Formation of Uniaxially Strained Si/Ge Channels on SiGe Buffers Strain-Controlled with Selective Ion Implantation

Abstract

We fabricate uniaxially strained SiGe channels on SiGe buffer layers containing the uniaxial strain. For introducing the uniaxial strain into SiGe buffer layers, a selective ion implantation technique is developed. Laterally selective ion implantation with a stripe pattern is performed into a Si substrate, followed by SiGe overgrowth in the whole region. Large strain relaxation of SiGe occurs only in the ion-implanted area. This relaxed SiGe provides shear stress to the neighboring strained SiGe in the unimplanted area, leading to the uniaxial strain relaxation. The amount of the uniaxial relaxation strongly depends on the stripe line width, indicating high controllability of the strain states. On the strain-controlled SiGe buffer, the uniaxially strained SiGe channel with the higher Ge concentration is found to be pseudomorphically grown. This result indicates that this technique has a high potential to realize high-mobility Si/Ge channels with uniaxial strain.