Directions for advancement of MIT-LL CCDs for x-ray astrophysics applications

Charge coupled devices remain the scientific tool of choice for x-ray imaging spectrometers for astrophysics applications due to their deep depletion depths, low noise, and uniform Gaussian energy response. These qualities provide advantages over both monolithic and hybridized CMOS sensors in this application space, but relative to these alternatives come most significantly at the cost of frame rate. This work at MIT’s Lincoln Laboratory in collaboration with MIT’s Kavli Institute and Stanford’s KIPAC presents current directions of pursuit in design, fabrication, and architecture towards the end of improved CCD performance at elevated data rates. Advanced sense nodes designed for low noise, high speed operation requires pushing towards high conversion gain and high transconductance sense transistors both through enhancement of current generation JFETs and refinement of design for future generation SiSeRO nodes [single electron sensitive readout]. Larger devices require lower capacitance parallel gates to support charge transfer towards output nodes at the requisite pixel rates. Transition from triple-poly to single poly gate structures reduces this capacitance while maintaining high charge transfer efficiency to high transfer rates across many cm² devices. Architecturally, enhanced parallelization with increased port counts and densities supports elevated data rates for any given pixel rate. Close integration to support ASICs handles this elevated data rate without undue multiplication of support electronics.