Self-assembled omnidirectional high temperature vibration sensor array and manufacturing method
By self-assembled omnidirectional high-temperature vibration sensing array based on two-dimensional crystal piezoelectric materials, the three-dimensional microtube structure reduces the chip area and power consumption, solving the problem of limited application of existing vibration sensors in high-temperature environments, and achieving omnidirectional, high sensitivity and self-power detection capabilities.
Patent Information
- Application Number
- CN202210687914.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-06-17
- Publication Date
- 2025-03-18
- Estimated Expiration
- 2042-06-17
Smart Images
Figure CN115096430B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of vibration sensors, and in particular to a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials and a manufacturing method thereof. Background Art
[0002] Piezoelectric vibration sensor is a vibration detection device that converts vibration signals into electrical signals, and converts vibration signals into corresponding currents according to the piezoelectric effect. Among them, the self-assembled vibration sensor unit based on two-dimensional crystal piezoelectric materials realizes the detection of omnidirectional vibration through array integration. Omnidirectional vibration sensors play a very important role in aerospace, national defense, military, transportation and other fields. However, since the more mature type is the multi-axial vibration sensor represented by the combined three-axial direction, this type of sensor is easily affected by vibrations in other directions and is not easy to decouple. At the same time, due to the differences in each axial vibration element, they are easily limited in accuracy and sensitivity. In addition, due to the limitations of the packaging method, this type of sensor has a large size and high power consumption, and the overall reliability is easily affected, which limits the application scope of this type of sensor.
[0003] In order to overcome the problems of combined multi-axis vibration sensors and realize miniaturized omnidirectional vibration detection, researchers have turned their attention to monolithic integrated omnidirectional vibration detection. Wei et al. demonstrated a new MEMS vibration sensor based on single-crystal lithium niobate film manufactured using standard microelectromechanical system (MEMS) technology, designed and optimized the structure of the four-cantilever MEMS vibration sensor, and improved the performance of the device. He et al. introduced a three-axis accelerometer using a single mass block. The sensitive structure consists of a detection mass block and eight cantilever beams. 12 piezoresistive structures are symmetrically placed on the cantilever beams, which can be used to detect three-dimensional acceleration and significantly reduce the cross-axis sensitivity. However, due to the limitations of multi-cantilever coupling and the small vibration sensitive area, the accuracy is relatively low and the range is limited. Moreover, the process of this type of device is complex and cannot be fully mass-produced by semiconductor planar technology, resulting in high cost. In addition, there is little research on high-temperature applications of existing monolithic integrated omnidirectional vibration sensors, which further limits the scope of application. Summary of the invention
[0004] The purpose of the present invention is to provide a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials and a method for manufacturing the same. The three-dimensional microtube structure can greatly reduce the chip footprint and device power consumption, thereby greatly improving the comprehensive performance of the omnidirectional vibration sensor to solve at least one of the technical problems existing in the above-mentioned background technology.
[0005] In order to achieve the above object, the present invention adopts the following technical solutions:
[0006] In one aspect, the present invention provides a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials, comprising:
[0007] Single crystal silicon substrate (1);
[0008] a sacrificial layer formed on the single crystal silicon substrate;
[0009] A stress layer (3) formed on the sacrificial layer;
[0010] A heterojunction is formed on the stress layer, the heterojunction comprising a gate electrode (4), a dielectric layer (5), a two-dimensional crystal piezoelectric material layer (6), a source electrode (7) respectively located on both sides of the upper and lower edges of the two-dimensional crystal piezoelectric material layer, a drain electrode (8) and a nano-protective layer (9) structure arranged in sequence; the stress layer enables the heterojunction to self-assemble into a semicircular three-dimensional structure; and a multi-layer (≥3) circular array is performed on the above structure to obtain a three-dimensional self-assembled omnidirectional piezoelectric vibration sensor array structure (10).
