Temperature Stability Analysis of CMOS-SAW Devices by Embedded Heater Design

The design, finite element (FE) modeling, and electrical characterization of an embedded heater in complementary metal-oxide-semiconductor (CMOS) are presented. The heater is used to analyze the temperature stability behavior of CMOS-surface acoustic wave (SAW) devices. The heater employs n-well layer of standard CMOS technology to provide high efficiency resistive heating without physically perturbing the SAW architectures and performances. A detailed 3-D model and FE investigation is laid out to characterize the heat, current, temperature, and thermal energy distributions within the substrate and the piezoelectric material of interest ZnO. Electrical characterization based on Wheatstone configuration is presented to analyze the temperature stability of the sputtered ZnO and the CMOS-SAW delay lines. A temperature coefficient of frequency of -48.815/degC for the fabricated SAW devices with operating frequency of 322.5 MHz is obtained. The experimental results show close agreement with the FE simulations. The results demonstrate that the embedded heater design can be used as a robust analytical tool to investigate temperature stability of CMOS-SAW devices and potentially be utilized as an on-chip element for chemical, biological, and temperature sensor applications.