Sensor device and method of producing a sensor device by direct atomic layer processing

Abstract

The disclosure relates to a sensor device and method for producing a sensor device, comprising a substrate and an array of sensing elements for interacting with an environment, wherein each sensing element includes a thin-film deposit of material on the substrate so as to provide the sensing elements with mutually different sensitivity properties.

Description

[0001] Title: Sensor device and method of producing a sensor device by direct atomic layer processing

[0002] FIELD

[0003] The disclosure relates to sensor devices and methods, particularly to electrochemical sensor devices, and method of producing sensor devices.

[0004] BACKGROUND

[0005] Various types of sensors include a sensing element including a sensory structure and operate on the principle of a detectable property change of the sensory structure caused by the interaction between the sensory structure and the environment, such as a target chemical compound or molecule or light.

[0006] The sensory unit of sensors is typically chosen depending on the application requirements. A key component is the sensory material of the unit itself, such as metals, metal oxides, polymers or composite materials. Among metal oxides, tin dioxide (SnCh), zinc oxide (ZnO), or tungsten oxide (WO3) are some of the most used materials. When a target chemical compound interacts with the metal oxide surface, it causes a measurable change in the sensory material’s properties, such as electrical or chemical.

[0007] While sensor devices have seen significant improvements in the past decades, there remains a need for improved functionality and performance.

[0008] SUMMARY

[0009] It is an object to propose an improved sensor device and method, particularly an improved electrochemical sensor device such as a gas sensor device and method. It is also an object to propose a method to enhance performances of contemporary sensor devices. It is also an object to provide a multi-faceted sensor device and method, such as a gas sensor for detecting gas mixtures and discriminating between the individual gases in the gas mixtures.

[0010] An aspect provides method of producing a sensor device, comprising, by direct atomic layer processing (DALP), depositing a first thin-film of material for a first sensing element at a controlled first position on the substrate and a second thin-film of material for a second sensing element at a controlled second position on a substrate, wherein the first thin-film of material and the second thin-film of material have mutually different properties so as to provide the first sensing element and the second sensing element with mutually different sensitivity characteristics.

[0011] DALP may comprise locally depositing thin-films of material, particularly the first and second thin-films of material, at controlled positions and / or along a controlled spatially controlled trajectory on the substrate. A precursor outlet nozzle may be moved relative to the substrate between controlled positions, and along a spatially controlled trajectory, while locally depositing material. Moving the precursor outlet nozzle and the substrate relative to each other while locally supplying one or more precursors to the substrate with the outlet nozzle allows for depositing an atomic layer of material at desired distinctive positions and along a desired trajectory on a substrate. Dimensions and positions of the atomic layers on the substrate can accordingly be controlled by DALP. The precursor outlet nozzle may particularly be configured for selectively supplying different precursors to the substrate. The precursor can hence be varied between thin-films of material for depositing thin-films of different compositions and structures at desired spatial locations on the substrate.

[0012] DALP thus allows for patterning or directly writing materials onto controlled positions on the substrate, and hence provides flexibility as to the location, thicknesses, microstructures and compositions of the thin film layers of the sensing elements, as well as to the type of substrate. DALP is therefore highly time- and cost-efficient for depositing the thin films described herein compared to conventional ALD systems and methods, and therefore enables for high-throughput and high-volume manufacturing of sensor devices, and also for enhancing the performance of already existing sensor devices. DALP accordingly allows for flexibility in the sensor design, as it enables to provide multiple sensor elements on a single substrate to, for example, increase the sensing range, enhance selectivity, enhance specificity, and / or reduce crosssensitivity. The sensing elements may sense various physical quantities to obtain a multi-faceted sensor device. The sensor device can be for example be produced to sense one or more of a temperature, humidity, chemical compound substance or composition, electrochemical reactions, wavelengths, plasmons, strain, etc. The sensor device may hence be an electrochemical sensor, a photodetector, a catalytic sensor, a plasmonic sensor, a strain sensor, a temperature sensor, a semiconductor sensor, or a combination thereof.

[0013] DALP also allows for processing of semiconductor dies after singulation from a wafer, which can be particularly beneficial for fabrication of semiconductor sensors. In addition to the deposition of layers, DALP may also be used for etching layers, and cleaning surfaces.

