PREVAIL-Electron projection technology approach for next-generation lithography

This paper is an overview of work in the IBM Microelectronics Division to extend electronbeam lithography technology to the projection level for use in next-generation lithography. The approach being explored—Projection Reduction Exposure with Variable Axis Immersion Lenses (PREVAIL)—combines the high exposure efficiency of massively parallel pixel projection with scanning-probe-forming systems to dynamically correct for aberrations. In contrast to optical lithography systems, electron-beam lithography systems are not diffraction-limited, and their ultimate attainable resolution is, for practical purposes, unlimited. However, their throughput has been—and continues to be—the major challenge in electron-beam lithography. The work described here, currently continuing, has been undertaken to address that challenge. Novel electron optical methods have been used and their feasibility ascertained by means of a Proof-Of-Concept (POC) system containing a Curvilinear Variable Axis Lens (CVAL) for achieving large-distance (>20 mm at a reticle) beam scanning at a resolution of <100 nm, and a high-emittance electron source for achieving uniform illumination of a 1-mm section of the reticle. A production-level prototype PREVAIL system, an “alpha” system, for the 100-nm node has been under development jointly with the Nikon Corporation. At the writing of this paper, its electron-optics subsystem had been brought up to basic operation and was being prepared for integration with its mechanical and vacuum subsystem, under development at Nikon facilities.