Ultrashallow TiC Source/Drain Contacts in Diamond MOSFETs Formed by Hydrogenation-Last Approach

Abstract

Applying the hydrogen (H) radical exposure at the last step of MOSFET fabrication process, an oxygen (O)-terminated channel was converted to a H-terminated one to obtain subsurface hole accumulation for field-effect transistor operation. Low-resistive titanium carbide (TiC) source/drain and alumina gate oxide were resistant to the hydrogenation process. The shallow TiC side contacts (~ 3 nm in depth) to the hole accumulation layer (channel) showed good ohmic contacts with a specific contact resistance of 2 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> -7 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> ¿·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . For diamond MOSFETs with the TiC ohmic layer, the saturated maximum drain current and maximum transconductance reached 160 mA/mm and 45 mS/mm, respectively. An <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fT</i> of 6.2 GHz and an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 12.6 GHz were obtained. The hydrogenation-last approach is a nondestructive method for the fabrication of diamond MOSFET with high production yield.