Thermoelectric sensor for fingerprint thermal imaging

A fingerprint sensor comprising:

• a plurality of thermoelectric sensors arranged in a two-dimensional array including a plurality of signal processing circuits on a single chip, said chip having a hot-junction region and a cold-junction region wherein said cold-junction region surrounds said hot-junction region, whereby a ridge of a fingerprint produces a temperature gradient between said hot-junction region and said cold-junction region when said ridge of said fingerprint closes or contacts said thermoelectric sensor, said thermoelectric sensor further converting said temperature gradient into an electrical voltage signal;
• a silicon substrate;
• a field oxide layer or a trench isolation layer on said silicon substrate acting as a thermal-isolation structure;
• at least a thermocouple connected in series to form a thermopile, wherein said hot-junction region of said thermopile is located at a central portion of said field oxide layer and said cold-junction region is located on a thin oxide layer which is surrounding said field oxide layer;
• and
• a heat pipe structure comprising at least an interconnection layer and at least a via hole metal, wherein said heat pipe structure is located between said central portion of said field oxide layer and a passivation layer which is on a surface of said substrate.