DE102017201549A1 - Thermal detector device - Google Patents

Abstract

A thermal detector device (100), comprising: - at least two detector chambers (10, 20); - wherein in each detector chamber (10, 20) different internal pressures (V1, V2) is formed; and - wherein in each detector chamber (10, 20) a detector element (13, 23) is arranged, with which an incident measuring radiation (OP) is convertible into an electrical signal.

Description

The invention relates to a thermal detector device. The invention further relates to a method for producing a thermal detector device.

State of the art

In the optical measurement technology for temperature measurement, thermal detectors such as thermopiles, pyrodetectors or diode arrays are used, as for example DE 600 03 885 T2 is known. With the mentioned detectors can be advantageously realized a non-contact temperature detection. Depending on the application, a detector with a corresponding temperature sensitivity is selected. If, for example, a small temperature difference is to be detected, a detector with high detectivity (V / W) is required. If a measurement of high temperatures is required, such as in case of fire, it is advantageous to use a detector which has a lower detectivity in order not to overdrive in the high temperature range. Especially in applications for very different temperature ranges, a detector is necessary, which provides high dynamics.

The construction of a thermal detector is typically based on the thermal decoupling of the actual sensor element from the environment in order to detect in this way small temperature differences that arise on the sensor element due to the change in the object temperature. When the object temperature changes by 1 Kelvin (K), the change on the sensor element is typically a few mK due to the infrared power absorbed.

So that this temperature difference can occur on the sensor element, the sensor elements are thermally decoupled. This happens on the one hand by a defined mechanical suspension of the sensor, as in 1 is shown by way of example on a pixel element and on the other by the enclosed vacuum of the sensor element.

For example, said thermal decoupling can be conventionally achieved by a wafer bonding process in which two wafers are vacuum-tightly bonded together. The volume between the two wafers in which the sensor element is placed typically has an absolute pressure of less than 1 mbar. This value very much determines the sensitivity of the sensor. The higher the pressure, the lower the sensitivity of the sensor.

mit den Parametern:

P

Strahlungsleistung

A

Fläche

σ

Stefan-Boltzmann-Konstante

A detection of very different temperature ranges with high temperature resolution is conventionally possible with a detector only with very high technical effort. In particular, the detection of different temperature ranges that are far apart, for example, people detection, measuring range 20 ° C to 50 ° C, fire detection 200 ° C to 1000 ° C technically possible only with great effort. This can be justified by the physical T ⁴ law (Stefan Boltzmann law): $$\text{P}=\mathrm{\sigma }\times \text{A}\times {\text{<figure-callout id="4" label="T" filenames="DE102017201549A1\_0003.png" state="{{state}}">T</figure-callout>}}^4$$

with the parameters:

P

radiant power

A

area

σ

Stefan-Boltzmann constant

The relationship of equation (1), which indicates the thermally radiated power (radiant power) of an ideal blackbody as a function of its temperature, is in 3 clarified. One recognizes several courses of spectral specific radiation (in W / m ² μm) or spectral radiance (in W / m ² μmsr) as a function of the wavelength W (in μm). The individual courses are applied at different temperatures (in K) of a black radiation body.

Furthermore, the evaluation of thermodetectors is a limiting factor, since the electrical voltage ranges in the amplifier stages and analog-to-digital converters are limited and a working point design for a high temperature measuring range is technically very difficult and costly. High dynamics and a high resolution of the sensor are therefore very difficult to achieve together. This requires a costly change in the design or in the ASIC design for each application.

Disclosure of the invention

It is an object of the present invention to provide an improved non-contact thermal detector.

• - wenigstens zwei Detektorkammern;
• - wobei in jeder Detektorkammer ein unterschiedlicher Innendruck ausgebildet ist; und
• - wobei in jeder Detektorkammer ein Detektorelement angeordnet ist, mit dem eine auftreffende Messstrahlung in ein elektrisches Signal umwandelbar ist.

According to a first aspect, the object is achieved with a thermal detector device, comprising:

• - at least two detector chambers;
• - wherein a different internal pressure is formed in each detector chamber; and
• - In each detector chamber, a detector element is arranged, with which an incident measuring radiation is convertible into an electrical signal.

