Ying-Che Tseng

AC floating body effects and the resultant analog circuit issues in submicron floating body and body-grounded SOI MOSFET's

We report the extensive study on ac floating body effects of different SOI MOSFET technologies. Besides the severe kink and resultant noise overshoot and degraded-distortion in partially depleted (PD) floating body SOI MOSFETs, we have investigated the residue ac floating body effects in fully depleted (FD) floating body SOI MOSFETs, and the different body contacts on PD SOI technologies. It is important to note that there is a universal correlation between ac kink effect and Lorentzian-like noise overshoot regardless of whether the body is floating or grounded. In addition, it was found that third-order harmonic distortion is very sensitive to floating body induced kink or deviation on output conductance due to the finite voltage drop of body resistance. These results provide device design guidelines for SOI MOSFET technologies to achieve comparable low-frequency noise and linearity with Bulk MOSFETs.

Comprehensive study on low-frequency noise characteristics in surface channel SOI CMOSFETs and device design optimization for RF ICs

Low-frequency (LF) noise, a key figure-of-merit to evaluate device technology for RF systems on a chip, is a significant obstacle for CMOS technology, especially for partially depleted (PD) silicon-on-insulator (SOI) CMOS due to the well-known kink-induced noise overshoot. While the dc kink effect can be suppressed by either using body contact technologies or shifting toward fully depleted (FD) operation, the noise overshoot phenomena still resides at high frequency for either FD SOI or poor body-tied (BT) SOI CMOSFETs. In this paper, floating body-induced excess noise in SOI CMOS technology is addressed, including the impact from floating body effect, pre-dc kink operation, and gate overdrive, followed by the proposal of a universal LF excess noise model. As the physical mechanism behind excess noise is identified, this paper concludes with the suggestion of a device design methodology to optimize LF noise in SOI CMOSFET technology.

AC floating-body effects in submicron fully depleted (FD) SOI nMOSFETs and the impact on analog applications

We report the impact of submicron fully depleted (FD) SOI MOSFET technology on device AC characteristics and the resultant effects on analog circuit issues. The weak DC kink and high frequency AC kink dispersion in FD SOI still degrade circuit performance in terms of distortion and low-frequency noise requirements. These issues raise concerns about FD devices for mixed-mode applications. Therefore, further device optimization such as source/drain engineering is still necessary to solve the aforementioned issues for FD SOI. On the other hand, partially depleted SOI MOSFET with body contact structures provide an alternative technology for RF/baseband analog applications.

Empirical correlation between AC kink and low-frequency noise overshoot in SOI MOSFETs

Low-frequency (LF) noise overshoot has been empirically correlated with the frequency dependence of the kink effect in floating body SOI MOSFETs. Based on the correlation between these unique ac characteristics in SOI, a new mechanism is proposed to explain the well-known kink-related noise overshoot. Also, device solutions for suppressing LF noise overshoot will be discussed.

Floating body induced pre-kink excess low-frequency noise in submicron SOI CMOSFET technology

The well-known post-kink Lorentzian-like noise overshoot has been empirically correlated to the ac kink effect in the SOI CMOSFET in the past. This work demonstrates the existence of a 1/f/sup 2/ excess noise spectrum (<100 Hz) superimposed upon 1/f noise in partially depleted (PD) floating body SOI CMOS when devices are biased in the pre-kink region (before the dc kink onset voltage). While the impact ionization phenomenon is negligible in the pre-kink region, the new observed pre-kink excess noise provides a new insight into the body voltage instability and current fluctuation in the SOI CMOSFET.

Phase noise characteristics associated with low-frequency noise in submicron SOI MOSFET feedback oscillator for RF IC's

Phase noise in silicon-on-insulator (SOI) MOSFET feedback oscillators for RF IC applications is investigated. The observed correlation between the oscillators high frequency phase noise and the transistors low-frequency noise characteristics demonstrates that the phase noise overshoot still exists in partially-depleted (PD) floating body SOI nMOS Colpitts oscillators. These results suggest that kink-induced effects associated with low-frequency components of the signal are upconverted into the ideally kink-free high frequency domain operation mode of PD floating body SOI oscillators.

Device design methodology to optimize low-frequency noise in advanced SOI CMOS technology for RF ICs

This paper reports on a comprehensive study of low-frequency (LF) noise in surface-channel dual-poly SOI CMOS-FETs. A new understanding of the pre-kink and post-kink excess noise mechanisms as well as the impact of this excess noise on RF ICs are presented.

AC floating body effects in partially depleted floating body SOI nMOS operated at elevated temperature: an analog circuit prospective

AC floating body effects in PD SOI nMOSFETs operated at high temperature are investigated. Both source/body and drain/body junction diode characteristics are greatly influenced by temperature, significantly impacting the ac kink effect as well its low-frequency (LF) noise characteristics. This is especially true for the pre-dc kink operation at high temperature. The increase of junction thermal generation current becomes an important body charging source and induces the LF Lorentzian-like excess noise.

Minimizing body instability in deep sub-micron SOI MOSFETs for sub-1 V RF applications

We report an extensive study on the SOI body instability and the noise constraint dependence on device scaling for sub-1 V RF SOI CMOS applications. Also, the device parameters associated with these issues are addressed.

Local floating body effect in body-grounded SOI nMOSFETs

Summary form only given. In this paper, the width dependence of the kink effect and the low frequency noise overshoot in the body grounded H-gate SOI MOSFETs have been studied. These phenomena are related to the local floating body effects resulting from the intrinsic body impedance. Also, it is suggested that the unique low frequency noise overshoot in SOI can be a sensitive tool to evaluate the efficiency of the body contact.