| 摘要 |
PURPOSE: An image sensor having a test pattern is provided to improve production yield and reduce the change of photo characteristic of image sensor by self-evaluating the characteristic of a p-epitaxial layer formed on a wafer. CONSTITUTION: The test pattern is made up of a high doping density p++ substrate(40), a low doping density p-epitaxial layer(20), two p+ region(31,32) connected to the p-epitaxial layer and a p+ region(33) connected to the p++ substrate. N type wells(10) and three pads(61,62,63) connecting p+ region to a metal wire are formed, where the N type wells(10) define only 3 p+ dopant region as an active region. When measuring current between two p+ regions, reverse bias voltage is applied to the p+ region connected to the p++ substrate so as to remove electron current through p++ substrate between p+ region. Resistance of p-epitaxial layer is evaluated from dividing applied voltage by the measured current between two p+ regions.
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