy Electron-beam Proximity Lithography (LEEPL) by the wafer-flow process. We have examined the membrane flatness and image placement (IP) accuracy, which are essential qualities to be assured. We summarize the results as follows: Masks with membranes of 13 MP and 20MPa stress satisfy the membrane flatness requirement of less than 2 µm while a mask with a 6 MPa membrane does not. Maps of the distortion induced by the wafer-flow process are obtained for the masks with 13 MPa and 20 MPa membranes and their performance is explained in terms of the contraction of the mask substrate. The out-of-plane distortion for a 3 mm x 3 mm block of dense hole patterns with an opening ratio, ranging from 10% to 40%, has been evaluated. The distortion induced by the block has been evaluated and the effect of the local magnification correction on the IP error is examined. Maps of the distortion induced by the wafer-flow process and 4 x 4 blocks of 10% and 20% opening are obtained for a mask with 13 MPa membrane and the distortion induced by the blocks is estimated in 3σ. The uncorrectable IP error for the mask with the blocks of 10% opening is estimated to be 10 nm (in 3σ), which satisfies the specification for LEEPL masks.

6-inch circle template fabrication for patterned media using a conventional resist and new chemically amplified resists

“…This hard-mask process for quartz substrate was evolved since alternating phase-shifting mask process development 5) , and in the case of silicon substrate this was from stencil mask process. 6) Although a rotary stage e-beam writer is required for patterned media, a spot-beam writer with 100 kV acceleration voltage and XY stage (100 kV-SB: JEOL-JBX9300FS) was employed for hard-mask process development. ICP-type dry-etching tool for advanced photomask was used for hard-mask and substrate etching.…”