Horizontal light-emitting diode and method for manufacturing the same

Abstract

The present invention provides a horizontal short-wavelength infrared light-emitting diode with an emission wavelength range of 1100 to 2000 nanometers (nm) and a method for manufacturing the same. [Solution] The horizontal light-emitting diode includes a permanent substrate, an epitaxial composite layer, a first conductivity type electrode, a second conductivity type electrode, and an ohmic contact layer. The epitaxial composite layer has a light-emitting layer with an emission wavelength of 1100 to 2000 nanometers (nm). The light-emitting layer is placed on the permanent substrate. The first conductivity type electrode is placed on the permanent substrate and electrically connected to the epitaxial composite layer. The second conductivity type electrode is placed on the epitaxial composite layer, electrically connected to the epitaxial composite layer, and located on the same side as the first conductivity type electrode and the permanent substrate. The ohmic contact layer forms an ohmic contact with the first conductivity type electrode. The ohmic contact layer is sandwiched between the epitaxial composite layer and the first conductivity type electrode. The thickness of the ohmic contact layer is 1 micrometer or less.

Description

Technical Field

[0001] The present invention relates to a horizontal light-emitting diode and a manufacturing method thereof, and particularly to a horizontal short-wavelength infrared light-emitting diode and a manufacturing method thereof.

Background Art

[0002] A light-emitting diode (LED) has advantages such as high brightness, small size, low power consumption, and long lifespan, and is widely applied to lighting and display products. FIG. 1 shows a conventional horizontal red light and infrared light-emitting diode with a wavelength range of 590 to 1100 nanometers (nm). This horizontal light-emitting diode includes a sapphire substrate 10, a substrate bonding layer 11, a P-type gallium phosphide (GaP) epitaxial layer 12, a light-emitting layer 13, an N-type gallium phosphide epitaxial layer 14, an N-type electrode 15, and a P-type electrode 16.

[0003] Since both the P-type gallium phosphide epitaxial layer 12 and the N-type gallium phosphide epitaxial layer 14 are compound semiconductor layers with a high doping concentration, these two types of epitaxial layers respectively form good ohmic contacts with the N-type and P-type electrodes. On the other hand, in a conventional red light and infrared horizontal light-emitting diode element, the thickness of the P-type gallium phosphide epitaxial layer 12 is 1 to 10 micrometers (μm). Therefore, when performing the photolithography etching process of the P-type electrode 16 in the manufacturing process, the P-type gallium phosphide epitaxial layer 12 has a sufficient thickness, and the etching depth in the P-type gallium phosphide epitaxial layer 12 can be effectively controlled to ensure that the subsequent metal evaporation process of the P-type electrode 16 proceeds smoothly.

[0004] However, the epitaxial structure of the above-described horizontal light-emitting diode (LED) cannot be applied to horizontal short-wavelength infrared (SWIR) LEDs with an emission wavelength range of 1100-2000 nanometers (nm). Therefore, there is an urgent need in the industry to develop innovative horizontal LED structures and manufacturing methods to meet the technical needs of short-wavelength infrared horizontal LEDs. [Overview of the project]

[0005] The main objective of the present invention is to provide a high-brightness horizontal light-emitting diode and a method for manufacturing the same, applicable to short-wavelength infrared (SWIR) light-emitting diodes with a wavelength range of 1100 to 2000 nanometers (nm). The present invention discloses a light-emitting diode structure that improves the brightness of the light-emitting diode and expands the application range of back-end products in the industry by precisely controlling the etching stop depth of the P-type ohmic contact layer and simultaneously reducing the absorption of light generated from the light-emitting layer.

[0006] To achieve the above objective, the present invention provides a horizontal light-emitting diode. The light-emitting diode includes a permanent substrate, an epitaxial composite layer, a first conductivity type electrode, a second conductivity type electrode, and an ohmic contact layer. The epitaxial composite layer has a light-emitting layer with an emission wavelength of 1100 to 2000 nanometers (nm). The light-emitting layer is mounted on the permanent substrate. The first conductivity type electrode is mounted on the permanent substrate and electrically connected to the epitaxial composite layer. The second conductivity type electrode is mounted on the epitaxial composite layer, electrically connected to the epitaxial composite layer, and located on the same side as the first conductivity type electrode and the permanent substrate. The ohmic contact layer forms an ohmic contact with the first conductivity type electrode. The ohmic contact layer is sandwiched between the epitaxial composite layer and the first conductivity type electrode. The thickness of the ohmic contact layer is 1 micrometer or less.

