Strained-silicon MOSFET process technology-control of impurity and germanium atoms at the hetero-interface

We investigated re-crystallization, the redistribution of arsenic and germanium, and the electrical properties of strained-silicon/Si0.7Ge0.3 heterostructures with implanted arsenic ions. Our aim was to acquire basic information regarding the fabrication of strained-silicon MOSFETs with low-resistance source and drain regions. The strained-silicon layers were completely re-crystallized with rapid thermal annealing at 900 °C or higher. Arsenic diffusivity was identical in strained and unstrained silicon but was higher than both of these in SiGe. Germanium recoil produced by implanting arsenic in the SiGe layer was observed. The solubility limit for arsenic was 2×1020 cm−3 in both strained and unstrained silicon but was lower, 1×1020 cm−3, in Si0.7Ge0.3. Electron mobility was greater in strained silicon than in unstrained silicon by about 20-30% and lower in Si0.7Ge0.3 than in silicon by about 20-30%. A thicker layer of strained silicon is thus desirable for reducing parasitic resistance in the source and drain region.