Gas sensor chip for thermal conductivity measurement and method for producing and operating such gas sensor chip

Abstract

The invention relates to a gas sensor chip for thermal conductivity measurement and to a method for producing and operating such a gas sensor chip. The invention relates to a gas sensor chip having a measurement chamber which has an opening such that an ambient gas can flow into the measurement chamber, a reference chamber which is filled with a reference gas and which is hermetically sealed, a first and a second measurement chamber beam which are arranged side by side and independently in the measurement chamber, the first and the second reference chamber beam being arranged between the measurement chamber and the reference chamber beam. The reference cavity beams are arranged side by side and independently in the reference cavity, and each of the measuring cavity beams and the reference cavity beams has a first conductor element and a second conductor element. The first and second conductor elements are electrically insulated from each other and can be operated as a sensor element and / or as a heating element for thermal conductivity measurement for ambient gases, respectively, on the basis of an operating mode of the gas sensor chip.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a gas sensor chip for performing a thermal conductivity measurement and to a method for manufacturing such a gas sensor chip and to a method for operating such a gas sensor chip. BACKGROUND

[0002] Gas sensor chips for thermal conductivity measurements can be used in various fields of application, for example in the automotive field, in the industrial field or also in the consumer goods field. Furthermore, such gas sensor chips can be designed for detecting and quantifying a wide range of gases, such as hydrogen, carbon dioxide, sulfur dioxide, refrigerant gases, etc. For detecting such ambient gases, the ambient gases are introduced into a measurement cavity of the gas sensor chip, a heating element is heated and the change in thermal conductivity in the measurement cavity is compared with the thermal conductivity in a hermetically sealed reference cavity. Here, the sensitivity of the gas sensor chip can be increased by a higher temperature at the sensor element. However, it is desirable that such a gas sensor chip provides even higher heating and / or additional diagnostic possibilities, for example for identifying malfunctioning components or for providing further measurement parameters and / or drift correction options. An improved gas sensor chip, an improved method for manufacturing a gas sensor chip and an improved method for operating such a gas sensor chip can help to solve these and further problems. SUMMARY

[0003] Various aspects relate to a gas sensor chip for performing a thermal conductivity measurement, having a measurement cavity with an opening such that an ambient gas can flow into the measurement cavity, a reference cavity which is filled with a reference gas and is hermetically sealed, first and second measurement cavity beams which are arranged side by side and independently in the measurement cavity, first and second reference cavity beams which are arranged side by side and independently in the reference cavity, wherein each of the measurement cavity beams and the reference cavity beams has first and second conductor elements, respectively, which are electrically insulated from each other and which can be operated as sensor elements and / or as heating elements for a thermal conductivity measurement for the ambient gas based on an operating mode of the gas sensor chip, respectively.

[0004] Various aspects relate to a method for manufacturing a gas sensor chip for thermal conductivity measurements, wherein the method comprises: providing a wafer; structuring a measurement cavity with an opening in the wafer, such that ambient gas can flow into the measurement cavity; structuring a reference cavity in the wafer; filling the reference cavity with a reference gas and sealing the reference cavity hermetically; structuring first and second measurement cavity beams side by side and independently in the measurement cavity; structuring first and second reference cavity beams side by side and independently in the reference cavity; structuring first and second conductor elements on or in each of the measurement cavity beams and the reference cavity beams, respectively, such that the first and second conductor elements are electrically insulated from each other and can operate as sensor elements and / or as heating elements for thermal conductivity measurements for ambient gas, respectively, based on an operating mode of the gas sensor chip.

[0005] Various aspects relate to a method for operating a gas sensor chip for thermal conductivity measurements, wherein the method comprises: providing a gas sensor chip having a measurement cavity with an opening such that ambient gas can flow into the measurement cavity, a reference cavity filled with a reference gas and sealed hermetically, first and second measurement cavity beams arranged side by side and independently in the measurement cavity, first and second reference cavity beams arranged side by side and independently in the reference cavity, wherein each of the measurement cavity beams and the reference cavity beams has first and second conductor elements, respectively, which are electrically insulated from each other and can operate as sensor elements and / or as heating elements for thermal conductivity measurements for ambient gas, respectively, based on an operating mode of the gas sensor chip; heating the measurement cavity and the reference cavity by means of the heating elements; and performing a thermal conductivity measurement by means of the sensor elements

[0006] Further features and advantages of the present application will become apparent to those skilled in the art from a review of the ensuing detailed description and the appended claims, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0007] The present disclosure is illustrated, by way of example, in the images of the accompanying drawings, in which like reference numerals indicate similar or like elements, features and aspects of the various examples. The elements in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the various examples. Features of the various examples shown can be combined, unless they are mutually exclusive.

[0008] Figure 1 A schematic cross-sectional view of a gas sensor chip is shown, which has a measurement cavity with two measurement cavity beams and a reference cavity with two reference cavity beams.

[0009] Figure 2 A cross-section through the measurement cavity and the reference cavity is shown in a top view. As in Figure 2As shown in the middle, each of the measurement cavity beam and the reference cavity beam has first and second conductor elements available for heating or measurement.

[0010] Figure 3 A schematic cross-section through a measurement cavity beam according to an example is shown, wherein the two conductor elements have different materials or material compositions.

[0011] Figure 4A and Figure 4B Various circuits that can be provided with the first and second conductor elements, namely a Wheatstone bridge circuit Figure 4A ) and a parallel circuit Figure 4B ) are shown.

[0012] Figure 5 Different operating modes in which a gas sensor chip can operate are shown in a table, wherein in the different operating modes different combinations of the circuit states of the two circuits of the first and second conductor elements, respectively, are present.

[0013] Figure 6 A schematic cross-section through a measurement cavity beam according to a further example is shown, wherein the first and second conductor elements are configured side by side in a semiconductor material of the measurement cavity beam.

[0014] Figure 7 A schematic cross-section through a measurement cavity beam according to a further example is shown, wherein the first and second conductor elements are configured side by side in a semiconductor material of the measurement cavity beam and an additional heating element is configured in a metallization above the conductor elements.

[0015] Figure 8 A schematic cross-section through a measurement cavity beam according to a further example is shown, wherein the first and second conductor elements are configured side by side in a metallization on the measurement cavity beam and an additional heating element is configured in a semiconductor material of the measurement cavity beam.

