DE102015220270A1 - Micromechanical optical sensor for media detection - Google Patents

Abstract

Micromechanical sensor (100), comprising:
A detector device (10) having a detector wafer (12) and a first cap device (11) arranged thereon, wherein the first cap device (10) is designed as a semiconductor cap wafer;
A second cap device (20) arranged on the first cap device (11), wherein the second cap device (20) is provided for receiving a test medium (21) and has at least one access opening for the test medium (21); in which
- The first cap means (11) and the detector wafer (12) and the second capping means (20) and the first capping means (11) by means of a connecting element (50) are interconnected; and
- A radiation generating means (40), wherein one of the radiation generating means (40) generated measuring radiation (S) through the test medium (21) on at least one detector element (13) of the detector wafer (12) is feasible.

Description

The invention relates to a micromechanical optical sensor for media detection and to a method for producing such a sensor.

State of the art

For the detection of certain components in liquids or gases already known optical measuring systems can be used. In this case, individual substances in the mentioned media or a substance concentration of these media can be detected by a spectroscopic measurement, wherein for such measurements at least one optical detector and at least one optical radiation source are needed. The sources used typically have a temperature between about 250 ° C to about 1000 ° C. Thus, usually safety measures must be taken if the substances to be measured are flammable.

Disclosure of the invention

It is an object of the present invention to provide an improved structure of a spectroscopic sensor over known sensors.

• – eine Detektoreinrichtung mit einem Detektorwafer und einer darauf angeordneten ersten Kappeneinrichtung, wobei die erste Kappeneinrichtung als ein Halbleiter-Kappenwafer ausgebildet ist;
• – eine auf der ersten Kappeneinrichtung angeordnete zweite Kappeneinrichtung, wobei die zweite Kappeneinrichtung zur Aufnahme eines Prüfmediums vorgesehen ist und wenigstens eine Zugangsöffnung für das Prüfmedium aufweist; wobei
• – die erste Kappeneinrichtung und der Detektorwafer und die zweite Kappeneinrichtung und die erste Kappeneinrichtung mittels eines Verbindungselements miteinander verbunden sind; und
• – eine Strahlungserzeugungseinrichtung, wobei eine von der Strahlungserzeugungseinrichtung generierte Messstrahlung durch das Prüfmedium auf wenigstens ein Detektorelement des Detektorwafers führbar ist.

According to a first aspect, the object is achieved with a micromechanical sensor, comprising:

• A detector device having a detector wafer and a first cap device arranged thereon, wherein the first cap device is designed as a semiconductor cap wafer;
• A second cap device arranged on the first cap device, wherein the second cap device is provided for receiving a test medium and has at least one access opening for the test medium; in which
• - The first cap means and the detector wafer and the second cap means and the first cap means are interconnected by means of a connecting element; and
• A radiation generating device, wherein a measuring radiation generated by the radiation generating device can be guided through the test medium to at least one detector element of the detector wafer.

Advantageously, in this way, a basic concept of the sensor can already be realized at the wafer level, whereby a compact design is supported. Furthermore, such a sensor can be manufactured efficiently with known methods of semiconductor micromechanics and requires only a small amount of assembly work. By using caps, an effective decoupling of the measuring radiation from the test media can be provided.

• – Ausbilden einer Detektoreinrichtung mit einem Detektorwafer und einer darauf angeordneten ersten Kappeneinrichtung, wobei die erste Kappeneinrichtung und der Detektorwafer mittels eines Verbindungselements verbunden werden;
• – Ausbilden einer zweiten Kappeneinrichtung auf der ersten Kappeneinrichtung, wobei ein Inneres des zweiten Kappeneinrichtung für ein Prüfmedium vorgesehen ist;
• – Verbinden der zweiten Kappeneinrichtung mit der ersten Kappeneinrichtung mittels eines Verbindungselements; und
• – Anordnen einer Strahlungserzeugungseinrichtung derart, dass Messstrahlung der Strahlungserzeugungseinrichtung durch das Prüfmedium und auf ein Detektorelement der Detektoreinrichtung führbar ist.

According to a second aspect, the object is achieved with a method for producing a micromechanical sensor, comprising the steps:

• - Forming a detector device with a detector wafer and a first cap means arranged thereon, wherein the first cap means and the detector wafer are connected by means of a connecting element;
• - Forming a second capping means on the first capping means, wherein an interior of the second cap means is provided for a test medium;
• - Connecting the second cap means with the first cap means by means of a connecting element; and
• Arranging a radiation generating device such that measuring radiation of the radiation generating device can be guided through the test medium and onto a detector element of the detector device.

