S.A. Audet

High-purity silicon soft x-ray imaging sensor array

Abstract A 256 element soft X-ray sensor array with separate x - and y -readout addresses fabricated on high-purity silicon (4kΩ cm) utilizing only standard integrated-circuit processing technologies is presented. The design of the 16 × 16 array of 250 × 250, μm 2 elements emulates that of a successful prototype. The principle of operation of the sensor is based on both the resistive and capacitive coupling of the elements in a matrix of sensing diodes. The columnar elements are resistively coupled to one output connection through the use of highly-doped polysilicon structures, while utilization of the double-layer metalization technique provides capactive coupling of those elements lying in the same row to a separate output connection. Experimental results demonstrated good sensor characteristics and confirmed two-dimensional position detection of incident radiation with minimal crosstalk.

High-purity silicon radiation-sensor array

Abstract A radiation-sensor array designed and fabricated on high-purity silicon (substrate resistivity 4 kω cm ± 35%) with separate x - and y -readout addresses is presented. The operation of the device is based on both the resistive and the capacitive coupling of the elements in the matrix of sensing diodes. A 3×3 matrix of 0.25 mm 2 elements has been integrated as a prototype. The columnar elements are resistively coupled to one output connection through the used of highly-doped polysilicon structures, while utilization of the double-layer metalization technique provides capacitive coupling of those elements lying in the same row to a separate output connection. Although the processing requirements included integrated-circuit fabrication techniques not commonly employed in the processing of silicon-radiation sensors, the array demonstrated good detector characteristics. Experimental results confirmed two-dimensional position detection with minimal crosstalk.

Monolithic integration of a nuclear radiation sensor and transistors on high-purity silicon

The physical operation of nuclear radiation sensors is briefly reviewed. A description is given of a typical experimental measurement-system setup, which can be divided into two parts: the application-specific part (including the detector and its associated electronics) and the computer-interfaced part (consisting of a multichannel analyzer). A number of recent improvements in the system design are discussed, and an extended description and a physical example are given of one of the most promising new ideas-the monolithic integration of both the radiation sensor and its associated electronics on one high-ohmic silicon substrate. The results proved to be a stimulus for making nuclear radiation sensors smart enough for direct digital input into computer systems. >

A 3 × 3 silicon drift chamber array for application in an electronic collimator

Abstract The mechanical collimator, used in combination with an Anger camera in nuclear-medical imaging studies, can be replaced with a radiation detector, which performs the function of electronic collimation. The two-detector system is based on the Compton scattering of incident gamma-photons. Although germanium is more efficient in the absorption of gamma-photons by the Compton process than silicon, silicon has advantages which cannot be overlooked when choosing a substrate material on which to fabricate the radiation detector to be used in the electronic collimator system. The semiconductor drift chamber (SDC) principle offers advantages in the construction of a two-dimensional radiation detector array. Simulations of the potential field within the detector array will be shown, as well as the design and processing sequence used in the fabrication of a 3 × 3 SDC array.

Integrating transistors on high-ohmic silicon

Abstract This paper presents a compatible technology for integrating both radiation detectors and transistors on the same high-ohmic silicon substrate. Using this technology, chips have been fabricated containing a number of test transistors (MOSFETs) with different geometries. Measurements on the devices showed a threshold voltage between 0 and -3 V, and a transconductance between 25 μA/V and 1.25 mA/V for aspect ratios between 0.7 and 50, respectively. The results demonstrate that transistors can be integrated together with radiation detectors onto one chip, which can lead to radiation detectors containing both detecting elements and signal-modification units, such as preamplifiers and multiplexers.

A silicon detection system for DNA-sequencing

Abstract Nowadays in DNA-sequencing the position of the radioactive bands, which represents the structure of the DNA molecule, is determined by using X-ray films. By using silicon position sensitive detectors, these measurements can be speeded up and the analysis be automated. In this article we present the experimental setup and the readout electronics of a new detection system for DNA-sequencing. The detector and readout electronics have been tested separately, and operate satisfactorily. The detection system has not been tested, because the detector and readout electronics are not assembled yet.

Compatible integration of radiation detectors and transistors

Abstract Until recently, smart nuclear radiation detectors were non-existent because of the substantial differences between the detector fabrication process and conventional IC processes. In this paper a fabrication process is presented which allows the compatible integration of both nuclear radiation detectors and (simple) MOSFET s. Test devices were fabricated containing two-dimensional nuclear radiation detectors and both polysilicon-gate and metal-gate PMOS transistors with a variety of geometries. The experimental results of the test devices show that MOS transistors can be monolithically integrated together with nuclear radiation detectors without degrading the detector quality. This opens up the way towards the development of smart nuclear radiation detectors.

Experimental detector chip for soft X-ray applications

Abstract In this paper an experimental chip is presented, which is made of high-ohmic silicon, containing both nuclear radiation detectors and transistors. The detectors have a two-dimensional position resolution and were fabricated according to two different multiplexing principles. The first principle is the capacitor-resistor multiplexing technique, which is superior with respect to crosstalk. The second principle is the capacitor-interconnect technique, which is superior with respect to energy measurement. The transistors were fabricated and operated under the same circumstances as the detectors and performed well. The measured parameters ( g m C gs = MHz –8 GHz ) indicate that these transistors are well suited to preamplification and multiplexing purposes. The combination of the presented detectors and transistors for soft X-ray measurement is a very good one, because the limited spatial resolution allows enough chip area for the integration of readout electronics and, when backside illumination is applied, the transistors are shielded from direct irradiation. Therefore it is concluded that the detector matrices and the transistors presented in this paper are well suited to the construction of detector matrices with on-chip signal processing for soft X-ray applications.

Contactless lifetime measurement in processed and preprocessed high-purity silicon radiation sensors

Abstract A contactless microwave method is presented for the measurement of the recombination lifetime of free carriers in high-ohmic silicon wafers (4 kω cm), which are used for the processing of (nuclear) radiation sensors. It is shown that the bulk lifetime can be measured following processing steps independent of surface parameters, when the intensity of the light source is kept low. The results of the measurements carried out by this method are compared with the results obtained by leakage current measurements. Good agreement is observed between the results.

High‐purity silicon radiation‐sensor array for imaging synchrotron radiation in digital‐subtraction angiography procedures

The possible integration of a recently fabricated high‐purity silicon radiation‐sensor array into experimental‐instrumentation systems currently being developed for digital‐subtraction angiography (DSA) procedures conducted with synchrotron radiation is discussed. In order to motivate the intended application of the sensor, the medical‐imaging techniques of conventional coronary angiography and DSA are briefly reviewed followed by a summary of the different system and detector designs currently in use.