Multi-shaped e-beam technology for mask writing

Abstract

Photomask lithography for the 22nm technology node and beyond requires new approaches in equipment as well as mask design. Multi Shaped Beam technology (MSB) for photomask patterning using a matrix of small beamlets instead of just one shaped beam, is a very effective and evolutionary enhancement of the well established Variable Shaped Beam (VSB) technique. Its technical feasibility has been successfully demonstrated [2] . One advantage of MSB is the productivity gain over VSB with decreasing critical dimensions (CDs) and increasing levels of optical proximity correction (OPC) or for inverse lithography technology (ILT) and source mask optimization (SMO) solutions. This makes MSB an attractive alternative to VSB for photomask lithography at future technology nodes.The present paper describes in detail the working principles and advantages of MSB over VSB for photomask applications. MSB integrates the electron optical column, x/y stage and data path into an operational electron beam lithography system. Multi e-beam mask writer specific requirements concerning the computational lithography and their implementation are outlined here. Data preparation of aggressive OPC layouts, shot count reductions over VSB, data path architecture, write time simulation and several aspects of the exposure process sequence are also discussed. Analysis results of both the MSB processing and the write time of full 32nm and 22nm node critical layer mask layouts are presented as an example.

Multi-shaped-beam (MSB): an evolutionary approach for high throughput e-beam lithography

“…A larger number of beamlets with a smaller maximum beamlet size leads to a higher shot count reduction for higher technology nodes; especially for the 1x direct write application. As an example, a maximum beamlet size of 400nm in a 8x8 beamlet matrix will allow an optimum shot count reduction and throughput gain for a 32nm node mask write application whereas a 50nm maximum beamlet size in a larger array of 32x32 beamlets will be the optimum setup for less than 22nm direct write applications [5].…”

Future of multiple-e-beam direct-write systems

“…Wafers/mask set There are attempts to take advantage of the much higher throughput enabled by multiple e-beam technology to speed up maskwriting and prototyping 5,6 . There are also efforts to develop systems capable of high volume manufacturing (HVM) of the most critical layers that have exhausted the economical imaging capability of optical lithography to mix with layers that can be economically exposed with optical lithography.…”