[0011] In a second aspect, the present invention provides a method for preparing a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material as described above, comprising the following steps:
[0012] preparing a single crystal silicon substrate (1);
[0013] forming a sacrificial layer on the single crystal silicon substrate (1);
[0014] forming a stress layer (3) on the sacrificial layer;
[0015] Preparing a gate electrode (4) on the stress layer (3);
[0016] forming a dielectric layer (5) on the stress layer (3) and the gate electrode (4);
[0017] forming a two-dimensional crystalline piezoelectric material layer (6) on the dielectric layer (5);
[0018] A source electrode (7) and a drain electrode (8) are prepared on the two-dimensional crystalline piezoelectric material layer (6), the source electrode (7) and the drain electrode (8) being located on both sides of the upper and lower edges of the two-dimensional crystalline piezoelectric material layer respectively;
[0019] forming a nano protective layer (9) on the source electrode (7) and the drain electrode (8);
[0020] The gate electrode, dielectric layer, two-dimensional crystal piezoelectric material layer, source electrode, drain electrode and nano-protective layer form a heterojunction;
[0021] etching the sacrificial layer;
[0022] The stress layer enables the gate electrode, the dielectric layer, the two-dimensional crystal piezoelectric material layer, the source electrode, the drain electrode and the nano-protective layer to self-assemble into a semicircular three-dimensional structure;
[0023] A multi-layer (≥3) circular array is performed on the above structure to obtain a three-dimensional self-assembled omnidirectional piezoelectric vibration sensor array structure (10).
[0024] Preferably, the multi-layer (≥3) self-assembled circular array of semicircular three-dimensional structures obtains a three-dimensional self-assembled omnidirectional piezoelectric vibration sensor array structure.
[0025] Preferably, the sacrificial layer is a metal layer that can be etched by an etching solution.
[0026] Preferably, the stress layer (3) is SU-8, silicon oxide or silicon nitride.
[0027] Preferably, the dielectric layer (5) is a tantalum pentoxide or boron nitride layer.
[0028] Preferably, the two-dimensional crystalline piezoelectric material layer (6) is a single layer or multiple layers of two-dimensional crystalline piezoelectric material.
[0029] Preferably, the gate electrode (4), the source electrode (7) and the drain electrode (8) are chromium-gold, titanium-gold, palladium-gold or titanium-platinum two-dimensional crystal electrodes.
[0030] Preferably, an adhesion layer is provided on the stress layer (3) and the two-dimensional crystal piezoelectric material layer (6), and the adhesion layer is made of chromium, titanium or palladium adhesion layer material with a thickness of 5nm-30nm; and a conductive layer is provided on the adhesion layer, and the conductive layer material is gold or platinum with a thickness of 10nm-100nm.
[0031] Preferably, the nano protective layer (9) is an aluminum nitride or silicon nitride layer.
[0032] Beneficial effects of the present invention:
[0033] (1) The present invention has the ability to detect omnidirectional vibration signals and can be integrated on a single chip. The device is a petal-like structure, and the device as a whole is composed of an array of self-assembled semicircular three-dimensional structure devices with multiple layers (≥3) inside and outside with different diameters and curvatures. Each of the semicircular three-dimensional structures is made by driving a planar two-dimensional device using a double stress layer of compression and tension. Due to its unique self-assembled curling structure, the proposed semicircular three-dimensional piezoelectric vibration sensor is sensitive to all vibrations perpendicular to the direction of the semicircular center axis (i.e., radial direction). The use of this special structure for circular array enables the device to have omnidirectional detection capabilities. At the same time, relying on a controllable planar preparation process, the monolithic integration of the entire omnidirectional sensor system can be achieved, which greatly reduces the structural complexity of the device system and reduces wiring, while also helping to reduce costs.
[0034] (2) The present invention has high-sensitivity detection capability and is resistant to high temperatures. The stress in the self-assembled structure can break the intrinsic symmetry of the two-dimensional crystal piezoelectric material, further improve the piezoelectric properties, and obtain a higher piezoelectric coefficient (graphene can reach 14.8×10 3 pC / N), thus laying the foundation for achieving ultra-high sensitivity. When vibration occurs, the radius of curvature of the semicircular three-dimensional structure changes, and the two-dimensional crystal piezoelectric material in the three-dimensional structure generates a piezoelectric potential. By detecting the piezoelectric current between the source and drain electrodes, high-sensitivity detection of vibration can be achieved. When the vibration intensity is small, the three-dimensional piezoelectric current can be amplified and regulated by applying source-drain bias and / or gate voltage, thereby improving sensitivity. In addition, because the entire device is protected by a nano protective layer independently developed by the project team, it can withstand extremely high temperatures, so it can achieve vibration detection in a wide temperature range while ensuring device reliability and stability.
