AVS 49th International Symposium
    Dielectrics Thursday Sessions
       Session DI+EL-ThM

Paper DI+EL-ThM5
Pulsed Plasma Enhanced MOCVD of High k Y@sub2@O@sub3@ Layers for Gate Dielectric Applications

Thursday, November 7, 2002, 9:40 am, Room C-107

Session: Issues for Gate Dielectrics
Presenter: C. Durand, CNRS/LTM, France
Authors: C. Durand, CNRS/LTM, France
B. Pelissier, CNRS/LTM, France
C. Vallee, CNRS/LTM, France
M. Bonvalot, CNRS/LTM, France
L. Vallier, CNRS/LTM, France
O. Joubert, CNRS/LTM, France
C. Dubourdieu, CNRS/LMGP, France
Correspondent: Click to Email
CMOS transistor scaling is rapidly reaching its limits with traditional SiO@sub2@ gate oxide due to increasing tunneling currents. Rare earth oxides, as high k materials to replace SiO@sub2@, have shown promising results. Here, we focus on the elaboration of Y@sub2@O@sub3@ thin films by an innovative technique, namely pulsed injection Plasma Enhanced Metal Organic Chemical Vapor Deposition (PE-MOCVD). In this technique, dissolved Y(thd)@sub3@ precursors are sequentially injected into an evaporator, which allows perfect reproducibility of the amount of precursors delivered to the plasma chamber and then onto the SiO@sub2@ (8 @Ao@)/Si substrate heated at 350@degree@C. An Ar/O@sub2@ plasma is applied to favor precursor decomposition and surface reactivity. Preliminary experiments have shown that no Y@sub2@O@sub3@ film is deposited on substrates heated at 350@degree@C by pulsed MOCVD only, whereas stoichiometric layers (typ. 5 nm thick) are obtained with the plasma. The plasma induces a lower deposition temperature compared to MOCVD. Based on X-rays Photoelectron Spectroscopy (XPS) and infrared spectroscopy studies of the initial stages of the thin film formation, it seems that metallic yttrium atoms react with SiO@sub2@ to form silicate compounds. The thickness of the initial SiO@sub2@ layer gradually changes leading to silicate layer formation. The SiO@sub2@ underlayer can be fully consumed. Y@sub2@Osub3@ thin films have been annealed at a temperature of 600@degree@C under several atmospheres. Subsequent XPS analyses indicate that carbon contamination can be reduced by half, independent of the annealing atmosphere Ar or O@sub2@, thereby suggesting densification of the layer. Further experiments are under way to determine optimum annealing conditions leading to fully oxidized Y@sub2@O@sub3@ layers without carbon atoms. Simultaneously, the behavior of the silicate interface during this annealing treatment will be carefully analyzed.