ULTRAHIGH VACUUM-SCANNING TUNNELING MICROSCOPY NANOFABRICATION AND HYDROGEN DEUTERIUM DESORPTION FROM SILICON SURFACES - IMPLICATIONS FOR COMPLEMENTARY METAL-OXIDE-SEMICONDUCTOR TECHNOLOGY/

The development of ultrahigh vacuum-scanning tunneling microscopy (UHV -STM)-based nanofabrication capability for hydrogen passivated silicon surfaces has opened new opportunities for selective chemical processi ng, down to the atomic scale. The chemical contrast between clean and H-passivated Si(100) surfaces has been used to achieve nanoscale selec tive oxidation, nitridation, molecular functionalization, and metalliz ation by thermal chemical vapor deposition (CVD). Further understandin g of the hydrogen desorption mechanisms has been gained by extending t he studies to deuterated surfaces. in these experiments, it was discov ered that deuterium is nearly two orders of magnitude more difficult t o desorb than hydrogen in the electronic desorption regime. This giant isotope effect provided the basis for an idea that has since led to t he extension of complementary metal oxide semiconductor (CMOS) transis tor lifetimes by factors of 10 or greater. Low temperature hydrogen an d deuterium desorption experiments were performed to gain further insi ght into the underlying physical mechanisms. The desorption shows no t emperature dependence in the high energy electronic desorption regime. However, in the low energy vibrational heating regime, hydrogen is ov er two orders of magnitude easier to desorb at 11 K than at room tempe rature. The enhanced desorption in the low temperature vibrational reg ime has enabled the quantification of a dramatic increase in the deute rium isotope effect at low voltages. These results may have direct imp lications for low voltage and/or low temperature scaled CMOS operation . (C) 1998 Elsevier Science B.V. All rights reserved.