Temperature stability improvement of thin-film thermopiles by implementation of a diffusion barrier of TiN

A new generation of thin-film thermopiles is presented with improved temperature stability due to the implementation of a diffusion barrier of titanium-nitride. Commonly thermocouples are made of aluminium and polysilicon or semi-metals materials as Sb, Te and Bi. Exposure to elevated temperature in the range of a few hundred degrees centigrade would affect the functionality of the devices and leads to system failure. Prior to this work an approach for the realisation of high-temperature stable thermopiles made of tungsten-titanium alloy and polysilicon has been reported. Due to implementation of a diffusion barrier of TiN at the thermoelectric contacts the diffusion processes could be suppressed to a great extend and the temperature stability of these thermoelectric devices has been further improved. Functionality of the diffusion barrier was verified using TOF-SIM and the temperature stability achieved was investigated by detailed measurements.