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Determining Doping Levels in Silicon Devices

IP.com Disclosure Number: IPCOM000082622D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Schick, JD: AUTHOR [+2]

Abstract

This technique allows measurement of differences in doping levels and also of absolute doping levels on devices of small geometry.

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Determining Doping Levels in Silicon Devices

This technique allows measurement of differences in doping levels and also of absolute doping levels on devices of small geometry.

A scanning electron microscope beam-induced current (EBIC) measurement allows a determination of doping concentrations, and also of variations of doping in a device.

For this measurement a PN junction or a Schottky barrier diode junction is essential. The device is sectioned at 90 degrees using a glass metallurgical polishing wheel and immediately after the section reaches the area of interest, the sample is given a thorough DI water rinse and then baked immediately for 30 minutes at 200 degrees C. The chip is bonded to a TO-5 header and the junction contacts are wire bonded to the pins. Both sides of the junction are connected across a high-gain current amplifier which is used to drive a cathode-ray tube (CRT). The sample is capacitively coupled to the amplifier so that a reverse bias can be applied to the junction, if desired.

The width of the depletion region is determined by the doping levels on both sides of the junction. The electrical junction is located at the maximum of the EBIC signal, which is obtained from a single trace across the junction and appears as shown in Figs. 1 and 2.

A relative measurement of the depletion width can be obtained by differentiating the EBIC signal with respect to time, while using the appropriate scan speed for the electron beam. The resulting curves a...