Sensor chip with integrated flow channel

Abstract

A first aspect of the invention relates to a sensor chip for measuring at least one flow parameter of a fluid. The sensor chip comprises a substrate with a front face and a rear face and a thermal sensor. The thermal sensor comprises a heating element and a sensor component, wherein the heating element is used to provide a heating field, and the sensor component is used to detect a temperature response based on the influence of the fluid on the heating field, said substrate having a monolithic design. Furthermore, the thermal sensor is positioned on the front face of the substrate, and a flow channel lies within the substrate and below the thermal sensor. The flow channel is produced by removing regions of the substrate, preferably starting from the rear face. The at least one flow parameter of the fluid can be measured by the thermal sensor as a result of the flow of the fluid within the flow channel. The invention additionally relates to a method for producing the sensor chip, to a flow sensor assembly, to the use of the sensor chip or the flow sensor assembly, and to a system.

Description

[0001] SENSOR CHIP WITH AN INTEGRATED FLOW CHANNEL

[0002] DESCRIPTION

[0003] The invention relates to the technological field of MEMS flow sensors. In a first aspect, the invention relates to a sensor chip for measuring at least one flow parameter of a fluid. The sensor chip comprises a substrate with a front side and a back side and a thermal sensor. The thermal sensor comprises a heating element and a sensor component, wherein the heating element serves to provide a thermal field and the sensor component serves to detect a temperature response that depends on the influence of the fluid on the thermal field. The substrate is monolithic. Furthermore, the thermal sensor is positioned on the front side of the substrate, and a flow channel is located within the substrate and below the thermal sensor, wherein the flow channel was formed by partially removing the substrate, preferably starting from the back side.Due to the flow of the fluid within the flow channel, at least one flow parameter of the fluid can be measured by the thermal sensor.

[0004] Furthermore, the invention relates to a method for producing the sensor chip, a flow sensor arrangement, a use of the sensor chip or flow sensor arrangement and a system.

[0005] Background and state of the art

[0006] Flow sensors are used in various applications involving flowing fluids and are designed to measure a flow parameter of the fluid. For example, the velocity, flow direction, and / or viscosity of the fluid can be detected using a flow sensor, without being limited to the parameters mentioned above. Typically, the influence of the flow, i.e., the influence resulting from the movement of the fluid, is utilized to perform the measurement by the flow sensor.

[0007] In some applications, it is common to provide a so-called bypass configuration in which a flow parameter of a fluid is measured. In a bypass configuration, a flow restrictor or flow limiter is installed within a main channel through which the fluid flows. The main channel can be, for example, a pipeline for transporting a liquid or within an industrial plant. Furthermore, a bypass (also bypass channel or side channel) is fluidically connected to the main channel. The flow restrictor results in a pressure drop, so that a pressure difference exists in the main channel depending on the flow of the fluid. If the bypass is appropriately connected to the main channel upstream and downstream of the flow restrictor, the fluid is guided into the bypass due to the pressure difference. The sensor used to measure the fluid can be positioned inside or adjacent to the bypass.A bypass configuration ensures reliable fluid transfer in sufficient proximity to the sensor without requiring the sensor to be located in the main channel, which could disrupt the fluid flow. Furthermore, the flow velocity of the fluid in the bypass channel is directly dependent on the pressure difference created in the main channel by the flow restrictor. By measuring the flow velocity of the fluid in the bypass channel, the flow behavior of the fluid in the main channel can also be monitored.

[0008] A proven functional principle for the operation of flow sensors in the state of the art is the thermal measurement principle. The flow sensor typically comprises a heating element and at least one temperature sensor. The heating element generates a thermal field that can be detected by the temperature sensor. When a fluid flows, the thermal field generated by the heating element is modulated. The modulation is detectable by the temperature sensor, with the modulation of the thermal field dependent on the fluid flow. A flow parameter can be determined by modulating the thermal field. The described measurement principle is advantageous in that it eliminates the need for mechanically moving components, thus reducing manufacturing costs and achieving high robustness.

[0009] Using so-called MEMS (microelectromechanical systems), thermal flow sensors can also be provided that have a very compact design (in the micrometer range), excellent functionality, and can be produced at low manufacturing costs.

[0010] A MEMS flow sensor that uses the described measuring principle is described, for example, in Billat et al. (2008). The flow sensor is constructed as a wafer stack, i.e., the flow sensor comprises multiple wafers or substrates stacked one on top of the other. In particular, the flow sensor disclosed in Billat et al. (2008) comprises a bottom substrate and a cover substrate that are connected to one another. Openings are etched along the bottom substrate, which function as inlet and outlet regions for the fluid. The cover substrate is structured such that it has a cavity facing the bottom substrate. A flow channel is introduced within the wafer stack so that the fluid can spread from the inlet region of the bottom substrate into the cavity of the cover substrate and then exit the flow sensor via the outlet region of the bottom substrate.A membrane is attached to the top surface of the lid substrate, on which a heating element and two thermopiles are located. The flow of the fluid within the flow channel modulates the thermal field generated by the heating element, which can be detected by the thermopiles. The bottom substrate is preferably formed by a glass wafer, while the lid substrate is formed by a silicon wafer.

[0011] A similar structure for a flow sensor is disclosed in Palmer et al. (2012). The flow sensor described therein also comprises a wafer stack comprising a bottom substrate and a lid substrate, each of which is provided by a silicon wafer. The lid substrate is connected to the bottom substrate by fusion bonding. The flow sensor is advantageously suited for integration into other silicon-based devices. A membrane is present on the lid substrate, to which three or five meander-like structures are applied to function as at least one heating element and as temperature sensors. The flow channel extends within the wafer stack along the bottom substrate and the lid substrate. Consequently, a fluid can pass through an inlet region within the bottom substrate into a cavity of the lid substrate and through the outlet region on the bottom substrate through the flow channel.

[0012] US 11,280,649 B2 discloses a flow sensor which is also constructed in multiple pieces as a stack. The flow sensor described in US 11,280,649 B2 comprises a substrate which is connected to a cover. The inlet region and the outlet region of the flow channel are located on the cover. A measuring component is attached to a membrane on the substrate. The flow channel is therefore defined by the inlet region and the outlet region on the cover as well as a volume between the substrate and the cover. The measuring component on the membrane, which in turn is positioned on the substrate, can be provided, for example, by a heating element and a temperature sensor. A filling material is located between the membrane or the measuring component and the edge of the substrate, so that the flow channel is spatially delimited.

[0013] US 6,124,632 discloses a monolithic silicon structure for controlling mass flow. The structure comprises a silicon chip positioned on a substrate. A channel extends within the silicon chip, through which a fluid can flow. Furthermore, an inlet region for the inlet and an outlet region for the outlet of the fluid are attached to the substrate. Furthermore, the structure has a valve control system comprising a valve structure and a base. A control circuit can be used to expose a section between the valve structure and the substrate by heating the valve control system, allowing fluid to flow between the inlet region and the outlet region.

[0014] Yang, Canqian, and Soeberg (1992) describe a monolithic sensor for measuring the volume flow of a liquid. The sensor comprises a glass plate on which a silicon chip is positioned. The silicon chip is formed from a wafer, in which a flow channel is formed on the front side, while the electronic components of the sensor are positioned on the back side. The flow channel was created by anisotropic etching using KOH etching. An aluminum cover is attached to the silicon chip, on which a fluid inlet and a fluid outlet are positioned. The sensor elements comprise three diodes, which form a reference diode, a heating diode, and a measuring diode.

[0015] EP 3457093 A1 describes a gas measuring device for a combustible gas. It also discloses a bypass channel that branches off from the main channel upstream of the flow resistance element and flows back into the main channel in the area of ​​the flow resistance element or downstream of it. A flow sensor is attached to the bypass channel to determine at least one characteristic of the gas flowing through the gas meter housing.

[0016] Although several proposals for the design and operation of flow sensors are already known and these demonstrate individually advantageous effects, there is still a need for optimization. In particular, state-of-the-art flow sensors are often characterized by the fact that they have a plurality of interconnected components. In particular, the more complex stack design leads to increased manufacturing costs and potential limitations in their application. Against this background, it would be desirable to offer an improved flow sensor or method for its production with which at least one flow parameter of a fluid can be measured.

[0017] Object of the invention

[0018] The object of the invention is to provide a device for measuring at least one flow parameter of a fluid and a method for its production, which eliminates the disadvantages of flow sensors known from the prior art. Preferably, the device is characterized by a compact structural design, which allows for simple and efficient production and, preferably, simultaneously enables the device to be used for a variety of applications.

[0019] Summary of the invention

[0020] The object of the invention is achieved by the independent claims. Further advantageous embodiments of the invention are disclosed in the dependent claims.

[0021] In a first aspect, the invention relates to a sensor chip for measuring at least one flow parameter of a fluid, comprising a substrate having a front side and a back side and a thermal sensor comprising a heating element for providing a thermal field and a sensor component for detecting a temperature response of the thermal sensor as a function of an influence of the fluid on the thermal field, characterized in that the substrate is monolithic, the thermal sensor is positioned on the front side of the substrate, and below the thermal sensor within the substrate there is a flow channel, which was formed by removing the substrate in regions, preferably starting from the back side, and has an inlet region for an inlet of the fluid into the flow channel and an outlet region for an outlet of the fluid from the flow channel,so that at least one flow parameter of the fluid can be measured based on the temperature response of the thermal sensor.

[0022] The sensor chip according to the invention is advantageously characterized by a high degree of compactness. In particular, no multiple substrates or complex structures are required to provide a flow channel through which the fluid can flow. Instead, the flow channel of the sensor chip is present in a single substrate or wafer. This represents a significant departure from the prior art, increases robustness, and simplifies its manufacture. Furthermore, the sensor chip according to the invention advantageously has a low height, which essentially corresponds to the height of the substrate or a flow channel formed therein. This provides a simple integration option for the sensor chip, for example, in a base plate, so that the sensor chip can be used for versatile applications for measuring flowing fluids.A further advantage of the sensor chip is that it can be manufactured using simple and proven processes in semiconductor technology and / or microsystem technology. In particular, production is quick and cost-effective. The simpler option for manufacturing the sensor results, among other things, from the fact that there is no need to connect different substrates to one another or to attach additional components to one or more substrates to design the flow channel. Instead of complex processes, the flow channel is formed by removing sections, preferably starting from the back, within a monolithic substrate. This can essentially be done in a single process step. The dimensions of the flow channel can be achieved with particular precision, depending on the desired application, by removing the substrate, as explained below.This advantageously enables mass production of the sensor chip at low cost and with a high degree of reproducibility.

[0023] By forming the flow channel directly within the monolithic substrate by removing portions of the substrate, particularly fine structuring with high precision is advantageously possible. The precise design options for the sensor chip, especially the flow channel, also prevent unwanted turbulence that could occur within the flow channel, particularly at the inlet area, and thus limit the measurement by the thermal sensor. In this respect, the sensor chip also achieves a high degree of sensitivity, enabling particularly precise measurement of at least one flow parameter of the fluid.

[0024] Furthermore, the fluidic properties of the flow channel can advantageously be adjusted particularly precisely and consistently. Thus, as explained in more detail below, the fluidic resistance of the flow channel according to the invention depends in particular on its width, which can be adjusted extremely precisely, for example, using known etching processes for the partial removal of the substrate. Error tolerances that could inherently arise in the formation of flow channels in assembled stacks due to the connection technology are avoided. By forming the flow channel within the monolithic substrate, it can also be ensured that the dimensions of the flow channel remain constant and, in particular, are not influenced by the flow behavior of the fluid in the flow channel itself.