[0016] Figures 9A to 9F Different possible solutions are shown how the positions of the first and second conductor elements in the first and second circuits can be exchanged by an adaptation of the circuit to provide additional diagnostic possibilities.

[0017] Figure 10 A gas sensor is shown having Figure 1 and Figure 2 a gas sensor chip.

[0018] Figure 11 A flow chart of an exemplary method for manufacturing a gas sensor chip is shown.

[0019] Figure 12 A flow chart of an exemplary method for operating a gas sensor chip is shown. DETAILED DESCRIPTION

[0020] In the following detailed description, references are made to the accompanying drawings and examples shown therein that form a part of the disclosure. It is understood that the aspects of the disclosure can be practiced without resorting to the details of specification and examples. In other instances, well-known structures and elements have not been shown in detail to avoid obscuring aspects of the disclosure.

[0021] Furthermore, to the extent that the terms "including", "contains", "having", "with" or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprising." The terms "coupled" and "connected," along with derivatives thereof, can have been used. These terms can be used to indicate that two elements co-operate or interact with each other, where it is not essential that there be a direct, physical or electrical contact between them, or that they be in direct contact with each other; intervening elements or layers can be present. Furthermore, the term "exemplary" should indicate an example and should not be construed as the best or optimal.

[0022] The efficient gas sensor chip, the efficient method for manufacturing a gas sensor chip and the efficient method for operating a gas sensor chip can for example reduce material consumption, chemical waste or ohmic losses and thus can save energy and / or save resources. Thus, the improved gas sensor chip, the improved method for manufacturing a gas sensor chip and the improved method for operating a gas sensor chip as explained in the present specification can at least indirectly contribute to a green technology solution "green technology", i.e. to a climate-friendly solution, which can enable a reduction of energy consumption and / or resource consumption.

[0023] Figure 1 A schematic cross-sectional view of a gas sensor chip 100 for performing a thermal conductivity measurement is shown. The gas sensor chip 100 has a measurement cavity 102 and a reference cavity 104. The measurement cavity 102 has an opening 114 such that ambient gas can flow into the measurement cavity 102. While the reference cavity 104 is filled with a reference gas and is hermetically sealed, i.e. no ambient gas can enter the reference cavity 104.

[0024] The known measurement principle of the gas sensor chip 100 is based on the detection of a change in the electrical resistance of an electrically heated resistor. The resistor is thermally decoupled from the rest of the substrate of the gas sensor chip 100 such that thermal energy is transferred as much as possible into the ambient gas or the reference gas surrounding the resistor. Different gases have different thermal conductivities and thus can be detected by the gas sensor chip 100.

[0025] The gas sensor chip 100 can be configured for use in a suitable gas sensor. For example, the gas sensor chip 100 can be configured for detecting and / or quantifying a gas such as hydrogen, carbon dioxide, sulfur dioxide, an inert gas, R32, R1234yf, R454, R744, etc. The gas sensor chip 100 may, for example, be configured for use in the automotive field, the industrial field, the consumer goods field, etc. The gas sensor 100 may, for example, be configured for detecting a hydrogen leak in a car. According to an example, the gas sensor chip 100 has a silicon chip (i.e. the measurement cavity 102 and the reference cavity 104 are at least partially configured in silicon).

[0026] As shown in Figure 1 , the measurement cavity 102 has a first measurement cavity beam 106 and a second measurement cavity beam 108. The first and second measurement cavity beams 106, 108 may, for example, be arranged centrally in the measurement cavity 102 (which can mean that opposite ends of the measurement cavity beams 106, 108 are connected with the walls of the measurement cavity 102 and freely float across the width of the measurement cavity 102) free-floating.

[0027] In a similar manner as the measurement cavity 102, the reference cavity 104 has a first reference cavity beam 110 and a second reference cavity beam 112. These reference cavity beams can also be free-floating and may, for example, be arranged centrally in the reference cavity 104. It is especially possible that the structure and / or the dimensions of the measurement cavity 102 and the reference cavity 104 or of the measurement cavity beams 106, 108 and the reference cavity beams 110, 112 are identical except for the presence of the opening 114 in the measurement cavity 102.

[0028] Figure 2 A top view of the measurement cavity 102 and the reference cavity 104 is shown from above. As shown in Figure 2 , the first and second measurement cavity beams 106, 108 or the first and second reference cavity beams 108, 110 may, for example, be arranged parallel to each other. The measurement cavity beams 106, 108 and the reference cavity beams 110, 112 can have any suitable shape or any suitable dimensions. For example, the measurement cavity beams 106, 108 and the reference cavity beams 110, 112 can have a length x in the range from about 300 pm to about 1.5 mm, for example about 500 pm, about 800 pm or about 1 mm. The measurement cavity beams 106, 108 and the reference cavity beams 110, 112 may, for example, have a width y in the range from about 10 pm to about 100 pm, for example about 30 pm, about 50 pm or about 70 pm. Furthermore, the measurement cavity beams 106, 108 and the reference cavity beams 110, 112 may, for example, have a thickness in the range from about 1 pm to about 10 pm, for example about 3 pm, about 5 pm or about 7 pm (wherein the thickness is measured perpendicular to the length x and the width y).

[0029] According to an example, the measurement cavity 102 and the reference cavity 104 are partially or completely constructed in a suitable semiconductor material, for example silicon. In this case, the measurement cavity beams 106, 108 and the reference cavity beams 110, 112 can also be composed of such a semiconductor material (where it is possible that suitable metallizations are arranged on the semiconductor material of the measurement cavity beams and the reference cavity beams 106-112, for example). In particular, in this case, the measurement cavity beams and the reference cavity beams 106-112 can be integrally constructed with the semiconductor material of the side walls of the measurement cavity 102 or the reference cavity 104.

[0030] Each of the measurement cavity beams 106, 108 and the reference cavity beams 110, 112 has a first conductor element 106a, 108a, 110a, 112a and a second conductor element 106b, 108b, 110b, 112b, respectively. The first conductor element 106a, 108a, 110a, 112a is electrically insulated from the second conductor element 106b, 108b, 110b, 112b in each measurement cavity beam 106, 108 and the reference cavity beam 110, 112, respectively. In other words, the first conductor element 106a, 108a, 110a, 112a can be part of a first electrical circuit, for example, and the second conductor element 106b, 108b, 110b, 112b can be part of a second electrical circuit, for example, wherein the two electrical circuits are separated from one another.