[0014] An exemplary DALP system and method is described in W02020 / 245230A1 and W02023 / 079030A2, the contents of which are incorporated herein by reference in their entirety

[0015] An aspect provides an atomic layer deposition method for producing a sensor device, comprising, by a precursor outlet nozzle, depositing a first thin-film of material for a first sensing element at a controlled first location on the substrate; moving the precursor outlet nozzle relative to the substrate from the controlled first location to a controlled second location; and by the precursor outlet nozzle, depositing a second thin-film of material for a second sensing element at the controlled second location on the substrate; wherein the first thin-film of material and the second thin-film of material have mutually different properties so as to provide the first sensing element and the second sensing element with mutually different sensitivity characteristics.

[0016] Optionally, at least one of the first thin-film of material and the second thin-film of material is configured to form at least part of a sensory structure of the respective first and second sensing elements, to detectably interact with an environment. It will be appreciated that the sensory structure’s detectable interaction with the environment provides the basis for the sensor measurement.

[0017] Optionally, at least one of the first thin-film of material and the second thin-film of material is configured to form at least part of a non- sensory structure of the respective first and second sensing elements, such as for forming a permeable barrier.

[0018] Optionally, the first thin-film of material and the second thin-film of material are deposited to have mutually different film thicknesses.

[0019] Optionally, the first thin-film of material and the second thin-film of material are deposited to have mutually different microstructures.

[0020] Optionally, the first thin-film of material and the second thin-film of material have mutually different material compositions.

[0021] Optionally, the first thin-film of material and the second thin-film of material have mutually different permeability to light, gas, fluid and / or plasma.

[0022] Optionally, the first thin-film of material and the second thin-film of material are deposited non-overlapping with each other.

[0023] Optionally, the method comprises, by direct atomic layer processing (DALP), depositing a first stack of thin-films of material for the first sensing element and a second stack of thin-films of material for the second sensing element on a substrate so as to provide the first sensing element and the second sensing element with mutually different sensitivity characteristics.

[0024] An aspect provides a sensor device, comprising a substrate and an array of sensing elements for interacting with an environment, wherein each sensing element includes a thin-film deposit of material on the substrate so as to provide the sensing elements with mutually different sensitivity characteristics. The plurality of different sensing elements can improve sensor performance, for example by increasing the sensing range, enhancing selectivity, enhancing specificity, enhancing sensitivity and / or reducing crosssensitivity. The sensing elements may sense various physical quantities to obtain a multi-functional sensor device. The sensor device may for example sense one or more of a temperature, humidity, chemical compound substance or composition, electrochemical reactions, wavelengths, plasmons, strain. The sensor device may hence be an electrochemical sensor, a photodetector, a catalytic sensor, a plasmonic sensor, a strain sensor, a temperature sensor, a semiconductor sensor, or a combination thereof.

[0025] Optionally, each sensing element includes a sensory structure configured to detectably physically and / or chemically interact with the environment. The interaction with the sensory structure forms a basis for the sensor measurement of the sensor device. An electrical property change of the sensory structure caused by its interaction with the environment may for example be detected, and hold valuable sensory information. The sensory structure may be connected to an electrode structure, e.g. of a semiconductor material, to capture and relay electronic signals indicative of the electrical property change of the sensory structure.

[0026] Optionally, one or more of the sensing elements include an electrode structure, particularly a semiconductor electrode structure, wherein the thin- film deposits of material are deposits on the electrode structure.

[0027] Optionally, the thin-film deposits of the sensing elements have mutually different material compositions. The sensing elements may for example be composed of respective materials or of substantially the same materials in different relative proportions.

[0028] Optionally, the thin-film deposits of the sensing elements have mutually different microstructures. Optionally, the sensing elements are configured for sensing mutually different physical quantities.

[0029] Optionally, one or more of the thin-film deposits include a permeable film for coating a sensory structure. The thin-film deposit may hence be or include a non-sensory or passive element of the sensor device, for providing a permeable barrier between the environment and the sensory structure of the sensing element. The permeable film preferably has known permeability properties, e.g. given its predetermined geometry and material composition, for a permeating medium to interact with sensory structure.

[0030] Optionally, the thin-film deposits of the sensing elements have mutually different film geometries. The thin-film deposits may for example have different film-thicknesses.

[0031] Optionally, the thin-film deposits of the sensing elements have mutually different film thicknesses.

[0032] Optionally, the sensing elements have a mutually different layering of thin-films. The sensing elements may for example have one or more of a different number of layers, a different ordering of layers, different layer compositions, different layer geometries, etc..