[0025] The possibility of a particularly precise specification of a fluidic resistance of the flow channel, which can be kept constant during the measurements, means that the sensor chip according to the invention is particularly suitable for measuring flows of a fluid in a so-called bypass configuration.

[0026] In a bypass configuration, the flow of a fluid in a main channel is determined by measuring a pressure drop in a secondary channel, the so-called bypass. The bypass is usually fluidically connected to the main channel at an inlet and outlet, allowing fluid to be introduced from the main channel into the bypass and returned from the bypass back to the main channel. In the main channel itself, a flow restrictor is located between the inlet and outlet areas, causing a pressure drop. The pressure difference generated by the flow restrictor can be measured based on the resulting flow through the bypass channel, allowing conclusions to be drawn about the flow behavior of the fluid in the flow channel.

[0027] The measurement accuracy of such a method depends directly on the most precise setting of a fluidic resistance, which must also remain constant during the measurement to avoid falsification of the measurement results. Both requirements can be ensured in a simple and robust manner by the sensor chip according to the invention.

[0028] The sensor chip serves, in particular, to measure at least one flow parameter of a fluid. Accordingly, in the context of the invention, the sensor chip can also be referred to as a flow sensor. The fluid refers to the medium that can flow, in particular, through the flow channel, of which at least one flow parameter is to be measured by the sensor chip. The fluid itself preferably refers to a medium that can continuously deform under the influence of shear forces. In particular, the fluid can be present as a liquid or as a gas.

[0029] The at least one flow parameter preferably refers to a quantity with which the fluid can be characterized in its physical and / or chemical properties.

[0030] Preferably, the flow parameter can be selected from a group comprising a flow velocity, a pressure, a volume flow, a flow frequency (in the case of an oscillating flow of the fluid), a concentration and / or composition of the fluid, without being limited to these preferred parameters.

[0031] Structurally, the sensor chip preferably comprises at least the (monolithic) substrate, the flow channel, a thermal sensor, which in turn comprises a heating element, and a sensor component. Further components for the sensor chip may also be preferred, which will be described below.

[0032] The thermal sensor preferably comprises a heating element and a thermal sensor. The heating element further serves, in particular, to provide a thermal field. The thermal field preferably refers to the heat emanating from the heating element. In this respect, the thermal field or heat is transferred to such an extent that the thermal field of the heating element can spread within the flow channel and be flowed through by the fluid. The terms thermal field and heat flow can be used synonymously in the context of the invention.

[0033] Preferably, the fluid influences the thermal field through its flow within the flow channel. This influence and the associated change in the thermal field can be measured by the sensor component of the thermal sensor. The change in the thermal field due to the fluid flow can also be referred to as modulation of the thermal field or modulation of a heat flow. The influence of the fluid on the thermal field, or the modulation, is reflected in particular in a temperature response, which is recorded by the sensor component of the thermal sensor. In other words, the sensor component serves to record a temperature response, which in turn depends on the modulation of the thermal field by the fluid.

[0034] The temperature response preferably refers to a measurement signal that is detected by the sensor component. The temperature response thus preferably represents a reaction of the thermal sensor, in particular of the sensor component, with respect to the properties or the flow of the fluid with regard to its effect on the thermal field. The sensor component can preferably be present as a temperature sensor, so that the temperature response is preferably detected by the temperature sensor. It can also be preferred for the sensor component to be provided by the heating element itself, so that the temperature response preferably represents a measurement signal of the heating element that is influenced by the flow of the fluid. The temperature response can preferably relate to a thermal variable that can be read out in particular by the sensor component, such as the temperature itself.The temperature response may preferably also mean an electrical signal, which can preferably be described by an electrical voltage and / or an electrical current.

[0035] Furthermore, the sensor chip preferably comprises a substrate. The substrate fulfills two functions in particular. On the one hand, the thermal sensor is preferably positioned on a front side of the substrate. Thus, the substrate acts as a carrier for the thermal sensor. On the other hand, the flow channel is located within the substrate, so that the substrate simultaneously serves to provide the flow channel. In other words, the substrate preferably functions both as a carrier for the thermal sensor and for a flow channel, which preferably also runs at least partially beneath the thermal sensor.

[0036] The substrate is preferably monolithic. In the context of the invention, monolithic means in particular a one-piece substrate. Thus, it is preferred that the substrate be present as a single substrate and not in multiple pieces by connecting (e.g., by bonding or gluing) two or more substrates. An unprocessed substrate, i.e., a substrate in which no flow channel has yet been introduced, can preferably be provided as a monolithic block (e.g., as a wafer). The monolithic design of the substrate avoids, in particular, a stack-like structure for the thermal sensor, i.e., according to the invention, multiple substrates are not stacked on top of one another and / or connected to one another.

[0037] Instead, the flow channel is incorporated into a single monolithic substrate. The front side preferably refers to an upper side of the substrate on which the thermal sensor is mounted, preferably on a membrane held by the substrate, as explained in more detail herein. Therefore, the statement that the flow channel runs beneath the thermal sensor preferably means that the flow channel runs on that side of the thermal sensor which is located within the substrate. Because the thermal sensor is mounted on an (upper) front side of the substrate, the integration of the flow channel within the substrate means that the flow channel is located beneath the thermal sensor.The terms above and below are therefore not to be understood in relation to a direction of gravity, but in relation to a defined (upper) front side with thermal sensor and (lower) back side of the substrate.

[0038] Preferably, the thermal sensor is located on the front side of the monolithic substrate, with a flow channel comprising an inlet region and an outlet region preferably being located below the thermal sensor and within the monolithic substrate. The flow channel, its inlet region, and its outlet region are thus preferably incorporated into one and the same monolithic substrate. The flow channel with the inlet and outlet regions preferably extends entirely within or along the monolithic substrate. This advantageously achieves a high degree of compactness for the design of the sensor chip and eliminates the need to construct a multilayer substrate to provide a flow channel.

[0039] This contrasts with known prior art approaches, in which the flow channel with inlet and outlet regions extends along a multilayer substrate. In US Pat. No. 6,124,632, for example, the flow channel is formed by positioning a monolithic silicon chip on a glass substrate, which includes an inlet and outlet region. The flow channel, comprising an inlet and outlet region, thus extends through the combined structure of a silicon chip and glass substrate, which are mounted together on a base plate, for example, a circuit board.

[0040] In Billat, S., et al. (2008), the flow channel also runs within a wafer stack, comprising a glass bottom substrate and a silicon cover substrate, which are bonded together. The inlet and outlet regions of the flow channel are formed in the glass bottom wafer. In the paper by Yang, Canqian, and Soeberg (1992), however, the inlet and outlet regions of the flow channel are provided in an aluminum cover, which is glued to a silicon chip. In these approaches, too, the flow channel runs through a composite structure with at least two components, i.e., a glass wafer and a silicon chip, or an aluminum cover and a silicon chip.

[0041] According to the invention, however, it is advantageously possible to form a flow channel with inlet and outlet areas in a monolithic substrate, which can preferably be applied directly to a base plate, for example a printed circuit board.

[0042] In addition to a particularly compact design, the complete integration of the flow channel into a monolithic substrate can advantageously reduce turbulence. Furthermore, the provision of a flow channel in a monolithic substrate allows for particularly precise manufacturing and dimensioning of the flow channel by removing the substrate in sections.

[0043] Preferably, the flow channel is formed by a partial removal of the substrate, starting from the rear side. The rear side of the substrate refers to a surface that is opposite the front side, i.e., preferably opposite an (upper) side of the substrate on which the thermal sensor is positioned. The partial removal of the substrate, starting from the rear side, can be carried out such that the flow channel corresponds essentially, or preferably exactly, to the height of the substrate in terms of its height. It can also be preferred that the partial removal of the substrate takes place such that a residual thickness remains on the substrate.In the case of a complete removal of the substrate along the height of the substrate to form a flow channel, a partial removal of the substrate can also be carried out in preferred forms starting from a front side of the substrate, wherein in this case too the removal is preferably carried out in such a way that the flow channel is open to the back side of the substrate.

[0044] The partial removal of the substrate to create the flow channel can be detected on the sensor chip, in particular by the flow channel being incorporated below the thermal sensor on the substrate itself. The partial removal of the substrate to create the flow channel particularly means the removal of sections of the substrate (e.g., using known etching methods) in order to configure the flow channel. In particular, a free volume is created within the substrate as a result of or after the partial removal of the substrate. This free volume forms the flow channel. The flow channel can thus preferably be delimited laterally by the substrate.

[0045] In other words, the flow channel preferably refers to the free volume within the substrate that was achieved by removing the substrate in sections. The flow channel particularly comprises an inlet region and an outlet region. Between the inlet region and the outlet region there is a spatial section through which the fluid can flow. The flow channel therefore particularly comprises the inlet region, the outlet region and the spatial section in between. In preferred forms, the flow channel can be delimited laterally by the substrate, while the flow channel is delimited at the top by a membrane that is held by the substrate. In preferred embodiments, the flow channel can also be delimited at the top by the substrate itself, provided that a residual upper thickness preferably remains when the substrate is removed from the rear.

[0046] At the bottom, however, the flow channel is preferably delimited by a further component, preferably a so-called base plate. The base plate, as explained in more detail with respect to the sensor arrangement according to the invention, preferably has two openings, which correspond to an inlet region for the fluid to enter the flow channel and the outlet region for the fluid to leave the flow channel. However, it may also be preferred for an inlet or outlet region of the flow channel to be formed not on a rear side of the substrate, but on the front side, for example by providing an opening in a front-side membrane that delimits the flow channel at the top.In this case, it may be preferred, for example, for a base plate to provide only one opening, which corresponds to an inlet region (or outlet region) of the flow channel, wherein a further opening on the front side of the sensor chip, for example within a membrane, corresponds to the outlet region (inlet region). Advantageously, the structuring of the flow channel can be carried out in one process sequence by removing the substrate in regions, preferably starting from a rear side. This can in particular be carried out in a single process step. It may also be preferred for several process steps to be carried out in order to provide the flow channel. The inlet region represents a transition region via which the fluid enters the flow channel.Accordingly, the outlet area represents a transition section of the flow channel through which the fluid can leave the flow channel.

[0047] Therefore, when measuring the at least one flow parameter by the sensor chip, it is preferred that the fluid flows into the flow channel from the inlet region and leaves the flow channel from the outlet region. This can be implemented, for example, in a bypass configuration in which the fluid flows from a main channel through the flow channel and returns to the main channel.

[0048] The flow channel, in particular, defines a path through which the fluid can flow within the sensor chip. The design of the flow channel can preferably also ensure sufficient proximity of the flowing fluid with respect to the thermal sensor, so that a measurement of flow parameters of the fluid is possible based on a modulation of the thermal field provided by the heating element. In other words, the flow channel provides a path for the flow of the fluid, through which the fluid can spread in order to be measured by the thermal sensor. As explained above, the thermal field is modulated or influenced by the fluid flowing through the flow channel, which can be determined by the temperature response to be recorded at the sensor component. Based on the temperature response, the at least one flow parameter of the fluid can be measured.

[0049] The sensor chip can be designed for different thermal measurement principles and can be configured to operate in one or different modes, preferably using an electronic circuit, to measure at least one flow parameter.

