Fourier-transform infrared investigations of Si1−yCy structures for hetero bipolar transistor applications

With the rapid proliferation of commercial SiGe hetero bipolar transistor (HBT) devices, incompatibilities with mainstream integration technologies become an important issue. A common problem in device processing is transient enhanced diffusion of boron out of the base region due to poly-emitter implantation and annealing. It has been shown that co-doping of the base with C can suppress the diffusion of B, but it is accompanied by strong C diffusion. By a combination of Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction and SIMS studies, we investigated in which form C is present in MBE grown Si1−yCy layers and in SiGe:C:B HBTs with implanted poly-Si emitter. With the FTIR technique we are sensitive to substitutional C, coherent and incoherent SiC precipitates and some C-containing complexes. With these techniques we studied the time-scale on which the metastable C-containing layer relax by SiC formation.