In this way, a different sensitivity of the measuring elements is realized by means of the different internal pressures prevailing in the detector chambers. Advantageously, this makes it possible to set a sensitivity of individual detector chambers of the detector device and thus to configure it flexibly for different purposes. The above-mentioned laws of the Stefan Boltzmann law are exploited.

• - Bereitstellen von wenigstens zwei Detektorkammern;
• - Anordnen von jeweils einem Detektorelement in jeder Detektorkammer; und
• - Ausbilden von unterschiedlichen Innendrücken in jeder der Detektorkammern.

According to a second aspect, the object is achieved with a method for producing a thermal detector device, comprising the steps:

• - providing at least two detector chambers;
• - arranging each one detector element in each detector chamber; and
• - Forming of different internal pressures in each of the detector chambers.

Preferred embodiments of the thermal detector device and the method of manufacturing a thermal detector device are the subject of dependent claims.

An advantageous development of the thermal detector device is characterized in that the different internal pressures in the detector chambers are set with getter elements. In this way, the different internal pressures in the detector chambers can be adjusted in a technically proven and known manner.

A further advantageous development of the thermal detector device is characterized in that the detector chambers are hermetically sealed by a laser reseal after forming the internal pressures. In this way, an alternative method of forming the different internal pressures in the detector chambers is provided.

A further advantageous development of the thermal detector device is characterized in that the detector device has an electronic evaluation circuit. Advantageously, a computing capacity for evaluating the detected radiation power is provided in this way.

Further advantageous developments of the thermal detector device provide that the electronic evaluation circuit is designed as an ASIC or as a multiplexer. In this way, different, the collection downstream evaluation services are provided.

The invention will be described below with further features and advantages with reference to several figures in detail. In this case, all disclosed features, regardless of their relationship in the claims and regardless of their representation in the description and in the figures form the subject of the present invention. Same or functionally identical elements have the same reference numerals. The figures are particularly intended to illustrate the principles essential to the invention and are not necessarily drawn to scale.

Disclosed method features are analogous to corresponding disclosed device features and vice versa. This means, in particular, that features, technical advantages and embodiments relating to the thermal detector device result analogously from corresponding embodiments, features and advantages relating to the method for producing a thermal detector device and vice versa.

• 1 eine Topologie einer herkömmlichen thermischen Detektorvorrichtung;
• 2 einen schematischen Verlauf einer Empfindlichkeit eines thermischen Detektors als Funktion eines Innendrucks im Sensor;
• 3 die prinzipiellen Abhängigkeiten des physikalischen Stefan-Boltzmann-Gesetzes;
• 4 eine schematische Darstellung einer vorgeschlagenen thermischen Detektorvorrichtung mit zwei Detektorkammern mit unterschiedlichen Innendrücken;
• 5 eine schematische Darstellung einer ersten Ausführungsform einer thermischen Detektorvorrichtung mit zwei Kammern mit unterschiedlichen Innendrücken;
• 6 eine schematische Darstellung einer zweiten Ausführungsform einer thermischen Detektorvorrichtung mit zwei Kammern mit unterschiedlichen Innendrücken;
• 7 eine schematische Darstellung eines thermischen Mehrkammerndetektors; und
• 8 eine prinzipielle Darstellung eines Ablaufs einer Ausführungsform eines Verfahrens zum Herstellen einer thermischen Detektorvorrichtung.

In the figures shows:

• 1 a topology of a conventional thermal detector device;
• 2 a schematic profile of a sensitivity of a thermal detector as a function of internal pressure in the sensor;
• 3 the principal dependencies of the physical Stefan Boltzmann law;
• 4 a schematic representation of a proposed thermal detector device with two detector chambers with different internal pressures;
• 5 a schematic representation of a first embodiment of a thermal detector device with two chambers with different internal pressures;
• 6 a schematic representation of a second embodiment of a thermal detector device with two chambers with different internal pressures;
• 7 a schematic representation of a thermal multi-chamber detector; and
• 8th a schematic representation of a sequence of an embodiment of a method for producing a thermal detection device.

