AT404758B - Miniature probe, process for its production and its use - Google Patents

Abstract

The invention relates to a miniaturized semiconductor probe for detecting thermophysical characteristics in fluid media, having at least one measuring cell which is arranged in a probe body and accommodates the medium, and in which there is arranged at least one electrical/thermal emitter/absorber/sensor (Em/Ab/Se) probe element which comes into contact with the medium, and having devices for supplying medium to and removing medium from the measuring cell and for supplying power to and removing power from the thermal emitter/absorber/sensor elements, as well as those for control, regulation, acquiring measurement data and/or processing measurement data, the probe element being designed as a web element 312, preferably a bridge-like web element, which is arranged in the measuring cell 7 so that the fluid flows around it freely on all sides, and provision is made for the web element 312 to be formed by a thermal emitter/absorber/sensor (Em/Ab/Se) element 1 based on a semiconductor material applied in layer fashion to at least one layer-like substrate 3 made of an insulating material. The invention also relates to the production and use of the probe. <IMAGE>

Description

AT 404 758 B

The present invention relates to a miniaturized semiconductor probe for recording thermophysical characteristic data and / or characteristic data derived therefrom in or from, in particular flowing, fluid media with at least one (m) arranged in a probe body, receiving the medium or through which the medium can flow or measuring channel in which (m) at least one electrical / thermal emitter / absorber / sensor (Em / Ab / Se) probe element coming into contact with the medium is arranged, and devices for supplying / disposing of the measuring cell with medium and the thermo -Emitters / absorber / sensor elements with energy as well as those for control, regulation, measurement data acquisition, conversion and / or processing, the probe element being freely surrounded or flushed around by the fluid in the measuring cell or in the measuring channel arranged, preferably bridge-like, web element is formed, process for their production and their use.

For reasons of simplification, instead of &quot; electrical / thermal emitter element &quot; more often the term &quot; thermo-emitter element &quot; or just &quot; emitter element &quot; used.

Previously published variants of micromechanically miniaturized, thermal sensors, in particular flow sensors, are characterized above all by relatively short response times, robustness, chemical resistance and compatibility with common microelectronic technologies and the resulting integrability with conventional electronic circuits for signal processing. The use of this sensor construction is particularly advantageous in the case of integration with likewise micromechanically miniaturized actuators (valves). In this way, flow regulators with extremely good dynamic properties can be implemented. In particular, reference is made to the publication by Masayosi Esashi, &quot; Integrated Micro Flow Control Systems &quot;, Sensors and Actuators A21-A23 (1990) 161-167.

In known thermal probes, thermal energy emitters and sensors are attached to at least one wall or wall element, e.g. made of glass, a or a respective measuring cell or flow channel and can therefore practically only over one of their surfaces with a sample to be examined, e.g. come into contact with a free flowing fluid.

Disadvantages of these known thermo-emitter sensors are therefore the fact that heat energy can only be given or absorbed to and from the fluid medium (s) on one side only, and only on its volume component (s) close to the wall, while a Part of the energy "migrates" into the cell or channel body and thus, if of course slightly, can interfere with the sensor environment or the vicinity.

In the same way changed or &quot; smeared &quot; the response characteristics of e.g. arranged at a distance from a thermal emitter, e.g. of a thermal sensor provided downstream of the same. In order to partially compensate for these disadvantages, higher amounts of heat have to be introduced into the fluid, which can have an adverse effect in particular on biological or heat-sensitive biological fluids.

To achieve a minimization of the power requirement or the required excess temperatures for the thermal measurement, e.g. For flow measurements on thermally sensitive, biological media or liquids close to the boiling point, attempts have been made to use modern vapor deposition and etching technology and “micromachining” to create probes whose energy emitters or absorbers and sensors have a low dead weight and “inertia”. and less &quot; connectivity &quot; have high contact with the fluid medium on the probe body housing the measuring cell. In such cells, the probe elements are arranged in the measuring cell so that they can be flushed around by the fluid medium. For example, they are designed as web elements freely penetrating the cell between opposing wall elements.

Elements based on electrical heating resistors are to be mentioned as thermal emitters; thermocouples and, in particular, resistance thermometers or thermistors can be considered as thermal absorber or sensor elements.

In the case of the web elements which have become known, the layers for thermal emission and those for temperature measurement are formed with metallic material, e.g. a desired, optimal resistance range is to be ensured by adjusting the layer thickness.

Disadvantages of these known probes with web-like sensor elements are, however, the relatively high conductivity of metallic resistance layers, which, for example, require higher energy input, and furthermore the relatively small changes in the electrical measured variables when the temperature changes, and also a relatively low mechanical stability which is practically only caused by the web carrier. Various embodiments of the probes in question are described in the publications mentioned below, but the technical solutions which can be found in these publications provide, with a single exception, thermo-emitter and / or sensor elements based on real electrical conductors. The specifically designed emitters / sensors according to EP-330 105 A2 are formed by thin layers of selectively etchable materials, such as Fe-Ni, Ti-W, Cr, Al, those according to US Pat. No. 5,205,170 A with electrically conductive material from the Group Ta, Pt, Pd, Ni and nickel alloys, those according to US 4,891,977 A with 2

AT 404 753 B

Au, Cr, Ti-W, Ni-Fe, those according to US-5 056 263 A e.g. with gold metallization and finally the emitter / sensor according to EP-375 399 A2 with a platinum element.

Disadvantages of such sensors based on conductor materials are their low specific resistance and &quot; flat &quot; Temperature resistance curve. They therefore require either relatively large or long resistance sections with unfavorable volume / area ratios or extremely small, in some cases then no longer fully reproducible material thicknesses, in which case the unfavorable use of increased useful capacities must also be taken into account.

The solid-state microanemometer according to US Pat. No. 5,231,877 A is interesting with regard to the sensor elements.

There, a sensor element, which is arranged in a recess of a carrier bridge element and cannot be washed around freely, is formed by in-situ-doped semiconductor material, which - generally speaking - is also provided as an emitter / sensor element material.

According to this US-A, the desired property values are achieved by micromachining or etching, that is to say by particularly costly controlled material removal until the desired property values are achieved.