Preferred embodiments of the micromechanical sensor are the subject of dependent claims.

An advantageous development of the micromechanical sensor is characterized in that the detector wafer has at least two detector elements, wherein one of the detector elements is designed as a measuring element and one of the detector elements as a reference element. In this way, a reference channel is provided, whereby advantageously the drift effects of the components over the life of the micromechanical sensor can be taken into account.

A further advantageous development of the micromechanical sensor is characterized in that at least one filter element is arranged on an inner surface of the first cap device, wherein the measuring radiation can be guided through the filter element onto the detector element of the detector wafer. In this way, a suitable wavelength for the measuring radiation and the test medium to be tested can be provided.

A further advantageous development of the micromechanical sensor is characterized in that the access opening of the second cap device as a through-opening is trained. In this way, measurements can be made in a flowing medium where it is particularly important to be able to quickly detect changes in the test medium.

Further advantageous developments of the micromechanical sensor provide that the second cap device is designed as a semiconductor cap or as a plastic cap or as a metal cap. In this way, depending on the application of the micromechanical sensor different cap concepts can be realized.

A further advantageous embodiment of the micromechanical sensor provides that it further comprises a third cap device arranged on the second cap device, wherein the third cap device is connected to the second cap device by means of a connecting element. This advantageously provides protection for the wafer stack arranged thereunder and / or a possibility for an integrative arrangement of a radiation source.

Further advantageous developments of the micromechanical sensor provide that the radiation generating device is arranged in the third cap device or on the second cap device or below the detector wafer. In this way, advantageously different positioning possibilities are provided for the radiation generating device, each with its own characteristics.

Further advantageous developments of the sensor provide that the filter element is arranged on an inner surface of the second cap device or on the detector element. As a result, different positioning possibilities for the filter element are advantageously provided.

A further advantageous development of the micromechanical sensor is characterized in that a reflection layer is arranged on an inner surface of the second cap device. In this way, a diameter of the media channel can advantageously be made even smaller because the measuring radiation passes through the test medium twice due to a reflection.

Further advantageous developments of the micromechanical sensor are characterized in that the second cap device is formed from a semiconductor material, in particular silicon or from plastic or from metal. In this way, advantageously different dimensions for the test medium can be provided.

A further advantageous development of the micromechanical sensor is characterized in that at least part of an electronic evaluation circuit for evaluating the measuring radiation impinging on the detector element is arranged on the detector wafer. In this way, a degree of integration of the sensor can advantageously be further increased.

Further advantageous developments of the micromechanical sensor provide that the radiation generating device is designed as one of the following: MEMS source, infrared source, LED, laser. In this way, different possibilities for the radiation generating device, each with specific characteristics and accuracies, are provided.

Further advantageous developments of the micromechanical sensor provide that the filter element is an active or a passive component. In this way, advantageously different technical implementation options for the filter element 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.

In the figures shows:

1 a conventional topology of a spectroscopic sensor;

2 a first embodiment of a micromechanical sensor;

3 a further embodiment of a micromechanical sensor;

4 a further embodiment of a micromechanical sensor;

5 a schematic representation of an arrangement of the micromechanical sensor in a media channel;

6 a plan view of the arrangement of 5 ; and

7 a basic sequence of an embodiment of the method according to the invention.

Description of embodiments

1 shows a simplified arrangement of a conventional spectroscopic sensor device. A radiation generator 40 emits a test radiation S, which is a test medium 21 traverses that represents an absorption path for the measurement radiation S. After the absorption path is an optical filter 14 arranged, which filters out a wavelength range of the measuring radiation S and the filtered-out area a detector 13 feeds, which generates an electrical voltage U from it. The electrical voltage U is determined by means of an electronic evaluation circuit 15 evaluated, whereby specific properties or changes of the test medium 21 can be determined.

