Dependence of channel electric field on device scaling

Abstract

It has been shown previously that the maximum channel electric field E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> in a MOSFET is the most important parameter relating to all hot-electron effects and that E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> can be represented as ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_{DS} - V_{DSAT})/l</tex> , where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</tex> may be regarded as the effective length of the velocity-saturation region. The dependence of l on device geometries and process parameters is investigated in this letter. From both experiment and two-dimensional (2-D) simulation, it is found that E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> has a form of ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_{DS} - V_{DSAT})/ 0.22T\min{ox}\max{1/3}X\min{j}\max{1/2}</tex> . Channel length affects the saturation voltage, thus influencing the maximum channel electric field. The scaling of oxide thickness and junction depth, however, often has even greater effects on channel field. This semiempirical model of E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> agrees with E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> deduced from I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SUB</inf> within about 5 percent; it can predict I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SUB</inf> , which has been empirically correlated with hot-electron degradations.