An abnormal phenomenon due to substrate bias modulation in theintegrated PIN photodiode sensor with dielectric isolation

摘要

An abnormal phenomenon was found in the integrated PIN photodiodesensors (which is named PIN Photo Integrated Circuits Sensor: PIN-PICS)combined with a bipolar IC in the same substrate. It was observed in theoptical device called “2 electric wires type photoelectricsensor”. It occurs at the time to drive the external LED byinternal timing generator. This phenomenon was investigated by threemethods, that is, the failure analysis the measurement of deviceparameters and both circuit and device simulations. These results showthat the problem was induced from the PIN structure forming PIN-PICS.When the switching noise was altered, the most of this noise wastransferred to preamplifier through parasitic capacitance of the PINphotodiode connected with a P+tab across a P-layer, and itdistorted the output waveform of preamplifier by differentialcomponents. Therefore, in order to prevent this phenomenon, it'snecessary to exchange the connection of parasitic capacitance fromP+tab to substrate. We confirmed that an Au backmetallization of 3000 Å thickness, or Au-Si alloy die bonding isthe most effective