Ion Implanted Silicon Bolometers Operating in the Temperature Range 0.1-4.2°K

Silicon bolometers have been obtained by phosphorous implantation on single crystal silicon substrates. These devices work like microcalorimeters. The wafer substrate acts as the energy absorber, while the implanted resistor is the temperature sensing element. For proper operation, the doping concentration of the thermistor is tailored near to the critical concentration of the metal insulator transition of the Si:P system. The optimum operating point is typically between 0.1 and 4.2K, depending on the specific application. In this work the basic physical principles of operation of thermal detectors are oulined, then the technology developed for the realization of high sensitivity, ion implanted thermistors is briefly discussed. Examples of applications of the device as molecular beam detector, alpha-particle or X-ray radiation detector is also presented

Silicon bulk micromachining for sensor technologies

Micromachining and related technologies are needed to develop a large variety of sensors and actuators, i.e. the basic components of Microsystems or MEMS (MicroElectroMechanical Systems) as they are also commonly called. Microsystems are designed and fabricated by integrating different micocomponents into one functional unit comprising of sensors, actuators, I.C.s for data processing etc. In this development a variety of micromachining technologies, ranging from the conventional silicon bulk and surface micromachining to LIGA and LASER techniques are employed, each one having specific merits for specific products. This review focuses on silicon bulk micromachining applied to the fabrication of sensors suitable for being integrated into Microsystems, which are under development at IRST Microsystem Division

Realisation of Silicon Microcalorimeters with Bulk Micromachining Technology

Monolithic silicon micro-calorimeters consisting of a small suspended thermal mass that houses a highly sensible thermistor have been realised with the aid of bulk micro-machining techniques. An ad hoc post process module has been developed and adapted to the already optimised thermistor process. This micro-machining module is based on wet etchin steps, two of them been specially studied to this purpose. This process is characterised by two important features: 1) aluminium passivation together with a high anisotropy; 2) surface roughness control. All solutions are based on TMAH. A potential problem withi process are unstable edges and notching effects at the base of the supporting beams. Both problems can be overcome with a proper design of the device and a proper control of the etching time

Analytical Model for the Ohmic-Side Interstrip Resistance of Double-Sided Silicon Microstrip Detectors

A compact, analytical model is derived for the n-side interstrip resistance of double-sided silicon microstrip detectors, allowing for fast and accurate prediction of the minimum p-stop (or p-spray) implant dose ensuring adequate interstrip isolation. The basic idea on which the proposed model relies is that the portion of the detector between two adjacent n-strips can effectively be reduced to an equivalent n-channel MOSFET. The interstrip resistance can be evaluated as the output resistance of this equivalent MOSFET using standard SPICE-like models. The influence of radiation-induced oxide charge and p-stop (or p-spray) voltage can be accounted for, by simply including into the threshold voltage expression, the induced flat-band voltage shift and body-effect term, respectivel

A comprehensive numerical simulation of heavily irradiated p-type and n-type silicon detectors

In the framework of the CERN-RD50 Collaboration, the adoption of p-type substrates has been proposed as a suitable mean to Improve the radiation hardness of silicon detectors up to fluences of 1016n/cm2. In this work the simulated electrical characteristics of Irradiated p-type and n-type detectors are reported, for comparison with experimental measurements collected from the literature. The behaviour of the silicon devices at a fluence of 1016n/cm2 shows better results In term of charge collection efficiency using a p-type silicon detector

Silicon Integrated Microcalorimeters

In this work we report preliminary results on ion implanted, silicon integrated microcalorimeters, whose design has been targeted to optimize the sensitivity of the device and to match the preamplifier electronics input impedance. Preliminary results of resistivity measurements in 0.05 to 4.2K temperature range carried out on first prototypes show that a reproducibility on the wafer better than +-5% can be achieved, thus allowing in perspective not only to reproducibly fabricate discrete devices, but also complete sensors based on 2D arrays of integrated microcalorimeters

Rivelatori di radiazione su silicio ad alta resistività

In questo lavoro vengono descritti i principi di funzionamento di rivelatori di radiazione ottenuti su substrati di silicio ad alta resistività, quali diodi pin, rivelatori a striscia, rivelatori a deriva, rivelatori a pixel e rivelatori criogenici. I fattori più importanti che limitano la risoluzione energetica sono analizzati e discussi; si considerano, inoltre, i vantaggi e gli svantaggi connessi alla integrazione dell`elettronica di front-end sullo stesso wafer insieme al rivelatore: Oltre ad un confronto fra diverse tecnologie di fabbricazione, si presentanoalcuni risultati preliminari riguardanti rivelatori realizati presso l`Istituto per la Ricerca Scientifica e Tecnologica (Irst) di Trent

A Low Leakage Process for Silicon Radiation Detectors

PIN radiation detectors and other test-structure have been fabricated on FZ high-resistivity (2kWcm, N-type silicon substrate by a planar process that features three different alternative extrinsic-gettering techniques. Extremely low leakage-current values have been measured for these devices, confirming the effectiveness of gettering procedures. In particular, phosphorus-doped polysilicon used as a gettering layer on the back-side of the wafer has provided the best results in terms of leakage-current and generation lifetime values

Extraction of bulk generation lifetime and surface generation velocity in high-resistivity silicon by means of gated diodes

We show that the accuracy of the gated diode method for measuring bulk generation lifetime and surface generation velocity in high resistivity silicon depends critically on the gate length of the test device, as a result of nonidealities affecting the gated diode operation. Minimization of the surface generation velocity measurement error requires the gate length to be suitably decreased, while long gate length structures are needed for accurate bulk generation lifetime extractio