[0007] In an embodiment of the horizontal light-emitting diode of the present invention, the ohmic contact layer is an indium gallium arsenide (InGaAsP) layer.

[0008] In an embodiment of the horizontal light-emitting diode of the present invention, the first conductivity electrode has a metal laminate, and the thickness of the metal laminate is less than 1 micrometer.

[0009] In an embodiment of the horizontal light-emitting diode of the present invention, the material for the metal layer is one or a combination selected from the group consisting of titanium (Ti), platinum (Pt), gold (Au), palladium (Pd), germanium (Ge), and zinc-gold (ZnAu).

[0010] In an embodiment of the horizontal light-emitting diode of the present invention, the epitaxial composite layer further includes a first compound semiconductor layer and a second compound semiconductor layer, wherein the first compound semiconductor layer and the second compound semiconductor layer sandwich a light-emitting layer, and the first compound semiconductor layer is placed between the light-emitting layer and the ohmic contact layer.

[0011] In an embodiment of the horizontal light-emitting diode of the present invention, the first compound semiconductor layer is a first-conductivity indium phosphide (InP) layer, and the second compound semiconductor layer is a second-conductivity indium phosphide (InP) layer.

[0012] In an embodiment of the horizontal light-emitting diode of the present invention, the permanent substrate is a silicon substrate, an aluminum nitride substrate, or a sapphire substrate.

[0013] In an embodiment of the horizontal light-emitting diode of the present invention, the horizontal light-emitting diode further includes a substrate bonding layer sandwiched between a permanent substrate and an epitaxial composite layer, wherein the substrate bonding layer is an aluminum oxide (Al2O3) layer or a silicon oxide (SiO2) layer.

[0014] To achieve the above objective, the present invention provides a method for manufacturing a horizontal light-emitting diode, comprising the following steps: An epitaxial composite layer is formed on an epitaxial growth substrate. The epitaxial composite layer has a light-emitting layer with an emission wavelength of 1100 to 2000 nanometers (nm). An ohmic contact layer is formed on the epitaxial composite layer. The thickness of the ohmic contact layer is 1 micrometer or less. A metal laminate is formed on the ohmic contact layer to form an ohmic contact with the ohmic contact layer. A substrate bonding layer is formed covering the epitaxial composite layer and the metal laminate. After bonding the permanent substrate to the substrate bonding layer, the epitaxial growth substrate is removed. A portion of the ohmic contact layer is etched, and etching is stopped at the metal laminate, thereby forming an electrode trench.

[0015] In an embodiment of the method for manufacturing a horizontal light-emitting diode of the present invention, the step of forming an ohmic contact layer is to form an indium gallium arsenide (InGaAsP) layer.

[0016] In an embodiment of the method for manufacturing a horizontal light-emitting diode of the present invention, the material for the metal stack is one or a combination selected from the group consisting of titanium (Ti), platinum (Pt), gold (Au), palladium (Pd), germanium (Ge), and zinc-gold (ZnAu).

[0017] In an embodiment of the method for manufacturing a horizontal light-emitting diode of the present invention, the step of forming an epitaxial composite layer includes forming a first compound semiconductor layer and a second compound semiconductor layer, wherein the first compound semiconductor layer and the second compound semiconductor layer sandwich a light-emitting layer, and the first compound semiconductor layer is placed between the light-emitting layer and the ohmic contact layer.

[0018] In an embodiment of the method for manufacturing a horizontal light-emitting diode of the present invention, the step of forming a first compound semiconductor layer and a second compound semiconductor layer is to form a first conductivity type indium phosphide (InP) layer and a second conductivity type indium phosphide (InP) layer.

[0019] In an embodiment of the method for manufacturing a horizontal light-emitting diode of the present invention, the step of preparing a permanent substrate is to prepare a silicon substrate, an aluminum nitride substrate, or a sapphire substrate.

[0020] In an embodiment of the method for manufacturing a horizontal light-emitting diode of the present invention, the step of forming a substrate bonding layer is to form an aluminum oxide (Al2O3) layer or a silicon oxide (SiO2) layer.

