Selective epitaxial Si/SiGe growth forV_Tshift adjustment in highkpMOS devices

Abstract

Downscaling of classical metal oxide semiconductor (MOS) devices resulted in a need to replace the gate oxide by high k dielectrics to keep the gate leakage under control. However, new device issues such as an uncontrollable shift in the threshold voltage in p-type MOS devices and a reduction in channel mobility were encountered. These issues can be overcome by the implementation of buried strained SiGe channels, grown by selective epitaxial growth, as demonstrated in this paper. The optimized high k gate fabrication scheme starts with the growth of a very thin oxide layer. Therefore, a Si cap layer is required because oxidation of SiGe leads to defects at the gate/channel interface. The Si growth rate is influenced by the underlying SiGe layer, during the deposition of the first atomic layers. Nevertheless, accurate thickness control of the Si cap is possible. The minimal required Si cap thickness and its dependence on Ge content in the underlying SiGe channel, for making high-quality dielectrics and maintaining low capacitive equivalent thickness, is extracted from charge pumping measurements, CV measurements and energy dispersive x-ray spectroscopy measurements. Device results demonstrate the successful implementation of buried SiGe channels in pMOS devices with high k gate dielectrics.

Ion yields and erosion rates for Si1−xGex(≤x≤1) ultralow energy O2+ secondary ion mass spectrometry in the energy range of 0.25–1 keV

“…This level of accuracy is certainly comparable with alternative analytical techniques such as energy dispersive x ray and Auger electron spectroscopy ͑Ϯ2 at. %͒, 21,22 while high resolution Rutherford backscattering and HRXRD offer Ϯ1 at. %.…”

Low temperature Si homo-epitaxy by reduced pressure chemical vapor deposition using dichlorosilane, silane and trisilane

“…Low thermal budget silicon (Si) growth is a main challenge in future CMOS technologies involving germanium [1] or buried strained SiGe [2,3] high mobility channels. Si cap on germanium or on strained SiGe layers, for passivation purpose, indeed require low temperature to avoid Ge up-diffusion [4] or SiGe strain relaxation, respectively [5].…”

Editors' Choice—Epitaxial CVD Growth of Ultra-Thin Si Passivation Layers on Strained Ge Fin Structures

“…The Si growth rate can also be affected by catalytic effects correlated with the composition of the underlying layer, especially during the initial stage of the growth. 25 In the initial stage of the Si growth, the growing surface changes from Ge (or SiGe) to SiGe with decreasing Ge content. The desorption rate of reaction by-products varies in function of the composition of the growing surface as the Si-H bound is stronger than the Ge-H bound.…”