The invention has now set itself the task of maintaining the construction of the probes described above, temperature, temperature and heat or material flow probes, which do not have the disadvantages of the previously known probes and with advanced, extreme Miniaturization, even with small changes in temperature, can provide the greatest possible change in the signals or measured values supplied by the probe, in particular temperature measured values. A miniature probe with high sensitivity, accuracy, reproducibility, small size and mechanical robustness should therefore be created. Furthermore, sensor elements provided on the basis of a layer of a composition and modification-defined semiconductor material applied to the carrier material and specifically dimensioned during application should be used for probes which can be used in resting and flowing fluids, since it has been shown that such layer sensor elements are the result of the significantly improved possibilities in the control of the manufacturing process can be produced with extremely small characteristic bandwidths, which represents a significant advantage over the sensor elements according to US Pat. No. 5,231,877 A described above, which are obtainable through technically complex and not optimally controllable material removal.

Compared to the sensor elements based on electrical, i.e. metallic, conductors known from the prior art, the new probe is also said to be robust, compact in design and highly reliable in use.

The above-mentioned objects are achieved in a probe of the type mentioned at the outset in such a way that the web element, which may be present in plurality, with at least one thermo-emitter / absorber / sensor, in particular vapor-deposited on at least one layer-shaped support made of an insulator material -Element is formed on the basis of a semiconductor material.

With the new probe type, both the integration of the emitter / sensor element into the ensemble of the measuring cell and the body containing the same as well as the thermal separation of several temperature sensors, in particular of small dimensions, e.g. when arranged as sensors which surround a thermal emitter and are preferably at a minimal distance from one another in the form of &quot; sensor arrays &quot;.

Together with the inexpensive design of spatially free webs, the intrinsic signal characteristics of the emitters and sensors are significantly improved compared to all previously known solutions, and new areas of application for thermal sensors open up. Of course, a high thermal coupling of the sensor to the measuring medium is achieved with a simultaneous reduction in the thermal coupling of the thermistor and macroscopic substrate (e.g. Si wafer) and a decisive reduction in the relevant thermal capacities. The size of the semiconductor resistor also enables successful further miniaturization of the thermistor carrier. Since the resistance values of the semiconductor sensor layer are high compared to the previously used resistance metals, and thus the thickness of the vapor-deposited sensor or emitter layer can be higher, it is possible that the same, together with the web element carrier, is of a mechanical type Significantly increasing stability - forms sandwich effect.

The thin-film thermophysical elements based on semiconductors are surrounded by the measuring medium at the top and bottom of the web, that is, thermally closely coupled to the measuring medium. This brings with it the particular advantages due to the higher sensitivity, particularly in the case of gases.

As far as miniaturization is concerned, the dimensions of the measuring cell or channel cross-section that can be easily achieved are the dimensions 0.9 x 0.3 mm 2, for a web element a width of up to about 15 μm with a material thickness of up to 10 μm for example, the carrier of the same, for example can only have a thickness of up to about 3 µm. The flow rates are e.g. at 0.3 mm2 channel cross 3

AT 404 758 B cutting area up to 4 l / h liquid medium of low viscosity, which corresponds to a flow speed of about 4 m / s. Surprisingly, even at these high flow velocities, no impairments of the micromechanical structure can be observed, and dynamic load changes, e.g. trapped gas bubbles do not lead to any disturbance or even destruction of the micromechanical structure, which ensures high signal fidelity at different loads. Typical values for the power to be used in the new probes - about only 10% of the power required for the previously known probes - are about 10 "2 to 10-3 mW for gaseous and liquid media. Typical values for the electrical supply of the emitters are about 100 uA and 20V.

The web elements can preferably as real bridges, but also as &quot; bridge torsi &quot; protruding into the cell. and furthermore, possibly with a trapezoidal or triangular shape, starting with both ends of the same wall element, projecting into the channel interior and extending in the channel direction, approximately balcony-like "bracket" elements. The advantage of this last-mentioned web element variant can be that two web elements can be arranged next to one another at the same position, based on the longitudinal extent of a measuring channel, which is useful for any transverse diffusion measurements, e.g. in flowing media can be beneficial.

According to a preferred embodiment of the invention it is provided according to claim 2 that the new probe is a with a doped pure semiconductor, in particular amorphous germanium or amorphous silicon, or a compound semiconductor, in particular silicon carbide or an Ill / V semiconductor, e.g. Gallium or indium arsenide, formed thermo-emitter and / or sensor element.

As a result of the high absolute value per se and the high temperature dependence of the specific resistance, the amorphous germanium, hereinafter referred to as &quot; a-Ge &quot; designated, for the manufacture of locally concentrated heating resistors and for a simultaneous, high-resolution temperature measurement proven to be particularly suitable.

The use of this material has the advantage of a direct, direct possibility of controlling the temperature of the heating element, because its temperature can be determined directly from the instantaneous value of the electrical resistance of the heating element itself, and if necessary, in particular by varying the useful power, without the aid of a further - necessarily spaced - temperature sensor. also be regulated. Very fine metallic conductor tracks are sufficient to supply the low heating current, which have the advantage of minimal heat dissipation.

The heating of the heating element made of a semiconductor material, and especially of a-Ge, required for the operation of a flow-through probe is typically only a few Kelvin, and the heating of the medium generally remains below 1 Kelvin. The electrical power required for the new thermistor material naturally depends strongly on the thermal conductivity of the measuring medium and, based on experimental experience, is a maximum of about 1 W per cm2 of heated surface in gases, typically around 4 W / cm2 in liquids (reference surface is the surface here the webs with approx. 0.2 mm2). In the case of gaseous fluids, the excess temperature in the center of the heating element is typically about 5K.

If, according to claim 3, in particular layer-like, energy / control / data conductor elements are bonded to the individual thermo-Em / Ab / Se element made of semiconductor material in the area of at least one of its longitudinal edges, preferably both mutually opposite longitudinal edges, which is applied in layers to the carrier , preferably vapor-deposited on the element, the advantage of an integral connection of supply and / or discharge and energy-consuming or data-emitting element is ensured without transition losses.

If - as provided according to claim 4 - the contours of the web elements or their supports, Thermo-Em / Ab / Se elements and energy / control / data conductor elements of the crystal structure or the crystal boundary profile of the measuring cell or measuring channel body or its lower part are meandering, formed, the particular advantage is given that the formation of undesired etching stop areas is prevented in the manufacture of the novel web elements; in addition, there is an increase in their total length or total area which is available for the fluid / web element and / or inverse energy transfer.

A material which is particularly outstanding for the support of the web elements from the point of view of production technology and for reasons of highly effective passivation during etching and the insulator effect, as has been found and is evident from claim 5, is silicon nitride (SiN *) and in particular low-temperature SiNx or silicon oxynitride (SiOuNv) represents.