A basic idea of the present invention is to provide an economically feasible, low-cost design concept for a spectroscopic liquid or gas sensor, wherein an encapsulated, flexible concept for media measurement is provided. As the radiation source, an infrared source can be used as an additional MEMS element or an LED or a laser. Due to the encapsulated concept, a decoupling of the radiation source is provided by a possibly inflammatory test medium, whereby an operational safety of the sensor can advantageously be significantly increased. A required absorption path for a measuring radiation in the test medium can be dimensioned by a cavern geometry in a cap, whereby an adaptation for different applications can be made quickly and inexpensively.

A possible variant of such a micromechanical sensor shows 2 in a cross-sectional view.

The basis is a detector wafer 12 with integrated detector elements 13 For example, in the form of integrated infrared detectors, wherein the detector elements 13 may also be formed as a detector array, for example, an infrared detector array. Typically, at least two detector elements 13 or -pixel required, wherein a detector element 13 as a reference and a detector element 13 is provided as a measuring pixel. The detector element 13 For example, it may be formed as a diode or as a resistive bolometer.

In this way, by means of the reference pixel, a reference channel for the measurement radiation S can be realized, which over a lifetime of the sensor 100 Consider drift effects. The detector elements 13 For this purpose, different wavelengths are applied. This is done by means of an optional, appropriately designed filter element 14 in the form of a bandpass filter disposed on an inner surface of a first capping means 11 fixed, preferably glued. In 2 are two filter elements 14 recognizable, wherein a filter element 14 for the measuring-detector element 13 is provided and a filter element 14 for the reference detector element 13 , If a narrowband radiation source (eg, a light emitting diode (LED) or a laser) is used instead of a broadband MEMS radiation source, the optical filter elements 14 also completely eliminated.

An electronic evaluation circuit 15 (eg an ASIC, not shown) is functional with the detector elements 13 of the detector wafer 12 connected. In this case, the evaluation circuit 15 at least partially on the detector wafer 12 or completely external to the detector wafer 12 be arranged.

The first cap device 11 fulfills, inter alia, a protective function for the sensitive detector elements 13 against environmental influences. For this purpose, in the first capping device 11 a vacuum may be provided to a particular variant of the detector element 13 to be able to train as sensitively as possible. The first cap device 11 is preferably applied to the detector wafer by means of a wafer bonding process 12 applied and by means of a connecting element 50 with the detector wafer 12 connected. The connecting element 50 is preferably a bonding frame, for example a sealing glass bonding frame or an aluminum-germanium bonding frame or a copper bonding frame, with which the first cap device 11 and the detector wafer 12 be bonded together.

A wafer bonding process may also be used to provide a second capping device 20 with the detector device 10 connect to. The second cap device 20 is formed so that it is laterally open and is connected only at both edges or only at the corners with the underlying wafer stack. Under the second cap device 20 becomes the test medium to be measured or tested 21 directed. A distance 22 between a lower edge of the second cap means 20 and an upper edge of the first capping means 11 defines a length of a radiation path of one of the radiation generating device 40 emitted measuring radiation S passing through the test medium 21 to be led. The distance 22 should have a lifetime of the sensor 100 remain essentially unchanged. Depending on the requirement of an application, the distance 22 be formed suitable by a corresponding cap design. It is conceivable for this purpose, a depression in the first cap device 11 to process the distance and thus the absorption length in the test medium 21 to increase.

Visible is also a third cap device 30 equipped with an integrated radiation generator 40 , eg in the form of an integrated MEMS radiator in a similar way to the second cap device 20 , for example, by a seal glass process is applied. An electrical contact of the radiation generating device 40 by means of electrical lines 16 can be realized through the wafer stack with known processes, such as through-silicon vias.

3 shows a further cross-sectional view of an embodiment of the micromechanical sensor 100 , In this case, an alternative positioning of the radiation generating device 40 recognizable. The radiation generator 40 is in this case on an upper side of the second cap device 20 within the circumferentially arranged connecting element 50 arranged. The third cap device 30 has only a passive protective function for the radiation generating device in this variant 40 , In this way, an electrical contacting of the radiation generating device 40 by means of cables 16 be significantly easier, because electrical contacts can be made with less effort, because they are not through the third capping device 30 must be led.

Is recognizable in the in 3 also shown that the filter elements 14 directly on the detector elements 13 are arranged, whereby an alternative detection principle is realized.