[0031] It should be noted that in the schematic illustration of Figure 2 the first and second conductor elements of the measurement cavity beams 106, 108 and the reference cavity beams 110, 112 are shown as being arranged side by side on the respective beams as viewed from above. However, it is also possible, as is shown subsequently, that the first and second conductor elements are arranged on the respective beams opposite one another.

[0032] According to an example, the first conductor elements 106a, 108a, 110a, 112a can be composed of a first material or a first material composition, and the second conductor elements 106b, 108b, 110b, 112b can be composed of a second material or a second material composition which is different from the first material or the first material composition. For example, the first conductor elements 106a, 108a, 110a, 112a can be composed of or have a doped semiconductor material (for example Si), and the second conductor elements 106b, 108b, 110b, 112b can be composed of or have a metal (for example Ag, Al, Au or Cu) or a metal alloy, for example. According to a further example, the first and second conductor elements are composed of the same material or the same material composition.

[0033] Based on the operating mode of the gas sensor chip 100, the first conductor elements 106a, 108a, 110a, 112a and the second conductor elements 106b, 108b, 110b, 112b can operate as sensor elements or heating elements for measuring the thermal conductivity of ambient gases, respectively. Operation as sensor elements means that the first conductor elements 106a, 108a, 110a, 112a of the first circuit or the second conductor elements 106b, 108b, 110b, 112b of the second circuit are connected in a known manner to form a Wheatstone bridge circuit to perform the measurement of the thermal conductivity of the ambient gas. Operation as heating elements means that the first conductor elements 106a, 108a, 110a, 112a of the first circuit or the second conductor elements 106b, 108b, 110b, 112b of the second circuit are connected in parallel to heat the ambient gas or a reference gas. Alternatively, it is possible that the first or second circuit is in an open state, meaning that there is no voltage across the corresponding conductor element.

[0034] As explained further below, the aforementioned states of the two circuits can be combined in different ways based on the operating mode of the gas sensor chip 100 (e.g., in one operating mode, the first circuit can provide a Wheatstone bridge circuit and the second circuit can provide a heating circuit, or the first circuit can be in an off state and the second circuit can provide a Wheatstone bridge circuit, etc.). The ability of the gas sensor chip 100 to combine the different states of the two circuits in different ways can, for example, allow for additional diagnostic possibilities, improved sensitivity, drift compensation, etc., as will be implemented in more detail below.

[0035] Figure 3 A detailed view of the cross-section of the first measuring cavity beam 106 according to a specific example is shown. The second measuring cavity beam 108 or reference cavities 110, 112 can have the same structure. In particular, in Figure 3 In the example, the first conductor element 106a and the second conductor element 106b are arranged in an overlapping manner.

[0036] exist Figure 3In the example shown, the first conductor element 106a is formed by a doped semiconductor material which is structured in a semiconductor substrate 116 of the first measurement cavity beam 106. The second conductor element 106b is arranged above the first conductor element 106a. The second conductor element 106b is formed by a metal or a metal alloy which is deposited on the semiconductor substrate 116. The conductor elements 106a, 106b are electrically insulated from each other by an intermediate layer 118. The intermediate layer 118 can be any suitable electrically insulating material. For example, the intermediate layer 118 can have or can be constituted by a nitride, for example silicon nitride, or the intermediate layer 118 can have or can be constituted by an oxide, for example silicon oxide. The intermediate layer 118 can have any suitable thickness, for example a thickness in the nanometer range or a thickness in the micrometer range.

[0037] According to Figure 3 In the example shown, the second conductor element 106b can also be covered by a cover layer 120. The cover layer 120 may, for example, be structured as a protective layer which protects the second conductor element 106b (and possibly also the first conductor element 106a) against environmental influences, for example against environmental gases. The intermediate layer 118 can be structured in a similar manner as a protective layer. The cover layer 120 can be a passivation layer. The cover layer 120 may, for example, have or be constituted by a nitride or an oxide, for example silicon nitride or silicon oxide. The cover layer 120 can have similar dimensions as the intermediate layer 118.

[0038] Figure 4A and Figure 4B An exemplary circuit based on the operating mode of the gas sensor chip 100 is shown, to which the first conductor elements 106a, 108a, 110a, 112a and the second conductor elements 106b, 108b, 110b, 112b can be connected to form the circuit. Here, the first conductor elements 106a, 108a, 110a, 112a form a first circuit 122 and the second conductor elements 106b, 108b, 110b, 112b form a separate second circuit 124.

[0039] In Figure 4A In the example shown, it is exemplarily shown for both circuits 122, 124 how the respective conductor elements can be connected to form a Wheatstone bridge circuit. In this state, the respective circuits of the first circuit 122 and the second circuit 124 can be operated for a thermal conductivity measurement for an environmental gas. In Figure 4B In the example shown, it is exemplarily shown for both circuits 122, 124 how the respective conductor elements can be connected in parallel. In this state, the respective circuits of the first circuit 122 and the second circuit 124 can be operated as a heating circuit for the measurement cavity 102 or the reference cavity 104.

[0040] Depending on the operating mode of the gas sensor chip 100, the two circuits 122, 124 can be operated in various combinations in a Wheatstone bridge circuit according to Figure 4A in a parallel circuit according to Figure 4B and in a switched-off state, i.e. in the absence of a voltage on the respective circuit.

[0041] In the table in Figure 5 nine different exemplary operating modes of the gas sensor chip 100 are listed. Here, "off" means that there is no voltage on the respective circuit, "bridge" means that the respective circuit is in a Wheatstone bridge circuit, i.e. can be used as a measurement circuit, and "parallel" means that the respective circuit is in a parallel circuit, i.e. can be used as a heating circuit. The numbering of the modes 1 to 9 is arbitrary and does not imply any particular order.

[0042] In mode 1, both circuits 122, 124 are in the switched-off state, i.e. the gas sensor chip 100 itself is switched off. In mode 5, both circuits are operated in a Wheatstone bridge circuit, i.e. two independent measurements can be carried out. In mode 9, both circuits 122, 124 are in a parallel connection, i.e. with this mode the maximum heating power can be achieved. One of the modes 2, 3, 4 and 7 can be used, for example, when only one of the circuits 122, 124 is required for measurement or heating and the other of the circuits 122, 124 can remain switched off. One of the modes 6 and 8 can be used when a measurement is carried out and at the same time the ambient gas and the reference gas should be heated.