[0033] Optionally, one or more of the sensing elements include a sensory structure coated with a, preferably non-sensory, permeable film, e.g. diffusive film. The permeable film can provide a barrier between a medium to be sensed and the active element of the sensing element. Depending on the application, the permeable film may be permeable to various media, such as liquids, plasma, gases and light. An intentional diffusion delay or frequencydependent optical transmission variations can for example be obtained by the permeable film. The diffusion delay is generally predetermined and governed by the known composition and the known thickness of the film and is dependent on the medium itself. The permeable film may particularly be diffusive film, more particularly a gas-diffusive film. Optionally, the sensory structure includes a metal oxide material, optionally coated with a permeable thin-film deposit of material. The sensor device may for example be a metal oxide semiconductor (MOS) sensor device.

[0034] Optionally, the sensing elements of the array are configured for interacting with a gas.

[0035] Optionally, one or more of the sensing elements include a sensory structure coated with a permeable thin-film deposit of material.

[0036] Optionally, the array includes a first sensing element having a first sensory structure coated with a first permeable thin-film deposit of material, and a second sensing element having an uncoated second sensory structure or a second sensory structure coated with a second permeable thin-film deposit of material having a different permeability compared to the first permeable thin-film.

[0037] Optionally, the first permeable film and the second permeable film are of the same material, and have a mutually different film thickness.

[0038] Optionally, the array includes a first sensing element having a first gas-sensory structure coated with a first gas-diffusive thin-film deposit of material, and a second sensing element having an uncoated second gas- sensory structure or a second gas-sensory structure coated with a second gas- diffusive thin-film deposit of material having a different gas-diffusive impedance compared to the first gas-diffusive thin-film. The first gas- diffusive film and the second gas-diffusive film may differ from each other in terms of material composition and geometry. It will be appreciated that the first gas-sensory structure and the second gas-sensory structure may be identical. The first gas-sensory structure and the second gas-sensory structure may alternatively differ from each other in terms of material composition and geometry.

[0039] Optionally, the first gas-diffusive film and the second gas-diffusive film are of the same material, and have a mutually different film thickness. Optionally, each permeable film has a film thickness of at most 20nm, particularly at most lOnm such as in a range of l-10nm.

[0040] Optionally, the sensor device comprises an enclosed chamber in which the sensing element is provided, a first gas inlet valve for controlling an inlet of a detectable gas into the chamber, a gas outlet valve for controlling an outlet of gas from the chamber, and a second gas inlet valve for controlling an inlet of an inert gas into the chamber.

[0041] Another aspect provides a sensor device comprising a sensing element for interacting with an environment, wherein the sensing element comprises a sensory structure coated with a permeable film. The sensory structure may optionally be part of an array of sensory structures. The permeable film provides a barrier between the sensory structure and the environment. It will be appreciated that any film described herein, including the gas-diffusive film, may be a thin-film deposit of material as described herein. It will also be appreciated that the coated sensory structure need not necessarily be a thin-film deposit of material itself, as various types of sensory structures are compatible with being coated with a permeable thin-film. The aspect particularly provides a gas sensor device comprising a sensing element for interacting with a gas, wherein the sensing element comprises a gas- sensory structure coated with a gas-diffusive thin-film

[0042] Another aspect provides a use of DALP for producing a sensor device such as described herein, particularly as a gas-sensor device as described herein. The use may include depositing a sensory structure and / or depositing a permeable coating film on a sensory structure. The use for example includes depositing a thin-film of material on a semiconductor structure postsingulation. The aspect particularly provides a use of DALP for enhancing performance of an existing gas sensor, particularly by coating a gas-sensory structure for the existing gas sensor with a gas-diffusive film. DALP hence enables an increase of performance of existing gas sensors, particularly by coating a gas-sensory structure of its sensor element with a gas-diffusive film. A particular aspect provides a gas sensor device comprising a sensing element for being exposed to the gas, wherein the sensing element comprises a gas-sensory structure coated with a gas-diffusive film.

[0043] Another aspect provides a method of detecting a gas with a gas sensor device such as described herein, having a sensing element for being exposed to the gas, wherein the sensing element comprises a gas-sensory structure coated with a gas-diffusive film. The method comprises exposing the sensing element to the gas; obtaining a signal from the sensing element indicative of an electrical property change of the gas-sensory structure over time; and determining the gas based on the signal.

