IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Dielectrics Tuesday Sessions
       Session DI-TuA

Paper DI-TuA1
Post-deposition Densification of Yttrium Oxide High Dielectric Constant Insulators Deposited by Oxygen Plasma Assisted Chemical Vapor Deposition

Tuesday, October 30, 2001, 2:00 pm, Room 130

Session: High K Dielectrics III
Presenter: D. Niu, North Carolina State University
Authors: D. Niu, North Carolina State University
R.W. Ashcraft, North Carolina State University
G.N. Parsons, North Carolina State University
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Understanding and controlling interface and bulk chemical stability of CVD high-k dielectrics is an important research issue. Several groups report that the equivalent oxide thickness of vapor deposited dielectrics changes during post-deposition processing, but mechanisms that control the changes are not well understood. We examine the effect of post-deposition annealing on yttrium-based high-k dielectrics formed by oxygen plasma assisted CVD at temperatures between 350 and 450°C. Using yttrium-based materials, our group has previously demonstrated dielectrics with equivalent oxide thickness of 10-12Å with k=14. In this work, depositions were compared on Si(100) using two different yttrium diketonate precursors introduced downstream from a remote oxygen plasma source. Physical film thickness ranged from <40Å to >1000Å, and films were characterized using IR, XPS and IV and CV electrical analysis, before and after annealing at temperatures >900°C. For the thin films, XPS indicates mixing of yttrium and oxygen with silicon at the substrate interface during deposition. Over a wide range of thickness, as deposited Y@sub2@O@sub3@ films show evidence for O-H and C-H bonds in the IR spectra. After annealing at 900°C in N@sub2@ (with >10@super-5@ Torr O@sub2@ pressure), the IR shows almost complete removal of O-H and C-H bonds. The films also show a remarkable decrease in macroscopic thickness (e.g. from 600Å to ~400Å after annealing at 900°C for 10 minutes), which cannot be accounted for simply by film crystallization. After anneal CV analysis shows good behavior, with evidence for positive fixed charge and substrate oxidation. This data suggests that density of as deposited CVD dielectrics is a critical issue, and hydroxyl bonds present in as-deposited films can react at the interface during post-deposition annealing. Approaches to control hydroxide incorporation and improve material stability will be presented and discussed.