Performance impact of post-regrowth channel etching on InGaAs MOSFETs having MOCVD source-drain regrowth

Andrew D Carter,A C Gossard,B J Thibeault,C.-Y Huang,S Lee,D C Elias,S Stemmer,V Chobpattana,J J M Law,M J W Rodwell,W J Mitchell

doi:10.1109/drc.2013.6633776

Abstract

Given low interface trap densities and low access resistances, InGaAs MOSFETs can provide greater on-state current than silicon MOSFETs at the same effective oxide thickness (EOT), and are thus strong candidates for use in VLSI. 1 Transconductance as high as 2.1 mS/μm (V ds =0.5 V) with 115 mV/decade (V ds =0.5 V) subthreshold swing has been reported 2 in planar III-V MOSFETs using a gate recess etch through the N+ InGaAs contact layer. It remains to be established whether the necessary etch depth control can be obtained at VLSI integration scales and 10-20 nm gate lengths. Using self-aligned regrowth of the N+ source and drain, III-V MOSFETs can be fabricated without requiring this gate recess etch; 3 1.9 mS/μm (V d =1 V) with 116 mV/decade (V ds =0.05 V) subthreshold swing was reported in a 55 nm L g InGaAs MOSFET with MOCVD source-drain regrowth. 4 Note that no post-regrowth etching of the channel surface is reported in (4). We have recently found 5 that InGaAs MOSFETs using MBE source-drain regrowth, subthreshold swing and transconductance are substantially improved by removing a 5 nm N+ InGaAs channel cap post-regrowth and immediately prior to gate dielectric deposition, suggesting damage to the channel surface during regrowth. Here, we report similar findings for MOCVD regrowth. We fabricated 65 nm L g In 0 . 53 Ga 0.47 As surface-channel MOSFETs in a gate-last process with self-aligned raised InGaAs S/D access regions formed by MOCVD regrowth. Removal of ~ 2.4 nm of the channel surface by digital etching improved the transconductance from 1.1 to 1.58 mS/μm (65 nm L g V d =0.5 V), and reduced the subthreshold swing from 326 to 110 mV/dec (1 μm L g , V ds =0.05 V). These results suggest that substantial surface damage arises, and must be addressed, in MOCVD regrowth III-V MOSFET processes.

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