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Kenneth Myers1 Patrick Lenahan1 Chadwin Young2

1, The Pennsylvania State University, State College, Pennsylvania, United States
2, The University of Texas at Dallas, Richardson, Texas, United States

Multi-gated metal oxide semiconductor field effect transistors (MOSFETs) have recently become important in high-performances CMOS integrated circuits. Multi-gated devices, commonly called FinFETs, have reduced short channel effects, allowing for greater scalability.[1] However, there is little in the literature about the atomic defects at the semiconductor-dielectric interface in FinFETs. In this study, we explore traps at the FinFET Si/dielectric interface with electrically detected magnetic resonance (EDMR). The devices involved in this experiment are on (100) silicon-on-insulator wafers with 90nm Si layers and 125nm buried oxides. The FETs have 1nm SiO2 and 2nm HfSiON/TiN/polySi-capped gate stacks with an effective oxide thickness of about 1.1nm. The body of the devices are lightly doped p-type at 2x1015/cm3. Each FinFET is configured as a gated diode with n+/p-/p+ with a fin length of 500nm, fin height of 80nm, and fin width of 50nm. For a single set of contacts, 500 fins are connected in parallel. Extensive electrical measurements on these devices have been reported by Young et al.[2][3]

In order to increase the defect density and maximize the size of the resonance response, we have irradiated the FinFETs to 1 MRad through exposure to a 60Co gamma source. During irradiation, a bias of +0.25V was applied to the gate contact. Pre irradiated EDMR spectra are weak and poorly resolved whereas quite strong signal to noise spectra appear after the irradiation.

Our EDMR measurements utilized a home-built spectrometer. The X-band (≈9.5 GHz) spectrometer includes a 4-inch Lakeshore electromagnet with a Micro-Now microwave bridge and a TE102 cavity. Spin dependent device current was measured with a Stanford Research Systems Low-Noise Current Preamplifier. The detection utilized a home-built virtual lock-in amplifier. Measurements were conducted at room temperature.

The observed EDMR spectra involve multiple overlapping lines with g values ranging from 2.0011 to 2.0084. Such g values are generally consistent with Pb centers (silicon dangling bonds), however the linewidths of these spectra are significantly broader than those typically observed for Pb center defects.

[1] Wann, C. H., Noda, K., Tanaka, T., Yoshida, M., & Hu, C. (1996). IEEE Transactions on Electron Devices, 43(10), 1742-1753.
[2] Young, C. D., Neugroschel, A., Matthews, K., Smith, C., Heh, D., Park, H., … Bersuker, G. (2010). IEEE Electron Device Letters, 31(7), 653–655.
[3] Young, C. D., Neugroschel, A., Matthews, K., Smith, C., Park, H., Hussain, M. M., … Bersuker, G. (2010). Proceedings of 2010 International Symposium on VLSI Technology, System and Application, VLSI-TSA 2010, 68–69.

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