Received 4 July 2016; revised 12 August 2016; accepted 17 August 2016. Date of publication 20 September 2016; date of current version 24 October 2016. The review of this paper was arranged by Editor C. C. McAndrew. Digital Object Identifier 10.1109/JEDS.2016.2603181 Characterization of RF Noise in UTBB FD-SOI MOSFET PRAGYA KUSHWAHA 1 (Student Member, IEEE), AVIRUP DASGUPTA 1 (Graduate Student Member, IEEE), YOGENDRA SAHU 1 , SOURABH KHANDELWAL 2 , CHENMING HU 2 (Fellow, IEEE), AND YOGESH SINGH CHAUHAN 1 (Senior Member, IEEE) 1 Department of Electrical Engineering, IIT Kanpur, Kanpur 208016, India 2 Department of Electrical Engineering and Computer Science, University of California at Berkeley, Berkeley, CA 94720, USA CORRESPONDING AUTHOR: P. KUSHWAHA (e-mail: kpragya@iitk.ac.in) This work was supported in part by the Semiconductor Research Corporation, in part by the Berkeley Device Modeling Center, in part by the Science & Engineering Research Board, and in part by the Ramanujan Fellowship Research Grant. ABSTRACT In this paper, we report the noise measurements in the RF frequency range for ultrathin body and thin buried oxide fully depleted silicon on insulator (FD-SOI) transistors. We analyze the impact of back and front gate biases on the various noise parameters; along with discussions on the secondary effects in FD-SOI transistors which contribute to the thermal noise. Using calibrated TCAD simulations, we show that the noise figure changes with the substrate doping and buried oxide thickness. INDEX TERMS Thermal noise, high frequency noise, device modeling, RF, FDSOI, MOSFET, electrical characterization. I. INTRODUCTION Ultra-thin body fully depleted (FD) silicon on insulator (SOI) transistors are being used at 28 nm and below due to their excellent electrostatic control [1]–[9]. Apart from digital applications, FD-SOI transistors are also getting a strong interest from RF circuit designers for high frequency appli- cations [10], [11]. At RF frequencies, thermal noise becomes an important factor in design of circuits as it decides the noise floor for the signal. It is well known that thermal noise is a function of the temperature and the conductivity of the channel. FD-SOI transistors have higher thermal noise compared to bulk transistors due to high lattice temperature originating from poor thermal conductivity of the buried oxide (BOX) [12]. Hence, careful analysis and measurements of thermal noise in such devices is of utmost importance. Although RF noise characterization for thick BOX FD-SOI transistors has been presented [13]–[15]; there is no work reporting the same for thin BOX FDSOI transistors. In this work, we report the measured data for an FD-SOI transistor with 8 nm thin channel and 25 nm thin BOX, and discuss the impact of the drain and the front/back gate biases on the high frequency noise. Fig. 1 shows the UTBB FD-SOI structure used in this study. The dependence of noise on the back gate bias is especially important as the back gate bias is often used to tune the threshold voltage (V th ) in these devices. Also, the substrate below the thin BOX plays an important role at RF frequencies and shows significant impact on the thermal noise. Hence, we also present an analysis of the impact of substrate resistivity and BOX thickness on the thermal noise. This paper is organized as follows: the measurement setup is described in Section II while the thermal noise and related parameters are defined and discussed in Section III. The sec- ondary effects inherent with FDSOI transistors are discussed in Section IV and the results are presented in Section V. Finally, the conclusions are drawn in Section VI. II. MEASUREMENT SETUP Fig. 2 shows the noise measurement setup used in this work. It includes a vector network analyzer, a noise figure meter (NFM) to measure noise power, a source-pull tuner to vary the impedance seen by the DUT and a noise source. The measurement setup is controlled by Keysight’s IC-CAP tool. The low noise amplifier (LNA) is used before the NFM to boost the weak noise signal, which increases the accuracy of the measurement [16]. In this work, we have measured the 2168-6734 c  2016 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission. VOLUME 4, NO. 6, NOVEMBER 2016 See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. 379