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Optical Integrated Circuit Probing Method and Apparatus

IP.com Disclosure Number: IPCOM000034997D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Greenfield, DA: AUTHOR [+3]

Abstract

By scanning a focussed broadband infrared light beam through the backside of a thinned integrated circuit (IC) while simultaneously exercising the circuit electronically, electrical state of discrete devices in the illuminated area are identified by a change in device power characteristics caused by induced free carriers. Synchronously scanning and electronically exercising two ICs speeds and enhances detection of differences between "good" and "bad" devices. Referring to the figure, a light source 2 having a level of infrared in its spectral output is collimated to strike beam splitter 4. Half of the input light energy goes through transfer lense system 6 and is reflected by mirror 8 into microscope A. The other half of the input light goes through adjustable neutral density filter wheel 10 and into microscope B.

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Optical Integrated Circuit Probing Method and Apparatus

By scanning a focussed broadband infrared light beam through the backside of a thinned integrated circuit (IC) while simultaneously exercising the circuit electronically, electrical state of discrete devices in the illuminated area are identified by a change in device power characteristics caused by induced free carriers. Synchronously scanning and electronically exercising two ICs speeds and enhances detection of differences between "good" and "bad" devices. Referring to the figure, a light source 2 having a level of infrared in its spectral output is collimated to strike beam splitter 4. Half of the input light energy goes through transfer lense system 6 and is reflected by mirror 8 into microscope A. The other half of the input light goes through adjustable neutral density filter wheel 10 and into microscope B. Microscopes A and B are comprised of identical elements: an eyepiece 12, beam splitter 14, narrow band interference filter 16, infrared photo diode 18, silicon pin diode 20, and objective lens 22. Thinned comparison chips 24 and 26 are placed under the microscope objectives 22 in chip sockets 28 and 30 which have cabling (not shown) to allow test operation of the two chips. Socket 28 is mounted on an adjustable stage 32 which permits precision adjustment of chip 24. Chip socket 30 is attached to mounting block 34. Adjustable stage 32 and mounting block 34 are affixed to motorized, precision x-y sta...