[0035] (3) The present invention has a large-scale detection capability and can achieve self-power supply. The device arrays with different curvatures in the self-assembled petal-shaped structure device array have different sensitivities to different vibration frequencies, so this structure enables the device to have a large-scale detection capability. At the same time, due to the piezoelectric effect, when the vibration intensity is large, self-powered detection can be achieved without applying source-drain bias and gate voltage. Capacitors can even be used to collect the piezoelectric current generated by the three-dimensional device during the vibration process to power the signal processing circuit and the wireless transceiver module, thereby realizing a self-powered wireless vibration detection system. In this way, the size, volume and complexity of the internal structure of the device can be greatly reduced.
[0036] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.
[0038] Figure 1 This is a schematic diagram of the structure of a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials according to an embodiment of the present invention.
[0039] Figure 2 Flowchart of a method for manufacturing a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials according to an embodiment of the present invention.
[0040] Among them: 1-single crystal silicon substrate; 3-stress layer; 4-gate electrode; 5-dielectric layer; 6-two-dimensional crystal piezoelectric material layer; 7-source electrode; 8-drain electrode; 9-nanometer protective layer; 10-piezoelectric vibration sensor array structure. DETAILED DESCRIPTION
[0041] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.
[0042] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.
[0043] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with that in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.
[0044] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or groups thereof.
[0045] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.
[0046] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.
[0047] In the description of this specification, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present technology and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present technology.
[0048] Unless otherwise clearly specified or limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected or set, or detachably connected or set, or integrally connected or set. For ordinary technicians in this field, the specific meanings of the above terms in this technology can be understood according to specific circumstances.
[0049] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.
[0050] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.
[0051] Example
[0052] In this embodiment, a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials is proposed. The sensor array is a petal-like structure, and the device as a whole is composed of multiple layers (≥3) of self-assembled semicircular three-dimensional device arrays with different diameters and curvatures inside and outside. The device array circles with different curvatures have different sensitivities to different vibration frequencies. This structure enables the device to have a large range and high sensitivity detection capability. Due to its unique self-assembled curled structure, the entire two-dimensional crystal piezoelectric material surface of the device can directly and in real time sense vibrations over a large area. This special structure can achieve the purpose of omnidirectional detection. At the same time, relying on a controllable planar preparation process, the realization of monolithic integrated omnidirectional high-temperature vibration sensing based on two-dimensional crystal piezoelectric materials becomes possible.
[0053] The high temperature vibration sensor array based on two-dimensional crystal piezoelectric material in this embodiment is a petal-shaped self-assembled omnidirectional high temperature vibration sensor array device in which the stress layer-driven heterojunction self-assembled structure array is formed.
[0054] like Figure 1 As shown, the self-assembled omnidirectional high-temperature vibration sensor array specifically includes: a single crystal silicon substrate 1, a sacrificial layer on the single crystal silicon substrate 1, a stress layer 3 covering the sacrificial layer, a gate electrode 4 made on the stress layer 3, a dielectric layer 5 on the stress layer 3 and the gate electrode 4, a two-dimensional crystal piezoelectric material layer 6 covered on the dielectric layer 5, a source electrode 7 and a drain electrode 8 are made on the two-dimensional crystal piezoelectric material layer 6, respectively located on both sides of the upper and lower edges of the two-dimensional crystal piezoelectric material layer, and a nano-protective layer 9 is covered on the source electrode 7 and the drain electrode 8. The gate electrode 4, the dielectric layer 5, the two-dimensional crystal piezoelectric material layer 6, the source electrode 7, the drain electrode 8 and the nano-protective layer 9 form a planar two-dimensional dielectric layer / two-dimensional crystal piezoelectric material / nano-protective layer heterojunction with gate, source and drain electrodes, and the stress layer 3 enables the planar two-dimensional dielectric layer / two-dimensional crystal piezoelectric material / nano-protective layer heterojunction with gate, source and drain electrodes to self-assemble into a semicircular three-dimensional structure after the sacrificial layer is etched. A multi-layer (≥3) circular array is performed on the above structure to obtain a three-dimensional self-assembled omnidirectional piezoelectric vibration sensor array structure 10.
