Impact of Heavy Boron Doping and Nickel Germanosilicide Contacts on Biaxial Compressive Strain in Pseudomorphic Silicon-Germanium Alloys on Silicon Saurabh Chopra 1 , Mehmet C Ozturk 1 , Veena Misra 1 , Kris McGuire 2 , and Laurie McNeil 2 1 Electrical and Computer Engineering, North Carolina State University, Raleigh, NC, 27695 2 Physics and Astronomy, UNC, Chapel Hill, NC, 27599 ABSTRACT In recent years, the semiconductor industry has increasingly relied on strain as a performance enhancer for both n and p-MOSFETs. For p-MOSFETs, selectively grown Si 1-x Ge x alloys in recessed source/ drain regions are used to induce uniaxial compressive strain in the channel. In order to induce compressive strain effectively using this technology, a number of parameters including recess depth, Si 1-x Ge x thickness (junction thickness), sidewall thickness, dopant density, dislocation density, and contact materials have to be optimized. In this work, we have studied the effects of heavy boron doping and self-aligned germanosilicide formation on local strain. Raman spectroscopy has been used to study the impact of heavy boron doping on compressive stress in Si 1-x Ge x films. Strain energy calculations have been performed based on Vegard’s law for ternary alloys and the effect of boron on strain in Si 1-x-y Ge x B y alloys modeled quantitatively. It will be shown that, owing to the smaller size of a boron atom, one substitutional boron atom compensates the strain due to 6.9 germanium atoms in the Si 1-x-y Ge x B y film grown pseudomorphically on silicon. The critical thickness of Si 1-x-y Ge x B y has been calculated for the first time based on kinetically limited critical thickness calculations for metastable Si 1-x Ge x films. It will be shown that the critical thickness of the alloy increases as the boron content in the alloy is increased, making boron concentration an additional parameter for optimizing strain in the MOSFET. Based on these conclusions, boron concentration can be used to preserve the strain for thicker Si 1-x-y Ge x B y films (compared to Si 1-x Ge x films) while keeping the dislocation density low. Furthermore, we show that NiSiGe contacts can have a profound impact on the SiGe strain. Our results indicate that NiSiGe introduces additional stress in the underlying Si 1-x-y Ge x B y , which further affects the strain induced in the channel. INTRODUCTION In applications where Si 1-x Ge x is heavily doped with boron, smaller boron atoms can partially compensate the strain in the alloy. This effect is similar to that of carbon in Si 1-x-y Ge x C y alloys. In this work, we have investigated the impact of boron on biaxial compressive strain in Si 1-x Ge x alloys pseudomorphically grown on Si. The stress in the epitaxial layers was characterized by Raman spectroscopy and theoretical calculations. Using boron strain compensation, the Ge content of the alloy can be substantially increased without increasing the stored strain energy. This phenomenon can be used to increase the critical thickness for a given Ge concentration, which can have many advantages. Critical thickness calculations for metastable Si 1-x-y Ge x B y alloys based on Houghton’s model [1] are reported for the first time as a function of boron and germanium concentrations. The calculations are further supported by Mater. Res. Soc. Symp. Proc. Vol. 913 © 2006 Materials Research Society 0913-D02-10