[0050] For example, the sensor chip can utilize an anemometric measuring principle, in which a heating element is preferably applied or embedded in a membrane, and the fluid flow is measured based on heat transfer into the fluid, which changes with the flow velocity. Thus, it may be preferable for the heating element to be supplied with a constant power or maintained at a constant temperature. The flow of the fluid within the thermal field results in a temperature decrease through convection or heat transfer if a constant power was supplied, or it results in a necessary increase in the power supplied to the heating element if the temperature of the heating element is to be kept constant.Convection is proportional to the fluid flow rate, so the fluid flow velocity can be determined by the temperature decrease or by increasing the power to maintain the temperature. Preferably, the sensor component can be formed by the heating element itself, which can determine a flow-dependent temperature decrease, for example, based on a temperature-dependent resistance.

[0051] It may also be preferred for the sensor chip to be designed for a calorimetric measuring principle. A calorimetric measuring principle preferably utilizes the fact that the temperature profile around the heating element changes due to convection caused by the flow of the fluid. Preferably, one, preferably two temperature sensors are positioned downstream and upstream of the heating element. Depending on the flow of the fluid, the temperature measured downstream and upstream of the heating element will differ. By measuring the temperature difference, it is possible to draw conclusions about a flow parameter of the fluid. The heating element can be heated with a constant voltage, a constant current, a constant power, or to a constant temperature.

[0052] Furthermore, it may be preferable to design the sensor chip for a so-called time-of-flight (TOF) measurement principle. This preferably measures the time between the moment a control signal is passed through the heating element and the time at which a maximum temperature rise is measured on a sensor component, for example, a temperature sensor, at a known distance from the heating element. The higher the flow rate, the shorter the so-called TOF.

[0053] By means of the sensor chip, in particular the temperature response of the thermal sensor, further properties of the fluid can preferably be determined, such as a thermal conductivity, a density, a pressure, a specific heat capacity, a thermal conductivity, a concentration and / or a composition of the fluid.

[0054] Those skilled in the art will know that, for example, a frequency-dependent temperature response can be used by means of an oscillating control to draw conclusions about the thermal conductivity and / or volumetric heat capacity of a fluid. For example, determining a phase between an oscillating control signal and a temperature response can be used, in particular, to determine thermal conductivity. The amplitude of a temperature response in the case of an oscillating control can depend, in particular, not only on the thermal conductivity but also on the volumetric heat capacity. Thus, the phase and amplitude of a temperature response compared to an oscillating control can be used, for example, to determine the thermal conductivity and / or volumetric heat capacity of the fluid.These thermal parameters can also be used to draw conclusions about, for example, the composition of the fluid and / or the concentration of a component within a mixed fluid. For example, if the thermal conductivity and / or volumetric heat capacity of various components of a mixed fluid, e.g., a mixed gas, is known, conclusions about the proportions of the individual components can be drawn by determining the thermal conductivity and / or volumetric heat capacity of the entire fluid.

[0055] In a preferred embodiment, the sensor chip is characterized in that the flow channel has a height which substantially corresponds to a height of the monolithic substrate, wherein a width of the flow channel at its narrowest section is preferably smaller than the height of the flow channel, preferably by a factor of 1, 5, 2, 3, 4, or more.

[0056] In a preferred embodiment, the sensor chip is characterized in that the flow channel has a substantially constant width, for example of less than 500 pm, preferably less than 100 pm, 50 pm or less than 30 pm, and wherein the height of the flow channel preferably corresponds substantially to the height of the substrate.

[0057] In a further preferred embodiment, the sensor chip is characterized in that the flow channel has at least one tapered and / or widened section, wherein the width of the tapered section is preferably less than 500 pm, preferably less than 100 pm, 50 pm or less than 30 pm and wherein the height of the flow channel preferably corresponds substantially to the height of the substrate.

[0058] A (minimum) width of the flow channel is preferably always smaller than a maximum height of the flow channel, which in particularly preferred embodiments is essentially constant and essentially corresponds to a height of the substrate or wafer. Preferably, a (minimum) width of the flow channel is at least a factor of 1, 5, 2, 3, 4, or 5 or more smaller than a (maximum) height of the flow channel. A minimum width preferably corresponds to the width of the flow channel at its narrowest section.

[0059] As explained below, the (minimal) width of the flow channel is particularly important for the characteristics of the fluidic resistance.

[0060] For the development of a fluidic resistance, it may be preferable to provide a flow section with a constant width, as stated above, preferably small compared to the height of the flow channel.

[0061] In this case, the thermal sensor is preferably positioned above any section of the flow channel, for example, in a central position relative to an inlet or outlet region. Central positioning preferably means positioning the thermal sensor on the front side such that the thermal sensor is mounted substantially along half (the length) of the flow channel. It may also be preferable to position the thermal sensor not centrally on the front side of the substrate, but closer to the inlet or outlet region.

[0062] The provision of a flow channel with an essentially constant width and height (corresponding to the height of the substrate) represents a particularly simple geometry for the flow channel, which both simplifies the manufacturing and ensures a uniform, easily measurable flow behavior of the fluid within the flow channel.

[0063] To increase the interaction area of ​​the thermal sensor with the fluid flowing in the flow channel, it may also be preferable to provide a widened region in the flow channel, wherein the widened region preferably has a greater width than other sections of the flow channel (such as, in particular, a tapered region). For embodiments of a flow channel in which the width varies, for example, to provide a widened section extending below the sensor component, it is further preferable that the height of the flow channel is substantially constant and corresponds to the height of the substrate or wafer.

[0064] In the case of a flow section with varying width, a tapered section preferentially determines the fluidic resistance.

[0065] A tapered section of the flow channel preferably refers to a section that has a smaller width compared to other sections of the flow channel. In particular, this means that it is preferred that the flow channel does not have a constant cross-section. It is preferred that the flow channel has sections that have different widths. The section of the flow channel with the smallest width can preferably be referred to as a tapered section in the context of the invention.

[0066] The height of the flow channel preferably corresponds substantially to the height of the substrate. In particular, the height of the flow channel corresponds substantially to the height of the substrate if a continuous, regional removal of the substrate was carried out to provide the flow channel. The height of the flow channel can preferably also result substantially from the height of the substrate less a remaining thickness on the substrate. Thus, the height of the flow channel preferably means the dimension that extends along the front and the back of the substrate, i.e. between the side of the substrate on which the thermal sensor is located and an opposite side from which the regional removal was carried out to provide the flow channel. The height of the flow channel is preferably constant along its length or its course along the fluid direction.However, it may also be preferred for the height to vary. In the latter case, a maximum height preferably corresponds essentially to the height of the substrate.

[0067] Terms such as substantially, approximately, etc. preferably describe a tolerance range of less than ± 20%, preferably less than ± 10%, particularly preferably less than ± 5%, even more preferably less than ± 2%, and especially less than ± 1%, and particularly include the exact value. Similar preferably describes quantities that are approximately equal. Partially preferably describes at least 5%, particularly preferably at least 10%, and especially at least 20%, in some cases at least 40% (or more).

[0068] The width and height of the flow channel preferably refer to a cross-sectional plane that is orthogonal to the fluid flow vector within the channel. While the height preferably refers to the extension of the channel from bottom to top or along the direction from a rear to a front side, the width of the flow channel preferably corresponds to a dimension that is orthogonal to the height. The product of width and height results in the cross-sectional area of ​​the flow channel.

[0069] The length of the flow channel preferably relates to an extension of the channel along the flow direction of the fluid within the flow channel. The length of the flow channel therefore preferably corresponds to a distance extending from the inlet region to the outlet region of the flow channel. Preferably, the length of the flow channel can essentially correspond to the length of a connecting line between the inlet and outlet regions of the monolithic substrate, for example, if the flow channel is essentially straight. It can also be preferred for the flow channel to be longer than the connecting line between the inlet and outlet regions, for example, if the flow channel is designed to be curved or winding.

[0070] In a further preferred embodiment, the sensor chip is characterized in that the flow channel has a height of approximately 100 - 1,000 pm, preferably approximately 200 - 500 pm, and / or a length of approximately 100 - 10,000 pm, preferably approximately 500 - 2,000 pm.

[0071] The flow channel can preferably have a substantially elongated shape, i.e. be shaped such that the length of the flow channel runs along the long side of the monolithic substrate and the length is greater than the width and / or height of the flow channel. It can also be preferred for the flow channel to have a winding shape. With a winding shape of the flow channel, the fluid makes at least one turn during its flow through the flow channel, i.e. a change of direction during the flow through the flow channel. In other words, it can be preferred for the flow channel to have one or more turning regions for the fluid and to be characterized by a meandering course. As a result, the path length of the flow channel can advantageously be extended many times beyond the length of the substrate, for example by a factor of 2, 3, 4, 5, 10 or more.

[0072] In a further preferred embodiment, the sensor chip is characterized in that the flow channel has a widened section, wherein the widened section preferably has a greater width than other sections of the flow channel. Analogous to the tapered section, the widened section of the flow channel can preferably be characterized as the section which has a greater width than other sections of the flow channel. In particular, the section which has the greatest width can be understood as the widened section of the flow channel. A widened section preferably has a width which is greater than a width of a tapered section by a factor of at least 20%, 50%, 100%, 200% or more.

[0073] In case of the presence of a widened and tapered section of the flow channel, the thermal sensor is preferably applied over the widened section on a front side of the sensor chip.

[0074] The section of the flow channel below the thermal sensor can be compared to a cavity of prior-art thermal flow sensors, which are incorporated into substrates as supports for the thermal sensor to provide thermal insulation. This is intended, in particular, to ensure that the thermal field provided by a heating element is predominantly, preferably essentially exclusively, influenced by the fluid, thus reducing the distortion of measurement results caused by heat conduction through the substrate.

[0075] In the prior art, a separate cavity is preferably introduced into a lid wafer, which is aligned with a flow channel in a lower bottom wafer. According to the invention, this is not necessary due to the integration of the flow channel into a monolithic substrate. Separate structures or cavities do not need to be introduced. Instead, a cavity is created directly beneath the thermal sensor, along with the provision of the flow channel, by removing sections of the substrate, preferably starting from the back side.

[0076] If the flow sensor preferably does not require a width greater than the minimum width of the flow channel with which a fluidic resistance can be adjusted, it may be preferable to provide the flow channel with a constant (preferably small) width. If this is not the case, a sufficiently large cavity can be provided below the thermal sensor by means of a correspondingly widened section.

[0077] Thus, the design of the flow channel allows for adjustment of fluid resistance and thus the sensitivity of the sensor chip. The width of the flow channel is particularly relevant for adjusting the resistance within the flow channel.

[0078] For the hydraulic resistance Rhyd within a flow channel, assuming that the width (w) of the flow channel is significantly smaller than the height (h), the following relationship applies:

[0079] Rhyd = Ap / AQ = 12*q*L / (w 3 *h), where Ap is the pressure difference between two points within the flow channel (e.g., an inlet and outlet area), AQ is the volume flow, q is the viscosity of the fluid, and L is the length of the flow channel. The hydraulic resistance Rhyd is therefore particularly dependent on the width (w 3 ), which exhibits a cubic antiproportionality as opposed to a simple proportionality to the height.

[0080] The relationship AQ = Av * A applies to the volume flow, where A denotes the cross-sectional area of ​​the flow channel with A = w * h.