Particularly intensive, low-loss thermal coupling of the heating or sensor element and the fluid medium can be achieved according to claim 6 with the particularly thin, preferably meandering web parts made possible by the invention, the carriers of which then have a material thickness of about 1 to 10 µm, in particular from about 3 to 7 µm. 4th

AT 404 758 B

The width of the webs is already minimized within the framework of the technology used. Typical ranges of the widths of the, preferably meandering, web elements are given in claim 7, they have values of between 10 and 120 µm, in particular from 60 to 70 µm.

An embodiment of the web elements according to claim 8 is particularly advantageous not only for reasons of production economy, but also because of the connection-free, integral and therefore mechanically highly stressable one-piece; It is distinguished by the fact that the supports of the web elements are connected with layers of the measuring cell or measuring channel body or from the lower part of the measuring cell or measuring channel body, or of the lower part thereof, which are essentially identical in material, in particular in one piece, with the same material thickness, layer-like, in particular formed by vapor deposition are. For the new probes, which are particularly suitable for accurate measurements in both stationary and flowing fluid media, particularly preferred characteristic values of their thermo-emitters / absorbers / sensor elements are mentioned in claims 9 and 10: probes which thermo are preferred -Emitter-absorber sensor elements with resistance values of about 10 to 500 kOhm, in particular from about 100 to 300 kOhm, (at 20 * C) and also those that have thermo-emitter / absorber / sensor elements with a sensitivity of Resistance change with the temperature of at least 1% / K, preferably of at least 2% / k.

A particularly favorable connection of the conductor elements to the heating and sensor elements and an almost loss-free guidance of energy and data is ensured by a construction of a preferred type according to claim 11, which provides that the energy / control / data conductor elements with at least one layered applied, in particular vapor-deposited, metal material are formed.

It is particularly preferred according to claim 12 if the energy / control / data conductor elements are formed with the layer sequence titanium-gold (silver) -titanium with layer thicknesses of titanium of approximately 20 to 40 nm and gold of approximately 80 to 120 nm are. Titanium serves as a diffusion barrier, and gold can be at least partially replaced by silver.

In the case of a special, integral form of training of the energy / control / data conductor elements and their supply and discharge lines according to claim 13, the advantage of eliminating any contact transition losses is given: They are characterized in that they are in the measuring cell or measuring channel with their -Body arranged or guided, in particular on the measuring cell or channel body lower part energy, control, data supply and discharge lines are formed in one piece from the same material.

In particular with regard to the production technology and further also on medium inertness, robustness, long service life, high property stability and minimized long-term changes, an embodiment of the web elements according to claim 14 is to be given particular preference, which provides that those connected to the insulating material, in particular SiNx or Si (OuNv), formed carrier-bound, in particular layer-like, Em / Ab / Se elements and their En / St / Da conductor elements fluid-medium-tight, with an insulating material, preferably with the same insulating material as the carrier, in particular with silicon nitride (SiN , J or silicon oxynitride Si (OuNv), coated, preferably enveloped by the same The thin SiNx or Si (OuNv) layer protects, but due to its delicacy has a negligible influence on the minimal energy exchange processes.

With regard to the characteristic values, particularly preferred for the new probes, in terms of local and thermal resolution, response times, power loss, accuracy and stability of their web elements, the embodiments and dimensions according to one or more of the following claims should be referred to:

Thus, it is provided according to claim 15 that the new probe comprises at least one web element which, in the case of thermal emission or sensor technology, has a local resolution of from 10 µm, preferably from 50 to 200 µm.

According to a further embodiment, it is advantageous if the new probe has at least one web element with a temperature resolution of at least 0.25 mK, in particular 0.1 mK.

Furthermore, as can be seen from claim 17, it can be favorable if the probe has at least one web element with an effective response time of at most 5 ms, preferably at most 3 ms, and a thermal response time of at most 0.5 ms, preferably of at most 0 , 3 ms.

In order to keep the influences of the measuring arrangement as small as possible, it is advantageous, as can be seen in claim 18, to ensure that the probe has at least one web element with a useful power of less than 1 mW.

The requirement for the highest possible precision can be met inexpensively if the probe comprises at least one web element which, with electronic linearization of the measured values supplied by it, has an accuracy of 0.1 K at temperatures in the range from 10'C to 60 * C having. 5

AT 404 758 B

Furthermore, the long-term reproducibility of the measurement data supplied by the new probes is often very important. It is therefore advantageous to ensure that the probe, as is apparent from claim 20, has at least one web element with long-term stability of better than 1% change in resistance value per year.

With a preferred arrangement of heating element and thermal sensors arranged next to or around it, e.g. Thermistors, according to Claim 21, which therefore provides that the probe has a plurality of spacing elements which are arranged spatially separated from one another, one of which can be supplied as a thermo by a power supply and control device with heating current / voltage pulses of the desired shape and height -Emissions- or heating element and at least one as a spaced from the heating element in the measuring channel arranged thermal sensor element, particularly precise heat and volume flow analyzes can be carried out.

If, as provided in accordance with claim 22, a plurality of thermal sensor elements at least on one side, in particular on both sides, preferably symmetrically in number and distance, from the thermal emission element - essentially a thermal sensor &quot; array &quot; forming - is arranged in the measuring channel or in the measuring cell, both a direction-dependent flow display is made possible and a media-independent calibration possibility of the flow of a fluid can be realized. In pulsed heating mode, a temperature wave arrives in the flowing medium to the temperature sensor arrays arranged one behind the other and a clear speed measurement is possible with location-dependent measurement of the temperature maxima. With knowledge of the dimension of the measuring channel, a media-independent volume flow measurement is thus made possible.

With regard to the configuration and design of the measuring cells or flow channels together with the web elements passing through them, channel shapes or cross sections according to one of the claims 23 and / or 25 explained below and / or an arrangement of the web elements according to claim 24 are particularly preferred.

It is therefore preferred if the measuring cell or the measuring channel has an essentially rectangular or square cross section.

Furthermore, it has proven to be advantageous if the respective individual web element is arranged essentially in the region of half the measuring cell or measuring channel height. With such an approximately central arrangement of the web element, edge influences are suppressed to a minimum.

Finally, dimensions of height and width of the, preferably rectangular, measuring cell or measuring channel cross-sectional area of 0.1 to 0.5 mm, or of 0.5 to 1.2 mm, in particular of approximately 0, have been found in practice. 3 to 0.9 mm, proven.

