Diode Temperature Sensors Research Articles

Peculiarities of injection phenomena in heavily doped silicon structures and development of radiation-resistant diode temperature sensors

Peculiarities of injection phenomena in heavily doped silicon structures and development of radiation-resistant diode temperature sensors

About manifestation of the piezojunction effect in diode temperature sensors

About manifestation of the piezojunction effect in diode temperature sensors

Effect of mechanical stress on operation of diode temperature sensors

Effect of mechanical stress on operation of diode temperature sensors

Effect of nonuniform doping profile on thermometric performance of diode temperature sensors

A theoretical investigation of the influence of a nonuniform doping concentration to the temperature response curve of diode temperature sensors is presented, which is the first effort in this field important for diffused diodes used as the temperature sensors. The current- voltage characteristic, from which the temperature response curve can be obtained, has been calculated using the model of a one-dimensional exponentially graded pnn junction with uniformly doped base region and the diffusion current of the minority carriers through the pnn junction. We show that depending on the doping gradient both contributions to the current coming from the electron and hole current components appear to be of the same order of magnitude. That is in contrast to the prediction of the widely used asymmetrical step junction model. It follows from numerical calculations that an effective shift of the tempera- ture response curve due to nonuniformly doped emitter region in the temperature equivalent can reach the value of about 20 K. The limiting temperature Tm in the temperature response curve that restricts its extent into the high temperature range has been analyzed depending on the excitation current, the doping concentration of the base, and the pnn junction depth.

Radiation-resistant silicon diode temperature sensors

Abstract We present a new type of silicon diode temperature sensors (DTSs) with high radiation resistance up to the dose of gamma irradiation ∼107 rad. Investigations of electrophysical and metrological characteristics of DTSs have been carried out in the range of temperatures 220–350 K and currents 10−11 to 10−2 A under gamma irradiation that allowed to reveal operating regimes with minimal influence of radiation on the device thermometric characteristics. A theoretical analytical model for the DTSs with almost ideal carrier transport has been proposed to explain the experimental behaviour of transport differential characteristics (ideality factor m, differential resistance) under irradiation. The observed non-monotonical dependencies of the ideality factor m on the current I are described well by the influence of generation–recombination and drift current components to the diffusion current of the minority carriers. The occurrence of a minimum in the m(I)-dependencies is due to a competition of these additional currents. The characteristic lifetimes of the minority carriers in the base and in the space-charge region of the diode structure have been determined. The DTSs are advanced devices with high sensitivity, accuracy, reproducibility, and easily adaptive with electronic equipment when operating in long circuits in radiation environments.

A Si MEMS microbearing with integrated safety sensors for surgical applications

A silicon micromachined bearing was designed and fabricated consisting of a pair of self-aligning v-grooves. The two Si v-grooves were bonded together to form the three-dimensional structure through solder bumps of 75μm diameter that provide alignment with a crucial vertical displacement tolerance. The microbearing includes integrated diode temperature sensors that serve to monitor a safe operating range under load. Current versus temperature curves and finite element analysis simulate the range of diode sensitivity. This three-dimensional structure, fabricated by silicon technology, demonstrates that a four to ten fold reduction in surgical cutting tool size can be achieved by utilizing the micromachined silicon microbearing in a micro-electromechanical system (MEMS) device. A prototype microtool has been bench tested and compared with realistic operating conditions. Based on this comparison, the microbearing holds promise for application in microsurgical cutting tools or as a MEMS cutting tool for surgical applications.

Limiting characteristics of diode temperature sensors

The criteria are formulated, which allow determination of the sets of electrophysical and design parameters of the diode temperature sensors (DTSs) providing either maximal extent of the temperature response curve (TRC) or the maximal sensitivity of DTSs. New method for a self-consistent device optimization is developed in the framework of model of the diffusion current flow through an abrupt asymmetric p–n junction, the ideality factor of which is assumed to be equal to unity. For Si-, GaAs-, and Ge-based DTSs with n +–p and p +–n junctions, the limiting TRCs and temperature dependencies of the sensitivity have been calculated. The experimentally measured metrology characteristics of DTSs have been shown to be within the range restricted by the established limiting characteristics.

Study of magnetic properties of a cryogenic temperature sensor diode

The magnetic properties of a cryogenic silicon diode temperature sensor (Lake Shore) are studied in the temperature range 5–255 K using a superconducting quantum interference device magnetometer. The M vs H curve at 5 and 250 K showed practically negligible magnetic hysteresis. The magnetization in a field of 100 Oe is found to be temperature independent to within 10% in the temperature range 5–255 K. The observed magnetization comes mainly from the packaging materials which includes ferromagnetic Kovar leads and nickel plating. We suggest a change of the construction materials. Our measurements show that, the existing diodes, if used in close proximity to the sample, in magnetization measurements, can be conveniently used only after background calibration.

Silicon diode temperature sensor without a kink of the response curve in cryogenic temperature region

By means of increasing the doping level of thermodiode base the silicon p 2+n +-type temperature sensors have been attained whose response curves do not exhibit the kinks in the cryogenic temperature range. The effect is connected with the suppression of freezing out of carriers to impurities in the diode base. It results in lowering of base resistance below junction one. Mechanisms responsible for the response curve form under this conditions are discussed. With this aim the sensors' current–voltage characteristics in wide ranges of temperatures and currents are measured and analysed.

