Optimization of Tracking Performance of CMOS Monolithic Active Pixel Sensors (original) (raw)
2007, IEEE Transactions on Nuclear Science
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 m 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.
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Particle trackingusingCMOS monolithic active pixel sensor
A novel monolithic active pixel sensor for charged particle tracking has been designed and fabricated in a standard CMOS technology. The device architecture is identical to a CMOS camera, recently being proposed as an alternative to CCD sensors for visible light imaging. The partially depleted thin epitaxial silicon layer is used as a sensitive detector volume. The sensor is a photodiode having a special structure, which allows the high detection efficiency required for tracking applications A first prototype was made of four arrays each containing 64 Â 64 pixels, with a readout pitch of 20 mm in both directions. An architecture allowing serial readout of the analogue information from each pixel has been implemented. To evaluate the tracking performance of such a device, series of tests have been performed using a highenergy particle beam. A detailed analysis of the beam test data presented in this work demonstrate close to 100% minimum ionising particle detection efficiency and a good enough signal-to-noise ratio of more than 30. #
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001
A novel Monolithic Active Pixel Sensor (MAPS) for charged particle tracking made in a standard CMOS technology is proposed. The sensor is a photodiode, which is readily available in a CMOS technology. The diode has a special structure, which allows the high detection e$ciency required for tracking applications. The partially depleted thin epitaxial silicon layer is used as a sensitive detector volume. Semiconductor device simulation, using either ToSCA based or 3-D ISE-TCAD software packages shows that the charge collection is e$cient, reasonably fast (order of 100 ns), and the charge spreading limited to a few pixels only. A "rst prototype has been designed, fabricated and tested. It is made of four arrays each containing 64;64 pixels, with a readout pitch of 20 m in both directions. The device is fabricated using standard submicron 0.6 m CMOS process, which features twin-tub implanted in a p-type epitaxial layer, a characteristic common to many modern CMOS VLSI processes. Extensive tests made with soft X-ray source (Fe) and minimum ionising particles (15 GeV/c pions) fully demonstrate the predicted performances, with the individual pixel noise (ENC) below 20 electrons and the Signal-to-Noise ratio for both 5.9 keV X-rays and Minimum Ionising Particles (MIP) of the order of 30. This novel device opens new perspectives in high-precision vertex detectors in Particle Physics experiments, as well as in other application, like low-energy beta particle imaging, visible light single photon imaging (using the Hybrid Photon Detector approach) and high-precision slow neutron imaging.
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IEEE Transactions on Nuclear Science, 2003
Active Pixel Sensor (APS) technology has shown promise for next-generation vertex detectors. This paper discusses the design and testing of two generations of APS chips. Both are arrays of 128 by 128 pixels, each 20 by 20 µm. Each array is divided into sub-arrays in which different sensor structures (4 in the first version and 16 in the second) and/or readout circuits are employed. Measurements of several of these structures under Fe 55 exposure are reported. The sensors have also been irradiated by 55 MeV protons to test for radiation damage. The radiation increased the noise and reduced the signal. The noise can be explained by shot noise from the increased leakage current and the reduction in signal is due to charge being trapped in the epi layer. Nevertheless, the radiation effect is small for the expected exposures at RHIC and RHIC II. Finally, we describe our concept for mechanically supporting a thin silicon wafer in an actual detector.
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Monolithic active pixel sensors (MAPS) are now well established as a technology for tracking charged particles, especially when low material budget is desirable. For such applications, sensors focus on spatial resolution and pixels with digital output or modest charge measurement ability are well suited. Within the European Union STRONG-2020 project, which focuses on experiments using hadrons, the TIIMM (Tracking and Ions Identifications with Minimal Material budget) joint research activity intends to expand granular MAPS capacity to energy-loss (ΔE) measurement for ion species identification. The TIIMM prototypes are developed in the Tower Jazz 180 nm CMOS image sensor (CIS) process. The Time-Over-Threshold (ToT) method is applied to the sensor for the energy-loss measurement. The main design details and the preliminary test results from laboratory measurements of the initial TIIMM prototype are presented in this work.
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A novel type of position and energy sensitive, monolithic pixel array with integrated readout electronics is proposed . Special features of the design are a reduction of the number of output channels and of the amount of output data, and the use of transistors on the high resistivity silicon. The number of output channels for the detector array is reduced by handling in parallel a number of pixels, chosen as a function of the time resolution required for the system, and by the use of an address decoder. A further reduction of data is achieved by reading out only those pixels which have been activated. The pixel detector circuit will be realized in a 3~Lm p-well CMOS process, which is optimized for the full integration of readout electronics and detector diodes on high resistivity Si. A retrograde well is formed by means of a high energy implantation, followed by the appropriate temperature steps. The optimization of the well shape takes into account the high substrate bias applied during the detector operation. The design is largely based on the use of MOS transistors on the high resistivity silicon itself . These have proven to perform as well as transistors on standard doped substrate. The basic building elements as well as the design strategy of the integrated pixel detector are presented in detail.
IEEE Transactions on Nuclear Science, 2000
We report on the performance of the MIMOSA8 (HiMAPS1) chip. The chip is a 128 32 pixels array where 24 columns have discriminated binary outputs and eight columns analog test outputs. Offset correction techniques are used extensively in this chip to overcome process related mismatches. The array is divided in four blocks of pixels with different conversion factors and is controlled by a serially programmable sequencer. MIMOSA8 is a representative of the CMOS sensors development option considered as a promising candidate for the Vertex Detector of the future International Linear Collider (ILC). The readout technique, implemented on the chip, combines high spatial resolution capabilities with high processing readout speed. Data acquisition, providing control of the chip and signal buffering and linked to a VME system, was made on the eight analog outputs. Analog data, without and with a 55 Fe X-ray source, were acquired and processed using off-line analysis software. From the reconstruction of pixel clusters, built around a central pixel, we deduce that the charge spread is limited to the closest 25 pixels and almost all the available charge is collected. The position of the total charge collection peak (and subsequently the charge-to-voltage conversion factor) stays unaffected when the clock frequency is increased even up to 150 MHz (13.6 s readout time per frame). The discriminators, placed in the readout chain, have proved to be fully functional. Beam tests have been made with high energy electrons at DESY (Germany) to study detection efficiency. The results prove that MIMOSA8 is the first and fastest successful monolithic active pixel sensor with on-chip signal discrimination for detection of MIPs.
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