Ge1-xSnx stressors for strained-Ge CMOS

In this paper, we propose the fabrication of whole strained Ge complementary metal oxide-semiconductor (CMOS) with Ge1-xSnx materials as stressors to outperform the state-of-the-art uniaxial compressive strained Si CMOS. Ge1-xSnx 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 Ge1-xSnx growth by using either B implantation or in situ Ga doping technique. In the B-implanted Ge1-xSnx formation case, fully strained B-doped Ge1-xSnx 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 Ge1-xSrx, growth. In this case, we can achieve fully strained Ga-doped Ge1-xSnx growth without Sn precipitation and any defect generation. Secondary, we have demonstrated the formation of Ni(Ge1-ySny) layers for metal/semiconductor contact and investigated the crystalline qualities. The formation of polycrystalline Ni(Ge1-ySny) layers on Ge1-xSnx layers with Sn contents ranging from 2.0% to 6.5% after annealing at from 350 degrees C to 550 degrees C can be achieved. Additionally, in the case of the Ni/Ge1-xSnx/Ge sample with a Sn content of 3.5%, an epitaxial Ni-2(Ge1-ySny) layer on a Ge1-xSnx layer was formed. However, the surface roughness due to the agglomeration of Ni(Ge1-xSnx) increases with increasing the Sn content and the annealing temperature. Therefore, a low thermal budget must be required for the formation of Ni(Ge1-xSnx) with high Sn content. (C) 2011 Elsevier Ltd. All rights reserved.