AVS 49th International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS-WeA

Paper AS-WeA8
A Study of the Microstructure and Electrical Properties of the Reoxidized HfO@sub 2@ upon Annealing Methods

Wednesday, November 6, 2002, 4:20 pm, Room C-106

Session: High-k Dielectric Characterization
Presenter: D. Lee, Yonsei University, Korea
Authors: D. Lee, Yonsei University, Korea
H.-E. Seo, Yonsei University, Korea
D.-H. Ko, Yonsei University, Korea
M.-H. Cho, Yonsei University, Korea
C.-W. Yang, Sungkyunkwan University, Korea
Correspondent: Click to Email
Hafnium oxide has been known as gate dielectric material to replace SiO@sub 2@ in MOS devices. First of all, for preparation of reoxidized HfO@sub 2@, Hf films were deposited on p-type Si(100) substrate by DC magnetron sputtering system. Next, Hf films were reoxidized by RTA(Rapid Thermal Annealing) and vertical furnace. They were analyzed by AFM, XRD, XPS, AES and HR-TEM. For ~50nm thick as-deposited Hf film, the HfO@sub 2@ layer was observed about ~5nm at the surface by HR-TEM. The HfO@sub 2@ layer increased to be ~15nm at 600°C in N@sub 2@ ambient. Especially, HfO@sub 2@ grains were shown not only at the surface of the Hf film but also at the silicide(Hf@sub 5@Si@sub 4@) grain boundaries. These grains of silicides on the Si substrate were not observed at the sample that annealed at 800°C for 30min in N@sub 2@ ambient, due to decompositing into HfO@sub 2@ and Si. And then the Si reacted with the oxygen that diffused from surface and accumulated on the interface of Si-substrate. For ~10nm thick as-deposited Hf films, it was observed that the HfO@sub 2@ films locally crystallized in the whole films and the interfacial layer between HfO@sub 2@ and Si substrate was about 8Å. After annealing by furnace as increasing anneal time and temperature in N@sub 2@ or O@sub 2@ ambient, also, the thickness of interfacial layer was increased to that of as-deposited film. As a result of measuring C-V and I-V, it was calculated that the value of CET was 51.5Å at -3V and dielectric constant was about 15.5 at 800°C for 5min in N@sub 2@ ambient. The leakage current of HfO@sub 2@ film decreased as the anneal temperature increased or time increased at constant temperature.