M. Sapor

Silicon ultra fast cameras for electron and γ sources in medical applications

Abstract SUCIMA (Silicon Ultra fast Cameras for electron and γ sources In Medical Applications) is a project approved by the European Commission with the primary goal of developing a real time dosimeter based on direct detection in a Silicon substrate. The main applications, the detector characteristics and technologies and the data acquisition system are described.

Hybrid active pixel sensors and SOI inspired option

Abstract Two novel pixel sensor concepts for future linear collider applications are presented in this paper: a hybrid pixel sensor characterized by a layout improving the single point resolution and a monolithic detector inspired by silicon on insulator (SOI) technology. The results of charge collection studies for the first prototypes of hybrid pixel sensors with interleaved pixels are reported and the new detector test structures are introduced. The technology and the readout architecture design for SOI sensors are also discussed.

Development of monolithic active pixel sensor in SOI Technology fabricated on the wafer with thick device layer

Monolithic active pixel detectors fabricated in SOI (Silicon On Insulator) technology are novel sensors of ionizing radiation, which exploit SOI substrates for the integration of readout electronics and a pixel detector. The fully depleted sensing diode has been manufactured under buried oxide (BOX) while read-out circuitry occupies upper silicon layer (‘device layer’). The development of the SOI detectors of ionizing radiation was started as a part of the SUCIMA project. During the project, it was proved that a monolithic SOI detector is a viable option for high-energy physics and medicine. The early prototypes suffered from significant leakage currents and soft breakdowns. These effects limited yield of production. Moreover, the p-wells (formed within the device layer and extended to the interface with the BOX), caused some local potential wells below the BOX at the top of depleted sensor area reducing the effective charge collection efficiency. The use a thicker device layer and optimized technology appeared to be a remedy.

Fully depleted monolithic active pixel sensor in SOI technology

An active pixel detector, which exploits wafer-bonded silicon on insulator (SOI) substrates for integration of the readout electronics with the pixel detector, is presented. The main concepts of the proposed monolithic sensor and the preliminary tests results with ionising radiation sources are addressed. Silicon on insulator is an alternative solution for a monolithic active pixel detector, which allows integrating a fully depleted sensor and front-end electronics active layers into one silicon wafer. The main idea of the sensor relies on the use of both monolithic silicon layers (device and support layers) of the SOI substrate for fabrication of pixel detector diodes and readout electronics. Such detectors can find wide range of applications, not only in particle physics but also in medicine, space science and many other disciplines. The sensor structure and the readout configuration have been developed and the measurements of a dedicated test structure have validated the new technology of the SOI detector. Small SOI sensor matrices with 8 by 8 channels have been recently produced and tested.

The two channel CMOS converter for silicon photomultiplier

The paper describes principles of IC designed for SiPM signal processing on the input and digital output, with sample rate 5-7 MSPS. Describe also functionality and applications of designed IC as well as results of simulations, hardware prototype of IC ADC realized in CMOS (AustriaMicrosystems C35134,035 mum) technology.

Design, Fabrication and Characterization of SOI Pixel Detectors of Ionizing Radiation

Development of a novel monolithic active pixel image sensor based on SOI technology is presented. Active pixel test matrices have been recently manufactured and are under extensive examination. This paper describes the concept of the device and shows the most recent results.

Fully differential charge to time converter and fast shaper readout circuit with gain compensation for SiPM

The implementation of fully differential readout method for Silicon Photomultipliers (SiPM) is presented. The front-end circuit consists of preamplifier with fast shaper and Charge to Time Converter (QTC). The fast shaper generates unipolar pulse. The peaking time for single photoelectron is equal to 3.6ns and the FWHM is 3.8ns. The pulse width of the QTC depends on the number of photons. The gain of SiPM is compensated by moderating the bias voltage. The polarization voltage is adjusted indirectly by tuning the output common mode voltage (VOCM) of fully differential amplifier. The advantage of the algorithm is the possibility to set the bias of each SiPM in the array independently so they all could operate in similar conditions (have similar gain and dark count rate).

Bandgap voltage reference and temperature sensor in novel SOI technology

A bandgap voltage reference together with absolute temperature sensor (PTAT) designed in 200 nm SOI technology is presented in this paper. Three slightly different versions were designed to verify the diode models available in the SOI process. For more extensive SOI process study the chip was fabricated on three different substrates. The bandgap reference circuit generates Vref = 1.27 V with 10 mV chip to chip spread. The best bandgap version has temperature coefficient -35 μV/K. Circuit design, simulations and comparison with measured performance are presented.

Self-Calibrating Gain Stabilization method for applications using Silicon Photomultipliers

Performance of Silicon Photomultipliers (SiPM) [1] strongly depends on bias voltage and temperature. The key aspect in low light detection is precision and stability of SiPMs gain. These requirements can be met by delivering accurate bias and keeping temperature on constant level. It is not very demanding task in case of single SiPM. However, in applications consisting of thousands of SiPMs it is much more problematic or even impossible to control the temperature of each detector (e.g. nuclear physics experiments). The paper presents a gain stabilization method that can be applied in multidetector measurements without the need to characterize gain-temperature-bias functions and parameters of all detectors used in the experiment.

Low voltage charge-pump-based Sigma-Delta Modulator using CMOS inverters as building blocks

The paper summarizes a concept of CMOS implementation of a new asynchronous sigma-delta modulator, based exclusively on CMOS inverters (or similar two-transistor blocks) as building blocks. The proposed a SigmaDelta-modulator is extremely suitable for low voltage operation and is fully compatible with digital CMOS, since there are only two transistors stacked in between supply rails. Circuit diagrams of particular functional blocks are presented. Selected simulation results with BSIM3v3 models provided by foundries are reported.