Silicon-germanium-based combined MBE and CVD processing for vertical "silicon-on-nothing" (SON) device technology

A combined molecular beam epitaxy (MBE) / chemical vapor deposition (CVD) processing sequence for the fabrication of vertical fully-depleted and partially-depleted "silicon-on-nothing" metal-oxide-semiconductor (MOS) devices is introduced. The key idea is that the transistor channel length as well as depletion width are determined by means of well defined epitaxial deposition in the sub-30nm regime. To obtain the "silicon-on-nothing" (SON) transistor channel a sacrificial layer made from Si1-xGe x and the selective wet-chemical removal of this layer is used. In a first step, this sacrificial layer, grown under biaxial compression by means of MBE, is used for physical channel length definition and to introduce uniaxial strain to the intrinsic silicon channel, grown afterwards by means of CVD. The thickness of the intrinsic Si layer defines the channel depletion width. In a final step the sacrificial Si1-xGex is selectively removed, and the uniaxial strained silicon channel, connecting source and drain, remains free standing.