| Type of Document |
Dissertation |
| Author |
Mo, Hongxiang , |
| Author's Email Address |
hmo@ncsu.edu |
| URN |
etd-12182003-143823 |
| Title |
FORMATION OF LOW-RESISTIVITY GERMANOSILICIDE CONTACTS TO PHOSPHORUS DOPED SILICON-GERMANIUM ALLOY SOURCE/DRAIN JUNCTIONS FOR NANOSCALE CMOS |
| Degree |
PhD |
| Graduate Program |
Electrical Engineering |
| Advisory Committee |
| Advisor Name |
Title |
| Mehmet Ozturk |
Committee Chair |
| Douglas Barlage |
Committee Member |
| Gregory Parsons |
Committee Member |
| Veena Misra |
Committee Member |
|
| Keywords |
- SiGe
- germanosilicide
- contact reistance
- silicide
- silicon germanium
- MOSFET
- source drain
|
| Date of Defense |
2003-12-15 |
| Availability |
unrestricted |
Abstract
Conventional source/drain junction and contact formation processes can not meet the stringent requirements of future nanoscale complimentary metal oxide silicon (CMOS) technologies. The selective Si1-xGex source/drain technology was proposed in this laboratory as an alternative to conventional junction and contact schemes. The technology is based on selective chemical vapor deposition of in-situ boron or phosphorus doped Si1-xGex in source/drain areas. The fact that the dopant atoms occupy substitutional sites during growth make the high temperature activation anneals unnecessary virtually eliminating dopant diffusion to yield abrupt doping profiles. Furthermore, the smaller band gap of Si1-xGex results in a smaller Schottky barrier height, which can translate into significant reductions in contact resistivity due to the exponential dependence of contact resistivity on barrier height. This study is focused on formation of self-aligned germanosilicide contacts to phosphorous-doped Si1-xGex alloys. The experimental results obtained in this study indicate that self-aligned nickel germanosilicide (NiSi1-xGex) contacts can be formed on Si1-xGex layers at temperatures as low as 350¢XC. Contacts can yield a contact resistivity of 1E-8 ohm-cm2 with no sign of germanosilicide induced leakage. However, above a threshold temperature determined by the Ge concentration in the alloy, the NiSi1-xGex/Si1-xGex interface begins to roughen, which affects the junction leakage. For phosphorus doped layers considered in this study, the threshold temperature was around 500¢XC, which is roughly 100¢XC higher than the threshold temperature for NiSi1-xGex contacts formed on boron doped Si1-xGex layers with a Ge percentage of ~ 50%. Nickel and zirconium germanosilicides were also considered as contact candidates but they were found to result in a contact resistivity near 1E-7 ohm-cm2.
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