| 摘要 |
<p>A method and an apparatus for detecting an electric field in the active regions (403) of an integrated circuit (405) disposed in a semiconductor. In one embodiment, a laser beam (407) is operated at a wavelength greater than approximately 0.9 microns. The laser beam is focused onto a P-N junction, such as for example the drain of a MOS transistor, through the back side of the semiconductor substrate. As a result of free carrier absorption, the laser beam is partially absorbed near the P-N junction. When a signal is impressed on the P-N junction, the degree of free carrier absorption will be modulated in accordance with the modulation of the depletion region near the P-N junction. The laser beam passes through the P-N junction region, reflects off the oxide interface and the metal behind the junction, and returns back through the P-N junction and back out of the silicon surface. Amplitude modulation in this reflected laser beam is detected with an optical detection system.</p> |
