O. Miller

A novel CMOS monolithic active pixel sensor with analog signal processing and 100% fill factor

We have designed and fabricated a CMOS monolithic active pixel sensor (MAPS) in a novel 0.18 micrometer image-sensor technology (INMAPS) which has a 100% fill factor for charged particle detection and full CMOS electronics in the pixel. The first test sensor using this technology was received from manufacture in July 2007. The key component of the INMAPS process is the implementation of a deep p-well beneath the active circuits. A conventional MAPS design for charged-particle imaging will experience charge sharing between the collection diodes and any PMOS active devices in the pixel which can dramatically reduce the efficiency of the pixel. By implementing a deep p-well, the charge deposited in the epitaxial layer is reflected and conserved for collection at only the exposed collection diode nodes. We have implemented two pixel architectures for charged particle detection. The target application for these pixels is for the sensitive layers of an electromagnetic calorimeter (ECAL) in an international linear collider (ILC) detector. Both pixel architectures contain four n- well diodes for charge-collection; analog front-end circuits for signal pulse shaping; comparator for threshold discrimination; digital logic for threshold trim adjustment and pixel masking. Pixels are served by shared row-logic which stores the location and time-stamp of pixel hits in local SRAM, at the bunch crossing rate of the ILC beam. The sparse hit data are read out from the columns of logic after the bunch train. Here we present design details and preliminary results.

Design and performance of a CMOS study sensor for a binary readout electromagnetic calorimeter

We present a study of a CMOS test sensor which has been designed, fabricated and characterised to investigate the parameters required for a binary readout electromagnetic calorimeter. The sensors were fabricated with several enhancements in addition to standard CMOS processing. Detailed simulations and experimental results of the performance of the sensor are presented. The sensor and pixels are shown to behave in accordance with expectations and the processing enhancements are found to be essential to achieve the performance required.

Beam test results of FORTIS, a 4T MAPS sensor with a signal-to-noise ratio exceeding 100

We have tested the first 4T Monolithic Active Pixel Sensor (MAPS) for particle physics, FORTIS in a beam test. We have measured a signal-to-noise ratio of more than 100 for MIPs due to the excellent noise performance of the 4T architecture. Two versions of the sensor were tested; with and without deep P-well areas in-pixel. The deep P-well areas allow the incorporation of PMOS transistors inside the pixels without signal charge loss. The measured position resolutions were around 2 μm.

TPAC: A 0.18 micron MAPS for digital electromagnetic calorimetry at the ILC

For the ILC physics program, the detectors will need an unprecedented jet energy resolution. For the electromagnetic calorimeter, the use of a highly granular silicon-tungsten calorimeter has been proposed. We have developed a Monolithic Active Pixel-based readout for such a calorimeter, which will have extremely fine granularity and will make use of a digital readout. The first generation chip (TPAC1) implements a 168x168 array comprising 50x50 μm2 pixels. Each pixel has an integrated charge pre-amplifier and comparator. TPACI has been manufactured in the 0.18 μm INMAPS process which includes a deep p-well. We present results of the performance of the TPACI chip together with comparison to simulations and give an outlook to the second generation chip.