Micromachined resonant temperature sensors: Theoretical and experimental results

This paper describes the study of quartz, temperature sensors based on new bulk acoustic wave microresonators operating in thickness modes. First, we compare the thermal sensitivity and the electromechanical coupling coeffici ents of singly or doubly rotated cuts. These investigations allow us to sel ect some cuts with both a good thermal sensitivity and piezoelectric charac teristics. In the second part, emphasis is placed on the micromachining of resonators suspended by four bridges. These two theoretical considerations lead to the choice of three cuts. Experimental measures are then presented. The temperature - frequency characteristics of the resonators are measured over the range 20 to 100 C. Motional resistances and Q factors are determi ned at room temperature.