Technologies
From ITLWiki
Much of our work is aimed at developing new technologies which benefit astronomy and imaging science in general. The links below jump to some of the more important of these technologies. Also see our References section for technical papers.
Backside Processing
The process of optimizing a detector for backside illumination in order to improve its quantum efficiency and range of spectral response is referred to as backside processing. This is the largest area of expertise at ITL and accounts for a significant amount of our effort. Backside processing refers to the sequence of steps required to convert a front illuminated CCD (as fabricated at a semiconductor manufacturer's foundry) into a highly optimized detector suitable for low light level scientific and industrial imaging.
While most of our processing is performed at the die level, we have developed a process for hybridizing and back processing 150 mm wafers. CCD wafers are hybridized to aluminum nitride ceramic substrates with indium bumps and laser drilled vias and then thinned as a complete wafer. Backside coating and dicing follow, yielding fully buttable backside devices which are no larger than the original CCD die. This represents a true 4-side buttable technology.
The individual process steps are described below.
Substrates provide mechanical and electrical support for hybridized detectors. They are made of either silicon or ceramic.
Wafer Probing
We characterize individual die as well as entire lot runs at the wafer level before proceeding with backside processing. Our tests include DC shorts and opens, AC functionality, cosmetics, CTE, and absolute gain. We perform these tests as low as -60C.Probing
Detector Characterization
We have developed software and hardware systems for detector characterization, usually aimed at fully testing CCDs and CMOS imagers for scientific applications. See also U of A Detector Characterization Program
Cameras
Cameras are heart of any imaging system and include the detector, dewar, electronic controller, and software. We are responsible for many cameras at the University of Arizona used for astronomical imaging. We also produce many cameras for detector characterization in our lab as well as some cameras for other external activities. Cameras
Detector Cleaning
Because of the complex material mixtures used with modern detectors, cleaning them is a difficult task. We have developed several processes to clean both our detectors while they are being processed and other devices after extended service or when contaminated. Critical Cleaning