Message Board Thread - "See Through Silicon"

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See Through Silicon TI-SR 6/1/2005
I work at a semiconductor manufacturing plant. The chips are made on a round slice of silicon (called a wafer) that at the start of manufacturing process is mirror like on both sides. When I used the infrared camera on the wafer, I can see through it. I expected it to reflect the infrared heat. Does anyone know why I can see through the silicon?
 
Re:See Through Silicon Gary Orlove 6/2/2005
Silicon is very transparent to IR radiation, we actually use it as a lens material for some IR cameras. I can't tell you why its transparent. Please see this link for more information on silicon, http://www.ispoptics.com/new_webpage/New%20ISP%20Pages/Page22.pdf .

Gary Orlove
Infrared Training Center
 
Re:See Through Silicon heatmover 7/14/2005
I used to do plastic package quality and reliability engineering support at Intel (when the 486 chip was just coming out). There were certain issues with certain chips having cratering defects on the bondpad sites. X-radiograms showed them some but had poor resolution, and scanning acoustic microscopy was then in the characterisation phases. I helped develop a procedure where the plastic-encapsulated package was backlapped through the die-attach pad, and viewed through the chip with an IR microscope operating (I think) at around 1.6-1.8 um. One could very easily see the circuitry--and the bondpad craters--this way.
 


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