Evaluation of thin film p-type single crystal silicon for use as a CMOS Resistance Temperature Detector (RTD)

Abstract

Temperature monitoring and thermal management of CMOS circuits / sensors is often required for long term circuit reliability and sensors temperature compensations. The ideal solution is to co-fabricate the temperature sensors along with the CMOS circuits and other sensors using CMOS materials and the same CMOS processes. In this paper we therefore, report on the fabrication and thermal characterization of such thin film temperature sensors. The thin film Resistance Temperature Detectors (RTDs) are made of single crystal p-type silicon on a silicon substrate using a Silicon on Insulator (SOI) Complementary Metal Oxide Semiconductor (CMOS) process. The influence of thin film length and width on the response of RTDs has been investigated. Furthermore, the effects of aluminum (Al) and tungsten (W) metallization used for power tracks on the response of RTDs have been studied. To assess the performance of the RTDs based on SOI CMOS p-type silicon, in addition to sensitivity and TCR, their power consumption, linearity, hysteresis, repeatability, reproducibility and expected life span have also been evaluated. The p-type silicon RTDs consume very less power (i.e. 0.9 μW only) and demonstrate a sensitivity of 13.88 Ω / oC, which is much higher than the previously reported CMOS RTDs and widely used non-CMOS platinum RTDs. The RTDs also exhibit a linear response (98.9% fsd), an excellent repeatability and significantly low hysteresis with maximum variation of 0.2% between forward and reverse cycle. These RTDs also boast good reproducibility, within the wafer and wafer to wafer, with maximum sensitivity variation of 1.3% between different tested samples. The expected life span of the RTD is > 10 years. These inexpensive RTDs are therefore, good candidates for use as temperature sensors on CMOS circuits / sensors system.