Growth kinetic and doping of Si and SiGe epi layers on fullsheet substrates

摘要

As the critical size of MOSFET becomes smaller and smaller and complexity of architectures increases, selective and non-selective depositions of in situ doped film become extremely attractive for the realisation of new devices architectures like, elevated sources/drains in CMOS or extrinsic bases in bipolar. Epitaxial layers were grown in a 200 mm industrial single wafer reactor. Firstly, we investigate the boron incorporation in Si/SiGe non-selective epitaxy based on SiH_4/GeH_4/B_2H_6/H_2 chemistry at low temperature (550-750℃). The influence of temperature and germanium content on the boron incorporation is presented. Sheet conductivity deduced from four probes measurements varied from 1.8 x 10~4 to 1.9 x 10~5 S m~(-1) as deposited. We demonstrate that both the boron incorporation and the film conductivity are improved in SiGe compared to Si, In addition, combining the dose of substitutional boron atoms, deduced from the X-ray diffraction shift, with the resistivity results, we could infer a significant enhancement of the hole mobility in SiGe compared to Si (at least for moderate doping levels around 1 x 10~(20) h/cm~3). In a second part, the high boron-doping of selective Si epitaxy based on SiH_2Cl_2/B_2H_6/HCl/H_2 chemistry at reduced pressure (< 20 Torr) and at low temperature (700-850℃) is examined. Boron incorporation is observed to decrease with increasing HCl flow and the electrical doping level to increase with temperature. We also report a strong increase of the growth rate with the dopant flow (six times higher for B_2H_6/DCS = 0.01) that will be discussed. Epitaxies that are fully selective against Si_3 N_4 have been demonstrated with conductivity as high as 7.8 x 10~4 Sm~(-1).