Understanding of strain effects on high-field carrier velocity in (100) and (110) CMOSFETs under quasi-ballistic transport

Abstract

We systematically study the strain effects on high-field carrier velocity (v) in (100) and (110) short-channel n/pFETs by means of substrate bending experiment. v and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dsat</inf> increase by strain is determined not only by low-field mobility (μ) enhancement (Δμ/μ) but also by the modulation of saturation velocity (v <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</inf> ). It is found that v <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</inf> increases more by strain in smaller-Δμ/μ devices. The difference of Δμ/μ is compensated by v <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</inf> change. As a result, Δv/v of (100)/(110) n/pFETs converge in sub-30nm regime. The superiority of (110) CMOS to (100) CMOS is maintained in terms of both I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dlin</inf> and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dsat</inf> at highly-strained conditions.