Backthinning is just what it sounds like, literally thinning the backs of the devices. Backthinning is done because most customers with scientific requirements require the absolute maximum performance and sensitivity in the devices.

In order to use every last photon of light that is available, the best thing to do is to turn the ccd over and shine the light through the back. Unfortunately because of the thickness of silicon a lot of performance is lost before the light gets to the part that works. In order to minimize that effect we have to remove a major part of the silicon from the back side of the surface until it is about 15 microns. This is about the thickness of a human hair and very high sensitivity and performance are achieved.

The wafers are first attached to support wafers (pictured below) and then thinned. A common process of thinning the wafers is for them to be immersed in an acid bath. The acid eventually thins the wafers down to their desired thickness.

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