[0021] In an embodiment of the method for manufacturing a horizontal light-emitting diode of the present invention, it further includes a step of performing metal evaporation, thereby forming a first conductive type electrode in the electrode trench.

[0022] Those skilled in the art can understand other objects of the present invention, as well as the technical means and embodiments of the present invention, by referring to the drawings and the embodiments described below.

Brief Description of the Drawings

[0023] [Figure 1] Schematic diagram of a conventional horizontal red light and infrared light-emitting diode [Figure 2A] Schematic diagram of the manufacturing process of a horizontal light-emitting diode in an embodiment of the present invention [Figure 2B] Schematic diagram of the manufacturing process of a horizontal light-emitting diode in an embodiment of the present invention [Figure 2C] Schematic diagram of the manufacturing process of a horizontal light-emitting diode in an embodiment of the present invention [Figure 2D] Schematic diagram of the manufacturing process of a horizontal light-emitting diode in an embodiment of the present invention [Figure 2E] Schematic diagram of the manufacturing process of a horizontal light-emitting diode in an embodiment of the present invention [Figure 2F] Schematic diagram of the manufacturing process of a horizontal light-emitting diode in an embodiment of the present invention [Figure 2G] Schematic diagram of the manufacturing process of a horizontal light-emitting diode in an embodiment of the present invention [Figure 3] Schematic diagram of the structure of a horizontal light-emitting diode in an embodiment of the present invention [Figure 4] Flowchart of the manufacturing process for a horizontal light-emitting diode in an embodiment of the present invention [Modes for carrying out the invention]

[0024] The present invention will be described below through examples. These examples illustrate the embodiments of the present invention and are not intended to limit the invention to any particular environment, application, or specific configuration described therein. Therefore, while the examples illustrate the present invention, they do not limit it. Components not directly related to the present invention are omitted and not shown in the embodiments and drawings. The dimensional relationships of the components in the drawings are for ease of understanding and do not limit the actual dimensions.

[0025] This invention discloses a horizontal light-emitting diode and a method for manufacturing the same. Figure 2A shows that a buffer layer 101 and an N-type ohmic contact layer 102 are epitaxially grown on an epitaxial growth substrate 100 by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) technology. Specifically, the epitaxial growth substrate 100 is an indium phosphide (InP) substrate, but is not limited thereto. The buffer layer 101 is an N-type indium phosphide (InP) epitaxial layer, which adjusts the lattice matching between the epitaxial growth substrate and the epitaxial composite layer during the growth of the subsequent epitaxial composite layer, reducing stress caused by lattice mismatch in the subsequent epitaxial process, and thereby improving the thin film quality of the epitaxial layer.

[0026] Specifically, the N-type ohmic contact layer 102 is an N-type indium gallium arsenide (InGaAs) epitaxial layer. Its lattice constant lies between that of indium phosphide (InP) and the multiple quantum well structure. Therefore, the N-type indium gallium arsenide epitaxial layer also functions as a buffer layer, further adjusting the lattice matching of the subsequent epitaxial layer. Furthermore, the N-type indium gallium arsenide epitaxial layer optimizes carrier injection efficiency. By adjusting its energy band gap with the gallium-to-indium ratio, it controls electron and hole transport, ensuring that more carriers are injected into the light-emitting layer and thus increasing luminescence efficiency. In particular, the N-type ohmic contact layer 102 functions as an interface for the device and the N-type electrode to form an ohmic contact. The N-type indium gallium arsenide epitaxial layer employs sulfur (S), selenium (Se), or silicon (Si) as a dopant, with a doping concentration of 10 18 ~10 20 cm -3 This concentration range reduces the Schottky barrier and enables low-resistance ohmic contact.

[0027] Next, the growth of an epitaxial composite layer continues on the N-type ohmic contact layer 102. This composite layer includes a first compound semiconductor layer 105, an emissive layer 104, and a second compound semiconductor layer 103. The emissive layer 104 is a multiple quantum well (MQW) structure made of indium gallium arsenide (InGaAsP) quaternary compound semiconductor and is located between the first compound semiconductor layer 105 and the second compound semiconductor layer 103. In this embodiment, the emission wavelength of the multiple quantum well is 1100 to 2000 nanometers (nm). Specifically, the first compound semiconductor layer 105 is a first conductivity type (P-type) indium phosphide (InP) epitaxial layer, and the second compound semiconductor layer 103 is a second conductivity type (N-type) indium phosphide (InP) epitaxial layer. Note that the materials in the above embodiment are merely examples, and the present invention is not limited to these materials. In practical applications, the material and its composition can be adjusted according to the emission wavelength. For example, the epitaxial layer may be made of aluminum gallium arsenide (AlGaAs), indium gallium arsenide (InGaAs), or the like.

