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Contactless Measuring Method

IP.com Disclosure Number: IPCOM000092221D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Wells, OC: AUTHOR

Abstract

This contactless method is for measuring the properties of a PN junction. Normally, if a PN junction is irradiated with electrons, it becomes forward biased. This occurs whenever sufficient electron-induced minority carriers diffuse to the junction. However, if the electron beam is focused onto a metal pad which is in contact with one side of the junction, the carriers can recombine in the metal and, if the other side of the device is grounded, a backward bias can be applied. The potential on the metal pad can then be measured by passing secondary electrons through an energy analyzer so that, under favorable conditions, a plot of their reverse current versus voltage characteristics can be obtained.

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Contactless Measuring Method

This contactless method is for measuring the properties of a PN junction. Normally, if a PN junction is irradiated with electrons, it becomes forward biased. This occurs whenever sufficient electron-induced minority carriers diffuse to the junction. However, if the electron beam is focused onto a metal pad which is in contact with one side of the junction, the carriers can recombine in the metal and, if the other side of the device is grounded, a backward bias can be applied. The potential on the metal pad can then be measured by passing secondary electrons through an energy analyzer so that, under favorable conditions, a plot of their reverse current versus voltage characteristics can be obtained.

For obtaining the current-voltage characteristic using the contactless method, diode 1, having metal contact pad 2 at its surface, is mounted in the evacuated specimen chamber of scanning electron microscope 3 or similar electron optical instrument at an angle of 45 degrees for example. Beam current I(b), from a cathode, not shown, is injected into P-type diffused region 4 disposed in N-type substrate 5. The current I(net) is equal to I(b)-I(sec) where I(sec) is the combined secondary and backscattered currents. I(net) is measured with an electrometer, not shown, connected between the device and ground. The beam voltage is set at approximately 5 kV and the beam current is varied. The back- bias on the PN junction is measured by adjusting cu...