CMOS-MEMS Technology for Signal Processing, Sensing, and Actuation
Strong demands from the Internet of Things (IoT) and Industry 4.0 are expected to enable “Trillion Sensors Era” where a variety of sensors are required to meet miniaturization, low power, and system integration. In the past decades, SoC (system on chip) works very well in the semiconductor industry to bring most of the circuit building blocks on the same substrate, thus reducing the chip size and cost while enhancing the overall circuit performance. However, the emerging applications necessitate the communication and interaction between the electronic world and non-electronic (i.e., physical) world where MEMS sensors, actuators, and micromechanical signal processors (e.g., transducers) are key to bridging these two domains. However, the one-product-one-process nature of the MEMS devices impedes the SoC while the SiP (system in package) is often used to combined sensors/actuators and their interface circuits at the cost of form factor, power, and performance.
In recent years, the CMOS-MEMS technology, referred to as MEMS on top of CMOS in this talk, offers inherently monolithic integration of MEMS and IC, small form factor, fast turnaround time, mass production, low cost, and easy prototyping. The CMOS-MEMS technology has been thoroughly studied in the National Tsing Hua University (NTHU) more than one decade and potentially plays a strategic role in the IoT of Taiwan thanks to the strong IC and semiconductor industry in Taiwan. By redirecting the “more Moore” resources into the “more-than-Moore”, the NTHU has demonstrated a variety of micro transducers using the CMOS-MEMS technology supported by our local CMOS foundries.
In this talk, I will present the recent progress of the high-Q integrated micromechanical signal processors, physical sensors, and actuators using the “CMOS-MEMS technology” to enable monolithic integration of MEMS and IC in frequency control and sensing/actuation applications targeted for the “Trillion Sensors Era”. This talk will cover four major parts, including (i) the fabrication technologies of the CMOS-MEMS resonators/sensors and their associated interface circuitry; (ii) the performance enhancement of the resonators on the motional impedance, quality factor, power handling, thermal stability, frequency tuning, and parasitic feedthrough; (iii) the implementation of the CMOS-MEMS resonators for frequency generation (i.e., oscillators), frequency selection (i.e., filters), and resonant sensing functionalities; and (iv) the various transduction mechanisms realized in CMOS-MEMS. In the first part, various fabrication technologies in the 0.35m and 0.18m CMOS technology nodes will be presented, showing their own features and advantages. In the second part, several strategies in the design aspects and material points of view will be described in order to enhance the performance of the CMOS-MEMS devices. In the third part, designs and experimental results of the CMOS-MEMS oscillators, filters, sensors, and actuators will be presented. In the last part, different transductions used in CMOS-MEMS resonators will be covered mainly targeted for sensor applications. We take full advantage of the IC and semiconductor strength in Taiwan to develop several CMOS-MEMS platforms towards single-chip implementation for the potential IoT applications.