[0081] Therefore, the quotient of pressure difference and flow velocity (R s trö= Ap / Av), calculate as follows:

[0082] Rströ = Rhyd * A = 12*q*L / (w 3 *h) * A = 12*q*L / w 2 .

[0083] The relationship between pressure difference and flow velocity (R s trö= Ap / Av) independent of the height of the channel and inversely proportional to the square of the width (w 2) of the flow channel. By precisely adjusting the width of the flow channel, a particularly accurate determination of the pressure difference Ap can be obtained based on a measurement of the flow velocity Av in the flow channel. The length of the sensor chip preferably refers to the dimensions along its long side. The height and width of the sensor chip preferably refer to dimensions of the sensor chip that are orthogonal to one another and are also each aligned perpendicular to the length of the sensor chip. The height of the sensor chip can preferably also be understood as a thickness. The sensor chip can preferably have a length of 200 - 10 000 pm, preferably between 500 - 5 000 pm, particularly preferably 800 - 2 000 pm. The height of the sensor chip is preferably 100 - 1 000 pm, preferably 200 - 500 pm. The width of the sensor chip is preferably 100 - 1 000 pm, preferably 400 - 800 pm.

[0084] Preferably, the flow channel is covered at least in sections by a membrane attached to the front side of the monolithic substrate. The membrane thus preferably acts as an upper boundary of the flow channel.

[0085] Preferably, the membrane can completely cover the flow channel. This embodiment is particularly preferred if the partial removal of the substrate to form the flow channel involves complete etching of the substrate in the vertical direction, so that without applying a membrane as a covering layer, the sensor channel would be open at the top.

[0086] However, the membrane preferably serves not only to cover the flow channel from above (and thus for media separation), but also as a carrier for the thermal sensor, which is preferably applied to the membrane. The region of the membrane on which the thermal sensor is located can also be referred to as the sensor region or sensor membrane, while regions of the membrane that primarily serve as a cover outside the sensor region can also be referred to as the cover layer. Thus, the membrane, in particular the sensor region of the membrane, can preferably be understood as an intermediate component that is present between the thermal sensor and the flow channel, and in particular also between the thermal sensor and the fluid that can flow within the flow channel.

[0087] In a further preferred embodiment, the sensor chip is characterized in that a wall of the flow channel is coated with a protective layer, wherein the protective layer preferably comprises a material selected from a group comprising polysilicon, silicon dioxide, silicon nitride, aluminum oxide, aluminum nitride, perfluorodecyltrichlorosilane (FDTS), per- and / or polyfluorinated alkyl compounds (PFAS) and / or parylene.

[0088] The wall of the flow channel preferably refers to sections of the monolithic substrate that enclose the partially removed area to provide the flow channel. The protective layer advantageously enables protection of the monolithic substrate, for example, against aggressive fluids that could attack the substrate material or the wall of the flow channel through undesirable chemical reactions. For example, the protective layer can provide corrosion protection. Furthermore, hydrophobization or hydrophilization can also advantageously be achieved in order to make the flow of the fluid through the flow channel more efficient. The aforementioned materials for the protective layer have proven successful in achieving the desired advantageous effect depending on the application and can also be coated onto the wall of the flow channel using simple methods.To measure the at least one flow parameter, a thermal sensor comprising a heating element and a sensor component is used. As explained above, various operating modes or measurement principles can preferably be implemented for this purpose.

[0089] The heating element constantly provides a thermal field that can be influenced by the fluid flow within the flow channel. This influence is captured by the temperature response recorded by the sensor component.

[0090] In a preferred embodiment, the sensor chip is characterized in that the heating element is an electrical heating element, preferably a heating resistor.

[0091] The heating element preferably refers to the component of the thermal sensor from which the heat field or heat flow emanates by releasing heat energy. An electric heating element preferably refers to a heating element capable of converting electrical energy into heat energy, which in the context of the invention is used as a heat field and transferred to the sensor component, preferably the temperature sensor. In an electric heating element, the heat energy or heat field is preferably generated by using an electrically conductive material through which an electric current flows and is heated by Joule heat. A heating resistor has proven particularly suitable for this purpose, comprising in particular metallic alloys that do not melt and / or oxidize even at the particularly high temperatures they can reach.

[0092] In a further preferred embodiment, the sensor chip is characterized in that the sensor component is formed by a temperature sensor, wherein the temperature sensor is preferably selected from a group comprising a thermocouple, a diode, a thermistor and / or a thermopile.

[0093] The temperature sensor is preferably a component of the thermal sensor which is capable of measuring the thermal field, in particular the modulation of the thermal field by the fluid, i.e. the influence of the fluid on the thermal field.

[0094] A thermistor preferably means a component comprising an electrical resistance whose value changes reproducibly with temperature. Thermistors are divided into thermistors and cold thermistors based on their temperature behavior. A thermistor has a negative temperature coefficient and is able to conduct electrical current better when hot than when cold. A cold thermistor has a positive temperature coefficient and is able to conduct electrical current better when cold than when hot. In the context of the invention, a thermistor or a cold thermistor can preferably be used as a thermistor. By means of a thermistor, conclusions about a modulation of the thermal field and thus at least one flow parameter of the fluid can be determined in a simple and precise manner based on a changing electrical resistance.

[0095] A thermocouple preferably refers to an arrangement comprising a pair of electrically conductive materials that are connected to one another at one end and allow a conclusion to be drawn about the measured temperature due to the thermoelectric effect. Electrical energy is generated when there is a temperature difference along the arrangement. A thermopile refers to an element that has multiple thermocouples. The thermocouples of the thermopile are preferably connected electrically in series and thermally in parallel.

[0096] The measuring point of the thermocouple or thermopile is referred to as the hot end or hot junction and forms one end of a thermocouple. The other end, analogously referred to as the cold end or cold junction, represents a reference junction used to determine a temperature difference. Preferably, an electronic circuit and / or a processing unit for processing the temperature measurement is connected to the cold junction.

[0097] A diode can also function as a temperature sensor and thus as a preferred sensor component. This can be exploited, for example, by the fact that the forward voltage of a diode changes essentially linearly with temperature. The higher the temperature, the lower the forward voltage, and vice versa. Accordingly, the change in the forward voltage can be used to draw conclusions about a change in temperature.

[0098] In a further preferred embodiment, the heating element itself functions as a sensor component, i.e., a sensor component can preferably be provided by the heating element without a temperature sensor being used as a sensor component. The effect of the heating element as a sensor component can, for example, be enabled in the same way as the 3-omega method known from the prior art. In the 3-omega method, a thermal property, such as thermal conductivity, is determined. A heating element itself is used as a temperature sensor and is fed with an oscillating control signal. Due to the fed-in power, the temperature of the heating element changes at the same frequency as the control signal. The amplitude and the phase shift compared to the fed-in power depend on the thermal conductivity and the frequency.The temperature oscillations lead to resistance oscillations in the heating element, which can be described, among other things, by a resistance amplitude, which in turn depends on a temperature coefficient of the electrical resistance of the heating element. From this, the voltage across the heating element can be calculated by applying Ohm's law. This voltage contains a component with three times the frequency (3 μJ) and a corresponding amplitude proportional to the temperature amplitude of the heating element.

[0099] In a further preferred embodiment, the sensor chip is characterized in that the sensor chip has a membrane on which the thermal sensor is positioned, wherein the membrane preferably comprises an electrically conductive material and / or a dielectric material, wherein the electrically conductive material is preferably selected from a group comprising a semiconductor and / or a metal, in particular silicon, polysilicon, graphene, chalcogenide, wherein the dielectric material is preferably selected from a group comprising silicon nitride, silicon dioxide, aluminum oxide, aluminum nitride, polyimide and / or a polymeric material. The membrane denotes a preferred component of the sensor chip, which is designed to be flat and is preferably applied to the front side of the monolithic substrate and covers the flow channel at least in sections.The flat design of the membrane preferably means that dimensions such as a length and / or width are many times greater than a height or thickness of the membrane orthogonal thereto. Thus, the length and / or width can be greater than the thickness by a factor of 1.5, 2.5, 10, 100, 1,000, 10,000, or more. The thickness of the membrane is preferably between approximately 0.1 and 20 μm, preferably between approximately 0.2 and 10 μm, particularly preferably between approximately 0.5 and 5 μm, and most particularly preferably between approximately 0.5 and 2 μm.

[0100] As explained above, the membrane preferably serves both as a support for the thermal sensor (particularly in a sensor area of ​​the membrane) and as a cover (both in the sensor area and in areas outside the sensor area where the flow channel would otherwise be open to the front). The preferred materials for the membrane are advantageously well-suited for both functions.

[0101] The preferred membrane should, on the one hand, provide thermal insulation of the heat field provided by the heating element (particularly in a sensor area) and serve as a support for the thermal sensor. On the other hand, the membrane should ensure reliable media separation by covering at least some of the flow channel, preferably completely.

[0102] The preferred materials for the membrane have proven advantageous in that, in addition to their excellent design options, they also offer reliable thermal insulation, thus reducing or eliminating heat conduction through the membrane. This further improves the accuracy of the measurement results, so that the influence of the fluid on the thermal field remains essentially relevant. Furthermore, the preferred materials have proven particularly advantageous in terms of processing for the membrane and sufficient mechanical stability.

[0103] In particular, the membrane is preferably designed to avoid any vibrations caused by the flow of the fluid in order to reduce distortions of the measurement result.

[0104] The area of ​​the membrane on which the thermal sensor is positioned preferably comprises a dielectric material. The membrane can also preferably comprise an electrically conductive material, so that electrical contact with the thermal sensor can be provided particularly easily.

[0105] In a preferred embodiment, the membrane extends above the flow channel on the front side of the monolithic substrate. The membrane covers the flow channel so that the fluid cannot leave the flow channel via the front side and / or nothing can enter the flow channel from the outside via the front side. The membrane thus represents an upper boundary of the flow channel. The membrane preferably comprises a sensor region, i.e. a region of the membrane on which the thermal sensor is attached in order to measure the at least one flow parameter of the fluid. The membrane can preferably also comprise a cover region, i.e. a region which essentially serves to cover the other regions of the flow channel which are not covered by the sensor region. For this purpose, it can be preferred for the membrane to be of single-layer or multi-layer design.

[0106] In particular, the membrane may comprise several layers of materials formed vertically or horizontally to fulfill both a supporting function for the thermal sensor and a covering function for covering the flow channel.

[0107] Preferably, the cover region may comprise the same material as the sensor region of the membrane. It may also be preferred for the cover region and the sensor region to comprise different materials. It may also be preferred for the cover region to comprise multiple materials, for example, layers stacked vertically on top of one another, in order to obtain a particularly stable region for covering the flow channel.

[0108] In a further preferred embodiment, the sensor chip is characterized in that the sensor chip has an electronic circuit and / or is connected to an electronic circuit, wherein the electronic circuit is configured to control the heating element and / or to determine the at least one flow parameter of the fluid based on the temperature response of the thermal sensor.

[0109] For the purposes of the invention, an electronic circuit preferably refers to a combination of individual electrical or electromechanical elements in a functional arrangement. The electronic circuit preferably allows data or electrical signals to be sent, received, and / or processed.

[0110] Preferred electronic circuits include, without limitation, an integrated circuit (IC), application-specific integrated circuits (ASIC), a programmable logic device (PLD), a field-programmable gate array (FPGA), a microprocessor, a microcomputer, a programmable logic controller, and / or other electronic, preferably programmable, circuit.

