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Mechanism for improvement of n-channel metal-oxide-semiconductor transistors by tensile stress.
- Source :
- Journal of Applied Physics; Aug2010, Vol. 108 Issue 3, p034506, 12p, 2 Diagrams, 11 Graphs
- Publication Year :
- 2010
-
Abstract
- This paper investigates the physics behind the overall on-current (I<subscript>on</subscript>) improvement of n-channel metal-oxide-semiconductor (NMOS) transistors by uniaxial tensile stress. The strain-induced change in subthreshold off-current (I<subscript>off</subscript>) is related to the following strain-induced effects: (i) mobility enhancement, (ii) reduction in the saturation threshold voltage (V<subscript>th,sat</subscript>), and (iii) improvement in subthreshold swing (S<subscript>ts</subscript>). By selecting transistors whose I<subscript>off</subscript> is less sensitive to the statistical variation in gate length, we studied the effects of process-induced tensile stress on I<subscript>on</subscript> and I<subscript>off</subscript> of NMOS transistors. We found that both externally applied tensile stress and process-induced tensile stress led to a bigger percentage increase in subthreshold I<subscript>off</subscript> compared to the percentage increase in I<subscript>on</subscript>. Our explanation is that the increase in I<subscript>off</subscript> is mainly due to an increase in mobility and a decrease in V<subscript>th,sat</subscript> by tensile stress. The improvement of subthreshold swing by tensile stress can lead to a decrease in subthreshold I<subscript>off</subscript>; for the time being, this seems to be a relatively minor effect. Since the subthreshold I<subscript>off</subscript> is more sensitive to change in V<subscript>th,sat</subscript> than I<subscript>on</subscript>, the increase in subthreshold I<subscript>off</subscript> can be removed by a slight adjustment in V<subscript>th,sat</subscript> without too much effect on I<subscript>on</subscript> such that tensile stress can bring about an overall I<subscript>on</subscript> improvement in NMOS transistors despite increase in both I<subscript>on</subscript> and I<subscript>off</subscript> by tensile stress. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00218979
- Volume :
- 108
- Issue :
- 3
- Database :
- Complementary Index
- Journal :
- Journal of Applied Physics
- Publication Type :
- Academic Journal
- Accession number :
- 52929526
- Full Text :
- https://doi.org/10.1063/1.3447843