Description of embodiments

A core idea of the invention is in particular to realize a flexible adaptation of pressure ratios in a thermal multi-channel sensor. Due to the different pressure conditions or vacuums and the resulting different degrees of thermal decoupling of the actual sensor elements, the individual sensor chambers have different sensitivities on a detector chip. As a result, in each case a high degree of dynamics and a high degree of detection are made possible in a simple manner for different applications.

Furthermore, the sensitivity of the individual detectors on the sensor chip in a medium sensor can be adapted to different optical line parameters, which are selected for example by optical filters (transmission, bandwidth, etc.).

• - Keine Anpassung an das Design (z.B. Sensoraufhängung, Dotierung, Materialauswahl, Absorptionsschichten, usw.), um unterschiedliche Anforderungen an die Empfindlichkeit zu realisieren
• - Eine einfache und schnelle Anpassung an unterschiedliche Applikationen
• - Unterschiedliche Applikationen können mit hohen Anforderungen an Dynamik und Auflösung des Sensors bedient werden
• - Kosteneffizientes Konzept, dessen Realisierung auf hochvolumenfähigen Waferprozessen basiert
• - Hohe Skalierbarkeit: eine Anzahl der unabhängigen Detektorkammern kann applikationsspezifisch gewählt werden
• - Hohe Flexibilität: Druckverhältnisse in den einzelnen Detektorkammern können applikationsspezifisch gewählt werden und können im Prozess vergleichsweise einfach geändert werden.

Advantageously, this results, among other things, in the following advantages:

• - No adaptation to the design (eg sensor suspension, doping, material selection, absorption layers, etc.) to realize different sensitivity requirements
• - A simple and fast adaptation to different applications
• - Different applications can be operated with high demands on dynamics and resolution of the sensor
• - Cost-efficient concept, the realization of which is based on high-volume wafer processes
• - High scalability: a number of independent detector chambers can be chosen application-specific
• - High flexibility: Pressure conditions in the individual detector chambers can be selected specific to the application and can be changed comparatively easily in the process.

1 shows in a plan view of a conventional thermal detector device 100 in the form of a measuring pixel. Visible are two L-shaped suspension elements, with which the thermal detector device 100 is separated from the surrounding substrate, whereby a high thermal decoupling of the thermal detector device from the surrounding substrate is provided. The higher this thermal decoupling, the higher the sensitivity of the thermal detector device 100 ,

2 shows an exemplary course of the sensitivity E of the thermal detector device 100 as a function of an internal pressure V in a detector chamber. Visible are a first internal pressure V1 and a second, lower internal pressure V2. It can be seen that the sensitivity of the thermal detector device 100 with increasing internal pressure defined in the detector chamber decreases.

4 shows a schematic cross-sectional view through the proposed thermal detector device 100 in the form of a two-channel detector with second detector chambers 10 . 20 , In this case, the thermal detector device comprises 100 two dense, separate detector chambers 10 . 20 , The detector chambers 10 . 20 can be realized by hermetically sealing two wafers (wafer with the sensor chip and optional ASIC circuit and a cap wafer) by a wafer bonding process. A thermal measuring radiation OP strikes a detector element arranged in the detector chamber 10, 20 13 . 23 and generates in this way an electrical signal (eg, an electrical voltage signal), which subsequently with an optional electronic evaluation circuit 50 can be evaluated or forwarded. The electronic evaluation circuit can be designed, for example, as an application-specific electronic circuit (ASIC). For example, the electronic evaluation circuit may also be designed as a multiplexer, that of the detector elements 13 . 23 generated electrical signals for further evaluation forwards.

5 shows in principle how the different internal pressures V1 and V2 in the detector chambers 10 . 20 can be generated or set. First, the two detector chambers 10 . 20 tightly realized and initially include the first internal pressure V1 (typically a few mbar), which when bonding by means of a first getter element 11 is set. To the second internal pressure V2 in the second detector chamber 20 For example, an amount of the getter material used to fine tune the pressure ratios in the detector chambers 10 . 20 is used appropriately. This is done by a correspondingly dimensioned second getter element 21 realized.

