Fabrication of a high-resolution mask by using variable-shaped electron beam lithography with a non-chemically amplified resist and a post-exposure bake

• Photomasks have been fabricated by VSB 50 keV EBL.
• Examine PEB temperature dependence of CD error.
• Resist sensitivity by changing PEB temperature has been verified.
• Demonstrate the use of PEB with non-CAR resist helps suppress proximity effect and high resolution technique.

A high-resolution technique was developed for fabrication of photomasks for 10-nm-technology nodes and beyond. Current mask manufacturing techniques use a chemically amplified resist (CAR) photoresist material that has a complex mechanism of acid generation that obscures the criteria for selecting the polymer, quencher, and crosslinker for industrial purposes. It is therefore important to validate non-CAR materials as alternative solutions for mask fabrication. In this research, diluted ZEP520A was used as a non-CAR material in conjunction with a JBX9000 electron-beam lithography (EBL) tool. Additionally, a post-exposure bake (PEB) is normally used in mask fabrication. The PEB method was also used in this research, and we investigated its temperature dependence. Critical dimensions (CDs) of 1:1 line-and-space, isolated space, and isolated line patterns on a diluted ZEP520A resist were measured and showed CD shrinkage, an extension effect, and retention of the integrity of the shape after the PEB process. A resolution of the order of 20 nm was attained and the insights gained from optimization of the PEB process might be usefully applied in advanced methods for fabricating masks of the next generation.

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