Far UV Spectroscopic Ellipsometry of Electronic Materials

Oregon Health & Science University, Portland OR

Investigators

Abstract

0218288 Freeouf The objectives of this project are to build upon the successful construction of a Far UV spectroscopic ellipsometer and apply this tool to improve the PIs understanding of new materials - and of older materials becoming newly important. The PI intends to share the impact of this new, next-generation tool by collaborative research with a variety of colleagues from many disciplines throughout the country. The project should train at least one PhD student at OGI and assist the research efforts of others at many locations. This effort will emphasize materials of technological importance and concentrate upon proposed high-K gate dielectrics such as HfO2. This system offers a substantially increased photon energy limit (hv < 9 eV) over conventional systems (hv < 6.5 eV), thereby permitting us the PI to examine critical point structures that would otherwise only be accessible at a synchrotron radiation source. This energy range especially impacts studies of wide band gap materials; both dielectrics such as HfO2 and wide band gap semiconductors such as diamond, SiC, and GaN are of immediate and urgent interest. This permits the PI to impact the current semiconductor industry search for materials with which to replace SiO2 as the gate dielectric in CMOS technology. It has permitted the PI to study surface damage layers on polished SiC surfaces, since the higher energies available also offer increased sensitivity to surface films. He seeks funding to continue to apply this instrument to such studies. He has partnerships with several groups that seek to strengthen his own efforts by using the information available from the proposed studies. The specific area of emphasis will be on high-? dielectrics for future CMOS technologies. This international effort is driven by the fundamental limitation upon CMOS scaling that is imposed by the onset of tunneling through a thin barrier layer. This quantum mechanical effect appears to restrict the use of SiO2 based gate dielectrics, even with the addition of nitride layers, to greater than 1 .0 nm thickness, and will fundamentally impact device design and production in this decade. In fact, the 2001 editio of the International Technology Roadmap for Semiconductors envisions these materials being required by 2005 for low power logic chips. The PI has already applied his current system to the study of some of these materials and established that there are clear areas where he extended photon energy range provides new and unique information. He seeks to build a database of dielectric response for many of the candidate materials, and to use this database in the study of these films as deposited upon silicon substrates. His partnerships permit him to study materials deposited by e-beam, jet vapor deposition, molecular beam epitaxy, and atomic beam deposition. The details of these depositions can strongly alter the interface and the film itself - as he has demonstrated for HfO2 already. At the same time it is crucial to ascertain what impact absorption involving the d-levels of transition metal and rare earth elements in these candidate materials will have upon the electrical properties of transistors containing those materials. The PI's studies will help to clarify the location and properties of these energy levels.