The company has developed a computer-controlled test rig that illuminates sections of the wafer in turn. Integrating the results enables the whole wafer to be tested automatically for an array of large sensors or sensors that cover an entire 12-inch wafer.
Martin Kingdon, Presto Engineering’s sales vice president said other laboratories are not geared up for fast commercial testing while Presto can do this in small- to medium-sized test runs at a cleanroom facility in Meyreuil, France, near Aix-en-Provence.
Presto’s Teradyne IP750Ex based test solution provides an 80mm by 100mm high intensity illumination at up to 10klux with a uniformity of +/-2 percent. Built-in IR filtering prevents heat damage. Sensors of up to 32 million pixels can be tested on 300mm-diameter wafers at clocking frequencies of 200MHz.
Commercial testing of small image sensors is relatively easy as the small areas involved are easy to illuminate with a controlled, uniform test pattern of light. But, as the area increases, it becomes harder to maintain the uniformity across the test area of an individual sensor due to the limitation of the optics. By illuminating sections of the wafer in turn, Presto is able to merge the results together to test the functionality of the image sensors on the wafer.
Larger image sensors are being demanded by medical imaging and aerospace that can require whole wafer-sized, image sensors and are transitioning from CCD to CMOS solutions. Similarly, security and military applications, etc. are all wanting larger, better sensors to provide the resolution required to provide clear sharp images, as well as other 4K resolution cameras.
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