An ultra-thin oxide sub-1 Ⅴ CMOS bandgap voltage reference

摘要

This paper presents a sub-1 Ⅴ CMOS bandgap voltage reference that accounts for the presence of direct tunneling-induced gate current. This current increases exponentially with decreasing oxide thickness and is especially prevalent in traditional (non-high-κ∕metal gate) ultra-thin oxide CMOS technologies (t_(ox)＜3 nm), where it invalidates the simplifying design assumption of infinite gate resistance. The developed reference (average temperature coefficient, T_(C_AVG), of 22.5 ppm∕℃) overcomes direct tunneling by employing circuit techniques that minimize, balance, and cancel its effects. It is compared to a thick-oxide voltage reference (T_(C_AVG)= 14.0 ppm∕℃) as a means of demonstrating that ultra-thin oxide MOSFETs can achieve performance similar to that of more expensive thick(er) oxide MOSFETs and that they can be used to design the analog component of a mixed-signal system. The reference was investigated in a 65 nm CMOS technology with a nominal V_(DD) of 1 Ⅴ and a physical oxide thickness of 1.25 nm.