Effects of the technology scaling down to 28nm on Ultra-Low Voltage and Power OTA performance using TCAD simulations

In this paper, the effect on the performances of the technology scaling down to 28nm (bulk and planar) is studied on a specific Ultra-Low Voltage/Power (ULV/P) OTA [4] design. This study is carried out for 90nm and 28nm technology node OTA using specifically the shortest available channel length and benchmarked with the original OTA in 180nm. First, the TCAD simulation (Synopsys) of the design implemented with the corresponding iPDK's are performed and the electrical parameters are extracted. We deduced that the short channel devices still conserve a good dc gain explained by physics considerations. Then, the performance analysis based on the power consumption and Figure-Of-Merit leads to conclude that alike the large signal performance, the small signal performance is maintained with a significant power dissipation reduction making the 28nm technology still an interesting choice for small-signal applications. However, a specific study of the variability (process variation) of the transistor performance shows that OTA implemented in 28nm node may provide a poor fabrication yield suggesting to consider ULV/P OTA design immune to the variability introduced by low technology node.