Impact of SOI thickness fluctuation on threshold voltage variation in ultra-thin body SOI MOSFETs

Threshold voltage variation due to quantum confinement effect in ultra-thin body silicon-on-insulator (SOI) MOSFETs is examined. It is experimentally demonstrated that threshold voltage variation drastically increases when SOI layer is thinned down to 3 nm. A percolation model is used to estimate the contribution of surface roughness to V/sub th/ variation. The method to suppress the threshold voltage variation is also proposed, and around 15% reduction in threshold voltage variation is experimentally demonstrated by applying substrate bias. The reason of the suppression can be explained by quantum confinement effect induced by substrate bias.

[1]  L. Selmi,et al.  Low field mobility of ultra-thin SOI N- and P-MOSFETs: Measurements and implications on the performance of ultra-short MOSFETs , 2000, International Electron Devices Meeting 2000. Technical Digest. IEDM (Cat. No.00CH37138).

[2]  H. Lifka,et al.  Influence of high substrate doping levels on the threshold voltage and the mobility of deep-submicrometer MOSFETs , 1992 .

[3]  S. Horiguchi,et al.  Quantum-mechanical effects on the threshold voltage of ultrathin-SOI nMOSFETs , 1993, IEEE Electron Device Letters.

[4]  M. Ieong,et al.  Examination of hole mobility in ultra-thin body SOI MOSFETs , 2002, Digest. International Electron Devices Meeting,.

[5]  A. Toriumi,et al.  Subband structure engineering for performance enhancement of Si MOSFETs , 1997, International Electron Devices Meeting. IEDM Technical Digest.

[6]  P. Solomon,et al.  Six-band k⋅p calculation of the hole mobility in silicon inversion layers: Dependence on surface orientation, strain, and silicon thickness , 2003 .

[7]  A. Toriumi,et al.  Experimental study of threshold voltage fluctuation due to statistical variation of channel dopant number in MOSFET's , 1994 .

[8]  Shinichi Takagi,et al.  Characterization of inversion-layer capacitance of holes in Si MOSFET's , 1999 .

[9]  T. Hiramoto,et al.  Impact of quantum mechanical effects on design of nano-scale narrow channel n- and p-type MOSFETs , 2001, International Electron Devices Meeting. Technical Digest (Cat. No.01CH37224).

[10]  Toshiro Hiramoto,et al.  Enhancement of adjustable threshold voltage range by substrate bias due to quantum confinement in ultrathin body SOI pMOSFETs , 2003 .

[11]  T. Numata,et al.  Experimental study on carrier transport mechanism in ultrathin-body SOI nand p-MOSFETs with SOI thickness less than 5 nm , 2002, Digest. International Electron Devices Meeting,.

[12]  Anil Kumar,et al.  Analytical model of body factor in short channel bulk MOSFETs for low voltage applications , 2004 .

[13]  Andrew R. Brown,et al.  Increase in the random dopant induced threshold fluctuations and lowering in sub-100 nm MOSFETs due to quantum effects: a 3-D density-gradient simulation study , 2001 .