[0111] Preferably, the electronic circuit is configured to receive measurement data from the sensor component and / or to transmit control signals, such as control commands, to the heating element to generate the thermal field.

[0112] The electronic circuit can preferably be configured to regulate the heating element depending on the measurement data from the sensor component. The electronic circuit is preferably configured to issue a command to generate the heat field to the heating element after a measurement by the sensor component, for example to increase, maintain constant, or decrease the heat output. In particular, it can be preferred for the electronic circuit to execute one or more of the above-mentioned operating modes in order to measure at least one flow parameter based on the temperature response due to the influence of the flow of the fluid on the heat field. In preferred embodiments, the electronic circuit can also be configured to process the measurement data recorded by the sensor component with regard to the modulation of the heat field.Processing data preferably means that the electronic circuit is configured to perform computing operations and / or computing steps, for example with recorded measurement data of the sensor component.

[0113] The electronic circuit can thus be implemented as an evaluation, readout, and / or control electronics unit, which enables control of the heating element, readout of the sensor component, and / or evaluation of the measured data. If an evaluation is performed, the electronic circuit can also be referred to as a processing unit.

[0114] The term "computing unit" preferably refers to any device or unit that can be configured to perform computing operations. The computing unit is preferably, for example, a processor, a processor chip, a microprocessor, and / or a microcontroller, which is preferably configured to evaluate the modulation of the thermal field. The computing unit can also preferably be a programmable circuit board. The computing unit can also preferably comprise a computer-usable or computer-readable medium, such as a hard disk, random access memory (RAM), read-only memory (ROM), flash memory, etc.

[0115] Method steps for determining the at least one flow parameter of the fluid, as described herein, are preferably carried out by the electronic circuit or computing unit. The phrase "configured to" preferably means that computer code and / or software is installed on the electronic circuit or computing unit to carry out the method step, for example, to check the extent to which a modulation of the heat field was induced and which parameters of the fluid were decisive for this. The computer code and / or software for evaluating the modulation of the heat field can be written in any programming language or a model-based development environment, e.g., in C / C++, C#, Objective-C, Java, Basic / VisualBasic, MATLAB, Simulink, StateFlow, Lab View, and / or Assembler.

[0116] The computer code and / or software, which is preferably installed on the electronic circuit or processing unit, in particular to evaluate the modulation of the thermal field, can be considered technical features because a direct physical effect of the thermal sensor, for example, the supply of a control signal for a heating element or the detection of a temperature change by the sensor component, is utilized. Functional descriptions of the computer code and / or software can therefore be considered preferred and defining embodiments of the invention.

[0117] The electronic circuit can be positioned differently, for example, on the sensor chip itself. It may also be preferred for the electronic circuit to be located on a base plate of a flow sensor assembly or on a motherboard on which the flow sensor assembly is mounted. The electronic circuit preferably has a data connection to the sensor chip, in particular the thermal sensor. In a further preferred embodiment, the sensor chip is characterized in that the sensor component is electrically connected to a connection.

[0118] The connection preferably serves as a data connection, in particular an electrical connection between a preferred electronic circuit and the thermal sensor. Depending on the positioning of the electronic circuit, for example, on a base plate configured as a printed circuit board or a separate mainboard, different embodiments for a connection can be provided.

[0119] In a preferred embodiment, the connection is selected from a group comprising a connection pad, a conductor track, a conductor track strip, a bonding wire, a solder connection, an electrically conductive adhesive, a bump and / or a via.

[0120] A connection pad preferably comprises an electrically conductive material, which is applied to a spatially restricted section of the sensor chip to enable electrical contact. An insulating layer can preferably be applied, which delimits the section to be contacted in such a way that a free area remains. The free area can then be filled with the electrically conductive material.

[0121] Conductor tracks (also called conductive paths or conductive lines) preferably refer to electrically conductive connections with a two-dimensional layout, i.e., along a plane, which can also be referred to as a conductor track or metallization plane. The connection between individual conductor tracks can preferably be provided by vias. To prevent short circuits or high leakage currents, high electrical insulation from one another is preferred.

[0122] Conductor strips are strips preferably made of a conductive material. These strips are preferably longer than they are wide. They are primarily used for electrical connections and can be applied, for example, using printing processes.

[0123] Bond wires refer to an electrical connection option that is particularly used when components have previously been bonded. Bond wires are characterized by their particularly thin nature. This enables easy contacting of component connection pins. A bond wire can preferably have a diameter of approximately 15-500 μm, preferably 15-100 μm, particularly preferably 15-50 μm or 100-500 μm. A bond wire can comprise a material selected from a group comprising gold, aluminum, copper, their compounds, and / or alloys.

[0124] A solder connection preferably means an electrical connection using a solderable material. The solderable material preferably refers to a material that melts after the application of a certain temperature, so that the melting process causes the material to spread and thus the covering and / or filling of a specific area with the material. A preferred solder material can be selected from a group comprising silver, copper, tin, zinc, and their compounds and / or alloys. An electrically conductive adhesive is preferably characterized in that solidification and thus a strong electrical connection can be provided without the application of pressure and / or heat. Instead, solidification of the electrically conductive adhesive takes place after a certain time interval. An electrically conductive adhesive preferably comprises an adhesive and an electrically conductive filler.The adhesive can preferably be selected from a group comprising epoxy resin, silicone, acrylic, and / or bismaleimide. The electrically conductive filler can preferably be selected from a group comprising gold, nickel, palladium, platinum, and / or silver.

[0125] A bump preferably refers to a substantially hump-shaped connecting element. The connecting element is particularly characterized by its hump-shaped configuration. This can be provided by an electrically conductive material, in particular also by an electrically conductive adhesive and / or a solder material. Preferably, a plurality of bumps are used. Bumps can preferably be applied to an underside of the sensor chip, for example, to enable electrical contact with at least one section of a base plate. Bumps can preferably be applied using thin-film technology, electroplating, or stencil printing.

[0126] A via preferably refers to a substantially vertically extending electrical connection. Different levels of the sensor chip can be electrically connected to one another by means of a via. To provide a via, a region of the monolithic substrate is preferably removed, for example, in the form of a substantially vertically extending cavity, and filled with a conductive material extending vertically, i.e., along the height or thickness of the monolithic substrate.

[0127] The above-mentioned preferred options for forming the connection have proven advantageous in that they are reliable and robust and can be provided easily by a person skilled in the art using known means of the prior art.

[0128] In a further preferred embodiment, the sensor chip is characterized in that the sensor component is coated with a passivation layer, wherein the passivation layer preferably comprises a material selected from a group comprising silicon oxide, silicon nitride and / or polyimide.

[0129] The passivation layer preferably refers to an arrangement that can comprise one or more material layers. The passivation layer is preferably coated on the thermal sensor to effect passivation. In this case, passivation particularly relates to the electrical insulation of components of the thermal sensor. This advantageously prevents or reduces the risk of an electrical short circuit. The preferred materials mentioned have proven particularly suitable for this purpose.

[0130] In a further preferred embodiment, the sensor chip is characterized in that the substrate comprises a semiconductor material, wherein the semiconductor material is preferably selected from a group comprising monosilicon, polysilicon, silicon carbide, silicon germanium, germanium, gallium arsenide, and / or gallium nitride. These materials are particularly simple and cost-effective to process in semiconductor and / or microsystem technology and are also well suited for mass production. These materials are also particularly well suited for doping and / or coating in order to achieve the desired electrical, mechanical, thermal, and / or optical properties in specific areas. The aforementioned materials offer a variety of advantages due to the usability of standardized manufacturing techniques, which are also particularly suitable for the integration of additional components, such as electronic circuits.

[0131] In further preferred embodiments, the substrate can also comprise glass or ceramic. Both materials are also characterized by good processability, with the use of ceramic in particular enabling high wear resistance to be achieved. Glass advantageously combines high chemical and thermal resistance with good electrical insulation properties and low optical absorption.

[0132] In a further aspect, the invention relates to a method for producing a sensor chip according to the above-described, comprising the following steps: a) providing a substrate which has a front side and a back side and is monolithic, b) removing the substrate in regions, preferably starting from the back side, to attach a flow channel comprising an inlet region and an outlet region in the substrate, c) positioning a thermal sensor on the front side.

[0133] The average person skilled in the art recognizes that explanations, technical features, definitions and advantages of the sensor chip and preferred embodiments of the sensor chip also apply to the method for manufacturing the sensor chip, and vice versa.

[0134] This manufacturing process has proven to be a particularly process-efficient method for producing the sensor chip, as the flow channel can be provided directly within a monolithic substrate. A complex construction of a substrate stack to form a flow channel and / or cavity beneath a thermal sensor, as is known, for example, from the prior art, is unnecessary.

[0135] In particular, production is quick and cost-effective. The simpler option for manufacturing the sensor results, among other things, from the fact that it is not necessary to connect different substrates to one another or to attach additional components to one or more substrates to design the flow channel. Instead of complex processes, the flow channel is advantageously formed by removing sections within a monolithic substrate, preferably starting from the back. This can essentially be done in a single process step. The dimensions of the flow channel can be achieved with particular precision according to the desired application by removing the substrate. This advantageously enables mass production of the sensor chip at low cost and with a high degree of reproducibility.

[0136] By forming the flow channel directly within the monolithic substrate by removing portions of the substrate, particularly fine structuring with high precision is also advantageously possible. The precise design option of the sensor chip, in particular of the flow channel, also advantageously prevents unwanted turbulence that could occur within the flow channel, particularly at the inlet area, and thus limit the measurement by the thermal sensor. In this respect, the sensor chip also achieves a high degree of sensitivity, enabling particularly precise measurement of at least one flow parameter of the fluid.

[0137] Furthermore, the fluidic properties of the flow channel can advantageously be adjusted particularly precisely and consistently. The fluidic resistance or flow resistance, which is relevant to the context of the invention, depends in particular on the width of the flow channel, which can be adjusted extremely precisely, for example, using known etching processes for the region-by-region removal of the substrate. Error tolerances that could inherently arise when forming flow channels in assembled stacks due to the connection technology are avoided. By forming the flow channel within the monolithic stack, it can also be ensured that the dimensions of the flow channel remain constant and, in particular, are not influenced by the flow behavior of the fluid in the flow channel itself.

[0138] Preferably, the substrate is first provided, which has a front side and a back side and is monolithic. After the substrate has been provided, it is preferred that the substrate is removed in regions, preferably starting from a back side. The region-by-region removal of the substrate serves in particular to provide the flow channel, which comprises an inlet region and an outlet region for the fluid. Preferably, the region-by-region removal of the substrate takes place continuously along the height or thickness of the substrate, so that the height of the flow channel essentially corresponds to the height of the substrate. It can also be preferred that the region-by-region removal of the substrate takes place in such a way that a residual thickness remains on the substrate (for example when the substrate is removed starting from a back side).In this case, the height of the flow channel essentially corresponds to the height of the substrate minus the height of the residual thickness.

[0139] The partial removal of the substrate to create the flow channel is preferably carried out by means of an etching process. The etching process is preferably selected from a group comprising wet-chemical etching processes and / or dry etching processes, preferably physical and / or chemical dry etching processes, particularly preferably reactive ion etching and / or reactive ion deep etching (DRIE, Bosch process).

[0140] The aforementioned preferred etching methods are known to those skilled in the art. Depending on the desired configuration of the flow channel on the substrate structure, advantageous methods can be selected to ensure efficient implementation of the flow channel formation. Furthermore, the etching methods advantageously make it possible to adjust the dimensions of the flow channel and thus its fluidic properties, such as its fluidic resistance, with particular precision.