[0055] It should be noted that the sacrificial layer is not shown in the figure because it has been etched.
[0056] In this embodiment, the gate electrode 4, the dielectric layer 5, the two-dimensional crystalline piezoelectric material layer 6, the source electrode 7, the drain electrode 8 and the nano-protective layer 9 constitute a planar two-dimensional heterojunction with gate, source and drain electrodes. The stress layer 3 enables the heterojunction to self-assemble into a semicircular three-dimensional structure after the sacrificial layer is etched.
[0057] In this embodiment, the sacrificial layer is a metal layer that can be etched by the etching solution, such as aluminum (Al), copper (Cu) and other metal materials. The etching solution will not affect the stress layer 3, the gate electrode 4, the dielectric layer 5, the two-dimensional crystal piezoelectric material layer 6, the source electrode 7, the drain electrode 8 and the nano protective layer 9. The manufacturing method is to place the single crystal silicon wafer 1 in a mixture of hydrogen peroxide and sulfuric acid in a ratio of 1:4, boil the silicon wafer at 85 degrees Celsius for 15 minutes, remove surface stains, rinse with deionized water, and dry; use photolithography technology, thin film deposition technology and stripping technology to make a sacrificial layer on the single crystal silicon wafer 1, and the thickness of the sacrificial layer is 10 to 200nm.
[0058] In this embodiment, the stress layer 3 is SU-8, silicon oxide (SiO x ) or silicon nitride (SiN x ) and other stress layer materials with high light transmittance. The preparation method is: depositing SiN by plasma enhanced chemical vapor deposition technology xlayer; using photolithography technology to form a photoresist mask layer in the stress layer 3 region; using reactive ion etching to remove the SiN without photoresist coverage x layer; and cleaning the photoresist with acetone, leaving the stress layer 3 pattern, thereby completing the preparation of the stress layer 3.
[0059] In this embodiment, the dielectric layer 5 is a tantalum pentoxide (Ta2O5) or boron nitride (BN) dielectric layer. It should be noted that the dielectric layer 5 in the present invention can be other conventional dielectric layers with equivalent properties, and is not limited to tantalum pentoxide (Ta2O5) or boron nitride (BN) in the present invention. The preparation method is: depositing the dielectric layer 5 with a thickness of 5-50nm by thin film deposition techniques such as plasma enhanced chemical vapor deposition technology or atomic layer deposition; forming a photoresist mask layer in the dielectric layer 5 region by photolithography technology; removing the dielectric layer 5 without photoresist coverage by reactive ion etching; cleaning the photoresist with acetone, leaving the dielectric layer 5 pattern, and completing the preparation of the dielectric layer 5.
[0060] In this embodiment, the two-dimensional crystalline piezoelectric material layer 6 is a two-dimensional crystalline piezoelectric material such as a single layer or multiple layers of graphene or reduced graphene oxide.
[0061] In this embodiment, the gate electrode 4, the source electrode 7 and the drain electrode 8 are two-dimensional crystal electrodes of chromium / gold (Cr / Au), titanium / gold (Ti / Au), palladium / gold (Pd / Au) or titanium / platinum (Ti / Pt). The thickness of the chromium (Cr), titanium (Ti) or palladium (Pd) adhesion layer material is 5nm-30nm, and the thickness of the gold (Au) or platinum (Pt) conductive layer is 10nm-100nm.
[0062] Among them, the preparation method of the gate electrode is as follows: forming a photoresist opening in the gate electrode 4 area by photolithography; depositing metal material by thermal evaporation, electron beam evaporation or magnetron sputtering technology; using a stripping process to remove the photoresist and the metal material attached to the photoresist, leaving the electrode pattern, and completing the preparation of the gate electrode 4.