A cross section of another embodiment of the micromechanical sensor 100 shows 4 , In this variant, the radiation generating device 40 (For example, an infrared source) on a bottom of the detector wafer 12 arranged. The measuring radiation S therefore first passes through the detector wafer 12 and the first cap device 11 and at one in the second capping means 20 arranged metallic reflection layer 23 (For example, aluminum or copper) reflects and passes from there to the detector element 13 ,

The second cap device 20 is thus designed as a completely passive device without electrical wiring and is merely used as a guide element for the test medium 21 used. In this variant, thus advantageously eliminates the third cap means 30 , The electrical contacting of the radiation generating device 40 can also be much easier than in the variant of 3 be educated.

A number of the measuring channels is application-dependent, conceivable are, for example, one to sixteen measuring channels or an even higher number of measuring channels. In this case, a detector array with a suitable number of individual detectors or pixels can be used.

5 shows an exemplary arrangement or integration of the micromechanical sensor 100 in a media channel 80 (For example, a fuel line of a motor vehicle). The concept is similar to integration of a mass air sensor into an air intake line of a motor vehicle. In this case, the detector stack described above is in a housing 90 integrated so that an electrical contact to the outside, for example to an electronic control unit or to another evaluation unit is possible.

At the same time, the housing concept allows a corresponding seal by means of a sealing element 70 , so that the test medium to be measured 21 can not escape. The sealing element 70 For example, it may be formed as a screw cap, similar to that known in high-pressure sensors in internal combustion engines. The sensor element is ideally placed such that the media channel of the second capping device 20 parallel to the flow direction of the medium in the media channel 80 is aligned to ensure the most efficient flow possible. Alternatively, the sensor could also be in a bypass (not shown) of the media channel 80 be arranged so as to have a flow rate of the medium in the media channel 80 as little as possible.

In case of using the sensor 100 in a stationary medium (eg for measuring fuel in a tank, not shown), the second cap means 20 preferably only one media access opening.

6 shows a plan view of the arrangement of 5 , It can be seen that only the media-carrying part of the sensor 100 in the media channel 80 protrudes and thereby the flow in the media channel 80 as little as possible affected.

Further realization possibilities of the micromechanical sensor not shown in FIGS 100 result from an almost arbitrary combination of the embodiments described above. Advantageously, the described concept can also be used for the measurement of highly concentrated gases, whereby gases can be measured, for example, under high pressures.

A kind of macroscopic implementation of the described sensor concept is also conceivable, whereby printed circuit boards are used instead of semiconductor wafers. In this case, a sensor element in a housing (for example in a TO39 cell) can be used as the detector.

Similarly, the concept may be used for other optical sensors operating in the near-infrared, visible, or other optical domains. The type of detector and the source must be coordinated. It is important in any case that the radiation generator 40 , the detector element 13 and the distance 22 within the second capping means 20 are coordinated.

It is also conceivable that the filter element 14 is formed as an active filter element. This is the filter element 14 electrically driven, whereby a wavelength or a selectivity of the filter element 14 is changeable.

The second capping device shown in the aforementioned embodiments 20 is preferably a semiconductor wafer, in particular a Si wafer, but may alternatively be a plastic material or a metal (eg stainless steel). In this way, so-called macroscopic concepts of the invention can be implemented.

6 shows a schematic flow diagram of an embodiment of a method for producing a micromechanical device.

In one step 200 a formation of a detector device takes place 10 with a detector wafer 12 and a first capping means disposed thereon 11 , wherein the first cap means 11 and the detector wafer 12 by means of a connecting element 50 get connected.

In one step 210 a second capping device is formed 20 on the first cap device 11 wherein an interior of the second cap means 20 for a test medium 21 is provided.

In one step 220 is a connection of the second capping device 20 with the first cap device 11 by means of a connecting element 50 carried out.

Finally, in one step 230 arranging a radiation generating device 40 performed such that a measuring beam S of the radiation generating device 40 through the test medium 21 and to a detector element 13 the detector device 10 is feasible.

In summary, the present invention proposes a micromechanical sensor and a method for producing a micromechanical sensor, which realizes a micromechanical realization of a sensor concept for spectroscopic measurements at the wafer level, e.g. for use in a fuel sensor system in the automotive sector.

Advantageously, with the proposed sensor lengths of optical measuring sections can be dimensioned in a simple manner, which are each adapted to a specific application. Advantageously, compared to conventional sensors that have many individual components assembled on a printed circuit board, a cost-effective and easy-to-implement sensor concept can be implemented. As a result, thereby a large and cost-effective design freedom for spectroscopic sensors can be realized.

