High k Gate Insulator

The various electrical and material properties of dielectrics are even more important along with the progress of our process technology. When thickness of oxide becomes very thin, carriers which can only be accelerated by electric field in inversion are no longer confined by the insulator and they will easily penetrate through the insulator to form a large number of leakage currents. The goal to low power consumption couldn’t be achieved and those devices are barely adopted. In this thesis, the alternative high-k dielectrics made by atomic layer chemical vapor deposition are used to instead of silicon dioxide. Therefore, the probability of carries directly penetrating through the insulator will be reduced with thick high-k film, and then charges can be kept in surfaces.
The residual water was left in those deposited films and defects within insulators were formed due to overall chlorine during the process of atomic layer deposition. The problems could be eliminated by rapid thermal annealing after the deposition in order to enhance the good electrical characteristics of those films. According to the photography from transmission electron microscopy, we find that the intentionally grown chemical oxide became thicker after high temperature and long time annealing. It shown that the residual oxygen in the chamber penetrated through the high-k film and reacted with silicon to form silicon dioxide. The best we can do so far is to deposit high-k film with EOT below 1.5nm.
However, all the high-k films were all crystallized after annealing at 600OC. This resulted in the increase of leakage currents.
On the other hand, the interface trap charges with high-k dielectrics are larger than those with silicon dioxide. We will do our best to solve these problems.