Ge1−Sn stressors for strained-Ge CMOS

In this paper, we propose the fabrication of whole strained Ge complementary metal–oxide-semiconductor (CMOS) with Ge 1− x Sn x materials as stressors to outperform the state-of-the-art uniaxial compressive strained Si CMOS. Ge 1− x Sn x materials have larger lattice constant than that of Ge, which can apply the strain into Ge channel region. Firstly, we have demonstrated p-type doped Ge 1− x Sn x growth by using either B implantation or in situ Ga doping technique. In the B-implanted Ge 1− x Sn x formation case, fully strained B-doped Ge 1− x Sn x layers with no Sn precipitation can be obtained even after solid phase epitaxial regrowth (SPER). However, the serious dislocation generation in the layer was occurred during SPER. This is caused by the point defects introduced by B implantation. In order to avoid this crystal damage, we have also demonstrated in situ Ga-doped Ge 1− x Sn x growth. In this case, we can achieve fully strained Ga-doped Ge 1− x Sn x growth without Sn precipitation and any defect generation. Secondary, we have demonstrated the formation of Ni(Ge 1− y Sn y ) layers for metal/semiconductor contact and investigated the crystalline qualities. The formation of polycrystalline Ni(Ge 1− y Sn y ) layers on Ge 1− x Sn x layers with Sn contents ranging from 2.0% to 6.5% after annealing at from 350 °C to 550 °C can be achieved. Additionally, in the case of the Ni/Ge 1− x Sn x /Ge sample with a Sn content of 3.5%, an epitaxial Ni 2 (Ge 1− y Sn y ) layer on a Ge 1− x Sn x layer was formed. However, the surface roughness due to the agglomeration of Ni(Ge 1− x Sn x ) increases with increasing the Sn content and the annealing temperature. Therefore, a low thermal budget must be required for the formation of Ni(Ge 1− x Sn x ) with high Sn content.