AVS 46th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM2-ThA

Paper EM2-ThA8
Film-Formation Mechanisms and Step Coverage of (Ba,Sr)TiO@sub 3@ Films Grown by MOCVD

Thursday, October 28, 1999, 4:20 pm, Room 611

Session: Silicon Carbide and Dielectrics on Si
Presenter: Y. Gao, Pacific Northwest National Laboratory
Authors: Y. Gao, Pacific Northwest National Laboratory
T.T. Tran, Pacific Northwest National Laboratory
S. Thevuthasan, Pacific Northwest National Laboratory
M.H. Engelhard, Pacific Northwest National Laboratory
P. Alluri, Motorola, Inc.
Correspondent: Click to Email
Isotopic labeling experiments (@super 18@O@sub 2@) have been carried out to understand the film-formation reactions in the MOCVD growth of (Ba,Sr)TiO@sub 3@ (BST) thin films using Ba(thd)@sub 2@, Sr(thd)@sub 2@, and Ti(O-iPr)@sub 2@(thd)@sub 2@ as the metalorganic precursors. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals both M@super 18@O and M@super 16@O (M= Ba, Sr, Ti) in the BST films, indicating that the oxygen in the BST films originates from both the gas phase oxidants (@super 18@O), and the precursor ligands (@super 16@O). The amount of @super 18@O and @super 16@O in these films was also determined by nuclear reaction analysis (NRA). The results are in agreement with the TOF-SIMS data. Thus, the isotopic labeling study reveals two film-formation reactions: oxidation and thermal decomposition of the precursor molecules during the MOCVD growth. The results show that about two thirds of M-O bonds in the original precursors are preserved in the BST films grown at 650 °C in O@sub 2@. However, more precursor molecules are oxidized by O@sub 2@ at 590 °C, indicating that the ligand substitution by O@sub 2@ plays an important role in the film-formation at lower temperatures. Use of a 50%@super 18@O@sub 2@-50%N@sub 2@@super 16@O mixture results in a reduction of @super 18@O incorporation in the BST film, indicative direct involvement of N@sub 2@O in the film-formation reactions. Addition of N@sub 2@O in O@sub 2@ also appears to improve film surface morphology and step coverage. The BST films deposited at 650 °C in the 50%O@sub 2@-50%N@sub 2@O mixture exhibit conformal step coverage, excellent crystallinity, and good dielectric properties. The correlation between the film-formation mechanisms, step coverage, crystallinity, and dielectric properties will be discussed in this presentation.