[0044] In use, electrical properties of the gas-sensory structure change upon contact with the gas, as the gas-sensory structure chemically interacts with the gas. The coating with the gas-diffusive film enhances the selectivity and specificity of the gas sensor by controlling the diffusion rate of gas molecules through the gas-diffusive film. The gas-diffusive film allows gasses to diffuse through it, and thereby provides a diffusive impedance between a gascontaining space and the gas-sensory structure. An intentional diffusion delay is accordingly obtained by the coating of the sensory structure with the gas-diffusive film, wherein the diffusion delay is generally predetermined and governed by the known composition and the known thickness of the film and is dependent on the gas itself. An observed diffusion delay for a predetermined gas-diffusive film coating can hence be linked to a specific gas. In addition to the measured electric property change of the structure, the diffusion delay, e.g. between exposure to the gas and detection of the electric property change of the structure, caused by the coating of the gas-sensory structure can accordingly enrich the sensor information obtainable by the sensor device to enhance selectivity and specificity.

[0045] Optionally, the gas-sensory structure includes a metal oxide material. Optionally, the gas-sensory structure is a first gas-sensory structure coated with a first gas-diffusive film, and wherein the gas sensor device further comprises a second sensing element having an uncoated second gas-sensory structure or a second gas-sensory structure coated with a second gas-diffusive film having a different gas-diffusive impedance compared to the first gas-diffusive film. Each sensing element accordingly interacts differentially with the gas, creating a fingerprint of that gas. The use of multiple sensing elements with different gas-diffusive characteristics and associated diffusion delays can accordingly enhance selectivity and specificity of the sensor device. It furthermore enables the sensing device to selectively detect and discriminate different gases in a mixture of gases.

[0046] Optionally, the first gas-diffusive film and the second gas-diffusive film are of the same material and have a mutually different film thickness. Varying the thickness of the gas-diffusive films across the different sensing elements provides a controlled way to obtain a predictable and reliable diffusion delay difference between the multiple sensing elements.

[0047] Optionally, the gas-diffusive film has a film thickness of at most 20nm, particularly at most lOnm such as in a range of l-10nm. Such ultrathin films ensure rapid diffusion of gases through the films, thus providing a quick response time, while also providing a practically measurable diffusion delay.

[0048] Optionally, the device comprises an enclosed sample chamber in which the sensing element is provided, a first gas inlet valve for controlling an inlet of a detectable gas into the chamber, a gas outlet valve for controlling an outlet of gas from the chamber, and a second gas inlet valve for controlling an inlet of an inert gas into the chamber. The enclosed chamber with controllable gas inlet and outlet valves allows for precise dosing and purging of gases. It particularly allows for time-based control of the valves to accurately ascertain a time difference between inlet of the detectable gas in the chamber and a detection of the gas by gas-sensory structure. Optionally, the gas is determined based on a dissimilarity between the signal indicative of the electrical property change of the gas-sensory structure over time and a reference signal. The reference signal may for example be predetermined, e.g. from various calibration measurements with different gases. The reference signal may also correspond to a signal obtained from another sensing element of the sensor device, indicative of the electrical property change of the associated gas-sensory structure over time. The dissimilarity between the sensor signals from the respective sensing elements of the same sensing device may be indicative of the specific gas.

[0049] Optionally, the sensing element is exposed to the gas at a first time, and wherein the method comprises determining, based on the signal, the electrical property change of the gas-sensory structure at a second time, and determining the gas based on a difference between the first time and the second time and / or based on the determined electrical property change. The temporal latency between the exposure to the gas and the detection of the electrical property change of the structure, can reveal gas-specific information about the gas. Additionally, or alternatively, the determined electrical property change may be dependent on the gas-diffusive film, and can therefore reveal gas-specific information about the gas.

[0050] Optionally, the gas-sensory structure is a first gas-sensory structure coated with a first gas-diffusive film, and wherein the gas sensor device further comprises a second sensing element having an uncoated second gas-sensory structure or a second gas-sensory structure coated with a second gas-diffusive film having a different gas-diffusive impedance compared to the first gas-diffusive film, the method comprising exposing the first sensing element and the second sensing element to the gas; obtaining a first signal from the first sensing element indicative of an electrical property change of the first gas-sensory structure over time; obtaining a second signal from the second sensing element indicative of an electrical property change of the second gas-sensory structure over time; determining the gas based on a dissimilarity between the first signal and the second signal. For detecting a single gas introduced to the sensor device, the first signal and the second signal can give a distinguishable time -dep endent signal, providing a unique identifier of the gas and indicative, e.g. proportional, to the amount of the gas introduced. If a mixture of gases is introduced to the sensor device, the first signal and the second signal may each include a convoluted response of the structure to the different gases in the mixture, wherein a time-shift and a magnitude shift between the first signal and the second signal caused by the respective film coatings facilitate deconvoluting of the first and second signal to determine each gas in the mixture.

