Structural and electrical characterisation of ion-implanted strained silicon
Horan, Ken and Lankinen, Aapo and O'Reilly, Lisa and Bennett, N.S. and McNally, Patrick J. and Sealy, B.J. and Cowern, N.E.B. and Tuomi, T. (2008) Structural and electrical characterisation of ion-implanted strained silicon. Materials Science and Engineering: B, 154-155 . pp. 118-121. ISSN 0921-5107
Full text available as:
The production of low resistance ultra-shallow junctions for e.g. source/drain extensions using low energy ion-implantation will be required for future CMOS devices . This architecture will require implants which demonstrate high electrical activation and nm range depth profiles. We investigate the properties of Sb implants in tensile strained silicon due to their potential to satisfy these criteria, and the carrier mobility enhancements associated with tensile strained silicon. Low energy (in this case 2 keV)implants coupled with Sb’s large atomic radius are capable of providing ~ 10 nm implant depths. In addition to this, Sb, in the presence of tensile strain demonstrates higher electrical activation when compared with the more traditional n-type dopant As .
We now report on the initial results of an ongoing systematic study over a wide silicon tensile strain range (from 0.4 to 1.25 % strain) in order to establish clear strain-related trends. Graded Si1-xGex virtual substrates (VS) with are used as template substrates, upon which tensile strained Si layers are grown. Prior to implantation the 0.1 ≤ x ≤ 0.3 quality of the strained layer and SiGe buffer is assessed using UV micro-Raman spectroscopy (μRS), synchrotron x-ray topography (SXRT) and high resolution x-ray diffraction (HR-XRD). For measurements of strain following implantation, HR-XRD is found to be more useful than μRS due to additional carrier-concentration induced Si
Raman peak shifts in the Raman spectra , these obscure small changes in the strain state, and result from the degenerate doping levels achieved in these samples (~7x1020 cm-3).
Using x-ray techniques, we find clear evidence of tilt in the SiGe VS at Ge concentrations > 23% (i.e. ε > 0.9 %), this tilt impacts on the quality of the strained Si. In
addition to this, stacking faults have been detected non-destructively in the higher strain samples (ε = 1.25%, VS = Si0.7Ge0.3) using SXRT in transmission mode.
Archive Staff Only: edit this record