Seebeck Effect Detection on Biased Device without OBIRCH Distortion Using FET Readout

Laser Stimulated Seebeck Effect Imaging (SEI) is widely used in Microelectronics Failure Analysis, namely when performed through chip backside. The SEI signal shapes are often not easy to interpret though, mostly because of superposition of additional OBIRCH (Optical Beam Induced Resistivity Change). Here, a SEI detection technique independent of OBIRCH interference is presented. When a thermoelectric voltage is generated on an interconnect that drives FET inputs (gate conductor), the voltage influences the FET channel conductance almost currentless producing drain output shift that can be detected as Thermal Laser Stimulation (TLS) signal. As FET output current is clearly separate from the gate, it cannot interfere with the thermoelectric effects in the gate conductor. A full characterization of the structure for several circuit models is presented. Test structures for SEI may be improved when designed with FET readout. Also on ICs SEI can be done with nominal supply voltage as long as the Seebeck junction is located in a gate conductor circuit.