Continuous Image Writer with improved critical dimension performance for high-accuracy maskless optical patterning
We report on the development of a production tool for fast optical maskless patterning. The Continuous Image Writer (CIW) combines the advantages of direct writing by using a programmable mask with the advantages of conventional optical lithography by using the same lithographic process for image formation in photoresist. An electronically programmable spatial light modulator (SLM) is imaged onto the substrate by passing a demagnifying Fourier optics. The use of short pulses of a KrF excimer laser allows the imaging of the extended image field of the SLM without stopping the substrate carrying stage during exposure. This results in short writing times. Based on experience with a production-like prototype of the CIW [Proc. SPIE 4000 (2000) 866] we have investigated the various contributions to image quality such as address grid, stitching errors, and SLM quality. This paper describes a method for achieving a critical dimension performance well suited for the generation of photomask and wafer patterns for present and future technology nodes. The present configuration of the CIW makes it an ideal tool for the fabrication of photomasks as well as for direct-write applications for low volume production.
maskless patterning continuous image writer (ciw) optical lithography spatial light modulator (slm) photomasks duv