[0043] Since the gas sensor chip 100 has two circuits 122, 124 with the possible states shown in Figure 5 additional possibilities for measurement or diagnosis arise compared to conventional devices. With the gas sensor chip 100 it is possible, for example, to carry out measurements in different temperatures by heating, for example, using both circuits 122, 124 or only one of the circuits 122, 124. Here, the thermal inertia of the gas sensor chip 100 can be used in order to switch, for example, after heating with both circuits 122, 124 in mode 9, into another mode in which at least one of the circuits 122, 124 is operated as a Wheatstone bridge, i.e. for example mode 8 or mode 5. Due to the thermal inertia, after such a switch the temperature only decreases gradually and not abruptly. By carrying out measurements at higher temperatures, for example, the sensitivity of the gas sensor chip 100 can be increased.

[0044] An exemplary measurement cycle, i.e. a sequence of operating modes for performing a measurement, can be as follows: Mode 1 -> Mode 3 -> Mode 2 -> Mode 1, where in this sequence the measurement is performed in Mode 2 and is heated up in the preceding Mode 3. An exemplary measurement cycle for measuring at a higher temperature can be as follows: Mode 1 -> Mode 9 -> Mode 5 -> Mode 1, where the measurement is performed in Mode 5.

[0045] An exemplary measurement cycle at a relatively low temperature is as follows: Mode 1 -> Mode 2 (measurement) -> Mode 1; and Mode 1 -> Mode 3 -> Mode 2 (measurement) -> Mode 1. An exemplary measurement cycle at a relatively medium temperature is: Mode 1 -> Mode 5 (measurement) -> Mode 1; and Mode 1 -> Mode 8 (measurement) -> Mode 1. An exemplary measurement cycle at a relatively high temperature is: Mode 1 -> Mode 6 -> Mode 2 (measurement) -> Mode 1; and Mode 1 -> Mode 9 -> Mode 2 (measurement) -> Mode 1.

[0046] As mentioned above, two circuits 122, 124 can be used to perform two independent measurements, but wherein the measurement elements 106a and 106b or 108a and 108b or 110a and 110b or 112a and 112b are thermally coupled. This can be used, for example, to compensate for drift in the gas sensor chip 100. An exemplary measurement cycle for such a redundant measurement is: Mode 1 -> Mode 5 (measurement) -> Mode 1; and Mode 1 -> Mode 9 -> Mode 5 (measurement) -> Mode 1.

[0047] As mentioned above, the gas sensor chip 100 can be used to perform measurements at various temperatures, for example first at a relatively low temperature and then at a relatively high temperature. The first measurement at a low temperature can be used, for example, to determine the offset of the gas sensor chip 100 with minimal influence of ambient gas or reference gas. The second measurement at a higher temperature can then be used to measure the gas effect. Furthermore, due to the possibility of setting different temperatures in the measurement chamber 102 or the reference chamber 104, a temperature spectroscopy of the ambient gas can be performed.

[0048] An exemplary measurement cycle for such measurements at different temperatures is: Mode 1 -> Mode 2 (first measurement) -> Mode 3 -> Mode 2 (second measurement) -> Mode 1; and Mode 1 -> Mode 5 (first measurement) -> Mode 9 -> Mode 5 (second measurement) -> Mode 1. Here, the first measurement is performed at a lower temperature and the second measurement is performed at a higher temperature, respectively.

[0049] Figure 6A schematic cross-section through the measurement cavity beam 200 is shown, which can be similar or identical to the measurement cavity beam 106, except for the differences described below. The measurement cavity beam 200 can be present in the gas sensor chip 100 instead of the first measurement cavity beam 106. In a similar manner, the second measurement cavity beam 108 and the reference cavity beams 110, 112 can also be replaced by the same structure as the measurement cavity beam 200.

[0050] Unlike the measurement cavity beam 106 (cf. Figure 3 ), the two conductor elements 106a, 106b can be arranged side by side in the measurement cavity beam 200 instead of on top of each other. However, the two conductor elements 106a, 106b of the measurement cavity beam 200 can in particular be composed of the same material or the same material composition, for example of a suitably doped semiconductor material. Since the two conductor elements 106a, 106b are manufactured by the same process, it can be ensured that the two conductor elements 106a, 106b can have the same or almost the same resistance value. In this case, the first conductor element 106a and the second conductor element 106b are interchangeable between the two circuits 122, 124 without distorting the measurement results.

[0051] Figure 7 A schematic cross-section through a further measurement cavity beam 300 is shown, which is similar or identical to the measurement cavity beam 200, except for the differences described below.

[0052] In particular, the measurement cavity beam 300 has, in addition to the two conductor elements 106a, 106b, an additional heating element 310 arranged on the measurement cavity beam 300. The heating element 310 can be electrically insulated from the conductor elements 106a, 106b, for example by the intermediate layer 118. As shown in Figure 7 , the additional heating element 310 can be arranged above the conductor elements 106a, 106b and can be composed of a different material or a different material composition, in particular a metal or a metal alloy.

[0053] Due to the additional heating element 310, both conductor elements 106a, 106b can be used for measurement at the same time, while the heating element 310 is used for heating the ambient gas or the reference gas. Alternatively, one or both of the conductor elements 106a, 106b can be used for heating in addition to the heating element 310, whereby the achievable temperature can be increased. This can for example improve the sensitivity of the gas sensor chip 100.

[0054] Figure 8A schematic cross-section through a further measurement cavity beam 400 is shown, which is similar or identical to the measurement cavity beam 300, except for the differences described below. In particular, in the measurement cavity beam 400, the additional heating element 310 is configured in the semiconductor substrate 116 as a doped region, while the two conductor elements 106a, 106b are configured in a structured metal layer. In other words, the design of the additional heating element 310 and the conductor elements 106a, 106b is interchanged compared to the measurement cavity beam 300.

[0055] According to an example, in the measurement cavity beam 400, the additional heating element 310 can also be omitted, that is to say, the measurement cavity beam 400 has two conductor elements 106a, 106b configured in the metallization on the semiconductor material of the measurement cavity beam 400.

