Method and apparatus using an infrared laser based optical probe for measuring electric fields directly from active regions in an integrated circuit
First Claim
1. A method for detecting an electric field in an integrated circuit, the method comprising the steps of:
- operating a laser beam at a wavelength near a band gap of a semiconductor of the integrated circuit;
focusing the laser beam through a back side of the semiconductor on an active region of the semiconductor;
detecting an amplitude modulation of a reflected laser beam from the active region through the back side of the semiconductor; and
,attributing the amplitude modulation of the reflected laser beam to the electric field in the active region of the semiconductor.
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Accused Products
Abstract
A method and an apparatus for detecting an electric field in the active regions of an integrated circuit disposed in a semiconductor. In one embodiment, a laser beam is operated at a wavelength near the band gap of a semiconductor such as silicon. The laser beam is focused onto a P-N junction, such as for example the drain of an MOS transistor, through the back side of the semiconductor substrate. As a result of photo-absorption, the laser beam is partially absorbed in the P-N junction. When an external electric field is impressed on the P-N junction, such as when for example the drain of the transistor switches, the degree of photo-absorption will be modulated in accordance with the modulation in the electric field due to the phenomenon of electro-absorption. Electro-absorption also leads to electro-refraction which leads to a modulation in the reflection coefficient for the light reflected from the P-N junction/oxide interface. The laser beam passes through the P-N junction region, reflects off the oxide interface and metal behind the junction, and returns back through the P-N junction and back out of the silicon surface. Any amplitude modulation in this reflected laser beam is detected with an optical detection system, and is attributed to a corresponding modulation in the electric field in the P-N junction due to the combined effects of electro-absorption and electro-refraction.
124 Citations
29 Claims
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1. A method for detecting an electric field in an integrated circuit, the method comprising the steps of:
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operating a laser beam at a wavelength near a band gap of a semiconductor of the integrated circuit; focusing the laser beam through a back side of the semiconductor on an active region of the semiconductor; detecting an amplitude modulation of a reflected laser beam from the active region through the back side of the semiconductor; and
,attributing the amplitude modulation of the reflected laser beam to the electric field in the active region of the semiconductor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A device for detecting an electric field in an integrated circuit, comprising:
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a laser configured to provide a laser beam at a wavelength near a band gap of a semiconductor of the integrated circuit; an objective lens positioned in front of the laser so as to focus the laser beam on an active region of the integrated circuit through a back side of the semiconductor; a beam splitter positioned between the laser and the objective lens; and
,a detector positioned to detect a reflected laser beam reflected from the active region through a back side of the semiconductor, through the objective lens and through the beam splitter, the detector configured to detect an amplitude modulation of the reflected laser beam wherein the amplitude modulation is attributable to the electric field at the active region. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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Specification