[0028] As shown in Figure 2A, epitaxial growth of a compound semiconductor layer is continued on the epitaxial composite layer. In a specific embodiment, this compound semiconductor layer is a P-type ohmic contact layer 106, for example, a zinc-doped indium gallium arsenide (Zn-doped InGaAsP) epitaxial layer, with a thickness of 1 micrometer or less, preferably 500 to 5000 angstroms (Å), but not limited thereto. The doping concentration of this zinc-doped indium gallium arsenide (Zn-doped InGaAsP) epitaxial layer is 10 18 ~10 20 cm -3This concentration range reduces contact resistance and ensures the formation of good ohmic contact at the interface with the subsequent metal layer. Furthermore, in short-wavelength infrared light-emitting diodes with a wavelength range of 1100 to 2000 nanometers (nm), it is necessary to add a highly doped epitaxial layer to the epitaxial structure in order to form good N-type and P-type ohmic contact with the N-type and P-type electrodes. For example, in this embodiment, an N-type ohmic contact layer 102 (indium gallium arsenide (InGaAs) epitaxial layer) and a P-type ohmic contact layer 106 (indium gallium arsenide phosphide (InGaAsP) epitaxial layer) are used. However, these highly doped epitaxial layers are narrow bandgap materials and absorb some of the light, thereby reducing the light emission output of the light-emitting diode. To overcome the above problem, the present invention significantly reduces the thickness of the N-type and P-type ohmic contact layers in a SWIR light-emitting diode to 1 micrometer or less.

[0029] Next, a metal layer 107 is deposited on the P-type ohmic contact layer 106 by methods such as vapor deposition or sputtering. This metal layer 107 is one or a combination selected from the group consisting of titanium (Ti), platinum (Pt), gold (Au), palladium (Pd), germanium (Ge), and zinc-gold (ZnAu), and its thickness is less than 1 micrometer, preferably 2000 to 5000 angstroms (Å). The purpose of placing the metal layer 107 on the P-type ohmic contact layer 106 is to function as an etching stop layer in subsequent processes, thereby precisely controlling the etching depth of the P-type electrode in the horizontal light-emitting diode structure. Further details will be described later.

[0030] As shown in Figure 2B, a patterning process is performed on the metal stack 107 and the P-type ohmic contact layer 106 to expose a portion of the upper surface of the first compound semiconductor layer 105. Next, a roughening treatment is performed on the exposed upper surface of the first compound semiconductor layer 105. That is, the P-type indium phosphide (InP) epitaxial layer is roughened. After that, a deposition process for the substrate bonding layer 108 is carried out. For example, an aluminum oxide (Al2O3) layer or a silicon oxide (SiO2) layer is deposited on the roughened upper surface of the first compound semiconductor layer 105 to form the substrate bonding layer 108. As shown in Figure 2C, a wafer bonding process is then performed to bond the epitaxial growth substrate 100 to the permanent substrate 109. The permanent substrate 109 is a silicon substrate, an aluminum nitride substrate, or a sapphire substrate, but is not limited to these materials. Also, the upper surface of the substrate bonding layer 108 has appropriate flatness. To ensure that the epitaxially grown substrate is smoothly bonded to the permanent substrate during the wafer bonding process, it is necessary to appropriately control the total thickness of the metal lamination 107 and the P-type ohmic contact layer 106, so as not to let it become too thick, which would adversely affect the bonding strength between wafers. The technical feature of the present invention is that, despite the limitations on the total thickness of the metal lamination 107 and the P-type ohmic contact layer 106, the metal lamination 107 can be used as an etching stop layer for the ohmic contact layer 106, thereby solving the challenge of controlling the etching depth.

