REBL DPG lenslet structure: design for charging prevention

KLA-Tencor is currently developing Reflective Electron Beam Lithography (REBL), targeted as a production worthy multiple electron beam tool for next generation high volume lithography. The Digital Pattern Generator (DPG) integrated with CMOS and MEMS lenslets is a critical part of REBL. Previously, KLA-Tencor reported on progress towards a REBL tool for maskless lithography below the 10 nm technology node. However, the MEMS lenslet structure suffered from charging up during writing, requiring the usage of a charge drain coating. Since then, the TSMC multiple e-beam team and the KLA-Tencor REBL team have worked together to further develop the DPG for direct write lithography. In this paper, we introduce a hollow-structure MEMS lenslet array that inherently prevents charging during writing, and preliminary verification results are also presented.