With dimensions of the channel cross section of e.g. 0.9 mm wide and about 0.3 mm deep ensures that low-viscosity liquids up to a few liters / hour and gases up to a few liters / minute can be pumped through the sensor without extreme pressure drops. The channel depth can be controlled by the selected duration of the etching process during its manufacture and can easily be adapted to particular requirements.

Further improvements, in particular also with regard to minimizing energy losses and geometric changes, are brought about by a measuring cell or channel lining according to claim 26, in which the walls or wall elements of the measuring cell or the measuring channel are poorly chemically resistant and / or abrasion-resistant thermally conductive silicon nitride or an organic polymer are coated.

In a similar sense, the choice of material for the measuring cell or measuring channel body according to claim 27 is to be given particular preference, which consists in particular in that the measuring cell or measuring channel body with a mechanically stable, chemically inert, low electrical and material having thermal conductivity with a low coefficient of thermal expansion, preferably with a silicon single crystal or silicon wafer material. A microstructurally fault-free homogeneity of the silicon wafer material is advantageous.

In order to be able to compensate for external influences on the physical happenings in the measuring cell or in the measuring channel - in itself due to the new design, in particular in the previously described variants, which are already extremely minimized anyway - a control device according to claim 28 is advantageous, which includes: there is that at least one thermal sensor (ambient sensor) for detecting the temperature of the probe body is arranged in the measuring cell or measuring channel body, preferably in close proximity to the cell or channel.

To ensure trouble-free, realistic conditions and conditions for the extremely subtle and micro-based measurements with the new probe, a configuration of the measuring cell or measuring channel body with an inflow and possibly outflow device according to claim 29 is particularly advantageous , in particular, 6

AT 404 758 B that inflow and / or outflow bodies are assigned to the measuring cell or measuring channel body on the fluid medium inlet and / or outlet side, and also an embodiment in which the said inflow and outflow bodies end flush with the measuring cell or the measuring channel Have fluid guides.

Another essential object of the invention are methods for the production of probes with the material-newly designed web elements, as have been described in detail so far.

In a manufacturing method which is particularly preferred because of its technically problem-free feasibility and the achievement of robust, accurate measuring probes of the new type within the scope of the invention, it is provided that at least one surface of a, preferably cuboid, blank of a lower part of the probe body, preferably by vapor deposition, with at least one layer of a passivation or. Insulator material is coated - that a layer of a semiconductor emitter / absorber / sensor material, preferably amorphous germanium or silicon, is applied, in particular vapor-deposited, to this insulator layer at least in the region of the web element provided, preferably in accordance with the shape provided for this is that - at least one (e) energy / control / data conductor element or conductor track is applied to the same in accordance with the lithography provided in each case - that the web element structure now formed, preferably over the entire surface, with a passivation or Insulator layer is coated, that - after exposure of - the floor plan of the measuring cell or measuring channel lower part to be formed and the (which) projecting in the same, in particular penetrating the web elements (s) - in the passivation or Insulator layer and the emitter / absorber / sensor layer - while remaining the web elements of the measuring cell or measuring channel lower part incorporated into the lower part of the probe body, in particular etched, and - that finally the ensemble of the lower part of the probe body, fluid sealingly combined with a probe body upper part having the upper part of the measuring cell or measuring channel, preferably in alignment with the lower part of the cell or channel, preferably by gluing.

The introduction of high-resistance, but still conductive semiconductors, in particular amorphous germanium, instead of metal films, may have limitations for the technology of the sensor, which at first glance has a certain disadvantage when using this material, which, however, is caused by the Advantages described above is far overcompensated. The disadvantage is particularly the sensitivity of germanium in its amorphous phase to temperatures that are too high. If the process temperatures are too high, recrystallization phenomena and irreversible changes in the specific resistance and its temperature dependence can occur. After coating the measuring cell body with germanium, relatively low process temperatures are therefore advantageous. This concerns above all the production of the passivation of the sensor material, e.g. through an insulator layer. For the passivation of thermally sensitive samples, a specially developed plasma CVD process for the deposition of SiN * passivation layers can advantageously be used, which is compatible with substrate and process temperatures below 100 &quot; C works. In order to keep the thin, self-supporting thermistor carrier as free as possible from mechanical stresses, the first thin insulation layer is also produced directly on the silicon wafer using this low-temperature process. Then the vaporization with Ge takes place at a residual gas pressure of approx. 10-7 Torr. After the germanium layer has floated, the conductor tracks are lithographed and vapor-deposited with Ti-Au-Ti (e.g. 30 nm - 100 nm - 30 nm). Subsequent to stripping the paint, the second passivation layer is deposited, e.g. from SiNx.

After the windows required for the anisotropic etching of the wafer have been exposed with the aid of an RIE process in both passivation layers, the etching of the flow channel takes place. After the electrical connections have been bonded, the sensor is assembled. First, an approximately 0.15 mm thick intermediate piece made of silicon, into which an opening of the dimensions of the channel has been micro-etched, is glued in alignment on the channel. The entire silicon trench is now around 0.3 mm deep, and the thermistor bars are located approximately halfway up the cross section. The channel is finally closed with a transparent polymethyl methacrylate cover, in which supply lines are also fastened.

In accordance with the above statements, the method features according to the following two claims are of particular advantage in order to obtain high-quality probes according to the invention:

According to claim 32 it is provided that the passivation or insulation material, in particular silicon nitride, is applied by a combined plasma CVD process at substrate and process temperatures of below 100 * C and according to claim 33 that the semiconductor material is amorphous Germanium 7

AT 404 758 B and / or silicon, for which thermo-emitters / absorbers / sensor elements are applied at residual gas pressures in the range of about 10-7 bar.

With regard to the possibilities of using the new probes, only a few particularly preferred fields of application are mentioned here, which in particular form the subject matter of claims 34 to 38 and whose characteristics are essentially the following: For fast, highly sensitive temperature measurements in human and animal tissue e.g. a puncture sensor has been constructed that can be replaced during normal or pathological brain activity, see claim 34.

The new technology used to implement resistance thermometers makes it possible to integrate several sensors on one carrier of a probe. By heating one sensor with simultaneous temperature measurement using a second sensor, a precise heat flow measurement is made possible. Such a measuring arrangement on a needle was e.g. for detection of minute liquid flows - e.g. of physiological fluids, such as liquor. A use is therefore provided, the essential features of which are that one of the at least two emitter / sensor elements of the probe is operated as a heating element and at least one other of the emitter / sensor elements is operated as a thermal sensor element , and the probe is used for heat flow measurements and for the detection of minimal fluid movements or flows in animal or human tissue.

