Progress in proximity electron lithography: demonstration of print and overlay performance using the low-energy electron beam proximity-projection lithography β tool

Abstract

The lithographic performance of the low-energy electron-beam proximity-projection lithography (LEEPL) tool is demonstrated in terms of printability and overlay accuracy to establish the feasibility of proximity electron lithography (PEL) for the 65-nm technology node. The CD uniformity of 5.8 nm is achieved for the 1× stencil mask, and the mask patterns are transferred onto chemically amplified resist layers, coupled with a conformal multilayer process with the mask-error enhancement factor of nearly unity. Meanwhile, the overlay accuracy of 27.8 nm is achieved in the context of mix and match with the ArF scanner, and it is also shown that real-time correction for chip magnification, enabled by the use of die-by-die alignment and electron beam, can further reduce the error down to 21.3 nm. On the basis of the printability of programmed defects, it is shown that the most critical challenge to be solved for the application to production is the quality assurance of masks such as defect inspection and repair.