[0141] The thermal sensor is preferably positioned on the front side of the monolithic substrate. The thermal sensor can measure at least one flow parameter of the fluid based on the temperature response. The flow channel runs below the thermal sensor in or along the substrate. A membrane is preferably applied before the thermal sensor is positioned on the front side of the substrate. With a preferred application of a membrane, the thermal sensor is preferably positioned on it. The membrane can preferably be applied such that it completely covers the flow channel.

[0142] To apply the thermal sensor, preferred deposition or coating processes can be used to design the components, such as a temperature sensor, a sensor component, electrical connections, etc.

[0143] In a further aspect, the invention relates to a flow sensor arrangement comprising a sensor chip as described above and a base plate, wherein the base plate has at least one opening which corresponds to the inlet region for an inlet of the fluid into the flow channel and / or the outlet region for an outlet of the fluid from the flow channel, wherein the base plate preferably has two openings which correspond to the inlet region for an inlet of the fluid into the flow channel and / or the outlet region for an outlet of the fluid from the flow channel.

[0144] The average person skilled in the art recognizes that explanations, technical features, definitions and advantages of the sensor chip and of preferred embodiments of the sensor chip and of the method for manufacturing the sensor chip also apply to the flow sensor arrangement according to the invention, and vice versa.

[0145] For the purposes of the invention, a flow sensor arrangement preferably refers to a device which comprises at least the sensor chip and a base plate. The base plate preferably refers to a component which acts as a carrier for the sensor chip, so that the sensor chip can be placed on the base plate. In preferred forms, the flow sensor arrangement can furthermore also comprise a cover, for example a cap, which is connected to the base plate in such a way that the sensor chip is enclosed within the housing-like components of the base plate and cover. A flow sensor arrangement comprising a base plate and cover can therefore preferably also be referred to as a sensor package, which serves to protect the sensor chip and facilitates its integration into other components, such as a mainboard.

[0146] By providing a sensor chip with a monolithic substrate in which the flow channel is formed, direct mounting of the monolithic sensor chip in a package is advantageously enabled. The base plate and cover preferably serve as a package to protect the monolithic sensor chip. The base plate can preferably be a circuit carrier, in particular a printed circuit board, thus enabling compact integration and electrical contacting with low outlay.

[0147] Preferably, the back of the substrate of the sensor chip is attached to the base plate. The base plate comprises at least one, preferably two openings, wherein in the latter case a first opening corresponds to the inlet region and a second opening to the outlet region of the flow channel. The correspondence here preferably means that in particular a fluidic connection exists between the inlet region and the first opening and between the outlet region and the second opening of the base plate. It may be preferred that the sensor chip is applied to the base plate in such a way that the inlet region is located substantially directly above the first opening of the base plate and the exit region is located substantially directly above the second opening of the base plate.As a result, a measurement can then be carried out by means of the flow sensor arrangement in such a way that the fluid initially flows via the first opening of the base plate and the inlet area along the flow channel and leaves the flow sensor arrangement after flowing through the outlet area and the second opening of the base plate.

[0148] However, it may also be preferred for the base plate to provide only one opening corresponding to an inlet region (or outlet region) of the flow channel, with a further opening on the front side of the sensor chip, for example, as an opening within a membrane, corresponding to the outlet region (or inlet region) of the flow channel. In this case, the inlet or outlet region of the flow channel is preferably not formed on the back side of the substrate, but rather on the front side, for example, by providing an opening in a front-side membrane that delimits the flow channel at the top.

[0149] In a further preferred embodiment, the flow sensor arrangement is characterized in that the base plate is flat at least on one side facing the sensor chip and forms a lower boundary of the flow channel.

[0150] A lower boundary of the flow channel preferably means that the base plate enables the flow channel to be covered from the rear side. The base plate therefore preferably represents a lower wall of the flow channel. While the flow channel, as explained above, is preferably enclosed laterally by the substrate, the flow channel is preferably bounded from above by a membrane and from below (except in the inlet and / or outlet areas) by the base plate.

[0151] The at least one opening, preferably two openings, on the base plate ensure that the fluid enters the flow channel via the inlet area and leaves the flow channel via the outlet area.

[0152] A substantially flat design of the base plate at least on a side facing the sensor chip preferably means that on the side facing the sensor chip, the base plate has no unevenness, elevations, or depressions, but is preferably substantially smooth in order to provide a smooth lower boundary of the flow channel. The side of the base plate facing away from the sensor chip can have such unevenness. However, the base plate preferably has an overall flat, planar design in which the base plate has a substantially constant height or thickness. The height or thickness is preferably many times smaller than a length and / or width of the base plate, preferably by a factor of 2, 3, 4, 5, 10 or more.

[0153] Preferably, the base plate has a substantially uniform, flat geometric shape and, apart from the two openings, no further geometric structures. A substantially flat design of the base plate has proven advantageous for a precise connection between the sensor chip and the base plate.

[0154] Preferably, a connecting agent is applied between the rear side of the substrate and the side of the base plate facing the substrate, for example on the base plate itself or on the rear side of the substrate, whereby the sensor chip can be connected to the base plate. In this case, it can happen that part of the connecting agent, which can be present as an adhesive, for example, penetrates into the flow channel. Accordingly, the height of the flow channel would correspond to the height of the monolithic substrate minus the height of the penetrated connecting agent. However, it is preferred that the height of the flow channel essentially corresponds to the height of the monolithic substrate. In particular, it is preferred that a connecting agent essentially does not penetrate into the flow channel or penetrates only slightly.

[0155] In a further preferred embodiment, the flow sensor arrangement is characterized in that the base plate is a circuit carrier, preferably a printed circuit board.

[0156] A circuit carrier preferably refers to a component comprising an electrically insulating material on which electrically conductive connections (conductor tracks) and / or electronic components or assemblies are present. A circuit carrier therefore preferably refers to a carrier for electronic components or electrically conductive connections, which serves both for mechanical fastening and for electrical connection. Since electronic components are preferably present on or in the circuit carrier, electrical connections in particular are present on or in the circuit carrier, which are mediated, for example, by wire bonds, conductor tracks and / or conductor track strips. The circuit carrier therefore functions both as a mechanical carrier and for an electrical connection for implementing electrical functions. The electrical connections of the circuit carrier serve, in particular, for the electrical contacting of components.The insulating material of the circuit carrier preferably defines a basic shape of the circuit carrier, in particular to provide mechanical contact with the sensor chip.

[0157] A printed circuit board is preferably used as the circuit carrier. A printed circuit board preferably refers to the flat type of circuit carrier known in the art, which includes electrical connections and provides mechanical support for surface-mounted and / or socketed components. A printed circuit board preferably comprises fiberglass, an epoxy, and / or another composite material as the insulating material. A printed circuit board is advantageous in that the two openings corresponding to the inlet and outlet regions of the flow channel on the sensor chip can be provided particularly easily.Furthermore, they are characterized by a high level of stability, so that even the measurement of flows with a high hydrodynamic pressure can still be carried out accurately and reliably using the flow sensor arrangement, without having to be exposed to the risk of possible mechanical deformations caused by the fluid and thus a falsification of the measurement results.

[0158] In a preferred embodiment, the base plate comprises an electrically insulating material, preferably with electrical connections attached thereto. For the electrically insulating material, materials that can be used as a substrate in printed circuit boards (printed circuit board materials) are particularly preferred. The base plate can preferably be formed from a material, preferably a printed circuit board material, selected from a group comprising plastics (e.g., polyimides), fiber-reinforced plastics (e.g., glass-fiber-reinforced plastics such as GRP) and / or hard paper (a material comprising paper and a phenolic and / or epoxy resin), without being limited to these examples. For example, it may be preferable to use FR1, FR2, FR3, FR4 and / or FR5 for the electrically insulating material. The average person skilled in the art knows that FR1 and FR2 preferably comprise phenolic resin and paper, with FR1 having a higher glass transition temperature (approx.130°C) than FR2 (approx. 105°C). With FR3, an epoxy resin is preferably used instead of a phenolic resin, so it comprises an epoxy resin and paper. FR4 comprises an epoxy resin and a glass fiber fabric. Other non-limiting examples of circuit board materials are CEM1, CEM2 and CEM3. CEM1 comprises glass fabric surfaces with a paper core in combination with an epoxy resin. CEM2 has higher glass transition temperatures than CEM1 and also comprises paper and a woven glass fiber surface. CEM3 has an essentially similar structure to FR4, but uses a glass fleece instead of a glass fabric.

[0159] Preferably, the circuit carrier, preferably the printed circuit board, contains at least one electronic circuit, which is electrically connected to the thermal sensor, preferably via a connection. The base plate in the form of a printed circuit board thus not only allows a fluidic connection of the sensor chip to a channel or container, whose fluid content is to be measured, but can also simultaneously provide control and / or evaluation electronics.

[0160] It may also be preferred for the base plate, preferably in the form of a printed circuit board, to be connected to a main board on which the electronic circuit is located via further connections, for example a solder material. It may be preferred for the connection between the base plate and the main board to be made by means of a sealing ring, in particular a solder ring. The solder ring can preferably be connected to a further connection in order to enable an electrical and mechanical connection between a flow sensor arrangement comprising the sensor chip and the base plate. The main board has main board openings that correspond to the openings in the base plate. The electronic circuit is mounted on the main board, thus providing a data connection between the thermal sensor of the chip and the electronic circuit.Furthermore, the invention relates to a use of a sensor chip or a flow sensor arrangement according to the above-described for measuring a flow parameter of a fluid in a main channel in a bypass configuration.

[0161] The average person skilled in the art recognizes that explanations, technical features, definitions and advantages of the sensor chip, the method for producing the sensor chip and a flow sensor arrangement comprising a sensor chip as well as preferred embodiments of the above also apply to the use of the sensor chip or the flow sensor arrangement, and vice versa.

[0162] A bypass configuration preferably refers to the provision of a side channel (or bypass) to a main channel, into which the fluid to be measured can flow. In the context of the invention, the flow channel of the sensor chip forms the bypass or a partial section thereof. A main channel in combination with a sensor chip according to the invention or a flow sensor arrangement, whose flow channel forms the bypass or a partial section thereof, is also referred to as a bypass configuration in the context of the invention.

[0163] In a bypass configuration, the fluid to be detected or measured flows within the main channel. The bypass is fluidically connected to the main channel, allowing the fluid to be introduced from the main channel into the bypass and returned from the bypass back to the main channel. Furthermore, a bypass configuration preferably includes a flow restrictor within the main channel. The flow restrictor causes a pressure drop, in particular a pressure difference, in particular in a region of the main channel at the inlet area of ​​the sensor chip and in a region of the main channel at the outlet area of ​​the sensor chip. The pressure difference allows the fluid to enter the bypass. The fluid flows from the main channel into the bypass and from the bypass back into the main channel.

[0164] The use of the sensor chip or the flow sensor arrangement described above is advantageously particularly well suited for use in a bypass configuration and for measuring at least one flow parameter of the fluid. Advantageously, the use of the sensor chip or the flow sensor arrangement allows for an accurate, robust, stable, and cost-effective measurement of the at least one flow parameter of the fluid. It is preferred that the sensor chip or the flow sensor arrangement be introduced into or on the bypass. In other words, the sensor chip or the flow sensor arrangement is preferably introduced into the bypass, so that the actual measurement of the at least one flow parameter takes place within the bypass.