[0063] The preparation method of the source electrode and the drain electrode is as follows: forming photoresist openings in the source electrode 7 and the drain electrode 8 regions by photolithography; depositing metal materials by thermal evaporation or electron beam evaporation technology; using a stripping process to remove the photoresist and the metal material attached to the photoresist, leaving the electrode pattern, and completing the preparation of the source electrode 7 and the drain electrode 8.
[0064] In this embodiment, the nano-protective layer 9 is a nano-protective material with high temperature protection capability such as aluminum nitride (AIN) or silicon nitride (Si3N4). The preparation method thereof is as follows: depositing the nano-protective layer by plasma enhanced chemical vapor deposition technology; forming a photoresist mask layer in the nano-protective layer 9 region by photolithography technology; removing the nano-protective layer without photoresist coverage by reactive ion etching; cleaning the photoresist with acetone to leave the nano-protective layer 9 pattern, and completing the preparation of the nano-protective layer 9.
[0065] When etching the sacrificial layer, the chip is immersed in the etching solution of the sacrificial layer; the stress layer 3 drives the gate electrode 4, the dielectric layer 5, the two-dimensional crystal piezoelectric material layer 6, the source electrode 7, the drain electrode 8 and the nano protective layer 9 to self-assemble into a self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials.
[0066] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution disclosed in the present invention should be included in the scope of protection of the present invention.
Claims
1. A self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric materials, characterized in that: include: A single crystal silicon substrate (1); forming a sacrificial layer on the single crystal silicon substrate (1); A stress layer (3) formed on the single crystal silicon substrate (1); the stress layer (3) covers the sacrificial layer; A gate electrode (4) is fabricated on the stress layer (3), a dielectric layer (5) is provided on the stress layer (3) and the gate electrode (4), a two-dimensional crystal piezoelectric material layer (6) is covered on the dielectric layer (5), a source electrode (7) and a drain electrode (8) are fabricated on the two-dimensional crystal piezoelectric material layer (6) at both sides of the upper and lower edges of the two-dimensional crystal piezoelectric material layer, and a nano-protective layer (9) is covered on the source electrode (7) and the drain electrode (8); wherein the gate electrode (4), the dielectric layer (5), the two-dimensional crystal piezoelectric material layer (6), the source electrode (7), the drain electrode (8) and the nano-protective layer (9) form a planar two-dimensional dielectric layer / two-dimensional crystal piezoelectric material / nano-protective layer heterojunction with gate, source and drain electrodes, and the stress layer (3) enables the planar two-dimensional dielectric layer / two-dimensional crystal piezoelectric material / nano-protective layer heterojunction with gate, source and drain electrodes to self-assemble into a semicircular three-dimensional structure after the sacrificial layer is etched; The semicircular three-dimensional structure is arrayed in three or more layers to obtain a three-dimensional self-assembled omnidirectional piezoelectric vibration sensor array structure (10).
2. The self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material according to claim 1, characterized in that: The sacrificial layer is a metal layer that can be etched by an etching solution.
3. The self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material according to claim 1, characterized in that: The stress layer (3) is SU-8, silicon oxide or silicon nitride layer.
4. The self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material according to claim 1, characterized in that: The dielectric layer (5) is a tantalum pentoxide or boron nitride layer.
5. The self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material according to claim 1, characterized in that: The two-dimensional crystalline piezoelectric material layer (6) is a single layer or multiple layers of two-dimensional crystalline piezoelectric material.
6. The self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material according to claim 1, characterized in that: The gate electrode (4), source electrode (7) and drain electrode (8) are chromium-gold, titanium-gold, palladium-gold or titanium-platinum two-dimensional crystal electrodes.
7. The self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material according to claim 1, characterized in that: An adhesion layer is provided on the stress layer and the two-dimensional crystal piezoelectric material layer. The adhesion layer is made of chromium, titanium or palladium adhesion layer material with a thickness of 5nm-30nm; a conductive layer is provided on the adhesion layer. The conductive layer material is gold or platinum with a thickness of 10nm-100nm.
8. The self-assembled omnidirectional high-temperature vibration sensor array based on two-dimensional crystal piezoelectric material according to claim 1, characterized in that: The nano protective layer (9) is an aluminum nitride or silicon nitride layer.