Numerical Toolkit for Design an Analysis of CMOS FET based Terahertz Detectors
Final Report Abstract
Within the scope of this project, we have investigated on the utility of the TCAD based simulations to further improve the design of CMOS FET THz detectors. The drift-diffusion model was selected as the carrier transport model of choice for CMOS THz detectors, due to the fact that the transit times have nearly saturated in the production ready Si-CMOS technologies and the electric fields induced by the THz radiation to the MOSFET channel are very small in magnitude to allow for any thermally induced hydrodynamic like transport. The distributed transmission line model resembles to the drift equation and therefore it models the detector quite well for high frequencies, although it lacks any closed form solution. The 2-D TCAD simulations, on the other hand, are much more detailed and they can predict many other interesting effects such as the impact of device doping profiles on the THz detection behaviour. The TCAD results discussed here were simulated on the 0.13-µm transistor available from IHP Microelectronics with process simulated doping profiles. We also weighted upon the idea of developing a custom device simulator from scratch or use a powerful yet closed commercial software to focus more on the end results, and we opted for the latter choice. Still, we found the standard mixer simulation methods such as Harmonic Balance (HB) and Periodic Steady-State (PSS) to be quite challenging to converge for the device level THz detection behaviour, and therefore time-domain simulations were selected for most accurate and reliable results at the cost of computation time. The detector design has also been in continuous development. The detector biasing has been deliberated upon and common-gate differential detector, with a differential broadband ring antenna at the source, has been found to be the best choice for a good response and detector-antenna matching, and minimizing the read-out complexity. The systematic co-design procedure between the detector and the antenna has a great potential to further improve the detector sensitivity, and we have reported the lowest CMOS detector NEP of 14 pW/Hz0.5 at room temperature for 65 nm CMOS technology. Also, the integration density of CMOS has been leveraged upon to design systems such as hyperhemispherical lens integrated 1-k pixel CMOS THz camera. This project has served as a stepping stone to develop a deeper understanding into the THz detection behaviour, and we have also identified some avenues which can be undertaken in the future to further improve the detector performance, such as technology modification where TCAD simulations can play a central role. This problem can be tackled at multiple levels, and we are continuing to explore the different ideas.
Publications
- “A 1 k-pixel video camera for 0.7-1.1 terahertz imaging applications in 65-nm CMOS,” IEEE Journal of Solid-State Circuits, vol. 47, no. 12, pp. 2999–3012, Dec. 2012
R. Al Hadi, H. Sherry, J. Grzyb, et al.
(See online at https://doi.org/10.1109/JSSC.2012.2217851) - “On the co-design between on-chip antennas and THz MOSFET direct detectors in CMOS technology,” in 2012 37th International Conference on Infrared, Millimeter, and Terahertz Waves, Sep. 2012, pp. 1–3
J. Grzyb, H. Sherry, A. Cathelin, A. Kaiser, and U. R. Pfeiffer
(See online at https://dx.doi.org/10.1109/IRMMW-THz.2012.6380197) - “Toward low-NEP roomtemperature THz MOSFET direct detectors in CMOS technology,” Int. Conf. on Infrared, Millimeter, and Terahertz Waves, pp. 1740–1744, 2013
U. Pfeiffer, J. Grzyb, H. Sherry, A. Cathelin, and A. Kaiser
(See online at https://dx.doi.org/10.1109/IRMMW-THz.2013.6665522) - “THz direct detector and heterodyne receiver arrays in silicon nanoscale technologies,” Journal of Infrared, Millimeter, and Terahertz Waves, vol. 36, no. 10, pp. 998–1032, 2015
J. Grzyb and U. Pfeiffer
(See online at https://doi.org/10.1007/s10762-015-0172-6) - “Zero gate-bias terahertz detection with an asymmetric NMOS transistor,” in 2016 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz), Sep. 2016, pp. 1–2
R. Jain, H. Rücker, and U. R. Pfeiffer
(See online at https://dx.doi.org/10.1109/IRMMW-THz.2016.7758895)
