| The increasing drive to reduce the size of transistors to sub-100 nm dimensions for overall improved performance is ultimately limited by the control over the dopant profiles. Ultra-sharp profiles can be obtained by techniques like ion-implantation or low-temperature epitaxy, making the primary challenge to control thermal diffusion of dopants during subsequent fabrication steps after the initial profile is formed. This work examines two approaches to obtain structures with sharp doping profiles: (1) reduce the dopant diffusivity through the incorporation of substitutional carbon; and (2) reduce the thermal budget of the preparation steps for silicon epitaxy creating additional growth flexibility for novel design of structures with sharp dopant profiles.; This work's contribution to the first approach include: (i) development of a new gas chemistry in the Princeton rapid thermal chemical vapor deposition (RTCVD) reactor for increased substitutional carbon incorporation in low germanium concentration films, (ii) quantification of the substitutional carbon effect on the dopant diffusivities in and near SiGeC layers, (iii) discovery and understanding that substitutional carbon reacts directly with the silicon self-interstitial in a one-for-one “kick-out” like diffusion promotion reaction, (iv) measurement of the interstitial injection rate during oxidation, (v) demonstration that the carbon-interstitial reaction can effectively “sink” all excess interstitials introduced by ion-implantation or oxidation. Finally, a low temperature surface cleaning technique for RTCVD epitaxy was also developed as part of the second approach, which has been used to fabricate ultra-sharp phosphorus profiles. |
