A new type of sensor has been developed for applications in high radiation environments such as space. In this paper we present the pixel structure, fabrication cycle and measured performance of a family of active pixel charge injection devices designed in PMOS and respectively CMOS technology. A simple 8 by 8 prototype was developed in 1996. This was followed by a 40 by 54 array having 90 micrometers pixel size. This device has address decoders integrated on chip and, a transfer gate included in each pixel in order to eliminate feed-through noise. These circuits were fabricated at RIT using a 6 micrometers PMOS double polysilicon technology. A third 128 by 128 array having 41 micrometers pixel size has been designed and manufactured at a commercial foundry using 2 micrometers CMOS technology. The on-chip decoders allow resetting of selective regions of the chip.
A large format CID imager module capitalizes on CID large well capacity and radiation resistance to image dental x- rays. The model, which consists of the imager, conversion phosphor and ancillary electronics, is encapsulated in a 40 X 28 X 5 mm3 robust package that is lightproof, moisture-proof and meets FDA and RFI/EMI standards. Data exposure and readout is simple. The imager normally exists in an active reset mode until x-ray application automatically places the imager into a charge integration mode. Readout begins immediately upon completion of the x- ray exposure or manual application of an external trigger source. The imager returns to the reset mode once the data read out is complete. Pixels are arranged in an SVGA compatible 800H X 600V format. Each pixel is square and 38.5 microns/side. The imager is coated using a propriety phosphor deposition process that result in a limiting resolution of 9 LP/mm from an x-ray illumination source. Better than 2,000:1 dynamic range and shot-noise limited operation is achieved. Direct x-ray detection and attendant noise is minimized via the phosphor and epitaxial layer that lies beneath the pixel array. The imager/module architecture and electro-optical performance are described in detail here in.
A high-speed 512 X 512 charge injection device with selectable one to four video ports has been developed, fabricated, and tested beyond the designed speed of operation. The imager has four independently controllable video ports allowing for all possible combinations. This is accomplished by having each port hard wired to one out of every four rows sequentially. Each port is selected via a multiplexer in the sequence desired. The horizontal scanner was designed to operate up to 30 MHz. The device was tested at the wafer level to 42 Mhz element rate per port. This element rate allows a maximum of 168 MHz element rate with four ports operating in parallel.