Electrical characterisation of novel silicon MOSFETs and finFETs
Thomas, Stephen Michael (2011) Electrical characterisation of novel silicon MOSFETs and finFETs. PhD thesis, University of Warwick.Full text not available from this repository.
Official URL: http://webcat.warwick.ac.uk/record=b2521744~S15
To enable the advancement of Si based technology, necessary to increase computing
power and the manufacture of more compact circuits, significant changes to the
current planar transistor are a necessity. Novel transistor architectures and materials
are currently being researched vigorously. This thesis, on the electrical
characterisation of non-standard orientated MOSFETs and multi-gate transistors
displays detailed insight into the carrier transport and resulting performance limiting
mechanisms. The results are composed of three parts.
Firstly, the standard method of extracting carrier effective mobility from electrical
measurements on MOSFETs is reviewed and the assumptions implicit in this
method are discussed. A novel technique is suggested that corrects the difference in
drain bias during current-voltage and capacitance-voltage measurements. It is further
shown that the lateral field and diffusion corrections, which are commonly
neglected, in fact cancel each other. The efficacy of the proposed technique is
demonstrated by application to data measured on a quasi-planar SOI finFET at
300 K and 4 K.
The second part is based on the electrical characterisation of n+poly-Si/SiO2/Si nand
p- MOSFETs fabricated on (100) and (110) substrate orientations with the full
range of channel directions. In depth analysis of the electron and hole mobility was
performed at 300 K and 4 K. The 4 K mobilities were modelled in terms of ionised
dopant impurity, local SiO2/Si interface charge and roughness scattering
mechanisms. RMS (root mean squared) roughness values in the range 0.34 − 0.38nm
and correlation lengths of 2.0 − 2.3 nm were extracted revealing comparable
interface quality between the (100) and (110) surfaces.
The third part examines the electrical characterisation of TiN/HfSiO2/Si n- and pfinFETs.
Fin top surface and sidewalls are in the (100) and (110) planes
respectively. Fins have a height of 65 nm with widths in the range of 1872 nm
(quasi-planar) to 12 nm. Detailed analysis revealed vertical compressive strain
induced by the gate into the fin sidewalls, which enhanced the electron mobility by
60% above the (110) reference, whilst leaving the hole mobility unaffected.
Qualitative analysis of the 4 K mobilities suggests that roughness is higher on the
sidewalls than on the top surface. This was attributed to the damage caused by the
dry etch, used to pattern the fins. A model for remote charge scattering at the
HfSiO2/SiO2 interface was developed. 4 K mobilities from the quasi-planar n- and pfinFETs
were then modelled in terms of remote charge, ionised dopant impurity,
local SiO2/Si interface charge and roughness scattering mechanisms. Remote charge
densities of 8x1012 cm-2 were subsequently extracted. Scattering from these charges
was shown to be the dominant scattering mechanism in the quasi-planar n-finFET
mobility at 300 K.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||T Technology > TK Electrical engineering. Electronics Nuclear engineering|
|Library of Congress Subject Headings (LCSH):||Metal oxide semiconductor field-effect transistors -- Electric properties, Transistors -- Electric properties|
|Official Date:||April 2011|
|Institution:||University of Warwick|
|Theses Department:||Department of Physics|
|Supervisor(s)/Advisor:||Whall, Terry ; Leadley, David ; Parker, Evan, Prof.|
|Extent:||xxxi, 212 leaves : ill., charts|
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