The development of full field high resolution imprint templates

Abstract

Critical to the success of imprint lithography and Step and Flash Imprint Lithography (S-FIL^®) in particular is the manufacturing 1X templates. Several commercial mask shops now accept orders for 1X templates. Recently, there have been several publications addressing the fabrication of templates with 32nm and sub 32nm half pitch dimensions using high resolution Gaussian beam pattern generators. Currently, these systems are very useful for unit process development and device prototyping. In this paper, we address the progress made towards full field templates suitable for the fabrication of CMOS circuits. The starting photoplate consisted of a Cr hard mask (≤ 15nm) followed by a thin imaging layer of ZEP 520A. The EBM-5000 and the EBM-6000 variable shape beam pattern generators from NuFlare Technology were used to pattern the images on the substrates. Several key specifications of the EBM-6000, resulting in improved performance over the EBM-5000 include higher current density (70 A/cm²), astigmatism correction in the subfields, optimized variable stage speed control, and improved data handling to increase the maximum shot count limitation. To fabricate the template, the patterned resist serves as an etch mask for the thin Cr film. The Cr, in turn, is used as an etch block for the fused silica. A mesa is formed by etching the non-active areas using a wet buffered oxide etch (BOE) solution. The final step in the template process is a dice and polish step used to separate the plate into four distinct templates. Key steps in the fabrication process include the imaging and pattern processes. ZEP520A was chosen as the e-beam resist for its ability to resolve high resolution images. This paper documents the resolution and image placement capability with the processes described above. Although ZEP520A is slow relative to chemically amplified e-beam resists, it is only necessary to pattern 1/16^th the area relative to a 4X reduction mask. Write time calculations for 1X templates have also been performed, and are compared to 4X photomasks.