The right Sensor at the right time

The client needed a monolithic CMOS sensor array for a high sensitivity X-ray mammography system.  The device needed to be low cost with a 14 bit dynamic range.

Since X-rays cannot be focused down to a small focal plane, a very large CMOS device was needed in order to get a reasonable image area.  In addition, to make the device at a reasonable cost, the yield of the CMOS imagers needed to be very high, and the larger the die size, the lower the yield.  

Adept came up with a patented CMOS sensor that mates to an amorphous Selenium X-ray detector.  By using a 3um CMOS process (permitted by the large pixel size), a very large die was designed (pictured above).  To allow for large tiled arrays, the  die was designed with no peripheral circuitry on 3 out of the 4 sides, to minimize the distance between the active imaging areas.

To keep the yield high, Adept designed 2 redundant CMOS APS pixels for every detector pixel site.  This redundancy achieved a yield of nearly 85% on a wafer scale die.  The actual die measures a full 67mmx56mm and occupies the entire 4" wafer.  

The system using these devices is currently in clinical trials. 

Copyright © 2002 Adept IC Design
Last modified: October 18, 2000