Tri-layer heterostructures for improved PMOS enhancements preserved over a large processing temperature range

Saurabh Gupta, Minjoo L. Lee, Gianni Taraschi, Arthur Pitera, Eugene A. Fitzgerald

Research output: Contribution to conferencePaperpeer-review

Abstract

The impressive hole mobility enhancements obtained on dual channel heterostructures are very dependent on the Ge concentration of the compressively strained Si 1-yGe y layer and the relaxed Si 1-xGe x layer. Out-diffusion of Ge from the compressively strained Si 1-yGe y layer into the relaxed Si 1-xGe x layer and the top Si cap reduces the Ge concentration in the compressively strained layer. The diffusion coefficient for Ge interdiffusion in SiGe single crystals increases exponentially with increasing Ge concentration. The highest mobility dual channel heterostructures, which have highest Ge concentrations, are thus most prone to this out-diffusion. We present a thermally stable tri-layer heterostructure, in which a tensilely strained Si layer is present below the compressively strained Si 1-yGe y layer, which in turn is capped by a tensilely strained Si layer for SiO 2 compatibility. The underlying strained Si layer helps in reducing the Ge out-diffusion from the compressively strained layer during the high temperature processing steps. An abrupt profile between ε-Si 1-yGe y and the bottom Si is also maintained after the thermal processing which helps to maintain the valence band offset preventing the hole wavefunction from tunneling into the low mobility relaxed Si 1-xGe x layer. Better confinement of the hole wavefunction in the high mobility compressively strained Si 1-y/ Ge y, layer appears to be beneficial for the hole mobility.

Original languageEnglish (US)
Pages351-362
Number of pages12
StatePublished - Dec 1 2004
Externally publishedYes
EventSiGe: Materials, Processing, and Devices - Proceedings of the First Symposium - Honolulu, HI, United States
Duration: Oct 3 2004Oct 8 2004

Other

OtherSiGe: Materials, Processing, and Devices - Proceedings of the First Symposium
CountryUnited States
CityHonolulu, HI
Period10/3/0410/8/04

ASJC Scopus subject areas

  • Engineering(all)

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