CMOS device and circuit technologies for on-chip smart temperature sensor
This thesis work presents an all-CMOS on-chip smart temperature sensor for low voltage low power applications. Different temperature sensor front-end topologies have been designed and simulated in UMC 130nm process, AMI 0.5um process and IBM 90nm process respectively. The circuits designed in AMI 0.5um process and IBM 90nm process were fabricated and are being tested. The temperature sensor front-end in UMC 130nm process was designed to operate from 0°C to 120°C. The circuits designed in AMI 0.5um and IBM 90nm can be operated from -55°C to 125°C. Proportional-to-absolute-temperature (PTAT) voltage(s) and independent-of-absolute-temperature (IOAT) voltage with different sensitivities have been produced by different circuits. The temperature sensor front-end designed in UMC 130nm showed the capability to work as low as 0.6V. The one designed in AMI 0.5um operates from 1.2V. The one in IBM 90nm works from 0.5V -. Subthreshold MOSFETs, bulk-driven amplifier and Schottky Barrier Diodes (SBDs) have been adopted in different topologies for achieving low supply voltage and low power consumption. Dynamic element matching (DEM) and chopping have been used to improve the accuracy and robustness of the circuits. Different sizes of N-type Si SBDs were laid out and fabricated in AMI 0.5um process. The I-V relationships of these diodes have been characterized from -50°C to 120°C according to the test results. Model parameters such as ideality factor, effective barrier height and series resistance have been studied. The testing results showed the ability of SBDs to achieve the same current level and occupy a significantly smaller area compared with MOSFETs under the same process. The zero temperature coefficient (ZTC)-point-bias-voltage of SBDs are also lower than that voltage of MOSFETs. These characteristics imply great potential for using SBDs in low voltage low power circuit designs .