Cor Claeys

A Foveated Retina-Like Sensor Using CCD Technology

A CCD imager whose sampling structure is loosely modeled after the biological visual system is described. Its architecture and advantages over conventional cameras for pattern recognition are discussed. The sensor has embedded in its structure a logarithmic transformation that makes it size and rotation invariant. Simulations on real images using the actual sensor geometry have been performed to study the sensor performance for 2D pattern recognition and object tracking.

Impact of silicidation on the excess noise behaviour of mos transistors

The excess noise behaviour of silicided and non-silicided p- and n-channel MOSTs, biased in the ohmic region, has been investigated. Only a minor difference in noise and series resistance could be seen for the n-channel MOSTs. However, the noise in the non-silicided p-MOSTs was dominated by the noise in the series resistance. The series resistance for the non-silicided p-MOSTs was more than four times higher than for the silicided p-MOSTs. A modified model for the 1/f noise equivalent circuit is proposed, showing good agreement with experimental results and explaining the observed trend SId∝Idm with 0 < m < 4. The classical geometry dependence of the current noise in MOSTs is only valid if the noise in the series resistance is negligible.

A retinal CCD Sensor for fast 2D shape recognition and tracking

Abstract A human-retina-like image sensor has been developed for applications in robotics. The CCD imager has a circular pixel organization and the resolution is a decreasing function of the radius. Detailed software modeling resulted in an imager design consisting of four main parts: a circular CCD, a radial CCD, a coupler and an output structure. In order to avoid a blind spot in the center, a central fovea with a rectangular interline transfer imager is included. This paper outlines in detail the design concepts and reports on the electrical performance and functionality of the first prototypes.

Retinalike space variant CCD sensor

The retina is a smart sensor, but in the sense of intelligent design and not on-chip computing power. It uses a unique layout and elementary charge computing elements to implement in hardware a polar-exponential transform on visual data. The final chip includes a large section of photosites arranged in a circular pattern. Further, the pixels grow m size as radial distance increases. The retina also has a fovea (a high resolution area at the chips center) and the computational circuitry. The sensor works and will serve as the key component of a real-time imaging system.

Impact of the free electron distribution on the random telegraph signal capture kinetics in submicron n-metal–oxide–semiconductor field-effect transistors

In this letter, the role of the free electron distribution on the capture kinetics of repulsive random telegraph signals in deep submicron n-channel metal–oxide–semiconductor field-effect transistors is studied. The inversion layer density and profile is varied by changing simultaneously the substrate and the gate bias of the transistor which is in linear operation at a constant drain current I. Detailed results are obtained for a class of repulsive trap centers when charged by an electron, which show a I−m variation of the capture time constant, with m>1. Such a nonstandard behavior can be understood in the framework of the Coulomb blockade model, whereby the image charge of the trapped carrier is stored on the gate electrode and in the inversion and depletion layer in the silicon substrate. As is shown here the capture time constant is a unique function of the ratio of the inversion layer surface density and the squared thickness of the inversion layer.

Defect Analysis in Semiconductor Materials Based on p-n Junction Diode Characteristics

This paper aims at reviewing the possibilities of using p-n junction diodes for lifetime and defect analysis in semiconductor materials. In a first part, the theoretical basis of lifetime extraction based on p-n junction current-voltage and capacitance-voltage characteristics will be discussed. In the next parts, these methods will be applied to different cases relevant for advanced semiconductor materials and device processing. First, the impact of the initial interstitial oxygen content and thermal pre-treatment of Czochralski silicon substrates on the carrier generation and recombination lifetime is discussed. A comparison will also be made with epitaxial and Float-Zone silicon. In a next part, the impact of proton-irradiation damage on the diode behavior will be presented. In the final part, the application of the technique on SiGe and Ge based p-n junctions is described. Whenever possible and useful, the information extracted from p-n junction characteristics will be compared with direct lifetime measurements using microwave techniques. Additional defect information has also been gained from other well-known techniques like Deep- Level Transient Spectroscopy (DLTS), Electron-Beam-Induced Current (EBIC), etc and will be correlated with the p-n junction results. The review is wrapped up in a summary followed by an outlook on future evolution and requirements.

Observation of stacking faults and prismatic punching systems in silicon by light scattering tomography

This study demonstrates that it is possible to identify crystal defects in silicon by infrared light scattering tomography. Stacking faults with a central silicon oxide precipitate were observed. They were identified by scattering of the surrounding Frank-type dislocation loop. The results are verified by changing the direction of the incident laser beam. Punching systems, identified by defect etching and TEM, can be observed due to their characteristic defect arrangement.

On the Effect of Lead on Irradiation Induced Defects in Silicon

Different group IV impurities (Pb, C, and Sn) have been introduced in the melt during the growth of n-type Czochralski silicon. The samples have been irradiated with 1 MeV electrons to a fluence of 4x1015cm-2. The irradiation-induced defects have been studied by Deep Level Transient Spectroscopy (DLTS). It is shown that the formation of one of the irradiation-induced deep level is avoided by the Pb-doping. This level is located at 0.37 eV from the conduction band edge (EC) and shows an apparent capture cross-section of 7x10-15cm2. In addition, another irradiation induced deep level located at EC - 0.32 eV has been studied in more details.

Towards single-trap spectroscopy: generation-recombination noise in UTBOX SOI nMOSFETs

An overview is given on the possibilities of using generation-recombination (GR) noise as a tool for defect spectroscopy in semiconductor materials and devices. The method is illustrated by n-channel MOSFETs fabricated on silicon-on-insulator (SOI) substrates with an ultra-thin buried oxide (UTBOX). As will be shown, the use of fully depleted (FD) UTBOX devices offers some unique opportunities and challenges. In the first instance, one can apply the standard GR noise spectroscopy in function of the temperature to derive the relevant deep-level parameters like the activation energy, the capture cross section and the concentration. In addition, some new type of spectroscopy can be applied to defects in the silicon film by exploiting the front- and/or back-gate bias dependence of the Lorentzian noise parameters. Finally, it is shown that for small geometry transistors the GR noise is generated by one or only a few centres. This becomes obvious in the time domain, where the channel current exhibits random telegraph signal (RTS) fluctuations. The up and down time constants and the relative RTS amplitude can be used to derive the GR centre parameters and, moreover, its spatial location, when combined with numerical device simulations. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Nickel silicide Schottky-barrier detectors for short-wavelength infrared applications

The utilization of both cobalt and nickel silicides as Schottky detectors is presented with both theoretical and experimental supporting data. The uses considered are limited to those with a typical cut-off frequency of more than 2.2 microns, such as earth observation and satellite imaging spectroscopy. The theoretical calculations of key parameters of Schottky-barrier detectors are discussed, including quantum efficiency, the dark current, and the noise. Experimentally, Co and Ni layers were tested on silicon wafers at a variety of temperatures and layer thicknesses. Average values for the barrier height, activation analysis, and quantum efficiency are given and compared. The dark current for both Ni and Co is shown to be negligible below 140-160 K, and Ni quantum efficiencies are higher than those for Co, as is the measured barrier height. The theoretical and technological requirements are met by both cobalt and nickel silicides. The characteristics tested show that Ni and Co silicides are appropriate for realizing large focal planes with high dark current and responsivity homogeneity.