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Measuring The Work Functions Of PVD TaN, TaSiN And TiSiN Films With A Schottky Diode CV Technique For Metal Gate CMOS Applications

Published online by Cambridge University Press:  11 February 2011

James Pan ,
Christy Woo ,
Minh-Van Ngo ,
Bryan Tracy ,
Ercan Adem ,
Stephen Robie ,
Qi Xiang  and
Ming-Ren Lin
James Pan
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
Christy Woo
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
Minh-Van Ngo
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
Bryan Tracy
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
Ercan Adem
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
Stephen Robie
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
Qi Xiang
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
Ming-Ren Lin
Affiliation:
Advanced Micro Devices, Sunnyvale, California 95014, U.S.A.
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Abstract

The metal gate process becomes a promising candidate for sub-65nm CMOS, due to the elimination of polysilicon depletion effects, and the possibility of adjusting the CMOS threshold voltage without more threshold implants. Our goal is to process mteal films with tunable work functions, in order to meet the demand of sub-65nm metal gate CMOS.

PVD TaN films are deposited with various processing conditions. Auger analysis shows that by changing the nitrogen flow rate and the plasma power, the nitrogen content in the TaN films can be adjusted. In order to accurately determine the work function of these TaN materials, we have developed a Schottky Diode CV technique (or Metal-Silicon CV, or MS-CV). This approach not only improves the accuracy of the metal work function measurement, compared with the traditional MOS-CV technique (which is affected by the thickness and quality of the oxide), but also simplifies the fabrication.

With the MS-CV's, we have successfully measured the work functions of Ni and Co, and compared the data with published references. The work function of PVD TaN actually decreases with higher nitrogen content, according to the Auger data and the MS-CV measurement, ranging from 3.42 – 4.20 Volts. The MS-CV technique is shown to be independent to the size of the capacitors, and is little affected by the measurement frequency. By changing the frequency from 100KHz to 1MHz, the error in the work function is less than 50mV.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 745: Symposium N – Novel Materials and Processes for Advanced CMOS , 2002 , N3.2
Copyright
Copyright © Materials Research Society 2003

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References

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