[0056] In the gas sensor chip 100, in which the two conductor elements of the measurement cavity beam and the reference cavity beam are equivalent, as shown in Figures 6 to 8 , the conductor elements can be interchanged with one another without falsifying the measurement result. This can be used, for example, for the diagnosis of the gas sensor chip 100, for example in order to identify defective conductor elements. For this purpose, the circuits 122, 124 can be designed such that the position of the conductor elements in the respective circuit 122, 124 or the association of the conductor elements with one of the circuits 122, 124 can be changed.

[0057] In Figures 9A to 9F , various exemplary Wheatstone bridge circuits are shown, in which the individual conductor elements are arranged in different positions on the two circuits. For the sake of simplicity, the voltage sources of the circuits shown separately are omitted in Figures 9A to 9F (see Figure 3 ).

[0058] In the circuits shown in Figure 9A and Figure 9B , all first conductor elements 106a, 108a, 110a, 112a are part of the first circuit and all second conductor elements 106b, 108b, 110b, 112b are part of the second circuit. In Figures 9C to 9F , however, the first conductor elements 106a, 108a, 110a, 112a and the second conductor elements 106b, 108b, 110b, 112b are distributed over the two circuits in the circuit.

[0059] Figure 10A gas sensor 500 is shown, which has a gas sensor chip 100 and a control chip 510. The control chip 510 is configured for controlling the gas sensor chip 100. That is, the control chip 510 is configured, for example, for operating the gas sensor chip 100 in the different operating modes described herein. The control chip 510 can be an ASIC (application specific integrated circuit), for example. The gas sensor 500 can also have a package 520, which at least partially encapsulates the gas sensor chip 100 and the control chip 510 and is designed for protecting the gas sensor chip 100 and the control chip 510 from environmental influences. The package 520 can have or consist of a molded body or a plastic shell, for example.

[0060] Figure 11 is a flow chart of an exemplary method 600 for manufacturing a gas sensor chip for thermal conductivity measurements. The method 600 can be used for manufacturing the gas sensor chip 100, for example.

[0061] The method 600 has a process of providing a wafer in 601, a process of configuring a measurement cavity with an opening in the wafer in 602, such that ambient gas can flow into the measurement cavity, a process of configuring a reference cavity in the wafer in 603, a process of filling the reference cavity with a reference gas and sealing the reference cavity hermetically in 604, a process of configuring first and second measurement cavity beams side by side and independently in the measurement cavity in 605, a process of configuring first and second reference cavity beams side by side and independently in the reference cavity in 606, and a process of configuring first and second conductor elements on or in each of the measurement cavity beams and the reference cavity beams, respectively, in 607, such that the first and second conductor elements are electrically insulated from each other, respectively, and can operate as sensor elements and / or as heating elements for thermal conductivity measurements of ambient gas, respectively, based on an operating mode of the gas sensor chip.

[0062] According to an example, the method 600 has a process of arranging an upper cover wafer above the wafer and a process of arranging a lower cover wafer below the wafer. At this point, an upper part of the measurement cavity and the reference cavity is configured in the upper cover wafer and a lower part of the measurement cavity and the reference cavity is configured in the lower cover wafer, wherein the opening of the measurement cavity is configured in the lower cover wafer.

[0063] Figure 12 is a flow chart of an exemplary method 700 for operating a gas sensor chip for thermal conductivity measurements. The method 700 can be used for operating the gas sensor chip 100 in the manner explained herein, for example.

[0064] The method 700 has a process of providing a gas sensor chip in 701, wherein the gas sensor chip has a measurement cavity with an opening such that ambient gas can flow into the measurement cavity, a reference cavity which is filled with a reference gas and is hermetically sealed, first and second measurement cavity beams which are arranged side by side and independently in the measurement cavity, first and second reference cavity beams which are arranged side by side and independently in the reference cavity, wherein each of the measurement cavity beams and the reference cavity beams has first and second conductor elements, respectively, which are electrically insulated from each other and can be operated as sensor elements and / or heating elements for a thermal conductivity measurement with respect to the ambient gas, respectively, based on an operating mode of the gas sensor chip, a process of heating the heating elements in 702, and a process of performing a thermal conductivity measurement by means of the sensor elements in 703.

[0065] Examples

[0066] The gas sensor chip, the method for manufacturing the gas sensor chip, and the method for operating the gas sensor chip are subsequently explained in more detail by means of explicit examples.

[0067] Example 1 is a gas sensor chip for performing a thermal conductivity measurement, having a measurement cavity with an opening such that ambient gas can flow into the measurement cavity, a reference cavity which is filled with a reference gas and is hermetically sealed, first and second measurement cavity beams which are arranged side by side and independently in the measurement cavity, first and second reference cavity beams which are arranged side by side and independently in the reference cavity, wherein each of the measurement cavity beams and the reference cavity beams has first and second conductor elements, respectively, which are electrically insulated from each other and can be operated as sensor elements and / or heating elements for a thermal conductivity measurement with respect to the ambient gas, respectively, based on an operating mode of the gas sensor chip.

[0068] Example 2 is the gas sensor chip according to example 1, wherein the measurement cavity beams and the reference cavity beams have or consist of a semiconductor material, respectively, wherein the side walls of the measurement cavity and the side walls of the reference cavity at least partially consist of the semiconductor material, and wherein the measurement cavity beams are integrally constructed with the semiconductor material of the side walls of the measurement cavity and the reference cavity beams are integrally constructed with the semiconductor material of the side walls of the reference cavity.

[0069] Example 3 is the gas sensor chip according to example 1 or 2, wherein the first conductor elements of the measurement cavity beams and the reference cavity beams have or consist of a doped semiconductor material, respectively, and wherein the second conductor elements of the measurement cavity beams and the reference cavity beams have or consist of a metal or a metal alloy, respectively.

[0070] Example 4 is the gas sensor chip according to example 1 or 2, wherein the first and second conductor elements of the measurement cavity beam and the reference cavity beam respectively have or are composed of a doped semiconductor material.

[0071] Example 5 is the gas sensor chip according to example 4, further having an additional first heating element arranged on the measurement cavity beam and an additional second heating element arranged on the reference cavity beam, wherein the additional first and second heating elements have or are composed of a metal or a metal alloy.

[0072] Example 6 is the gas sensor chip according to example 1 or 2, wherein the first and second conductor elements of the measurement cavity beam and the reference cavity beam respectively have or are composed of a metal or a metal alloy.