Another preferred type of use of the new probes according to claim 36 is that at least one emitter - in particular heating element is used simultaneously with its energy output as a sensor - in particular temperature measuring sensor - for temperature measurement / regulation / control of itself.

To use the new probes with the web sensors, the following must also be carried out:

The measuring principle of the flow sensor can be used to detect unknown heat conduction of substances when the geometry of the sensor and the sensor carrier are known.

If no flow or convection is permitted in a flow sensor for gases or liquids, the shape of the propagation of the temperature wave only depends on the temperature conductivity when using the heat pulse method and with a suitable geometry.

With a suitable electronic evaluation of the time-dependent temperature curve, it is possible to determine the thermal conductivity.

Thus, a combination of both methods can be used to carry out a flow measurement independent of the medium, and the temperature and / or thermal conductivity of the medium can (can) be detected at the same time by applying heat pulses by detecting the temperature curve shape.

The new semiconductor technology enables a new use or operating mode of the probe or of its probe elements for the first time. Hiebei serves the semiconductor thermistor layer of at least one of the web elements of the probe as an integrally integral heat energy output temperature measuring element, with which any hysteresis or the like. is avoided.

A particularly advantageous application is covered by claim 37, according to which it is provided that - preferably according to claim 33 - self-sensor-controlled thermo-emitter elements a primary temperature and / or heat pulse of the desired shape and / or size to a possibly flowing - Medium is emitted and on the basis of the signals or signal sequences emitted by at least one sensor element spaced apart from said thermo-emitter element, the transit time and / or shape and / or size of the pulse arriving at the sensor element is determined and, if desired, to a computer unit is or will be passed on for analytical processing. So e.g. Pulses or impulse responses are given at constant temperature or at constant power or are finally analyzed and conclusions can then be drawn about the medium from the signals or signal sequences.

Furthermore, a thin-film bolometer could be constructed for use according to claim 38 to determine the neutral energy that can be generated or generated, which e.g. can be used to calibrate a satellite test chamber.

In this way, the bolometer can ultimately form a particle detector, which quantitatively determines the particle dose indirectly by converting the kinetic particle energy within an absorber into thermal energy. This can be detected by means of bolometric detection principles and the probe in question. 8th

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Examples:

General part:

Mass flow control Two mass flow controllers from MKS, model 259B, which can be calibrated for different types of gas, were used to provide defined gas flows. The usable control range extends from approx. 1 standard cubic centimeter to 100 standard cm3 or from approx. 20 standard cm3 to 2000 standard cm3 for N2 (for Ar and He these values have to be multiplied by 1.45), 100 standard With a channel cross-section of around 0.003 cm2, cm3 corresponds to a maximum flow velocity of 5.5 m / s, ie if compressibility is neglected, the maximum flow rate that can be achieved with these flow controllers is around 150 m / s.

Liquid flows were generated using a regulated syringe pump (range 1 ml / h to 4 l / h. 100 l / h correspond to approximately 0.1 m / s). Ethanol, water and glycerin were examined. Due to its high viscosity, glycerin could only be pressed through the channel, while the other liquids were also pumped through suction. Even at the highest available flows of approx. 4 l / h, no mechanical impairments of the micromechanical structure were observed and dynamic changes in load, e.g. trapped gas bubbles did not destroy the micromechanical structure.

Measured value acquisition: For all the investigations and operation of the sensor described below, a data acquisition device that can be adapted to the various measurement tasks and was controlled with the aid of a PC was used, with which the voltage curve on the heating element can be regulated and the resistance all simultaneously; Temperature sensors and the heating element with a sampling rate up to 2 kHz can be detected and measured. The measurement resolution is 15 bits in real terms (nominally 16 bits). By optoelectronic separation of the battery-powered measuring unit from the PC, the high-frequency interference signals generated by the PC and monitor could be effectively kept away from the measuring arrangement. The maximum possible temporal resolution is determined by the maximum data transfer rate of the electro-optical components used. Since the sampling rate of around 2.5 kHz, here for the transmission of a total of ten different measurement data, proved to be sufficient for all investigations carried out, no faster optoelectronic components were used.

Special part:

Example 1:

Determination of the thermal resistance in the fluid at rest (heat conduction)

With the device described above, the quasi-stationary thermistor characteristics of the heating thermistor and temperature sensors were recorded in various media in the area of interest.

For this purpose, the voltage at the thermistor was initially increased from 0.7 V in steps from approx. 0.1 V to 10 V and then reduced with the same step height. Care was taken to ensure that the voltage ramp was passed through sufficiently quickly to keep distortions caused by long-term effects (thermal drift) small. The diagrams of the normalized thermistor resistance over the electrical loss line shown in FIGS. 1b and 1b of the drawing show practically no hysteresis due to thermal inertia, that is to say reflect the thermal resistance of the heating thermistor at an approximately constant wafer temperature. The diagram was recorded with constant sensitivity of the current-voltage converter in the measured value acquisition, which is why the measured values fluctuate somewhat at the low powers. There is a decrease in the electrical resistance of the thermistor with increasing electrical useful or power loss. With an assumed average temperature dependency of the specific resistance of 2% / K, the excess temperature of the thermistor (right scale in the diagram) is calculated and furthermore the associated thermal resistance from the respective gradient of the quasi-stationary characteristic.

Since the heat conduction of the fluid decisively determined the value of the thermal resistance in all of the cases examined, it was also to be expected that for all media examined, convection would also be the 9th

AT 404 758 B has a lasting influence on thermal resistance.

Example 2:

Measurement of the flow dependency:

As in the investigation of the heat conduction conditions, the thermal resistance was also determined here from the quasi-stationary characteristic of sensor resistance vs. Power loss, now recorded at a given flow rate of the fluid.

The dependence of the thermal conductivity of the heater (heat emitter element) on the medium flow is shown for various fluids examined in FIG.

The measured characteristic shows the influence of the convective heat dissipation only from a certain, medium-dependent flow velocity, with smaller rivers no or only an extremely weak influence of the convective heat transport can be observed. This flow dependence begins at flow velocities ^ where the passage time of the fluid for a web width is approximately equal to the time in which a heat pulse from the heating element takes for the propagation to the next channel edge. These values are indicated by arrows in the diagram. b.a t2 b width of the Sinx web t channel depth a temperature conductivity.

