Development of built-in thermocouple applicable to micro power systems

Abstract

In the present thesis, the building thermocouples by using the chrome silicide which had very high electromotive force and the nickel which is a base metal, the fabricating method with the result, and the performances the thermocouples are verified to show the feasibility of the application as the built-in thermocouple in a micro reformer. Because the temperature measurement on the micro power system should be realized to measure temperatures on the areas of micro scales, the correlations between the junction sizes of the thermocouples and the electromotive forces should be verified. The junctions are varied in scales to 0.01 $mm^2$, 0.04 $mm^2$, and 0.16 $mm^2$ of each measuring condition. This point is the reason why RTDs cannot be applied on the micro size areas. Because the pattern gets too tiny to fabricate under general MEMS processes and measure the value of the resistance from the pattern. But the RTD pattern can be patterned on the side of cold junctions to evaluate the reference temperature by nickel nevertheless. In the fabrication procedure, the chrome silicide is sputtered to the thickness of 5000 Å. Before the lift-off process to pattern the film, it needs to anneal the substrate in $400^\circ C$ during 30 minutes. Because the chrome silicide is an alloy, it is necessary for the sputtered film to be crystallized at a certain condition. In the test, the creation junction temperature of $0^\circ C$ is accomplished in “Ice bath“ type. So, there is applied Peltier cooling element on the water jacket which is supplied cold water from the icebath. The Peltier element has the nature that maintains a certain temperature deviation between two parallel plates. So, once the bottom side can be kept on the temperature level as lower than $5^\circ C$, it is easy to maintain the temperature of the upper surface to $0^\circ C$ or lower level. The standard thermocouple has the value of Seebeck coefficient around $40 μV/^\circ C$. In the same manner, the relation...