[0031] As shown in Figure 2D, the epitaxial growth substrate 100 and buffer layer 101 (i.e., N-type indium phosphide epitaxial layer) are then removed from the opposite side of the permanent substrate 109, thereby exposing the N-type ohmic contact layer 102. The wafer is then inverted, positioning the permanent substrate 109 at the bottom of the horizontal light-emitting diode structure. Next, as shown in Figure 2E, a mesa etching process is performed to etch the N-type ohmic contact layer 102 and a portion of the epitaxial composite layer (including the second compound semiconductor layer 103, the light-emitting layer 104, and the first compound semiconductor layer 105), exposing the flat surface of the first compound semiconductor layer 105, which is then used for the subsequent placement of the P-type electrode.

[0032] As shown in Figure 2F, a photolithography and etching process is performed on the first conductive electrode to selectively etch a portion of the first compound semiconductor layer 105 and the P-type ohmic contact layer 106, and the etching is stopped by the metal laminate 107. In this process, the etching depth is precisely controlled to form a patterned electrode trench 110, which is used for subsequent electrode formation. If the metal laminate 107, which functions as an etching stop layer, is not installed in the light-emitting diode structure during the manufacturing process, the electrode etching process becomes difficult to control due to insufficient thickness of the P-type ohmic contact layer 106, and the subsequently formed electrode cannot form an ohmic contact.

[0033] As shown in Figure 2G, a metal deposition process is then performed to form a first conductivity type electrode 111 in the electrode trench 110 and electrically connect it to the metal laminate 107. The metal laminate 107 becomes part of the first conductivity type electrode 111. The first conductivity type electrode 111 is made of the same material as the metal laminate 107. Meanwhile, a second conductivity type electrode 112 is formed on the N-type ohmic contact layer 102, which electrically connects to the epitaxial composite layer. The second conductivity type electrode 112 is made of materials such as aluminum and gold-tin alloy, but is not limited to these. Figure 3 is a cross-sectional view of a horizontal SWIR light-emitting diode in an embodiment of the present invention. The first conductivity type electrode 111 and the second conductivity type electrode 112 are installed on the same side of the permanent substrate. A feature of the horizontal SWIR light-emitting diode of the present invention is that a metal laminate is installed below the P-type ohmic contact layer as an etching stop layer. This design solves the technical problems in light-emitting diodes in the SWIR wavelength range. The etching depth can be precisely controlled while controlling the thickness of the ohmic contact layer within a reasonable range.

[0034] Figure 4 is a manufacturing flowchart of the horizontal light-emitting diode of the present invention. First, in step S01, an epitaxial composite layer is formed on an epitaxial growth substrate. In step S02, an ohmic contact layer is formed on the epitaxial composite layer. The thickness of the ohmic contact layer is 1 micrometer or less. Next, in step S03, a metal laminate is formed on the ohmic contact layer. The metal laminate forms an ohmic contact with the ohmic contact layer. In step S04, a substrate bonding layer is formed to cover the epitaxial composite layer and the metal laminate. In step S05, the permanent substrate is bonded to the substrate bonding layer, and then the epitaxial growth substrate is removed. Finally, in step S06, a portion of the ohmic contact layer is etched, and the etching is stopped by the metal laminate. A detailed explanation of each element in the above manufacturing process has been given above and will not be repeated here.

[0035] The above-described embodiments illustrate embodiments of the present invention and describe the characteristic configuration of the present invention. The present invention is not limited to the above embodiments. Modifications or equivalent arrangements that can be easily made by those skilled in the art are also within the scope of the present invention. The scope of protection of the rights of the present invention shall be based on the claims. [Explanation of symbols]

[0036] 10 Sapphire substrate 11. Substrate bonding layer 12 P-type gallium phosphide epitaxial layer 13. Emitting layer 14N-type gallium phosphide epitaxial layer 15 N-type electrode 16 P-type electrode 100 Epitaxial Growth Substrates 101 Buffer Layer 102 N-type ohmic contact layer 103 Second compound semiconductor layer 104 Emitting layer 105 First compound semiconductor layer 106 P-type ohmic contact layer 107 Metal Lamination 108 Substrate bonding layer 109 Permanent Circuit Board 110 Electrode Trench 111 1st conductivity type electrode 112 Second conductivity type electrode

Claims

1. A horizontal light-emitting diode, Permanent circuit board and An epitaxial composite layer having an emissive layer installed on the permanent substrate and having an emission wavelength of 1100 to 2000 nanometers (nm), A first conductive electrode is placed on the permanent substrate and electrically connected to the epitaxial composite layer, A second conductive electrode is placed on the epitaxial composite layer, electrically connected to the epitaxial composite layer, and located on the same side as the first conductive electrode and the permanent substrate, The present invention includes an ohmic contact layer that forms an ohmic contact with the first conductivity electrode and is sandwiched between the epitaxial composite layer and the first conductivity electrode, A horizontal light-emitting diode in which the thickness of the ohmic contact layer is 1 micrometer or less.

