Grant: Collaborative Research and Development Grants

Two decades ago we pioneered the study of sequential two-photon processes, described as the photochemistry of reaction intermediates. We reviewed the topic in 1988. At the time we frequently talked about two-laser two-color photochemistry, since the laser used to make an intermediate was usually of a different wavelength than that used to irradiate it, frequently leading to products that could not be obtained with a single laser or with a lamp. We usually regarded the -sometimes unavoidable- occurrence of multiphoton processes taking place within a single high-energy laser pulse as a problem. On other projects, we worked on the development of new photoacid generators (PAG) for use in resists for microlithography. We also developed methods to measure acid generation in situ, or more accurately on wafer; these are now well established and widely used in industry. Much of this work was performed at a time when the features in computer chips were larger than the excitation wavelength employed in lithographic imaging. Little did we know that these two areas would 'blend' in the current decade to become the perceived solution to overcome physical limits to increase spatial resolution in tomorrow's computer chips. When Gordon Moore predicted in 1965 that the number of transistors per chip would double every 2 years, the preferred lithographic wavelength was 365 nm and typical features were 10-20 micron. That is, the feature was forty times larger than the wavelength of light that generated it. Moore's law has been followed for about 40 years but is approaching a physics barrier. Today 193 nm laser light is used and the usually quoted resolution limit is ~ 64 nm. Industry has already improved on 64 nm by using double exposure and immersion lithography. They aim at 35 nm features by 2009 and 22 nm shortly after, well below the usually quoted one half or one third of the wavelength. This project aims at obtaining spatial resolution as small as one ninth of the wavelength using two-photon techniques, and to use the new chemistry as a platform from which to explore the next generation lithography, widely expected to involve extreme UV light, essentially a form of soft x-rays.