If, for example, a higher absolute or internal pressure V2 in the second detector chamber 20 needed, becomes a smaller getter element 21 with less getter material in the second detector chamber 20 applied. This will be in the second detector chamber 20 less residual gas is concentrated, reducing the thermal resistance of the measuring pixel of the second detector chamber 20 larger than in the first detector chamber 10 is.

As a result, the incident measuring radiation OP, which is emitted by a measuring object (not shown), results in a lower temperature difference, as a result of which the effective sensitivity of the pixel is reduced.

Another possibility of realization of the thermal detector device 100 is based on a known laser reseal process, whereby also in this way the internal pressure in the detector chambers 10 . 20 can be adjusted with high precision.

6 shows schematically this implementation possibility with specific areas 12 . 22 the detector device 100 for the laser reseal process. For this purpose, after the bonding process, the respective detector chamber 10 . 20 in which the appropriate internal pressure is to be set, opened by a laser melting process. Due to the pressure conditions in the process chamber (not shown), a corresponding pressure also in the interior of the detector chamber 10 . 20 set. Subsequently, the detector chamber 10 . 20 in the laser reseal areas 12 . 22 closed or welded with the laser. This process can be for any detector chamber 10 . 20 be repeated.

For example, the mentioned process can proceed as follows: The detector chambers 10 . 20 are opened, then the pressure in the process chamber (not shown) and thus also in the detector chamber 10 . 20 set and the first detector chamber 10 is welded by laser. Thereafter, a further, lower pressure in the process chamber is set, resulting in a second internal pressure V2 in the second detector chamber 20 which is subsequently welded by means of laser.

This process can be repeated as often as necessary. In this way, for example, four detector chambers 10 . 20 . 30 . 40 be realized with suitable, equal or different internal pressures V1 ... V4, as in the plan view of the thermal detector device 100 from 7 shown schematically. As a result, in this way, the four detector chambers 10 , 20, 30, 40 are realized with the same or different sensitivities.

An embodiment of the proposed thermal detector device, not shown in FIG 100 provides that only a single detector chamber is provided, in which, as required, a different internal pressure is set in order to realize a corresponding sensitivity of the thermal sensor pixel.

8th shows a basic sequence of execution of the proposed method for producing a thermal detection device.

In one step 200 will provide at least two detector chambers 10 . 20 carried out.

In one step 210 each becomes a detector element 13 . 23 in each detector chamber 10 . 20 arranged.

Finally, in one step 220 forming different internal pressures V1, V2 in each of the detector chambers 10 . 20 carried out.

Although the invention has been described above by means of concrete examples of application, the person skilled in the art can realize previously or only partially disclosed embodiments, without departing from the gist of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 60003885 T2 [0002]

Claims (9)

A thermal detector device (100), comprising: - At least two detector chambers (10, 20); - In each detector chamber (10, 20), a different internal pressure (V1, V2) is formed; and - In each detector chamber (10, 20) a detector element (13, 23) is arranged, with which an incident measuring radiation (OP) is convertible into an electrical signal. Detector device (100) according to Claim 1 , characterized in that the different internal pressures (V1, V2) in the detector chambers (10, 20) are set with getter elements (11, 21). Detector device (100) according to Claim 1 or 2 , characterized in that the detector chambers (10, 20) after forming the internal pressures (V1, V2) are hermetically sealed by laser reseal. Detector device (100) according to one of the preceding claims, characterized in that the detector device (100) has an electronic evaluation circuit (50). Detector device according to Claim 4 , characterized in that the electronic evaluation circuit (50) is designed as an ASIC or as a multiplexer. A method of manufacturing a thermal detector device (100) comprising the steps of: - providing at least two detector chambers (10, 20); - arranging in each case a detector element (13, 23) in each detector chamber (10, 20); and - Forming of different internal pressures (V1, V2) in each of the detector chambers (10, 20). Method according to Claim 6 , wherein the different internal pressures (V1, V2) in the detector chambers (10, 20) are respectively set by getter elements (11, 21). Method according to Claim 6 or 7 , wherein after adjusting the internal pressures (V1, V2) in the detector chambers (10, 20), the detector chambers (10, 20) are each closed by a laser resealing process. Method according to one of Claims 6 to 8th , wherein for each detector chamber (10, 20) an electronic evaluation circuit (50) is provided.

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