The technical considerations of extending optical lithography

摘要

It is commonly accepted that optical lithography, including 157nm wavelength exposure, will enable manufacturing at the 70nm node. Translating the industry's official roadmap to an exposure tool roadmap, it is obvious that new wavelengths and optics with extremely high numerical aperture will be necessary. With the advance of the latter, depth of focus decreases and focus control becomes more critical. Polarization effects on both the reticle and the resist film must be critically reviewed for numerical apertures exceeding 0.8. Nevertheless, optical extension should preferably be supported by reduced field and large magnification scanners and is expected to take next-generation lithography to at least the 70nm node. Beyond this, next-generation lithography must be both technically feasible and cost-effective.