AVS 47th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuP

Paper TF-TuP23
Investigation of the W-TiN Metal Gate for Metal-Oxide-Semiconductor Devices

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: S. Youn, Sungkyunkwan University, Korea
Authors: S. Youn, Sungkyunkwan University, Korea
K. Roh, Sungkyunkwan University, Korea
S. Yang, Sungkyunkwan University, Korea
Y. Roh, Sungkyunkwan University, Korea
Y.C. Jang, Sungkyunkwan University, Korea
K.S. Kim, Sungkyunkwan University, Korea
N.-E. Lee, Sungkyunkwan University, Korea
Correspondent: Click to Email
Several research groups recently proposed that W-TiN metal gate deposited on thin SiO2 may be suitable for the deep-submicron MOSFETs. Although the previous work demonstrates the promising results, the roles of TiN have not been systematically studied. We present experimental results in the present work that the change of Ar to N2 ratio during the TiN deposition by the reactive sputtering decides the crystallinity of LPCVD W, as well as the electrical properties of the W-TiN/SiO2/Si capacitor. In particular we show that the threshold voltage can be controlled via changing the Ar to N2 ratio. MOS capacitors were fabricated on 4~7@ohm@-cm, (100) p-type Si wafers. Thermal oxidation of the Si was carried out at 850°C for 80 s using RTP, resulting in an oxide thickness of ~110Å. TiN thin films were then deposited directly on SiO2 by a reactive sputtering system. The Ar/N2 flow was changed from 1/6 to 6/6 sccm. RTP was used for the annealing of TiN at 600-800°C for 3 min. Then LPCVD W films were deposited on TiN; the temperature, pressure, and flow rate were 350°C, 0.7 Torr, and WF6/SiH4/H2=5/10/500 sccm, respectively. The LPCVD W/SiO2/Si MOS capacitor was also fabricated to investigate the roles of TiN. As compared to the results obtained from the LPCVD W/SiO2/Si MOS capacitor, the insertion of approximately 20 nm TiN film effectively prohibits the fluorine diffusion during the deposition and annealing of W films, resulting in negligible leakage currents at the low electric fields. In addition, XRD analysis indicated that the preferred orientations of TiN and W films were determined by the change of Ar to N2 ratio. For example, if the ratio of Ar/N2 flow increases, a strong W(211) peak was developed and the resistivity of CVD W-TiN gate slightly decreases. In addition, the flatband voltage of MOS capacitors was shifted to the positive gate voltage when the ratio of Ar/N2 flow increases. We interpreted that this positive shift may be caused by the work-function difference that is caused by the incorporation of N2 during the sputtering process.