[0073] Example 7 is the gas sensor chip according to example 6, further having an additional first heating element constructed in the measurement cavity beam and an additional second heating element constructed in the reference cavity beam, wherein the additional first and second heating elements have or are composed of a doped semiconductor material.

[0074] Example 8 is the gas sensor chip according to any of the preceding examples, wherein the first conductor elements of the measurement cavity beam and the reference cavity beam are part of a first electrical circuit and the second conductor elements of the measurement cavity beam and the reference cavity beam are part of a second electrical circuit, wherein the first electrical circuit and the second electrical circuit can be switched off independently from each other or can be operated as heating circuits or as measurement circuits, respectively, based on an operating mode of the gas sensor chip, wherein in the operation as heating circuits the conductor elements of the respective circuit are connected in parallel and in the operation as measurement circuits the conductor elements of the respective circuit are connected in a Wheatstone bridge circuit.

[0075] Example 9 is the gas sensor chip according to example 8, wherein the gas sensor chip is configured for operating in a sequence of different operating modes, respectively, based on which temperature a thermal conductivity measurement should be performed.

[0076] Example 10 is the gas sensor chip according to example 9, wherein the gas sensor chip is designed at least for performing thermal conductivity measurements at a relatively low temperature, a relatively medium temperature and a relatively high temperature.

[0077] Example 11 is the gas sensor chip according to any of examples 8 to 10, wherein in one of the operating modes both electrical circuits are operated simultaneously as measurement circuits in order to provide a redundancy of thermal conductivity measurements.

[0078] Example 12 is the gas sensor chip according to any one of the examples 8 to 11, wherein the gas sensor chip is configured to change the interconnection of the first and second conductor elements based on an operating mode of the gas sensor chip such that one or more of the first conductor elements of the first circuit reach the position of one or more of the second conductor elements of the second circuit and vice versa.

[0079] Example 13 is a gas sensor for performing a thermal conductivity measurement, having a gas sensor chip according to any one of the examples 1 to 12, a control chip configured to operate the gas sensor chip in various operating modes, and a package encapsulating the gas sensor chip and the control chip.

[0080] Example 14 is a method for manufacturing a gas sensor chip for thermal conductivity measurements, wherein the method comprises providing a wafer, configuring a measurement cavity with an opening in the wafer such that an ambient gas can flow into the measurement cavity, configuring a reference cavity in the wafer, filling the reference cavity with a reference gas and hermetically sealing the reference cavity, configuring first and second measurement cavity beams side by side and independently in the measurement cavity, configuring first and second reference cavity beams side by side and independently in the reference cavity, configuring first and second conductor elements on or in each of the measurement cavity beams and the reference cavity beams, respectively, such that the first and second conductor elements are electrically insulated from each other, respectively, and can operate as sensor elements and / or as heating elements for thermal conductivity measurements for the ambient gas, respectively, based on an operating mode of the gas sensor chip.

[0081] Example 15 is the method according to example 14, wherein configuring the first conductor elements of the measurement cavity beams and the reference cavity beams comprises a doping of a semiconductor material, and wherein configuring the second conductor elements of the measurement cavity beams and the reference cavity beams comprises depositing a metal or a metal alloy onto the measurement cavity beams and the reference cavity beams.

[0082] Example 16 is the method according to any one of the examples 14 or 15, further comprising configuring a first circuit with the first conductor elements in the wafer and configuring a second circuit with the second conductor elements in the wafer, wherein the first circuit and the second circuit are insulated from each other.

[0083] Example 17 is a method for operating a gas sensor chip for thermal conductivity measurements, the method comprising: providing a gas sensor chip having a measurement cavity with an opening enabling ambient gas to flow into the measurement cavity, a reference cavity filled with a reference gas and hermetically sealed, first and second measurement cavity beams arranged side by side and independently in the measurement cavity, first and second reference cavity beams arranged side by side and independently in the reference cavity, wherein each of the measurement cavity beams and the reference cavity beams has first and second conductor elements, respectively, which are electrically insulated from each other and can be operated as sensor elements and / or as heating elements for thermal conductivity measurements on the ambient gas, respectively, based on an operating mode of the gas sensor chip; heating the heating elements; and performing a thermal conductivity measurement by means of the sensor elements

[0084] Example 18 is the method according to example 17, wherein the first conductor elements of the measurement cavity beams and the reference cavity beams are part of a first electrical circuit and the second conductor elements of the measurement cavity beams and the reference cavity beams are part of a second electrical circuit, wherein the first electrical circuit and the second electrical circuit are independently from each other switched off or operated as heating circuit or as measurement circuit, respectively, based on the operating mode of the gas sensor chip, wherein in the operation as heating circuit the conductor elements of the respective circuit are connected in parallel and in the operation as measurement circuit the conductor elements of the respective circuit are connected in a Wheatstone bridge circuit.

[0085] Example 19 is the method according to example 18, further comprising: operating the gas sensor chip in an operating mode in which both electrical circuits are operated as heating circuit in order to heat the ambient gas and the reference gas and switching into a further operating mode in which both electrical circuits are operated as measurement circuit in order to perform a thermal conductivity measurement.

[0086] Example 20 is the method according to example 18, further comprising: operating the gas sensor chip in an operating mode in which both electrical circuits are operated as measurement circuit in order to perform a first thermal conductivity measurement at a relatively low temperature, switching into a further operating mode in which both electrical circuits are operated as heating circuit in order to heat the measurement cavity beams and the reference cavity beams and switching into the operating mode in which both electrical circuits are operated as measurement circuit in order to perform a second thermal conductivity measurement at a relatively high temperature.

[0087] Example 21 is the method according to example 18, further comprising: performing a temperature spectroscopy analysis on the ambient gas, wherein the temperature spectroscopy analysis comprises: operating the gas sensor chip in a sequence of alternating operating modes and thus setting alternating temperatures of the reference gas and the ambient gas and performing thermal conductivity measurements at the alternating temperatures.

[0088] Example 22 is the method of any one of examples 18 to 21, further comprising changing the interconnections of the first and second conductor elements such that one or more of the first conductor elements of the first electrical circuit reach the location of one or more of the second conductor elements of the second electrical circuit, or vice versa, and performing the thermal conductivity measurement with the changed interconnections.