In areas where the flow dependency dominates, the measured characteristic for all media is given by a power law th

G approximated in a very good approximation. G, h = thermal conductivity, Rlh = thermal resistance F = flow velocity, B * constant

The value of the exponent depends on the flowing medium and ranges from a = 0.17 (H2O) to α = 0.33 (Ar, N2). The exponent a - 33 is also obtained in the case of the thin plate with longitudinal flow in the event that the thickness of the thermal boundary layer is substantially less than that of the flow boundary layer.

The exponent a can be determined from the linear regression of the measuring points in the flow-dependent region of the characteristic curves (FIG. 2). The regression analysis of the characteristic curve Gth over F ° can be used to check the quality of this approximation. Taking into account the measured values from 100 standard cm3 to 3390 standard cm3 (12 measuring points) results in a correlation coefficient of 0.99997 for Ar, so the power law is an excellent approximation. Values close to 1 also result for the other media.

Comparison with the finite element simulation:

Some calculated results are presented in Figure 3 of the drawing. The qualitative agreement with the experiment is very good, quantitatively it is satisfactory considering the only two-dimensional approximation. In the characteristic curves for air, the thermal conductivity of the duct walls was varied arbitrarily (isothermal means λ = », adiabatic X = 0).

The family of curves shown for air illustrates the influence of the thermal conductivity of the duct walls on the characteristic curve at low flow velocities. It can be seen from the curve for adiabatic boundary conditions that the effect of convective cooling does not disappear even at low flow velocities. In order to explain the almost horizontal characteristics of small rivers, one must in this area in addition to the 10 increasing with increasing river

AT 404 758 B Heat removal by convection assume a second heat transport effect, the effect of which decreases with increasing flow. These two effects apparently compensate for each other in their flow dependency until the behavior is only dominated by convection.

Discussion of the results:

The sensitivity of the new probes and their sensors are high for a wide range of material parameters. The lower limit of the flow measurement range is determined by the geometry of the construction and by the temperature conductivity of the fluid. The thermal conductivity of the web determines the upper limit of the measuring range. It was calculated using FE simulation calculations assuming a simplified web geometry and perfect heat dissipation through the fluid at 20 mW / K. This value is almost an order of magnitude above the most real measured values. With the new probe design with web sensors, there are no limits to high fluxes even for aqueous solutions from the thermal conditions. The lower limit of the measuring range is wrongly proportional to the square of the channel depth. Since the flow rate only decreases linearly when the channel depth is increased, the measuring range can advantageously be expanded to small flow rates.

The invention and its practical application are explained in more detail with reference to the drawing:

FIGS. 1b and 2b and 2 and 3 show diagrams with the results of test series carried out with the new probes according to Examples 1 and 2. FIG. 4 shows a diagram of the probe body in a view transversely to the measuring channel axis, FIGS. 5 and 6 shows a layout for a probe according to the invention, in particular of its probe body with the meandering web elements and a &quot; detail view A &quot; 7 shows the section through one of the web elements having the thermal emitter / absorber / sensor elements according to the invention, FIG. 8 shows a photographic oblique view of one of the meandering, bridge-like web elements of the new probe type in the measuring channel, obtained by scanning electron microscope, and finally FIG. 9 schematically shows the arrangement of an inflow and outflow body on a probe body.

The diagrams in Fig.la and 1b relate to the determination of the thermal resistance in various static fluid media, i.e. practically their heat conduction, whereby in Fig.la for water (W) glycerol (G) and ethanol (E) and in Fig.lb for helium, nitrogen and argon, the changes in resistance or temperature increases in Kelvin as a function of the electrical power loss in mWatt for the web elements used in a probe according to the invention and having bar elements are given.

The diagram in FIG. 2 shows how, in the case of measurements of the flow dependency carried out in accordance with Example 2, the thermal conductance of a heating-web element changes as a function of the average flow rate in mm / s for the media water, ethanol, H2, He, Ar and N2 , with the &quot; kinks &quot; in the curves mark the beginning of the influence of convective heat dissipation only from a certain flow rate, which is individual and characteristic for a particular medium being examined.

3 serves to compare the real results with simulated measurement results which are obtainable using the finite element method. They represent the results of the finite element calculations for a two-dimensional model of the sensor.

There are the values for water, ethanol and helium as well as for air for &quot; isothermal &quot; Wall of the measuring channel of a probe according to the invention, further with &quot; adiabatic &quot; Wall, calculated from a duct wall made of silicon and, for a theoretical wall, from air. The characteristic &quot; kink &quot; in the curves.

4 shows how the measuring channel body is formed with a lower part 61 and an upper part 62, each of which contains the lower and upper measuring channel 72 having the opposite channel walls 73, 73 ', which together form the measuring channel 7. The channel 7 is freely penetrated at approximately half the height h by the web element 312, which itself has a support 3, e.g. made of SiNx, which here is integrally connected to a SiNx coating 63 of the measuring channel lower part 1. On the SiNx carrier 3 there is an emitter / absorber / sensor element 1, e.g. made of amorphous Ge, to which the energy / control / data conductor elements 2, 2 'are bound, in each case at the edge and at a distance from one another. The entire web ensemble is covered with a SiNx insulator / passivation layer 4. The conductor elements 2, 2 'are connected to connection conductors 22 or are formed in one piece.

5 schematically shows a layout of the overall concept for a micromechanically producible multifunctional heating element thermal sensor arrangement with semiconductor thermistors. A 0.9 mm wide, 9 mm long trench 71 with regular edges 73, 73 'is etched in a silicon wafer, which can be used together with a corresponding counterpart as a flow channel. The germanium thermistors 1 are along this flow channel on the one hand 50 µm to 80 µm wide and a few 11

Claims (37)

