Damien Grandjean

CMOS monolithic active pixel sensors for minimum ionizing particle tracking using non-epitaxial silicon substrate

Nonepitaxial, high resistivity silicon has been used as a substrate for implementation of CMOS monolithic active pixel sensors (MAPS) designed for high precision minimum ionizing particle tracking. The readout electronics circuitry is integrated directly on top of such a substrate using a standard commercial CMOS process. In this paper, measurements of these devices using a high-energy particle beam are presented. Efficient and performing MIP tracking is demonstrated for both small (20 /spl mu/m) and large (40 /spl mu/m) pixel readout pitch. Radiation hardness that satisfies many future particle physics applications is also proven. These results show that the use of epitaxial substrate for MAPS fabrication is not mandatory, opening a much larger choice of possible CMOS processes in the future.

Optimization of Tracking Performance of CMOS Monolithic Active Pixel Sensors

CMOS Monolithic Active Pixel Sensors (MAPS) provide an attractive solution for high precision tracking of minimum ionizing particles. In these devices, a thin, moderately doped, undepleted silicon layer is used as the active detector volume with the readout electronics implemented on top of it. Recently, a new MAPS prototype was fabricated using the AMS 0.35 mum OPTO process, featuring a thick epitaxial layer. A systematic study of tracking performance of that prototype using high-energy particle beam is presented in this work. Noise performance, signal amplitude from minimum ionizing particles, detection efficiency, spurious hit suppression and spatial resolution are shown as a function of the readout pitch and the charge collecting diode size. A test array with a novel readout circuitry was also fabricated and tested. Each pixel circuit consists of a front-end voltage amplifier, capacitively coupled to the charge collecting diode, followed by two analog memory cells. This architecture implements an on-pixel correlated double sampling method, allowing for optimization of integration independently of full frame readout time and strongly reduces the pixel-to-pixel output signal dispersion. First measurements using this structure are also presented

Monolithic active pixel sensors with in-pixel double sampling operation and column-level discrimination

Monolithic Active Pixel Sensors constitute a viable alternative to Hybrid Pixel Sensors and Charge Coupled Devices for the next generation of vertex detectors. Possible application will strongly depend on a successful implementation of on-chip hit recognition and sparsification schemes. These are not a trivial task, first because of very small signal amplitudes (/spl sim/mV), originated from charge collection, which are of the same order as natural dispersions in a CMOS process, secondly because of the limitation to use only one type of transistor over the sensitive area. The paper presents a 30 /spl times/ 128 pixel prototype chip, featuring fast, column parallel signal processing. The pixel concept combines on-pixel amplification with double sampling operation. The pixel output is a differential current signal proportional to the difference between the charges collected in two consecutive time slots. The readout of the pixel is two-phase, matching signal discrimination circuitry implemented at the end of each column. The design of low-noise discriminators includes automatic compensation of offsets for individual pixels. The details of the chip design are presented. Difficulties, encountered from being the first attempt to address on-line hit recognition, are reported. Performances of the pixel and discriminator blocks, determined in separate measurements, are discussed. The essential part of the paper consists of results of first tests performed with soft X-rays from a /sup 55/Fe source.

Optimization of tracking performance of CMOS monolithic active pixel sensors

CMOS monolithic active pixel sensors (MAPS) provide an attractive solution for high precision tracking of minimum ionizing particles. A thin, moderately doped, undepleted silicon layer is used in these devices as a detector active volume with the readout electronics implemented on top of it. A new MAPS prototype has been fabricated using recently available AMS 0.35 /spl mu/ OPTO process, featuring thick epitaxial layer. A systematic study of tracking performance of that prototype using high-energy particles beam is presented in this work. Noise performance, signal amplitude from minimum ionizing particles, detection efficiency, spurious hit suppression and spatial resolution are shown as a function of the readout pitch and the charge collecting diode size. A test array with a novel readout circuitry is included in the design. The circuit consists of a front-end voltage amplifier, capacitively coupled to the charge collecting diode and followed by two analog memory cells. This architecture implements an on-pixel correlated double sampling method, allowing for optimization of integration time independently of full frame readout and reducing pixel-to-pixel output signal dispersion. First measurements using this structure are presented.

Radiation hardness improved CMOS sensors as particle detectors in high energy physics and medical applications

The use of CMOS Monolithic Active Pixel Sensors for high precision minimum ionizing particle tracking has been proven to be a viable and powerful novel experimental technique. In this approach a lightly doped thin and partially depleted silicon epitaxial layer is used as a radiation sensitive detector volume. The readout electronics circuitry is integrated directly on top of epitaxy using standard commercial CMOS process. For the pixel pitch of 20/spl mu/m particle tracking precision of below 2/spl mu/m and full efficiency have been measured in the past. In this work measurements with CMOS MAPS fabricated on non-epitaxial, high resistivity substrate are presented. Efficient and performing MIP tracking is demonstrated, also for a large 40/spl mu/m pixel readout pitch. These results proves that the use of epitaxial substrate for MAPS fabrication is not mandatory, opening much larger choice of possible CMOS processes in the future.