[0165] In a further preferred embodiment, the use is characterized in that a flow restrictor is introduced into the main channel, wherein a fluidic connection between the sensor chip and the main channel is provided such that the inlet region of the sensor chip borders on a region of the main channel upstream of the flow restrictor, while the outlet region of the sensor chip borders on a region of the main channel downstream of the flow restrictor, so that a pressure difference across the flow restrictor can be measured based on a flow of the fluid through the flow channel of the sensor chip.

[0166] A flow restrictor preferably refers to a component that is incorporated in the main channel and serves to throttle the flow. In other words, the flow of the fluid can be regulated by a flow restrictor. A flow restrictor occupies an area of ​​the main channel such that a flow-through area of ​​the main channel is limited. The flow restrictor causes a pressure drop, so that a pressure difference occurs, in particular between an area of ​​the main channel at the inlet area of ​​the sensor chip (upstream of the flow restrictor) and an area of ​​the main channel at the outlet area of ​​the sensor chip (downstream of the flow restrictor). The pressure difference allows the fluid to flow from the main channel into the bypass and back to the main channel, whereby the magnitude of the pressure difference determines a flow velocity through the bypass.

[0167] The flow restrictor increases flow resistance within the main channel, resulting in a pressure difference. This can arise, without being limited to theory, from two effects. Firstly, the friction between the fluid and the surfaces of the flow restrictor (surfaces parallel to the flow) leads to a pressure drop that increases essentially linearly with the flow. Secondly, the end surfaces and their edges generate turbulence and thus a pressure drop that increases essentially quadratically with the flow. A pressure / flow characteristic curve therefore preferably includes a combination of linear and quadratic components.

[0168] A flow restrictor can preferably be selected from a group comprising a metering orifice (flow orifice) and / or a Venturi nozzle. It may also be preferred for the flow restrictor to comprise a honeycomb structure or a vane structure. The flow restrictor preferably comprises a surface area as large as possible, oriented parallel to the flow direction within the main channel, and a cross-section as small as possible.

[0169] The bypass in particular provides a fluidic connection between the sensor chip and the main channel in such a way that the inlet region of the sensor chip borders on a region of the main channel upstream of the flow restrictor. The outlet region of the sensor chip, in turn, borders on a region of the main channel that is downstream of the flow restrictor. Upstream and downstream are preferably related to the direction of the fluid flow in the main channel. Positioning the inlet region upstream means that the inlet region is in the direction of the fluid flow upstream of the flow restrictor, while the outlet region is in the direction of the fluid flow in the main channel downstream of the flow restrictor. The pressure difference across or along the flow restrictor in the main channel can thus be measured by the sensor chip within the bypass.

[0170] The fluid flows from the main channel into the bypass. This is primarily due to the fact that the pressure at the inlet of the main channel is higher than at the outlet. This pressure difference results from the flow restrictor in the main channel and depends on the flow behavior of the fluid in the main channel, such as the flow velocity.

[0171] Within the bypass, the sensor chip, particularly the thermal sensor, can detect the influence of the fluid on the thermal field via the temperature response. This can be used, for example, to determine the flow behavior within the fluid's flow channel.

[0172] The temperature response, for example, is sensitive to the flow velocity in the flow channel. Since the flow velocity in the bypass is directly related to the flow-dependent pressure difference in the main channel, this allows information about the flow in the main channel. The thermal sensor can also obtain other properties or flow parameters of the fluid, such as heat capacity and / or thermal conductivity. This enables monitoring not only of the flow behavior of the fluid in the main channel, but also of its composition.

[0173] Furthermore, the invention relates to a system comprising a. a sensor chip as described above or a flow sensor arrangement as described above and b. a main channel through which a fluid can be guided in a flowable manner, wherein a flow restrictor is introduced into the main channel and wherein a fluidic connection is provided between the sensor chip and the main channel in such a way that the inlet region of the sensor chip borders on a region of the main channel upstream of the flow restrictor, while the outlet region of the sensor chip borders on a region of the main channel downstream of the flow restrictor, such that a pressure difference across the flow restrictor can be measured based on a flow of the fluid through the flow channel of the sensor chip.

[0174] The average person skilled in the art recognizes that explanations, technical features, definitions and advantages of the sensor chip, the method of manufacturing the same, the flow sensor assembly also apply to the system, and vice versa.

[0175] The fluid which is to be detected by the sensor chip or the flow sensor arrangement, in particular whose at least one parameter is to be measured, flows through the main channel. At least one flow restrictor is preferably present in the main channel, and preferably also several flow restrictors. The flow restrictor causes a pressure difference in the area around the flow restrictor, in particular between an area of ​​the main channel which borders the inlet area and an area of ​​the main channel which borders the outlet area. In particular, the flow restrictor causes a higher pressure in the area of ​​the inlet area than in the area of ​​the main channel which borders the outlet area. This allows the fluid to flow in the direction of the sensor chip or the flow sensor arrangement in order to be measured.The system can in particular be provided by a bypass configuration in which the flow channel of the sensor chip forms the bypass or a portion thereof.

[0176] The aspects of the invention will be described below by way of example with reference to figures, without being limited to these descriptions.

[0177] Figures the characters

[0178] Fig. 1 Schematic representation of a preferred embodiment of the sensor chip.

[0179] Fig. 2 Schematic representation of a preferred embodiment of a

[0180] Flow sensor arrangement.

[0181] Fig. 3 Schematic representation of a system according to the invention.

[0182] Fig. 4 Schematic representation of a preferred embodiment of a

[0183] Flow sensor arrangement on a main board.

[0184] Detailed description of the characters

[0185] Fig. 1 AC shows various views of a preferred embodiment of a sensor chip 1 and a flow channel 5. Fig. 1A is a three-dimensional representation of the sensor chip 1. Fig. 1B is a plan view of the flow channel 5 and Fig. 1C represents a plan view of the sensor chip 1.

[0186] The sensor chip 1 is used to measure at least one flow parameter of a fluid. The sensor chip 1 comprises a substrate 3 with a front side V and a back side R. The sensor chip 1 further comprises a thermal sensor 9 comprising a heating element for providing a thermal field and a sensor component for detecting a temperature response of the thermal sensor as a function of an influence of the fluid on the thermal field. The substrate 3 is monolithic. Furthermore, the thermal sensor is positioned on the front side V of the substrate 3. A flow channel 5 is located below the thermal sensor within the substrate 3. The flow channel 5 is formed starting from a back side R by partially removing the substrate 3.The flow channel 5 has an inlet region 17 for the fluid to enter the flow channel 5 and an outlet region 19 for the fluid to exit the flow channel 5. Based on the temperature response of the thermal sensor 9, at least one flow parameter of the fluid can be measured.

[0187] The sensor chip 1 is advantageously characterized by a high degree of compactness. In particular, no multiple substrates or complex structures are required to provide a flow channel 5 through which the fluid can flow. Instead, the flow channel 5 of the sensor chip 1 is present in a single, monolithic substrate 3. This represents a significant departure from the prior art, increases robustness, and simplifies its manufacture. Furthermore, the sensor chip 1 advantageously has a low height, which essentially corresponds to the height of the substrate or a flow channel 5 formed therein. This provides a simple integration option for the sensor chip 1, for example, in a base plate, so that the sensor chip 1 can be used for versatile application purposes for measuring flows.

[0188] A further advantage of the sensor chip 1 is that it can be manufactured using simple and proven processes in semiconductor technology and / or microsystem technology. In particular, production is quick and cost-effective. The simpler option for manufacturing the sensor chip 1 results, among other things, from the fact that for the design of the flow channel 5 there is no need to connect different substrates to one another or to attach further components to one or more substrates. Instead of complex processes, the flow channel 5 is formed by removing sections within a monolithic substrate 3, preferably starting from the back side R. This can essentially be done in a single process step. The dimensions of the flow channel 5 can be particularly precise by removing the substrate 3 in accordance with the desired application.Advantageously, mass production of the sensor chip 1 is thus possible at low cost and with a high degree of reproducibility.

[0189] By forming the flow channel 5 directly within the monolithic substrate 3 by removing portions of the substrate, particularly fine structuring with high precision is advantageously possible. The precise design option of the sensor chip 1, in particular of the flow channel 5, also advantageously prevents unwanted turbulence that could occur within the flow channel 5, particularly at the inlet region 17, and thus limit the measurement by the thermal sensor. In this respect, the sensor chip 1 also achieves a high degree of sensitivity, enabling a particularly precise measurement of at least one flow parameter of the fluid.

[0190] Furthermore, the fluidic properties of the flow channel 5 can advantageously be adjusted particularly precisely and consistently. The fluidic resistance of the flow channel depends, in particular, on its width, which can be adjusted extremely precisely, for example, using known etching processes for the partial removal of the substrate 3. Error tolerances that could inherently arise in the formation of flow channels in assembled stacks due to the connection technology are avoided. By forming the flow channel 5 within the monolithic substrate 3, it can also be ensured that the dimensions of the flow channel 5 remain constant and, in particular, are not influenced by the flow behavior of the fluid in the flow channel 5 itself.

[0191] The possibility of a particularly precise specification of a fluidic resistance of the flow channel 5, which can be kept constant during the measurements, means that the sensor chip 1 is particularly suitable for measuring flows of a fluid in a so-called bypass configuration.

[0192] The flow channel 5 in Fig. 1 has a tapered section 21. The section of the flow channel 5 with the smallest width is referred to as the tapered section 21. Furthermore, the flow channel 5 has a widened section 7. The section of the flow channel 5 with the greatest width is referred to as the widened section 7. The widened section 7 of the flow channel 5 can be compared to a cavity of prior art thermal flow sensors, which are introduced onto substrates as carriers of the sensor component, in particular to effect thermal insulation. The aim of this is, in particular, to ensure that the heat field provided by a heating element is substantially influenced by the fluid and that no falsification of measurement results by the substrate itself occurs due to heat conduction.The expanded section 7 corresponds accordingly to the cavity of prior art thermal flow sensors, thus advantageously providing thermal insulation. Furthermore, a further advantage of the expanded section 7 in the context of the invention is that no separate attachment of a structure is required to achieve thermal insulation. Instead, the expanded section 7 can advantageously be created directly, together with the provision of the flow channel 5, by partially removing the substrate 3, preferably starting from the rear side R.

[0193] A membrane (not shown in its entirety) extends above the flow channel on the front side of the monolithic substrate. The membrane primarily serves to cover the flow channel and represents its upper boundary.

[0194] The membrane preferably also comprises a sensor region, i.e. a region of the membrane on which the thermal sensor 9 is attached in order to measure the at least one flow parameter of the fluid. In Fig. 1, the thermal sensor 9 is only illustrated flatly, but as explained in more detail herein, it can, for example, comprise a heating element and one or more temperature sensors which are present on or embedded in the membrane, in particular in its sensor region. In the embodiment shown, the sensor region of the membrane is attached in particular above the widened section 7 of the flow channel 5 on the front side V of the substrate 3, so that the thermal sensor 9 can be positioned in this region.

[0195] Fig. 2 shows a preferred embodiment of a flow sensor arrangement 11 according to the invention. The flow sensor arrangement 11 comprises a sensor chip 1 and a base plate 13. The base plate 11 comprises two openings 15, which correspond to the inlet region 17 for an inlet of the fluid into the flow channel 5 and to the outlet region 19 for an outlet of the fluid from the flow channel 5.