AT 404 758 B micrometer thin silicon nitride webs over the trench, on the other hand arranged on the nitride passivation layer 63 on the silicon crystal. It designates the number 7 the measuring channel recessed in the lower part 61 of the probe body for receiving or guiding a fluid medium; Conductor tracks 22, each serving as energy and data supply and discharge lines, go from the connecting surfaces 25 to the web elements 312, the middle one of which represents a heating energy emitter web 312 ', the thermosensor element elements which are increasingly spaced apart on both sides of 3 with distance from the heating element 312' Webs 312 &quot; is surrounded or flanked symmetrically, which form a thermal sensor array for flow measurements. With 66 two assembly-facilitating alignment marks for the assembly of measuring cell body lower part 61 and upper part 62, not shown, are designated. Finally, a substrate thermistor 8 is arranged in each case in the vicinity of the outer ends of the sensor arrays and is intended to compensate for disturbances or influences caused by the measuring cell body 6 during the measurements. 6 shows the &quot; Detail A &quot; from Fig. 5 in more detail, on the one hand the layout of a sensor element, e.g. a semiconductor layer thermistor 1, on the silicon nitride carrier 3 with the extending along both meandering longitudinal edges, on the a-germanium. 1, metallic energy / measurement data conductor elements 2, 2 'is shown and, on the other hand, a &quot; substrate thermistor &quot; 8 is housed in the measuring cell or channel body lower part 61 in the so-called bulk thermistor design. It should be noted that the electrical characteristic values of the substrate thermistor 8 shown here and those of the new web thermistors 2 are approximately the same. 7 shows in a detailed cross-sectional view how the a-germanium layer of a sensor element 1, e.g. of a thermistor, and on each of these, edge layers of the electrical conductor elements 2, 2 'are applied, the entire ensemble being enclosed in a fluid-tight manner by an SiNx insulator 4. The photograph of FIG. 8 clearly shows, in an oblique plan view, a lower part of the measuring channel body with a lower part of the measuring channel and a meandering web element that translates freely and translates, with an a-germanium sensor layer and the edge-lying conductor elements. Finally, FIG. 9 shows, by way of example only and schematically, how an inflow and outflow body 9, 9 ′ with channels 97 and 97 ″ each opening in the measuring channel 7 of the probe body 6 can be arranged on the probe body 6. 1. Miniaturized semiconductor probe for recording thermophysical characteristic data and / or characteristic data derived therefrom in or from, in particular flowing, fluid media with at least one (m) arranged in a probe body, receiving the medium or through which the measuring cell or measuring channel can flow, in which at least one electrical / thermal emitter / absorber / sensor (Em / Ab / Se) probe element coming into contact with the medium is arranged, and devices for supplying / disposing of the measuring cell with medium and the thermal emitter / Absorber / sensor elements with energy as well as those for control, regulation, data acquisition, conversion and / or processing, the probe element being arranged on all sides in the measuring cell or in the measuring channel (7) freely surrounded by the fluid or washed around, preferably bridge-like, web element (312) is formed, characterized in that the web element (312), which may be present in a plurality, with at least one thermo-emitter / absorber / sensor (Em / Ab / Se) element (1) based on a semiconductor material, which is applied in a layer-like manner, in particular by vapor deposition, to an insulator material. 2. Probe according to claim 1, characterized in that it is a with a doped pure semiconductor, in particular amorphous germanium or amorphous silicon, or a compound semiconductor, in particular silicon carbide (SixCy) or an Ill / V semiconductor, e.g. Gallium or indium arsenide, formed thermo-emitter and / or sensor element (1). 3. A probe according to claim 1 or 2, characterized in that on the individual, on the carrier (3) layer-like applied Thermo-Em / Ab / Se element (1) made of semiconductor material in the region of at least one of its longitudinal edges (11,12) , preferably both longitudinal edges lying opposite one another, in particular layer-like, energy / control / data conductor elements (2, 2 '), preferably vapor-deposited onto the element (1). 4. Probe according to one of claims 1 to 3, characterized in that the contours (11,12) of the web elements (321) or their carrier (1), Thermo-Em / Ab / Se elements and energy / control / data Conductor elements (2, 2 ') of the crystal structure or the crystal boundary profile of the measuring cell or measuring channel body (6) or its lower part (61) are formed in a meandering manner. 12 AT 404 758 B 5. Probe according to one of claims 1 to 4, characterized in that the carrier (3) of the web element (312) in a manner known per se with silicon nitride (SiNx), but in particular with low-temperature (SiNx) or with Siliconmoxinitrid (SiOuNv) is formed. 6. Probe according to one of claims 1 to 5, characterized in that the carrier (3) of the web elements (312) have a material thickness of 1 to 10 µm, in particular 3 to 7 µm. 7. Probe according to any one of claims 1 to 6, characterized in that the, preferably meandering, web elements (312) have a width of between 10 and 120 µm, in particular from 50 to 70 µm. 8. Probe according to one of claims 1 to 7, characterized in that the carrier (3) of the web elements (312) with essentially the same material thickness, layer-like, in particular formed by vapor deposition, zones (63) of the measuring cell or measuring channel Body (6) or of its lower part (61) are connected in an identical manner, in particular in one piece with the above-mentioned zones (63). 9. Probe according to one of claims 1 to 8, characterized in that it has thermal emitter absorber sensor elements (1) with resistance values of approximately 10 to 500 kOhm, in particular approximately 100 to 300 kOhm, (at 20 * C ) having. 10. Probe according to one of claims 1 to 9, characterized in that it thermo-emitter / absorber / sensor elements (1) with a sensitivity to the change in resistance with the temperature of at least 1% / K, preferably of at least 2% / K. 11. Probe according to one of claims 1 to 10, characterized in that the energy / control / data conductor elements (2,2 ') are formed with at least one layered, in particular vapor-deposited, metal material. 12. A probe according to claim 11, characterized in that the energy / control / data conductor elements (2,2 ') with the layer sequence titanium-gold (silver) -titanium with layer thicknesses of the titanium of about 20 to 40 nm and the gold from about 80 to 120 nm. 13. Probe according to one of claims 1 to 12, characterized in that the energy / control / data conductor elements (2,2 ') with their, in the measuring cell or measuring channel body (6) arranged or guided, in particular on Measuring cell or channel body lower part (61) applied, energy, control, data supply and discharge lines (21) are formed in one piece from the same material. 14. Probe according to one of claims 1 to 13, characterized in that the, in particular layer-like, Em / Ab / Se elements (1) bonded to the support (3) formed with the insulating material, in particular SiNx or Si (OuNv) ) and their En / St / Da conductor elements (2,2 ') fluid-medium-tight, coated with an insulating material, preferably with the same insulating material as the carrier (3), in particular with silicon nitride (SiNx) or silicon oxynitride (Si (OuNv)) , in particular enveloped by the same. 15. Probe according to one of claims 1 to 14, characterized in that it comprises at least one web element (312) which has a local resolution of 10 µm, preferably 50 to 200 µm, in the case of thermal emission or sensor technology. 