[0051] Optionally, the first sensing element and the second sensing element are exposed to the gas at a first time, and wherein the method comprises determining, based on the first signal, a first electrical property change of the first gas-sensory structure at a second time; determining, based on the second signal, a second electrical property change of the second gas-sensory structure at a third time; determining the gas based on a time difference between the second time and the third time and / or based on a difference between the first electrical property change and the second electrical property change. Hence, a method may be provided of detecting a gas with a gas sensor device having a first sensing element and a second sensing element for being exposed to the gas, wherein the first sensing element comprises a first gas- sensory structure coated with a first gas-diffusive film, and the second sensing element comprises an uncoated second gas-sensory structure or a second gas-sensory structure coated with a second gas-diffusive film having a different gas-diffusive impedance compared to the first gas-diffusive film, wherein method comprises exposing the first sensing element and the second sensing element to the gas at a first time; obtaining a first signal from the first sensing element indicative of an electrical property change of the first gas-sensory structure over time and determining, based on the first signal, a first electrical property change of the first gas-sensory structure at a second time; obtaining a second signal from the second sensing element indicative of an electrical property change of the second gas-sensory structure over time, and determining, based on the first signal, a first electrical property change of the first gas-sensory structure at a second time; and determining the gas based on a time difference between the second time and the third time and / or based on a difference between the first electrical property change and the second electrical property change. It will be appreciated that the first gas- sensory structure and the second gas-sensory structure may have be identically configured, or that the first gas-sensory structure and the second gas-sensory structure may have be differently configured.

[0052] Optionally, the gas is a gas mixture of a plurality of gases, wherein the method comprises differentiating the plurality of gases from one another. The differentiating may for example comprise deconvoluting one or more signals obtained from the one or more sensor elements.

[0053] Another aspect provides a method of producing a sensor device, such as described herein, comprising providing an array of electrode structures on a substrate, and depositing a respective thin-film of a sensory material on each of the electrode structures of the array to form an array of sensory structures with mutually different sensitivity properties.

[0054] Optionally, the method comprises depositing a thin-film of a permeable material on one or more of the thin-film deposits of sensory material so as to coat one or more sensory structures.

[0055] Another aspect provides a method of producing a gas sensor device, such as described herein, comprising providing an array of electrode structures on a substrate, and depositing a thin-film of a gas-sensory material on each of the electrode structures of the array.

[0056] Optionally, the method comprises depositing a thin-film of a gas- diffusive material on each of the thin-film deposits of sensory material.

[0057] Another aspect provides a method of producing a gas sensor device, such as described herein, comprising depositing a thin-film of a gas-diffusive material on one or more of gas-sensory structures so as to coat one or more gas-sensory structures with a gas-diffusive film. It will be appreciated that the one or more gas-sensory structures need not necessarily be thin-film deposits.

[0058] Optionally the method comprises depositing a thin-film of a gas- diffusive material on the one or more of the gas-sensory structures so as to coat the one or more sensing elements with a gas-diffusive film of a different film thickness.

[0059] It will be appreciated that the method as described herein or parts thereof may be computer-implemented.

[0060] It will be appreciated that any of the aspects, features and options described herein can be combined. It will particularly be appreciated that any of the aspects, features and options described in view of the device apply equally to the methods, and vice versa.

[0061] BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings in which:

[0063] Figures 1A and IB show a schematic representation of a sensor device;

[0064] Figure 2 shows a schematic representation of a sensor device for detecting a gas;

[0065] Figures 3A, 3B and 4A, 4B show exemplary sensor signals obtainable from the sensor device.

[0066] DETAILED DESCRIPTION

[0067] Figures 1A and IB show an example of a sensor device 10. The sensor device 10 includes a substrate 1, provided an array of sensing elements 2a-2o. Figure 1 shows a planar view of the sensor device 10, while figure IB shows a cross sectional view of the sensor device 10. Each sensing element 2a-2o comprises a thin-film deposit of material 3a-3o on the substrate 1 so as to provide the sensing elements 2a-2o with mutually different sensitivity properties. In this example, each sensing element 2a-2o includes a semiconductor electrode structure, wherein the thin-films are deposited on the respective semiconductor electrode structures. Other kinds of electrode structures are also envisioned.

