AVS 52nd International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS-WeM

Paper PS-WeM11
Damage-free Ultrathin Oxynitride Films Formed Using Pulse-Time-Modulated Nitrogen Plasma

Wednesday, November 2, 2005, 11:40 am, Room 304

Session: Advanced Gate Stack Fabrication
Presenter: S. Fukuda, Tohoku University, Japan
Authors: S. Fukuda, Tohoku University, Japan
C. Taguchi, Tohoku University, Japan
Y. Kato, Tohoku University, Japan
Y. Ishikawa, Tohoku University, Japan
S. Noda, Tohoku University, Japan
S. Samukawa, Tohoku University, Japan
Correspondent: Click to Email
Ultra thin Si oxynitride (SiO@sub x@N@sub y@) films have been identified as leading candidates to replace conventional SiO@sub 2@ gate dielectrics for present and future ultra large-scale integrated circuits. Remote plasma processes for top surface nitridation of thermally grown oxides have been developed and applied in complementary MOS device applications. However, it is much difficult to control the concentration and position of nitrogen in ultrathin Si oxynitride film by using plasma processing and there are many serious problems, such as plasma radiation damage and increases in interface state density due to N penetrating the SiO@sub 2@-Si interface. To overcome these problems, we have already proposed pulse-time-modulated (TM) plasma nitridation.@footnote 1@ The pulsed nitrogen plasma makes it possible to restrain injection of higher energy particles from plasma into the silicon dioxide film. Then, the concentration and position of nitrogen in ultrathin Si oxynitride film could be controlled by changing the pulse-on time in the TM N@sub 2@ plasma. Additionally, the TM plasma could drastically reduce the UV and VUV photon radiation damages to Si oxynitride film, because of low electron energy during pulse-off time in the TM plasma. As a result, by using the TM plasma nitridation, NBTI characteristics were about 200 % improved at the maximum. TM plasma is very promising candidate as the damage-free nitridation method for SiO@sub 2@ and high-k films. @FootnoteText@ @footnote 1@ S. Samukawa, Y. Minemura, and S. Fukuda, Jpn. J. Appl. Phys. Vol. 42 (2003) pp. L795-L797.