Investigations of ultra shallow junction ion implanted biaxial tensile strained silicon by means of X-Ray, Raman and photoacoustic techniques
Horan, Ken (2012) Investigations of ultra shallow junction ion implanted biaxial tensile strained silicon by means of X-Ray, Raman and photoacoustic techniques. PhD thesis, Dublin City University.
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The application of strain to the active channel region of the metal-oxide-semiconductor-ﬁeld-eﬀect-transistor (MOSFET) has become a necessary practice in integrated circuit (IC) fabrication. The introduction of strain allows increased carrier mobilities, and concomitant device performance enhancements, which are independent of MOSFET scaling. Biaxial tensile strained silicon ("-Si), resulting from epitaxial growth of silicon on a Si1!xGex virtual substrate gives rise to enhanced electron mobilities and, for certain dopants, increased electrical activation. For these reasons it is the material of interest in this thesis.
The prospects for industrial implementations of "-Si are heavily dependent on the eﬀects of device processing steps, and the controllability of defect and dopant proﬁles. Of special interest to the current work is the suitability of "-Si subjected to low energy antimony implants and low thermal budget rapid thermal anneal (RTA), for the production of ultrashallow, abrupt junctions, appropriate for future generation source-drain extensions (SDE).
Examined in the wider project are the eﬀects of strain on dopant activation and diﬀusion through Diﬀerential Hall and SIMS measurements carried out by project partners. These
measurements provide context for the work herein and demonstrate the desirability of "-Si as a n-MOSFET channel material.
For our part, the eﬀects of implant and anneal processes are investigated through both high resolution x-ray diﬀraction and micro-Raman (µ-Raman) spectroscopy. Synchrotron x-ray topography is used to identify the strain relaxation processes in both the "-Si epilayer and
the Si1!xGex virtual substrate. Data obtained during the project called into question the validity of traditional µ-Raman interpretations in the context of degenerately doped silicon, under these conditions additional theoretical considerations are necessary. The µ-Raman data presented herein demonstrates sensitivities to both implant damage and to dopant activation and these dependencies are
theoretically accouncted for.
Finally, Photoacoustic Spectroscopy is shown to be a technique capable of non-destructive detection of ion implant damage within the top ⇠10 nm of the silicon. These uniquely sensitive measurements araise due to the particular experimental set up used which invoke
a strong dependence on the thermal interface resistance within the sample.
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