[0068] The thin-film deposits may have different material compositions and / or different film thicknesses, to provide the sensing elements 2a-2o with mutually different sensitivity properties. The thin-film deposits may for example include different materials, or the same materials in different proportions. Each sensing element 2a-2o may hence interact differently with the environment, to provide the sensing elements 2a-2o with mutually different sensitivity properties. The sensor device 10 may hence, for example, sense multiple different physical quantities. Each thin-film deposit of material 3a-3o may for example be configured for interacting with a respective target chemical compound or molecule. Each thin-film deposit of material 3a-3o in this example forms at least part of a sensory structure of the sensing element 2a-2o. The sensing of the sensor device 10 is based on a detectable physical and / or chemical interaction between the sensory structure and the environment.

[0069] In this example, each of the sensing elements 2a-2o includes a thin- film deposit of a metal oxide, such as TiC , ZnO, HfO2, SnO2, MoOs, WO3, NiO, CU2O or Ga2C>3, forming the sensory structure 3a-3o of the sensing elements 2a-2o. The sensory structures 3a-3o of the sensing elements form active components of the sensor device 10, as their detectable physical and / or chemical interaction with the environment holds valuable sensory information about the environment. Alternatively or additionally, the thin- film deposit may be a non-sensory or passive component of the sensor device, 10, such as a permeable coating of a sensory structure. The coating may provide an intentional permeable barrier between the sensory structure and the environment. It will be appreciated that a coated sensory structure need not necessarily be a thin-film deposit of material itself. Various other types of sensory structures are compatible with being coated with a thin-film. In this example, at least some of the sensory structures 3a-3o are coated by a thin- film deposit of a permeable material. The permeable thin-film may be permeable in a predictable way to gases, liquids, plasma, and / or light. The permeable thin-film may be a gas-diffusive film, for example to provide an intentional gas diffusion delay between the coated sensory structures 3a-3o and the environment.

[0070] It will be appreciated that a thin-film as described herein encompasses a layer of material ranging from a fraction of a nanometer to several micrometers in thickness. Thin-films may in general be deposited on the same substrate, e.g. on top of another structure, and also by various techniques, such as molecular beam epitaxy, Langmuir-Blodgett method, atomic layer deposition (ALD) and molecular layer deposition (MLD).

[0071] The thin-films in this example are deposited on the substrate 1 by an atomic layer deposition (ALD) method, particularly by direct atomic layer processing (DALP). DALP, e.g. as described in as described in W02020 / 245230A1, comprises moving the substrate and a printer head relative to one another to deposit a thin layer of material along a controlled spatial trajectory on the substrate. Dimensions and positions of the atomic layers to be deposited are controllable by DALP, for example by a nozzle size and positioning of a printer head relative to a substrate. Moving the printer head and the substrate 1 relative to each other while supplying one or more precursors to the substrate with the printer head allows for depositing an atomic layer of contiguous material along a desired path on a substrate. It thus allows for patterning or directly writing materials onto the substrate 1, and hence provides flexibility as to the thickness, structure and composition of the thin -films, as well as to the type of substrate 1. The thin -films are in this example deposited as respective patches of different materials on the substrate, each patch forming part of a respective sensing element 2a-2o of the sensor device 10. The sensing elements 2a-2o are here arranged in a regular array, but it will be appreciated that other configurations are envisioned.

[0072] At least some of the sensing elements 2a-2o may include or be provided on a semiconductor electrode structure, being formed by a die that has been singulated from a wafer, and bonded to a substrate. Using DALP, the semiconductor structures may be covered after singulation with a thin- film deposit of material, such as a metal oxide and / or a permeable film. Production of the semiconductor sensor structures may hence remain unaltered, as DALP enables post-singulation processing of the semiconductor structures, particularly by deposition a thin-film on the semiconductor structure.

[0073] The sensor device 10 in this example comprises an optional heater 5 to bring the sensing elements 2a-2o up to optimal operating temperature. For certain applications, operating temperatures may for example be in a range of 400 to 1000 degrees Celsius.

[0074] Figure 2 shows a particularly example of a sensor device 10, here being embodied as a gas sensor device 10. The sensor device 10 in this example is hence arranged for sensing one or more chemical compounds being in a gas phase. Figure 2 shows a cross sectional view, similar to figure IB. Each sensing element 2a-2e in this example includes a metal oxide semiconductor (MOS) gas-sensory structures 3a-3d. The MOS gas-sensory structures 3a-3e form the active components of the sensor device 10, as they physically and / or chemically interact with the gas to be detected. The MOS structures 3a-3e may be deposited as respective separate layer on the substrate 1, for example with equal uniform layer thicknesses in the range of 1 nm-100 nm. The MOS structures 3a-3e may accordingly have a relatively high surface area per unit mass. The MOS structures may for example be generally composed of or include a metal oxide semiconductor material such as ZnO, SnO2, MoOs, TiO2, WO3, NiO, Ga2Os, HfO2, and CU2O.