Self-consistent method for optimization of parameters of diode temperature sensors

Self-consistent method for optimization of parameters of diode temperature sensors

Cryogenics

Lake Shore Cryotronics has introduced the Model 218 temperature monitor. The unit can read up to eight diode or resistance temperature sensors twice each second. All eight channels can be displayed continuously in Kelvin, Celsius, volts or ohms. The Model 218 supports a variety of sensor types, with diode sensors allowing temperature measurements down to 1.4 K. Two versions of the unit are available, one with an IEEE-488 interface and one with a serial interface. The Model 218 also features an alarm capability. Relays can be used with the alarm set-points in latching mode for error detection or in nonlatching mode for simple on/off control. The unit also includes two analogue voltage outputs, a printer interface and a data-logging facility.

Study of forward characteristics of a cryogenic temperature sensor diode

The current dependence of the forward voltage of a cryogenic silicon diode temperature sensor (CRYO Industries of America, Inc.) is reported here in the temperature range 10–300 K. The current values are varied from 10 nA to 0.1 A. The sensitivity of the diode is observed to increase for lower current values in the high temperature range. The rapid increase of the forward voltage at low temperatures is observed to be suppressed considerably by reducing the current. This study helps us to conclude that for all practical purposes such commercial diodes (prescribed for a particular current value of 10 μA) can be operated for a wider range of current values, with suitable calibration data.

Silicon diode temperature sensors for process systems

Thermocouples and platinum resistance thermometers are commonly employed in low temperature engineering and process cycles. This paper argues that temperature sensors based on silicon diodes provide superior performance, giving higher accuracy and fast response, with simpler instrumentation.

Test chips, test systems, and thermal test data for multichip modules in the ESPRIT-APACHIP project

This paper presents details of four multichip module cooling techniques using common test chips and test methods in the ESPRIT Project 2075, APACHIP. The project was concerned with the development of technology and manufacturing capabilities for single-chip packages and multichip modules. The paper presents descriptions and test results of cooling techniques investigated for multichip modules. These include heat pipes (Bull), immersion in inert fluid (GEC-Marconi), water-cooled thin membrane (GEC-Marconi), and direct-chip on water-cooled cold plate (Siemens Nixdorf Informationssysteme AG). Two 12 mm square thermal test chips are described that have been developed (NMRC) for characterization of thermal demonstrators. Test systems, established at four partner sites for diode temperature sensor calibration and thermal characterization of demonstrators, are described and compared. Statistical errors amounted to less than /spl plusmn/1%. Systematic errors were less than /spl plusmn/10%. The thermal rest data have enabled the project partners to compare the various cooling methods in terms of current and future system designs and to make decisions as to which system is most appropriate from both a technical and an economic viewpoint.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The influence of thermal gradients on the characterization of Schottky-barrier diodes

A simple and fast method of measuring the electrical performance of a packaged array of Schottky diodes as a function of temperature is described. The technique utilizes the device's ceramic package as the isolating thermal resistance. The effective thermal conductivity of the experimental arrangement is investigated, allowing the cooling times and temperature distribution of the system to be determined. In particular, attention is given to the variation between device operating temperatures and those obtained from a diode temperature sensor mounted in close proximity to the die. >

Measurement system induced errors in diode thermometry

Diode temperature sensors are capable of being used at the accuracy level of a few hundredths of a kelvin. However, in order to achieve this performance, proper measurement techniques must be used. Poorly shielded or improperly grounded measurement systems can introduce ac noise which will create an apparent shift in the dc voltage reading across a diode sensor. This results in a temperature measurement error which may approach several tenths of a kelvin. The presence of the ac noise in question is not obvious during normal usage and several quick tests are outlined to verify whether or not a noise problem exists. Experimental data and derivations from theoretical p-n junction characteristics are given which correlate the ac noise level with possible voltage/temperature measurement errors. These results can be used in estimating the accuracy and performance of a temperature measurement system. Several of the more common problems which introduce noise into diode circuitry are described.

Behaviour of semiconductor low temperature sensors in electromagnetic environments

The effect of an electromagnetic field, with frequencies in the 30 – 300 MHz range, on semiconductor cryogenic thermometers, eg silicon diode temperature sensors as well as silicon and germanium resistance thermometers, has been investigated at temperatures from 70 to 300 K. The changes in voltage drop or resistance versus temperature characteristics of the tested thermometers for various fixed frequencies of external electromagnetic field have been found. The frequency dependent electromagnetic field behaviour of the thermometers was studied and a resonance character of the ‘error’ ΔT has been evaluated. It has been shown that the semiconductor low temperature sensors may only be used for accurate recalibration in the presence of a well-known, low-intensity EM field at a constantly held frequency not corresponding with the maximum values of ΔT.

A portable meter for the assessment of human heat stress

An instrument has been developed which senses the factors in the environment which contribute to human heat stress and displays on a meter a composite heat stress index. This is the WBGT Index put forward by Yaglou et al. in 1956 defined as 0.7 (natural web bulb temperature)+0.2 (black 6 in globe temperature)+0.1 (dry bulb temperature). As was shown, it is possible to use a much smaller globe, eliminate the dry bulb sensor and still derive the same information as before. The result is a simplification which not only improves the speed of response but makes the instrument compact and easy to handle. Since the output of the silicon diode temperature sensors is linear with temperature, weighted summation can be effected by a simple resistive network. The electronics comprise chiefly two operational amplifiers. The taut-band meter has a hand calibrated scale and is protected against overload. Battery life is of the order of 700 h.