28 August 1995 Optical recognition of defective pins on VLSI chips using electron trapping material
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Abstract
A method is investigated for fast online inspection of pins on very large scale integrated (VLSI) circuit chips prior to mounting on circuit boards. We image the edge of the VLSI chip containing the pins to be inspected onto electron trapping material (ETM) using Argon light. This writes an image of the pins to be inspected onto the material. Then we image an identical chip type with perfect pins onto the electron trapping material using IR light. This performs a subtraction between the two images. The output is read out with another IR beam and summed onto a detector. If the output exceeds an electronic threshold, pins are considered damaged. We show experimental results with pins separated by 0.2 mm to show practicality and speed of the approach. A second approach is explored in which the grating effect of the pins is used to form a self image. The same procedure is followed except that imaging lenses are no longer required. We show that there is no advantage in using self imaging with this approach.
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Alastair D. McAulay, Alastair D. McAulay, Junqing Wang, Junqing Wang, } "Optical recognition of defective pins on VLSI chips using electron trapping material", Proc. SPIE 2565, Optical Implementation of Information Processing, (28 August 1995); doi: 10.1117/12.217670; https://doi.org/10.1117/12.217670
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