AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM+PS-ThM

Paper EM+PS-ThM4
Characterization of Thermal Annealing of Tantalum Pentoxide for High-k Dielectric Applications

Thursday, November 5, 1998, 9:20 am, Room 314/315

Session: Processing of High K Dielectrics for DRAMs
Presenter: R.L. Opila, Bell Laboratories, Lucent Technologies
Authors: R.L. Opila, Bell Laboratories, Lucent Technologies
J.P. Chang, Bell Laboratories, Lucent Technologies
G.B. Alers, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
Tantalum pentoxide is being studied as an alternative high dielectric constant material for storage capacitors or gate dielectrics. Since the oxide layers are thin, even for high dielectric constant materials, interfaces between the tantalum pentoxide and other thin film materials can greatly affect device electrical properties. This paper focuses on analyzing the bulk properties of the Ta@sub 2@O@sub 5@ film and the Ta@sub 2@O@sub 5@/TiN interface to assess a new TiN/Ta@sub 2@O@sub 5@/TiN storage capacitor structure that has lower contact resistance and higher specific capacitance than conventional poly-Si based capacitors. The effect of thermal annealing on the electrical performance of the capacitor will be presented. Angular Resolved X-ray Photoelectron Spectroscopy (ARXPS) has been used to characterize the interfacial composition and stoichiometry of tantalum pentoxide deposited by CVD processes at low temperatures. The amount of carbon incorporated in the film during the CVD process decreases with increasing process temperature. Reduced leakage current has been observed as the concentration of carbon in the film increases. Formation of TiO@sub 2@ was observed at the Ta@sub 2@O@sub 5@/TiN interface at an RTA temperature of 450°C. Significant amounts of titanium suboxides are also observed at the Ta@sub 2@O@sub 5@/TiN interface. The imperfect interface is thought to reduce the specific capacitance and increase leakage currents, perhaps through partial reduction of the Ta@sub 2@O@sub 5@. Correlation between the interface chemical states and the electrical performance will be presented.