[0196] The flow sensor assembly 11 refers to a device comprising at least the sensor chip 1 and a base plate 13. The base plate 13 refers to a component that acts as a carrier for the sensor chip 1, allowing the sensor chip 1 to be placed on the base plate.

[0197] The rear side R of the substrate 3 is mounted on the base plate 13. The base plate 13 comprises two openings 15, wherein a first opening 15 corresponds to the inlet region 17 and a second opening 15 corresponds to the outlet region 19 of the flow channel 5. The correspondence here means that, in particular, there is a fluidic connection between the inlet region 17 and the first opening 15 and between the outlet region 19 and the second opening 15 of the base plate 13. The sensor chip 1 can be applied to the base plate 13 such that the inlet region 17 is located substantially directly above the first opening 15 of the base plate 13 and the exit region 19 is located substantially directly above the second opening 15 of the base plate 13.As a result, a measurement can then be carried out by means of the flow sensor arrangement 11 in such a way that the fluid initially flows via the first opening 15 of the base plate 13 and the inlet region 17 along the flow channel 5 and leaves the flow sensor arrangement 11 after flowing through the outlet region 19 and the second opening 15 of the base plate 13.

[0198] The base plate 13 is flat on the side facing the sensor chip 1 and forms a lower boundary of the flow channel 5. A lower boundary of the flow channel 5 means, in particular, that the base plate 13 enables the flow channel 5 to be covered starting from the rear side R. The base plate 13 thus represents a lower wall of the flow channel 5. While the flow channel 5 is laterally encased by the substrate 3, the flow channel 5 is bounded from above by the membrane 9 and from below by the base plate 13.

[0199] The openings 15 on the base plate 13 ensure that the fluid enters the flow channel 5 via the inlet area 17 and leaves the flow channel 5 via the outlet area 19.

[0200] The base plate 13 has an overall flat, planar design, with the base plate 13 having a substantially constant height or thickness. A substantially flat design of the base plate 13 has proven advantageous for a precise connection between the sensor chip 1 and the base plate 13.

[0201] Fig. 3 shows a representation of the flow sensor arrangement 11, which is mounted on a main circuit board 29. The flow sensor arrangement 11 comprises a sensor chip 1, which is positioned on a base plate 13. A cap 41 serves to cover the sensor chip 1. The connection between the base plate 13 and the main circuit board 29 can be made by means of a sealing ring, in particular a solder ring 37. The solder ring 37 is attached via a further connection 39 in order to ensure an electrical and mechanical connection between a flow sensor arrangement 11, which comprises the sensor chip 1 and the base plate 13, and the main circuit board 29. The main circuit board 29 has main circuit board openings 31, which correspond to the openings 15 of the base plate 13. The electronic circuit 33 is mounted on the main board 19 so that a data connection is provided between the thermal sensor of the sensor chip 1 and the electronic circuit 33.

[0202] Fig. 4 schematically shows a preferred embodiment of a system 23 according to the invention, which comprises a flow sensor arrangement 11 and a main channel 25 through which a fluid can flow. Flow restrictors 27 are incorporated in the main channel 25. A fluidic connection is provided between the sensor chip 1 and the main channel 25 such that the inlet region of the sensor channel 5 borders on a region of the main channel 25 upstream of the flow restrictor 27, while the outlet region of the sensor channel 5 borders on a region of the main channel 25 downstream of the flow restrictor 27, so that a pressure difference across the flow restrictor 27 can be measured based on a flow of the fluid through the flow channel 5 of the sensor chip 1. The system 23 thus represents a bypass configuration in which the flow channel 5 of the sensor chip 1 forms the bypass 28 or a partial section thereof.

[0203] LIST OF REFERENCE SYMBOLS

[0204] V front

[0205] R back

[0206] 1 sensor chip

[0207] 3 Substrat

[0208] 5 flow channel

[0209] 7 Widened section

[0210] 9 thermal sensor

[0211] 11 Flow sensor arrangement

[0212] 13 Base plate

[0213] 15 Opening

[0214] 17 Entrance area

[0215] 19 Exit area

[0216] 21 Tapered section

[0217] 23 Systems

[0218] 25 Main channel

[0219] 27 Flow restrictor

[0220] 28 Bypass

[0221] 29 Mainboard

[0222] 31 Mainboard opening

[0223] 33 Electronic circuit

[0224] 35 Additional connection

[0225] 37 solder ring

[0226] 39 Anschlussverbindung

[0227] 41 Abdeckung, vorzugweise Kappe Literaturverzeichnis

[0228] Billat, S., et al. Monolithic integration of micro-channel on disposable flow sensors for medical applications. Sensors and Actuators A: Physical 145 (2008): 66-74.

[0229] Palmer, Kristoffer, et al. A highly integratable silicon thermal gas flow sensor. Journal of Micromechanics and Microengineering 22.6 (2012): 065015.

[0230] Shaterian, Zahra. Single-ended and differentially operated microwave microfluidic sensors for biomedical applications. Journal of Medical Signals and Sensors 13.2 (2023): 84.

[0231] Yang, Canqian, and Henrik Soeberg. "Monolithic flow sensor for measuring millilitre per minute liquid flow." Sensors and Actuators A: Physical 33.3 (1992): 143-153

Claims

PATENT CLAIMS 1. A sensor chip (1) for measuring at least one flow parameter of a fluid, comprising a substrate (3) having a front side (V) and a rear side (R), and a thermal sensor comprising a heating element for providing a thermal field and a sensor component for detecting a temperature response of the thermal sensor as a function of an influence of the fluid on the thermal field, characterized in that the substrate (3) is monolithic, the thermal sensor (9) is positioned on the front side (V) of the substrate (3), and a flow channel (5) is present below the thermal sensor within the substrate (3), which flow channel (5) was formed by removing the substrate (5 in certain areas, preferably starting from the rear side (R), and has an inlet region (17) for the fluid to enter the flow channel (5) and an outlet region (19) for the fluid to exit the flow channel (5).so that on the basis of the temperature response of the thermal sensor (9) the at least one flow parameter of the fluid can be measured., 2. Sensor chip (1) according to the preceding claim, characterized in that the flow channel (5) has a height which substantially corresponds to a height of the monolithic substrate, wherein a width of the flow channel (5) at its narrowest section is preferably smaller than the height of the flow channel, preferably by a factor of 1, 5, 2, 3, 4, or more.

3. Sensor chip (1) according to one or more of the preceding claims, characterized in that the flow channel (5) has a substantially constant width, for example of less than 500 pm, preferably less than 100 pm, 50 pm or less than 30 pm, and / or the flow channel (5) has at least one tapered section (21) or widened section (7), wherein the width of the tapered section is preferably less than 500 pm, preferably less than 100 pm, 50 pm or less than 30 pm.

4. Sensor chip (1) according to one or more of the preceding claims, characterized in that the flow channel (5) has a height of 100 - 1 000 pm, preferably of 200 - 500 pm, and / or a length of 100 - 10 000 pm, preferably of 500 - 2 000 pm.

5. Sensor chip (1) according to one or more of the preceding claims, characterized in that the sensor component is formed by a temperature sensor, wherein the temperature sensor is preferably selected from a group comprising a thermocouple, a diode, a thermistor and / or a thermopile and / or the heating element is an electrical heating element, preferably a heating resistor.

6. Sensor chip (1) according to one or more of the preceding claims, characterized in that the sensor chip (1) has a membrane which extends above the flow channel (5) on a front side (V) of the monolithic substrate, wherein the membrane preferably comprises a sensor region on which the thermal sensor (9) is positioned, wherein the sensor region of the membrane preferably comprises a dielectric material selected from a group comprising silicon nitride, silicon dioxide, aluminum oxide, aluminum nitride, polyimide and / or a polymeric material.

7. Sensor chip (1) according to one or more of the preceding claims, characterized in that the sensor chip (1) has an electronic circuit and / or is connected to an electronic circuit (33), wherein the electronic circuit is configured to control the heating element and / or to determine the at least one flow parameter of the fluid on the basis of the temperature response of the thermal sensor (9).

8. Sensor chip (1) according to one or more of the preceding claims, characterized in that the sensor component is electrically connected to a connection connection, wherein the connection connection is preferably selected from a group comprising a connection pad, a conductor track, a conductor track strip, a bonding wire, a solder connection, an electrically conductive adhesive, a bump and / or a through-hole.

9. Sensor chip (1) according to one or more of the preceding claims, characterized in that the substrate (3) comprises glass, ceramic and / or a semiconductor material, wherein the semiconductor material is preferably selected from a group comprising monosilicon, polysilicon, silicon carbide, silicon germanium, germanium, gallium arsenide, gallium nitride and / or indium phosphide.

10. A method for producing a sensor chip (1) according to one or more of the preceding claims, comprising the following steps: a) providing a substrate (3) which has a front side (V) and a back side (R) and is monolithic, b) removing the substrate (5) in regions, preferably starting from the back side (R), in order to attach a flow channel (5) comprising an inlet region (17) and an outlet region (19) in the substrate (3), c) positioning a thermal sensor on the front side (V).

11. Flow sensor arrangement (11) comprising a sensor chip (1) according to one or more of the preceding claims 1 - 9 and a base plate (13), wherein the base plate (13) has at least one opening (15) which corresponds to the inlet region (17) for an inlet of the fluid into the flow channel (5) and / or the outlet region (19) for an outlet of the fluid from the flow channel (5), wherein the base plate (13) preferably has two openings (15) which correspond to the inlet region (17) for an inlet of the fluid into the flow channel (5) and / or the outlet region (19) for an outlet of the fluid from the flow channel (5).

12. Flow sensor arrangement (11) according to the preceding claim, characterized in that the base plate (13) is flat at least on one side facing the sensor chip (1) and forms a lower boundary of the flow channel (5) and / or the base plate (13) is a circuit carrier, preferably a printed circuit board.

13. Use of a sensor chip (1) according to one of the preceding claims 1 - 9 or a flow sensor arrangement (11) according to one of the preceding claims 11 or 12 for measuring a flow parameter of a fluid in a main channel (25) in a bypass configuration.

14. Use according to the preceding claim, characterized in that a flow restrictor (27) is introduced into the main channel (25), wherein a fluidic connection between the sensor chip (1) and the main channel (25) is provided in such a way that the inlet region (17) of the sensor chip adjoins a region of the main channel (25) upstream of the flow restrictor (27), while the outlet region (19) of the sensor chip (1) adjoins a region of the main channel (25) downstream of the flow restrictor (27), so that a pressure difference across the flow restrictor (27) can be measured based on a flow of the fluid through the flow channel of the sensor chip (1).

15. System (23) comprising a. a sensor chip (1) according to one or more of the preceding claims 1 - 9 or a flow sensor arrangement (11) according to one of the preceding claims 11 or 12 and b. a main channel (25) through which a fluid can be guided in a flowable manner, wherein a flow restrictor (27) is introduced into the main channel (25) and wherein a fluidic connection between the sensor chip (1) and the main channel (25) is provided in such a way that the inlet region (17) of the sensor chip (1) adjoins a region of the main channel (25) upstream of the flow restrictor (27), while the outlet region (19) of the sensor chip (1) adjoins a region of the main channel (25) downstream of the flow restrictor (27), so that a pressure difference across the flow restrictor (27) can be measured based on a flow of the fluid through the flow channel (5) of the sensor chip (1).

Images