Microstructure Design And Manufacture Of Thermocouple Wave Power Meter

Because of their unprecedented flexibility Microelectromechanical systems(MEMS) develop very quickly these years. Their design and fabrication differ fromsemiconductor's. This paper tries to explain these differences by an example.Power measurements have taken an important role in electromagnetics.Combining semiconductor technology with an unusual structure--- a microbridgestructure, thermocouples overcome the drawbacks of low burnout level and parasiticreaction limiting their frequency range. In semiconductor thermocouple Ta ofrelatively low resistor-temperature coefficient and Si of relatively highthermoelectric power Seebeck coefficient are used as thermocouple materials.Microwave power dissipated in the tantalum resistive film generates the heat to raisethe temperature of the hot junction above that of the cold junction, thereby producinga dc voltage across the thermocouple. The temperature rises and the dc voltage isproportional to the power dissipated which is equal to the power of the source beingmeasured if the input impedance is suitably matched to the source impedance.The chip is fabricated by using a standard IC process, combining with MEMStechnology The sensor has sensitivity as high as 1. 1mV/mW over a frequency rangeof DC to 18GHz at a power lever form 10μW to 100 mW.