Effect of thin Si insertion at metal gate/high- k interface on electrical characteristics of MOS device with La 2O 3
The effect of a thin Si layer insertion at W/La2O3 interface on the electrical characteristics of MOS capacitors and transistors is investigated. A suppression in the EOT increase can be obtained with Si insertion, indicating the inhibition of diffusion of oxygen atoms into La2O3 layer by forming an amorphous La-silicate layer at the W/La2O3 interface. In addition, positive shifts in Vfb and Vth caused by Si insertion implies the formation of amorphous La-silicate layer at the top of La2O3 dielectrics reduces the positive fixed charges induced by the metal electrode. Consequently, a large improvement in mobility has been confirmed for both at peak value and at high Eeff of 1MV/cm with Si inserted nFETs. Although a degradation trend on EOT scaling has been observed, the insertion of thin Si layer is effective in pushing the scaling limit.