Electrical Characterization of nMOSFETs from a 180 nm Commercial Technology at Low Temperatures

This article aims to present experimental results of nMOSFETs from a 180 nm commercial CMOS technology, with different channel lengths, operating at temperatures ranging from 80 K to 300 K. The source-drain resistance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{R}_{\mathbf{SD}})$</tex>, threshold voltage <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{V}_{\mathbf{TH}})$</tex>, subthreshold slope (SS), low-field mobility <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\boldsymbol{\mu}_{\mathbf{0}})$</tex>, and the linear <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\boldsymbol{\theta}_{\mathbf{1}})$</tex> and quadratic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\boldsymbol{\theta}_{\mathbf{2}})$</tex> mobility degradation factors were extracted. The extraction of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{R}_{\mathbf{SD}}$</tex> yielded an average value of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{61.90} \pm \mathbf{3.83}\ \mathbf{\Omega}$</tex> all devices and temperatures. Comparing all the devices, as the temperature decreased, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{V}_{\mathbf{TH}}$</tex> showed an increase in its value between 22.3 % and 33.9 %; SS showed a decrease between 59.7 % and 62.1 % of its value; <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\mu}_{\mathbf{0}}$</tex> increased 162.4 % for the shorter device and 243.2 % for the longer device; <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\theta}_{\mathbf{1}}$</tex> varied less for longer devices; and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\theta}_{\mathbf{2}}$</tex> showed more variations in its values, being less intense in shorter devices. Analyzing the channel shortening, the rate of change <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{dV}_{\mathbf{TH}}/\mathbf{dT}$</tex> showed, in magnitude, a decrease from 0.696 mV/K to 0.561 mV/K, the rate of change dSS/dT showed an increase from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0.197}\ \mathbf{mV} /(\mathbf{dec} \cdot \mathbf{~K})$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0.223}\ \mathbf{mV}/(\mathbf{dec}\cdot \mathbf{K})$</tex>, and the ZTC was from 0.67 V to 0.77 V.