16. Probe according to one of claims 1 to 15, characterized in that it has at least one web element (312) with a temperature resolution of at least 0.25 mK, in particular 0.1 mK. 17. Probe according to one of claims 1 to 16, characterized in that it has at least one web element (312) with an effective response time of at most 5 ms, preferably of at most 3 ms, and a thermal response time of at most 0.5 ms, preferably of has a maximum of 0.3 ms. 18. Probe according to one of claims 1 to 17, characterized in that it has at least one web element (312) with a useful power of less than 1 mW. 19. A probe according to one of claims 1 to 18, characterized in that it comprises at least one web element (312) which, when the measured values supplied by it are electronically linearized, has an accuracy of 0 at temperatures in the range from 10 * C to 60 * C, 1 K has. 20. Probe according to one of claims 1 to 19, characterized in that it has at least one web element (312) with long-term stability of better than 1% change in resistance value per year. 21. Probe according to one of claims 1 to 20, characterized in that it has a plurality of spaced apart web elements (312), one of which is desired by a power supply and control device with heating current / voltage pulses Shape and height that can be supplied - a thermo-emission or heating element (312 *) and at least one is designed as a thermo-sensor element (312 ") arranged in the measuring channel (7) at a distance from the heating element (312 '). 22. A probe according to claim 21, characterized in that a plurality of thermal sensor elements (312 ”) at least on one side, in particular on both sides, preferably symmetrically in number and distance, from 13 AT 404 758 B thermo-emission element (312 ') - essentially forming a thermosensor array or - arranged in the measuring channel or in the measuring cell. 23. Probe according to one of claims 1 to 22, characterized in that the measuring cell or the measuring channel (7) has a substantially rectangular or square cross section. 22. Probe according to one of claims 1 to 23, characterized in that the web element (312) is arranged substantially in the region of half the measuring cell or measuring channel height (h). 25. Probe according to one of claims 1 to 24, characterized in that the dimensions of the height and width of the, preferably rectangular, measuring cell or measuring channel cross-sectional area 0.1 to 0.5 mm, or 0.5 to 1, 2 mm, in particular about 0.3 or 0.9 mm. 26. Probe according to one of claims 1 to 25, characterized in that the walls or wall elements (73, 21 ') of the measuring cell or the measuring channel (7) with a chemically resistant and / or abrasion-resistant, poorly thermally conductive silicon nitride or an organic polymer , are coated. 27. Probe according to one of claims 1 to 26, characterized in that the measuring cell :: - or measuring channel body (6) with a mechanically stable, chemically inert, low electrical and thermal conductivity material with a low thermal expansion coefficient , preferably with a silicon single crystal or silicon wafer material. 28. Probe according to one of claims 1 to 27, characterized in that in the measuring cell or measuring channel body (6), preferably in close proximity to the cell or channel (7), at least one thermal sensor (ambient sensor) (8) is arranged to detect the temperature of the probe body. 29. Probe according to one of claims 1 to 28, characterized in that the measuring cell or measuring channel body (6) on the fluid medium side and / or outflow side inflow and / or outflow body (9, 9 ') are assigned. 30. A probe according to claim 29, characterized in that the inflow and outflow bodies (9.9 ') into the measuring cell or the measuring channel (7) have aligned fluid guides (97, 97'). 31. A method for producing the new probe according to one of claims 1 to 30, characterized in that - at least one surface of a, preferably approximately cuboid, blank of a lower part of the probe body (61), preferably by vapor deposition, with at least one layer (63) a passivation or insulator material is coated, - that a layer (1) of a semiconductor emitter (absorber / sensor material) on this insulator layer at least in the region of the web element (3) provided, preferably in accordance with the shape provided for this preferably amorphous germanium or silicon is applied, in particular is vapor-deposited, - that at least one energy / control / data conductor element or track (2) is applied to the same in accordance with the lithography provided for a particular shape, - that the now pre-formed one Web element structure, preferably over the entire surface, is coated with a passivation or insulator layer (4) - that according to Frei laying of - in the passivation or insulator layer - the floor plan of the measuring cell or measuring channel lower part (71) to be formed and the (which) projecting in the same, in particular penetrating the web elements (s) (312) (63-3) and the emitter / absorber / sensor layer - while the web elements (312) remain, the measuring cell or measuring channel lower part (71) is worked into the probe body lower part (61), in particular is etched, and - Finally, the ensemble of the lower part of the probe body thus formed, fluid-sealing, is preferably aligned with the upper part (62) of the measuring cell or measuring channel (72) and has the upper part of the probe body (62), preferably by cell or lower part of the channel, preferably by gluing . 32. The method according to claim 31, characterized in that the passivation or insulation material, in particular silicon nitride (SiNx) is applied by a combined plasma-CVD process at substrate and process temperatures of below 100 * C. 33. The method according to claim 31 or 32, characterized in that the semiconductor material is applied amorphous germanium and / or silicon for the thermal emitter / absorber / sensor elements at residual gas pressures in the range of about 10 ~ 7 bar. 34. Use of a probe according to one of claims 1 to 30 in the form of a puncture probe for temperature measurements within defined micro-volume ranges in animal or human tissue, for example during normal or pathological brain activity. 35. Use of a probe according to one of claims 1 to 30 with the proviso that one of its at least two emitter / sensor elements is operated as a heating element and at least one further of the emitter / sensor elements is operated as a thermal sensor element for Heat flow measurements and for the detection of minimal fluid movements or flows in animal or human tissue. 14 AT 404 758 B 36. Use of a probe according to one of claims 1 to 30 for one of the purposes mentioned in claims 34 and 35 with the proviso that at least one emitter, in particular heating element, simultaneously with its energy output as a sensor, in particular as a temperature measuring sensor for Temperature measurement / regulation / control one is used. 37. Use of a probe according to one of claims 1 to 30, for one of the purposes mentioned in claims 34 to 36, with the proviso that by means of - preferably according to claim 33 - self-sensor-controlled thermo-emitter elements a primary temperature and / or heat pulse of the desired shape and / or size is emitted to an - if necessary flowing - medium and the transit time and / or shape and / or size is given on the basis of the signals or signal sequences which are spatially spaced apart from the said thermo-emitter element of the pulse arriving at the sensor element is determined and, if desired, passed on to a computer unit for analytical processing. 38. Use of a probe according to one of claims 1 to 30 as a bolometer for measuring the thermal energy generated by neutral particles (in nuclear physics). Including 8 sheets of drawings 15