[0075] The sensor device 10 is configured to detect the presence of gases, primarily by recording electrical property changes of the MOS gas-sensory structures 3a-3e due a physical and / or chemical interaction between the gas and the MOS structures 3a-3e. When different gases come in contact with the MOS structures 3a-3e, the electric conductivity of the MOS structures 3a-3e can change significantly. Upon contact of MOS structures 3a-3e to gas molecules, electrical conductivity of the MOS structures 3a-3e can change in dependence of the specific gas-MOS interaction such as chemical adsorption and desorption. When gas comes into direct contact with the MOS structures 3a-3e, a chemical reaction takes place, causing electrical properties of the MOS structures 3a-3e to change. The change in electrical properties of the MOS structures 3a-3e can be measured to ascertain what gas the MOS- structures are exposed to.

[0076] Here, each of the MOS gas-sensory structures 3a-3e is coated with a respective film 4a-4e of a permeable, here a gas-diffusive, material. The gas- diffusive films 4a-4e shield the respective MOS structures 3a-3e to provide a gas-diffusive barrier for the gas. The gas-diffusive films 4a-4e accordingly cause a diffusion delay between exposure of the sensing elements 2a-2e to a gas, and the detectable interaction of the gas with the underlying MOS structures 3a-3e. The diffusion delay may be gas-dependent, and can be measured to enrich sensor information obtainable from the sensor device 10. It will be appreciated that not all MOS gas-sensitive structures 3a-3e need to be coated with a gas-diffusive film.

[0077] In this example, the gas-diffusive films 4a-4e have mutually different gas-diffusive properties. Each gas-diffusive film 4a-4e accordingly provides a different gas diffusion impedance between the associated MOS structure 3a-3e and the exterior of the sensing elements 2a-2e, for causing varying diffusion delays across the different sensing elements 2a-2e. These diffusion delay variations can provide additional information about the detectable gas. It particularly allows for discriminating between various gases in a gas mixture. In this example, the gas-diffusive variations between the sensing elements 2a-2e are obtained by a different film thicknesses of the gas-diffusive films 4a-4e. Each gas-diffusive film 4a-4e is in this example composed of the same gas-diffusive material, but has a different film thickness. It will be appreciated that varying diffusive properties between the sensing elements 2a-2e may additionally or alternatively be obtained by varying material compositions of the films 4a-4e.

[0078] The gas-diffusive films 4a-4e are in this example deposited on the gas-sensory structures using DALP. The gas-diffusive films have, in this example, a film thickness of at most lOnm or 20nm such as in a range of 1- 20nm, or in a range of l-10nm. Such thin films 4a-4e provide rapid response times, while also providing a practically detectable diffusion delay. ALD can provide an accurate and uniform thin films 4a-4e, providing an accurate and predictable sensing response to the sensor device 10.

[0079] The gas sensor device 10 in this example also comprises an enclosure 6 delimiting an enclosed chamber 7 holding the sensing elements 2a-2e. A first gas inlet valve 8a is provided for controlling an inlet of a gas to be detected into the enclosed chamber 7. A gas outlet valve 9 is provided for controlling an outlet of the gas from the chamber 7. A second gas inlet valve 8b is provided for controlling an inlet of an inert gas into the chamber 7 for purging the chamber 7. The inlet valves 8a, 8b and the outlet valve 9 may be controlled by control unit 11.

[0080] Figures 3A-3B and 4A-4B show exemplary sensor signals a-e obtained by the sensor device 10 as shown in figure 2. Figures 3A and 3B show sensor signals a-e pertaining to the exposure of the sensing elements 2a-2e to a gas composed of a single detectable gas. Figures 4A and 4B show sensor signals a-e pertaining to the exposure of the sensing elements 2a-2e to a gas composed of a mixture of multiple detectable gases. Figures 3A and 4A show an example of sustained exposure of the sensing elements 2a-2e to a gas, while Figures 3B and 4B show an example of a pulsed exposure of the sensing elements 2a-2e to a gas.

