Performance of an Image Adjustment Device for SCALPEL

An important consideration for any of the proposed next generation lithography techniques, such as SCALPEL(R) (SCattering with Angular Limitation in Projection Electron-beam Lithography) is that they will be introduced as a "mix-and-match" complement to today's photolithography tools. In such an environment, it will be necessary to maintain accurate pattern overlay to previously exposed levels. Further, an ability to compensate for existing errors, such as die magnification or rotational misalignment, will provide an additional aid to achieving overlay. In contrast to optical lithography techniques, the electron-optics used in electron-beam exposure tools can be used to electronically manipulate an image's rotational alignment and scaling relative to the object plane. A novel image adjustment device, which provides decoupled magnification and rotation control independent of the primary optical system has been implemented in the SCALPEL Proof-of-Lithography (SPOL) exposure tool. Illustrative demonstration exposures, as well as a performance calibration and operational examples, are presented to show the utility of such an image adjuster in a SCALPEL-based system.