Wafer Level Packaged CMOS-SOI-MEMS Thermal Sensor at Wide Pressure Range for IoT Applications

Thermal IR sensors are widely used in various fields such as automotive, IoT applications, human intruder alert systems as well as smart building management (lighting, heating) or temperature sensing, with an increasing market forecast for the next years. Technologies currently in use for optical uncooled infrared devices are bolometers, thermopiles, and pyroelectric sensors. More recently, a new generation of uncooled thermal sensor based on CMOS-SOI-MEMS technology has emerged, dubbed “TMOS”.

The TMOS is a suspended, thermally isolated micro-machined floating transistor, which absorbs infrared radiation. The resulting temperature change is transduced into an electric signal. The TMOS operates in the subthreshold region, therefore requiring low power consumption, which is essential for wearable applications. Moreover, the inherent gain of the transistor results in the highest temperature sensitivity, compared to the commercial thermal sensors.

Wafer Level Packaging with a controlled vacuum quality is essential to ensure high performance and low cost. This paper focuses on the study of the thermal performance of a wafer-level packaged TMOS, where the pressure varies between deep high vacuum (0.01 Pa) and atmospheric pressure. The study is based on Finite Element Analysis (FEA) simulations performed by ANSYS software as well as analytical expressions. The measurements of vacuum quality in packaged devices are in line with the modeling and simulations.

The talk will describe the TMOS Wafer Level Packaging as well as the modeling and simulations and how to perform vacuum quality measurements of the packaged MEMS device. The talk will present the innovations and the maturity of the new generation of sensors, which are highly useful for wearable and consumer sensor applications.