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.

Claims (15)

Micromechanical sensor ( 100 ), comprising: - a detector device ( 10 ) with a detector wafer ( 12 ) and a first cap device ( 11 ), wherein the first cap device ( 11 ) is formed as a semiconductor cap wafer; - one on the first cap device ( 11 ) arranged second capping device ( 20 ), wherein the second cap device ( 20 ) for receiving a test medium ( 21 ) is provided and at least one access opening for the test medium ( 21 ) having; wherein - the first cap means ( 11 ) and the detector wafer ( 12 ) and the second cap device ( 20 ) and the first cap device ( 11 ) by means of a connecting element ( 50 ) are interconnected; and - a radiation generator ( 40 ), one of the radiation generating device ( 40 ) generated measuring radiation (S) through the test medium ( 21 ) on at least one detector element ( 13 ) of the detector wafer ( 12 ) is feasible. Micromechanical sensor ( 100 ) according to claim 1, characterized in that the detector wafer ( 12 ) at least two detector elements ( 13 ), one of the detector elements ( 13 ) as a measuring element and one of the detector elements ( 13 ) is formed as a reference element. Micromechanical sensor ( 100 ) according to claim 1 or 2, characterized in that at least one filter element ( 14 ) on an inner surface of the first cap device ( 11 ), wherein the measuring radiation (S) through the filter element ( 14 ) on the detector element ( 13 ) of the detector wafer ( 12 ) is feasible. Micromechanical sensor ( 100 ) according to one of the preceding claims, characterized in that the access opening of the second cap means is formed as a passage opening. Micromechanical sensor ( 100 ) according to one of the preceding claims, characterized in that the second cap device ( 20 ) is formed as a semiconductor cap or as a plastic cap or as a metal cap. Micromechanical sensor ( 100 ) according to one of the preceding claims, further comprising one on the second cap device ( 20 ) arranged third cap means ( 30 ), wherein the third cap device ( 30 ) with the second cap device ( 20 ) by means of a connecting element ( 50 ) are connected. Micromechanical sensor ( 100 ) according to claim 6, characterized in that the radiation generating device ( 40 ) in the third cap device ( 30 ) or on the second cap device ( 20 ) or below the detector wafer ( 12 ) is arranged. Micromechanical sensor ( 100 ) according to one of the preceding claims, characterized in that the at least one filter element ( 14 ) on an inner surface of the second cap device ( 20 ) or on the detector element ( 13 ) is arranged. Micromechanical sensor according to one of the preceding claims, characterized in that on an inner surface of the second cap device ( 20 ) a reflection layer ( 23 ) is arranged. Micromechanical sensor ( 100 ) according to one of the preceding claims, characterized in that the second cap device ( 20 ) is formed of a semiconductor material, in particular silicon or plastic or metal. Micromechanical sensor ( 100 ) according to one of the preceding claims, characterized in that at least part of an electronic evaluation circuit ( 15 ) for evaluating the on the detector element ( 13 ) incident measuring radiation (S) on the detector wafer ( 12 ) is arranged. Micromechanical sensor ( 100 ) according to one of the preceding claims, characterized in that the radiation generating device ( 40 ) as one of the following: MEMS source, infrared source, LED, laser. Micromechanical sensor ( 100 ) According to one of the preceding claims, characterized in that the filter element ( 14 ) is an active or a passive device. Method for producing a micromechanical sensor ( 100 ), comprising the steps: - forming a detector device ( 10 ) with a detector wafer ( 12 ) and a first cap device ( 11 ), wherein the first cap device ( 11 ) and the detector wafer ( 12 ) by means of a connecting element ( 50 ) get connected; Forming a second cap device ( 20 ) on the first cap device ( 11 ), wherein an interior of the second cap device ( 20 ) for a test medium ( 21 ) is provided; Connecting the second cap device ( 20 ) with the first cap device ( 11 ) by means of a connecting element ( 50 ); and - arranging a radiation generator ( 40 ) such that measuring radiation (S) of the radiation generating device ( 40 ) through the test medium ( 21 ) and to a detector element ( 13 ) of the detector device ( 10 ) is feasible. Use of a micromechanical sensor ( 100 ) according to one of claims 1 to 13 in a spectroscopic sensor device for liquid and / or gaseous test media ( 21 ).

Images