2. The horizontal light-emitting diode according to claim 1, characterized in that the ohmic contact layer is an indium gallium arsenide (InGaAsP) layer.

3. The horizontal light-emitting diode according to claim 1, characterized in that the first conductive electrode has a metal laminate, and the thickness of the metal laminate is less than 1 micrometer.

4. The horizontal light-emitting diode according to claim 3, characterized in that the material of the metal layer is one or a combination selected from the group consisting of titanium (Ti), platinum (Pt), gold (Au), palladium (Pd), germanium (Ge), and zinc gold (ZnAu).

5. The epitaxial composite layer further includes a first compound semiconductor layer and a second compound semiconductor layer. The first compound semiconductor layer and the second compound semiconductor layer sandwich the light-emitting layer, The horizontal light-emitting diode according to claim 1, characterized in that the first compound semiconductor layer is installed between the light-emitting layer and the ohmic contact layer.

6. The first compound semiconductor layer is a first-conductivity indium phosphide (InP) layer. The horizontal light-emitting diode according to claim 5, characterized in that the second compound semiconductor layer is a second conductivity type indium phosphide (InP) layer.

7. The horizontal light-emitting diode according to claim 1, characterized in that the permanent substrate is a silicon substrate, an aluminum nitride substrate, or a sapphire substrate.

8. The present invention further includes a substrate bonding layer sandwiched between the permanent substrate and the epitaxial composite layer, The substrate bonding layer is aluminum oxide (Al ２ O ３ ) layer or silicon oxide (SiO ２ The horizontal light-emitting diode according to claim 1, characterized in that it is a layer.

9. A method for manufacturing a horizontal light-emitting diode, A step of forming an epitaxial composite layer having an emissive layer with an emission wavelength of 1100 to 2000 nanometers (nm) on an epitaxial growth substrate, The process involves forming an ohmic contact layer having a thickness of 1 micrometer or less on the epitaxial composite layer, A step of forming a metal laminate on the ohmic contact layer that forms an ohmic contact with the ohmic contact layer, A step of forming a substrate bonding layer that covers the epitaxial composite layer and the metal laminate, The process involves bonding the permanent substrate to the substrate bonding layer, followed by removing the epitaxial growth substrate. A method for manufacturing a horizontal light-emitting diode, comprising the steps of etching a portion of the ohmic contact layer and stopping the etching in the metal stack, thereby forming an electrode trench.

10. The manufacturing method according to claim 9, characterized in that the step of forming the ohmic contact layer is to form an indium gallium arsenide (InGaAsP) layer.

11. The manufacturing method according to claim 9, characterized in that the material of the metal laminate is one or a combination selected from the group consisting of titanium (Ti), platinum (Pt), gold (Au), palladium (Pd), germanium (Ge), and zinc gold (ZnAu).

12. The step of forming the epitaxial composite layer includes forming a first compound semiconductor layer and a second compound semiconductor layer. The first compound semiconductor layer and the second compound semiconductor layer sandwich the light-emitting layer, The manufacturing method according to claim 9, characterized in that the first compound semiconductor layer is placed between the light-emitting layer and the ohmic contact layer.

13. The manufacturing method according to claim 12, characterized in that the step of forming the first compound semiconductor layer and the second compound semiconductor layer is to form a first conductivity type indium phosphide (InP) layer and a second conductivity type indium phosphide (InP) layer.

14. The manufacturing method according to claim 9, characterized in that the step of preparing the permanent substrate is to prepare a silicon substrate, an aluminum nitride substrate, or a sapphire substrate.

15. The step of forming the substrate bonding layer is performed by aluminum oxide (Al ２ O ３ ) layer or silicon oxide (SiO ２ The manufacturing method according to claim 9, characterized in that it involves forming a layer.

16. The manufacturing method according to claim 9, characterized in that it includes a step of performing metal deposition, thereby forming a first conductive electrode in the electrode trench.

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