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Magnetic Photoelectron Energy Analyzer for IC Laser Testing

IP.com Disclosure Number: IPCOM000061080D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Chiu, GL: AUTHOR

Abstract

This article describes an improved technique for collecting photoelectrons in an energy analyzer. Photoelectron energy analyzers use the same design as the secondary electron energy analyzer currently. A problem in the case of laser approach is that in order to focus the laser beam down to (or close to) the diffraction limit, the lens subtends a large solid angle above the device under test. All photoelectrons, which constitute the signal for voltage contrast of integrated circuit laser testing, liberated by a UV laser and emitted into the solid angle subtended by the lens are lost. This reduces the signal-to-noise ratio of laser IC testing by 1-3 orders of magnitude. This problem can be greatly improved by using a magnetic field to guide photoelectrons to the photoelectron detector.

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Magnetic Photoelectron Energy Analyzer for IC Laser Testing

This article describes an improved technique for collecting photoelectrons in an energy analyzer. Photoelectron energy analyzers use the same design as the secondary electron energy analyzer currently. A problem in the case of laser approach is that in order to focus the laser beam down to (or close to) the diffraction limit, the lens subtends a large solid angle above the device under test. All photoelectrons, which constitute the signal for voltage contrast of integrated circuit laser testing, liberated by a UV laser and emitted into the solid angle subtended by the lens are lost. This reduces the signal-to-noise ratio of laser IC testing by 1-3 orders of magnitude. This problem can be greatly improved by using a magnetic field to guide photoelectrons to the photoelectron detector. The drawing indicates the structure for this purpose. A magnetic field is applied above the surface of the chip. The photoelectrons, typically a few electron volts, gyrate around the magnetic field and eventually reach detectors at both ends. The gyroradius of an electron is given by r (in cm) = 3.37* sqrt (E (in eV)) / B ( in gauss). A pair of extraction and retarding grids separated closely (say, 1 mm) can be used to pull photoelectrons away from the surface of the water, if necessary. For example, a 1 eV photoelectron has a gyroradius of
0.034 cm with a 100 gauss magnetic field. A magnetic field of few hundred gausses is...