[0081] Each line a-e in figures 3A-3B and 4A-4B corresponds to a sensor signal a-e obtained from a respective sensing element 2a-2e of the sensor device 10 over time. Each line particularly represents the change of an electrical property of a respective MOS structure 3a-3e as a function of time. Due to the varying gas-diffusive film 4a-4e coatings of the MOS gas-sensory structures 3a-3b, the respective MOS structure responses are shifted in time relative to another. In general, the MOS structure 3a having the thinnest gas- diffusive film 3a coating generally gives a earliest response from the opening of the first inlet valve 8a, while the MOS structure 3a having the thickest gas- diffusive film 3a coating gives the latest response. Furthermore, the MOS structure 3a having the thinnest gas-diffusive film 4a coating generally shows a larger response magnitude, and the MOS structure 3a having the thickest gas-diffusive film 4a coating gives the smallest response magnitude.

[0082] The measurable electrical property change of the MOS structures 3a-3e as well as the relative time-delays caused by the diffusive film 4a-4e allows to accurately determine to what gas the sensing elements 2a-2e are exposed to in the situation of figures 3A-3B. The added film coatings thus enhance the sensor information obtainable from the sensor device 10.

[0083] The measurable electrical property changes of the MOS structures 3a-3e as well as the relative time-delays caused by the diffusive film 4a-4e furthermore allows to selectively distinguish the different gases of the gas mixture in the situation of figures 4A-4B, e.g. by deconvoluting the signals a- e.

[0084] Herein, the invention is described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein, without departing from the essence of the invention. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, alternative embodiments having combinations of all or some of the features described in these separate embodiments are also envisaged.

[0085] However, other modifications, variations, and alternatives are also possible. The specifications, drawings and examples are, accordingly, to be regarded in an illustrative sense rather than in a restrictive sense.

[0086] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other features or steps than those listed in a claim. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to an advantage.

Claims

Claims1. A method of producing a sensor device, comprising, by direct atomic layer processing (DALP), depositing a first thin-film of material for a first sensing element at a controlled first location on the substrate and a second thin-film of material for a second sensing element at a second controlled location on a substrate, wherein the first thin-film of material and the second thin-film of material have mutually different properties so as to provide the first sensing element and the second sensing element with mutually different sensitivity characteristics.

2. The method according to claim 1, wherein at least one of the first thin-film of material and the second thin-film of material is configured to form at least part of a sensory structure of the respective first and second sensing elements, to detectably interact with an environment.

3. The method according to claim 1 or 2, wherein at least one of the first thin-film of material and the second thin-film of material is configured to form at least part of a non-sensory structure of the respective first and second sensing elements, such as for forming a permeable barrier.

4. The method according to any of the preceding claims, wherein the first thin-film of material and the second thin-film of material are deposited to have mutually different film thicknesses.

5. The method according to any of the preceding claims, wherein the first thin-film of material and the second thin-film of material are deposited to have mutually different microstructures.

6. The method according to any of the preceding clams, wherein the first thin -film of material and the second thin-film of material have mutually different material compositions.

7. The method according to any of the preceding clams, wherein the first thin-film of material and the second thin-film of material have mutually different permeability to light, gas, fluid and / or plasma.

8. The method according to any of the preceding clams, comprising, by direct atomic layer processing (DALP), depositing a first stack of thin-films of material for the first sensing element and a second stack of thin-films of material for the second sensing element on a substrate so as to provide the first sensing element and the second sensing element with mutually different sensitivity properties.

9. An atomic layer deposition method for producing a sensor device, optionally according to any of the preceding claims, comprising by a precursor outlet nozzle, depositing a first thin-film of material for a first sensing element at a controlled first location on the substrate; moving the precursor outlet nozzle relative to the substrate from the controlled first location to a controlled second location; and by the precursor outlet nozzle, depositing a second thin-film of material for a second sensing element at the controlled second location on the substrate; wherein the first thin-film of material and the second thin-film of material have mutually different properties so as to provide the first sensing element and the second sensing element with mutually different sensitivity characteristics.

10. A sensor device comprising a substrate and an array of sensing elements for interacting with an environment, wherein each sensing element includes a thin-film deposit of material on the substrate so as to provide the sensing elements with mutually different sensitivity characteristics.

11. The sensor device according to claim 10, wherein one or more of the thin-film deposits are of a sensory material for detectably interacting with the environment.

12. The sensor device according to claim 10 or 11, wherein one or more of the thin-film deposits are of an non-sensory material, such as forming a permeable barrier.

13. The sensor device according to any of claims 10-12, wherein the thin-film deposits of the sensing elements have mutually different film thicknesses.

14. The sensor device according to any of claims 10-13, wherein the thin-film deposits of the sensing elements have mutually different microstructures .

15. The sensor device according to any of the preceding claims, wherein the thin-film deposits of the sensing elements have mutually different material compositions.

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