Precipitation and relaxation in strained Si1−yCy/Si heterostructures

Abstract

We have studied the thermal stability of Si1−yCy/Si (y=0.007 and 0.014) heterostructures formed by solid phase epitaxial regrowth of C implanted layers. The loss of substitutional C was monitored over a temperature range of 810–925 °C using Fourier transform infrared absorbance spectroscopy. Concurrent strain measurements were performed using rocking curve x-ray diffraction to correlate strain relaxation with the loss of substitutional C from the lattice. Loss of C from the lattice was initiated immediately without an incubation period, indicative of a low barrier to C clustering. The activation energy as calculated from a time to 50% completion analysis (3.3±5 eV) is near the activation energy for the diffusion of C in Si. Over the entire temperature range studied, annealing to complete loss of substitutional C resulted in the precipitation of C into β-SiC. The precipitates are nearly spherical with diameters of 2–4 nm. These precipitates have the same crystallographic orientation as the Si matrix but the interfaces between the Si and β-SiC precipitates are incoherent. During the initial stages of precipitation, however, C-rich clusters form which maintain coherency with the Si matrix so the biaxial strain in the heterostructure is partially retained.

Strain Loss in Epitaxial Si:C Films Induced by Phosphorus Diffusion

“…After 900 o C, 120s anneal, the effective substitutional carbon concentration in the P-doped Si:C is less than 0.2%. The films remain pseudomorphic for both cases, confirming that theory of strain loss through the loss of substitutional carbon into non-substitutional sites [8,9]. …”

Pulsed Laser Annealing of Silicon-Carbon Source/Drain in MuGFETs for Enhanced Dopant Activation and High Substitutional Carbon Concentration

“…2. Epitaxially grown Si 0.99 C 0.01 sample which had undergone RTA shows a 0.29% decrease in C sub , suggesting deactivation of carbon in Si 1−x C x [16], [17]. Displaced carbon atoms occupy the interstitial sites and do not contribute to the strain in the channel.…”

Chemical vapor deposition of Si:C and Si:C:P films—Evaluation of material quality as a function of C content, carrier gas and doping

“…Smearing of the epi layer peak as seen in the HR XRD spectra indicates epitaxial breakdown. before a C ad atom can cluster with another C ad atom (similar to Guiner Preston zones) giving rise to a defect nucleus [34] or can join an existing Si-C defect nucleus resulting in an increased size of the defect nucleus.…”