[0089] Example 23 is the method of example 22, wherein the measurement cavity beam and the reference cavity beam each have an additional heating element, and the ambient gas and the reference gas are heated by means of the additional heating elements in the changed interconnections.

[0090] Example 24 is an apparatus having means for performing the method of any one of examples 14 to 23.

[0091] It is to be understood that the description and the drawings are only illustrative of the principles of the proposed method and apparatus. Those skilled in the art will be able to implement various arrangements which, although not explicitly described or shown herein, embody the principles of the application and are included within its scope. Furthermore, all examples and embodiment outlined herein are principally intended to be only for illustrative purposes to aid the reader in understanding the principles of the proposed method and apparatus and are to be not construed as limiting. Furthermore, all statements as to the manner of operation or performance of the present application are intended to be illustrative only, and are not to be in any way limiting. It is the following claims, including any amendments thereto, which define the scope of the application.

Claims

1. A gas sensor chip (100) for performing thermal conductivity measurements, the gas sensor chip having: a measurement cavity (102) having an opening (114) enabling an ambient gas to flow into the measurement cavity (102), a reference cavity (104) filled with a reference gas and hermetically sealed, a first measurement cavity beam (106) and a second measurement cavity beam (108) arranged side by side and independently in the measurement cavity (102), a first reference cavity beam (110) and a second reference cavity beam (112) arranged side by side and independently in the reference cavity (104), wherein each of the measurement cavity beams (106, 108) and the reference cavity beams (110, 112) having a first conductor element (106a, 108a, 110a, 112a) and a second conductor element (106b, 108b, 110b, 112b), respectively, which are electrically insulated from each other and can be operated as sensor elements and / or as heating elements for thermal conductivity measurements with respect to the ambient gas based on an operating mode of the gas sensor chip (100), respectively.

2. The gas sensor chip (100) according to claim 1, wherein the measurement cavity beams (106, 108) and the reference cavity beams (110, 112) having or consisting of a semiconductor material, respectively, wherein the side walls of the measurement cavity (102) and the side walls of the reference cavity (104) at least partially consist of a semiconductor material, and wherein the measurement cavity beams (106, 108) are integrally configured with the semiconductor material of the side walls of the measurement cavity (102), and the reference cavity beams (110, 112) are integrally configured with the semiconductor material of the side walls of the reference cavity (104).

3. The gas sensor chip (100) according to claim 1 or 2, wherein the first conductor elements (106a, 108a, 110a, 112a) of the measurement cavity beams (106, 108) and the reference cavity beams (110, 112) having or consisting of a doped semiconductor material, respectively, and wherein the second conductor elements (106b, 108b, 110b, 112b) of the measurement cavity beams (106, 108) and the reference cavity beams (110, 112) have or consist of a metal or a metal alloy, respectively.

4. The gas sensor chip according to claim 1 or 2, wherein the first conductor elements (106a, 108a, 110a, 112a) and the second conductor elements (106b, 108b, 110b, 112b) of the measurement cavity beams (106, 108) and the reference cavity beams (110, 112) having or consisting of a doped semiconductor material, respectively.

5. The gas sensor chip (100) according to claim 4, further having: an additional first heating element (310) arranged on the measurement cavity beams (106, 108), an additional first heating element (310) arranged in the measurement cavity beam (106, 108), wherein the additional first heating element and the additional second heating element (310) have or consist of a metal or a metal alloy.

6. The gas sensor chip (100) according to claim 1 or 2, wherein the first conductor elements (106a, 108a, 110a, 112a) and the second conductor elements (106b, 108b, 110b, 112b) of the measurement cavity beam (106, 108) and the reference cavity beam (110, 112) have or consist of a metal or a metal alloy, respectively.

7. The gas sensor chip (100) according to claim 6, further having: an additional first heating element (310) configured in the measurement cavity beam (106, 108), an additional second heating element (310) configured in the reference cavity beam (110, 112), wherein the additional first heating element and the additional second heating element (310) have or consist of a doped semiconductor material.

8. The gas sensor chip (100) according to any one of the preceding claims, wherein the first conductor elements (106a, 108a, 110a, 112a) of the measurement cavity beam (106, 108) and the reference cavity beam (110, 112) are part of a first electrical circuit (122) and the second conductor elements (106b, 108b, 110b, 112b) of the measurement cavity beam (106, 108) and the reference cavity beam (110, 112) are part of a second electrical circuit (124), wherein, based on the operating mode of the gas sensor chip (100), the first electrical circuit (122) and the second electrical circuit (124) can be switched off independently from each other or can be operated as heating circuits or as measurement circuits, respectively, wherein, in operation as heating circuits, the conductor elements of the respective circuit (122, 124) are connected in parallel and, in operation as measurement circuits, the conductor elements of the respective circuit (122, 124) are connected in a Wheatstone bridge circuit.

9. The gas sensor chip (100) according to claim 8, wherein the gas sensor chip (100) is configured for operating in a sequence of different operating modes, respectively, based on which temperature the thermal conductivity measurement should be performed.

10. The gas sensor chip (100) according to claim 9, wherein the gas sensor chip (100) is designed at least for performing the thermal conductivity measurement at a relatively low temperature, at a relatively medium temperature and at a relatively high temperature.

11. The gas sensor chip (100) according to any one of claims 8 to 10, wherein in one of the operating modes, both circuits (122, 124) are operated as measurement circuits simultaneously in order to provide redundancy of the thermal conductivity measurement.

12. The gas sensor chip (100) according to any one of claims 8 to 11, wherein The gas sensor chip (100) is configured to change the interconnection of the first conductor elements (106a, 108a, 110a, 112a) and the second conductor elements (106b, 108b, 110b, 112b) based on an operating mode of the gas sensor chip (100) such that one or more of the first conductor elements (106a, 108a, 110a, 112a) of the first circuit (122) reaches the position of one or more of the second conductor elements (106b, 108b, 110b, 112b) of the second circuit (124) and vice versa.

13. A gas sensor (500) for performing a thermal conductivity measurement, the gas sensor having: a gas sensor chip (100) according to any one of claims 1 to 12, a control chip (510) configured to operate the gas sensor chip (100) in different operating modes, and a package (520) encapsulating the gas sensor chip (100) and the control chip (510).

