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Low‐Temperature Selective Growth of Heavily Boron‐Doped Germanium Source/Drain Layers for Advanced pMOS Devices
Author(s) -
Porret Clement,
Vohra Anurag,
Nakazaki Nobuya,
Hikavyy Andriy,
Douhard Bastien,
Meersschaut Johan,
Bogdanowicz Janusz,
Rosseel Erik,
Pourtois Geoffrey,
Langer Robert,
Loo Roger
Publication year - 2020
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201900628
Subject(s) - germanium , materials science , pmos logic , dopant , doping , boron , chemical vapor deposition , electrical resistivity and conductivity , dopant activation , analytical chemistry (journal) , contact resistance , silicon , optoelectronics , nanotechnology , chemistry , transistor , electrical engineering , organic chemistry , voltage , chromatography , layer (electronics) , engineering
The peculiarities of heavily boron‐doped germanium, selectively grown at low temperature by means of a cyclic deposition and etch chemical vapor deposition process, are investigated through the analysis of the structural and electrical material properties. The incorporation of B in Ge can exceed 6 × 10 20 cm −3 , close to a factor 100 above the solubility limit, without any significant degradation of the Ge:B crystalline quality, although high B‐doping induces an unwanted contraction of the Ge lattice. Micro‐Hall effect measurements and the multiring circular transmission line method are used to evaluate the active carrier concentrations and resistivities of Ti/Ge:B contacts. Even though the resistivity of as‐grown layers saturates for chemical B concentrations approaching 1 × 10 21 cm −3 and increases beyond that level, a contact resistivity below 3 × 10 −9 Ω cm 2 is obtained for the highest active doping concentration, showing that a compromise must be found to decrease the total contact resistance. Finally, first principles simulations are used to understand dopant deactivation mechanisms in the Ge:B system. In conclusion, the formation of boron‐interstitial clusters is most likely the cause for electrical performance degradation at high doping values.