14. A method (600) for manufacturing a gas sensor chip for thermal conductivity measurements, wherein The method (600) comprises: providing (601) a wafer, configuring (602) a measurement cavity with an opening in the wafer such that an ambient gas can flow into the measurement cavity, configuring (603) a reference cavity in the wafer, filling (604) the reference cavity with a reference gas and hermetically sealing the reference cavity, configuring (605) a first measurement cavity beam and a second measurement cavity beam side by side and independently in the measurement cavity, configuring (606) a first reference cavity beam and a second reference cavity beam side by side and independently in the reference cavity, and configuring (607) a first conductor element and a second conductor element on or in each of the measurement cavity beam and the reference cavity beam, respectively, such that the first conductor element and the second conductor element are electrically insulated from each other, respectively, and can operate as sensor elements and / or as heating elements for a thermal conductivity measurement for the ambient gas, respectively, based on an operating mode of the gas sensor chip.

15. The method (600) of claim 14, wherein Configuring (607) the first conductor element of the measurement cavity beam and the reference cavity beam comprises a doping of a semiconductor material, and wherein configuring (607) the second conductor element of the measurement cavity beam and the reference cavity beam comprises depositing a metal or a metal alloy onto the measurement cavity beam and the reference cavity beam.

16. The method (600) according to any one of claims 14 or 15, further comprising: configuring a first circuit in the wafer with the first conductor elements, and configuring a second circuit in the wafer with the second conductor elements, wherein the first circuit and the second circuit are insulated from each other.

17. A method (700) for operating a gas sensor chip for thermal conductivity measurements, the method (700) comprising: providing (701) a gas sensor chip, the gas sensor chip having: a gas sensor chip (100) according to any one of claims 1 to 12, a control chip (510) configured to operate the gas sensor chip (100) in different operating modes, and a package (520) encapsulating the gas sensor chip (100) and the control chip (510). The method (600) comprises: providing (601) a wafer, configuring (602) a measurement cavity with an opening in the wafer such that an ambient gas can flow into the measurement cavity, configuring (603) a reference cavity in the wafer, filling (604) the reference cavity with a reference gas and hermetically sealing the reference cavity, configuring (605) a first measurement cavity beam and a second measurement cavity beam side by side and independently in the measurement cavity, configuring (606) a first reference cavity beam and a second reference cavity beam side by side and independently in the reference cavity, and configuring (607) a first conductor element and a second conductor element on or in each of the measurement cavity beam and the reference cavity beam, respectively, such that the first conductor element and the second conductor element are electrically insulated from each other, respectively, and can operate as sensor elements and / or as heating elements for a thermal conductivity measurement for the ambient gas, respectively, based on an operating mode of the gas sensor chip. Configuring (607) the first conductor element of the measurement cavity beam and the reference cavity beam comprises a doping of a semiconductor material, and wherein configuring (607) the second conductor element of the measurement cavity beam and the reference cavity beam comprises depositing a metal or a metal alloy onto the measurement cavity beam and the reference cavity beam.

16. The method (600) according to any one of claims 14 or 15, further comprising: configuring a first circuit in the wafer with the first conductor elements, and configuring a second circuit in the wafer with the second conductor elements, wherein the first circuit and the second circuit are insulated from each other.

17. A method (700) for operating a gas sensor chip for thermal conductivity measurements, the method (700) comprising: providing (701) a gas sensor chip, the gas sensor chip having: a measurement cavity having an opening enabling an ambient gas to flow into the measurement cavity, a reference cavity filled with a reference gas and hermetically sealed, a first measurement cavity beam and a second measurement cavity beam arranged side by side and independently in the measurement cavity, a first reference cavity beam and a second reference cavity beam arranged side by side and independently in the reference cavity, wherein each of the measurement cavity beams and the reference cavity beams has a first conductor element and a second conductor element, respectively, which are electrically insulated from each other and can be operated as sensor elements and / or as heating elements for a thermal conductivity measurement with respect to the ambient gas based on an operating mode of the gas sensor chip, respectively; heating (702) the heating elements; and performing (703) the thermal conductivity measurement by means of the sensor elements.

18. The method (700) of claim 17, wherein the first conductor elements of the measurement cavity beams and the reference cavity beams are part of a first circuit and the second conductor elements of the measurement cavity beams and the reference cavity beams are part of a second circuit, wherein based on an operating mode of the gas sensor chip, the first circuit and the second circuit are switched off or operated as heating circuits or as measurement circuits independently from each other, respectively, wherein in the operation as heating circuits, the conductor elements of the respective circuits are connected in parallel and in the operation as measurement circuits, the conductor elements of the respective circuits are connected in a Wheatstone bridge circuit.

19. The method (700) according to claim 18, further comprising: operating the gas sensor chip in an operating mode in which both circuits are operated as heating circuits in order to heat the ambient gas and the reference gas, and switching into a further operating mode in which both circuits are operated as measurement circuits to perform the thermal conductivity measurement.

20. The method (700) according to claim 18, further comprising: operating the gas sensor chip in an operating mode in which both circuits are operated as measurement circuits to perform a first thermal conductivity measurement when the temperature is relatively low, switching into a further operating mode in which both circuits are operated as heating circuits to heat the measurement cavity beams and the reference cavity beams, and switching into an operating mode in which both circuits are operated as measurement circuits to perform a second thermal conductivity measurement when the temperature is relatively high.

21. The method (700) according to claim 18, further comprising: performing a temperature spectroscopy analysis on the ambient gas, wherein the temperature spectroscopy analysis comprises: operating the gas sensor chip in a sequence of alternating operating modes and thus setting alternating temperatures of the reference gas and the ambient gas, and performing the thermal conductivity measurement at the alternating temperatures.

22. The method (700) according to any one of claims 18 to 21, further comprising: the interconnection of the first conductor elements and the second conductor elements is changed such that one or more of the first conductor elements of the first circuit reaches the position of one or more of the second conductor elements of the second circuit and vice versa, and the thermal conductivity measurement is performed with the changed interconnection.

23. The method (700) of claim 22, wherein the measurement cavity beam and the reference cavity beam each have an additional heating element, and the reference gas and the ambient gas are heated by means of the additional heating elements when the interconnection is changed. the measurement cavity beam and the reference cavity beam each have an additional heating element, and the reference gas and the ambient gas are heated by means of the additional heating elements when the interconnection is changed.

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