A homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode and its fabrication method

Abstract

This invention discloses a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode (LED), relating to the field of optoelectronic displays. The structure includes: a substrate, a semiconductor buffer epitaxial layer, a first metal contact layer and a second metal contact layer disposed on the semiconductor buffer epitaxial layer, an LED-PN junction unit disposed on the semiconductor buffer epitaxial layer, and a fourth contact layer disposed on the upper semiconductor layer of the LED-PN junction unit. An opening region for receiving light to be detected is provided between the first metal contact layer and the second metal contact layer. The first metal contact layer, the semiconductor buffer epitaxial layer corresponding to the opening region, and the second metal contact layer constitute an MSM structural unit. The first metal contact layer, the semiconductor buffer epitaxial layer corresponding to the opening region, the second metal contact layer, the first metal layer, and the LED-PN junction unit are sequentially connected to form an electrical path with an external drive based on the light received by the opening region. This invention eliminates the need for additional MSM epitaxy fabrication, simplifying the process flow.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic displays, and in particular to a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode, and its fabrication method. Background Technology

[0002] Gallium nitride (GaN) materials offer numerous advantages in LED and MSM devices due to their high electron mobility, wide bandgap, high electron saturation drift velocity, good thermal conductivity, and high photoelectric efficiency. GaN-based detectors exhibit excellent photoelectric detection performance in the ultraviolet (typically 200 nm to 365 nm) band. This characteristic enables GaN ultraviolet detectors to achieve highly sensitive detection of ultraviolet light.

[0003] Metal-semiconductor-metal (MSM) photodetectors are a common type of photodetector, typically used to detect light of wavelengths such as visible, infrared, or ultraviolet. They consist of a semiconductor layer sandwiched between two metal electrodes. When light strikes the semiconductor surface, electron-hole pairs are generated, creating a current between the metal electrodes. MSM photodetectors offer advantages such as fast response and high sensitivity, making them widely used in communications, sensing, and optical imaging. Light-emitting diodes (LEDs) are semiconductor devices that convert electrical energy into light energy. When current passes through an LED chip, electrons and holes within the semiconductor material recombine, releasing photons and producing visible light. LEDs offer advantages such as low power consumption, long lifespan, and fast switching, making them widely used in lighting, displays, and communications.

[0004] Currently, MSM devices and LED devices are generally implemented using discrete component circuits, which requires additional connection resistors between devices and results in relatively poor performance. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode (LED). The present invention uses a buffer layer as an epitaxial layer to fabricate the MSM on the basis of the LED epitaxial layer, eliminating the need for additional MSM epitaxy and simplifying the process flow. This integration can reduce the connection resistance between devices, improve device performance and stability, and simplify the manufacturing process.

[0006] To achieve the above objectives, in a first aspect of the present invention, a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode is provided, the homogeneous integrated structure comprising:

[0007] Substrate;

[0008] Semiconductor buffer epitaxial layer;

[0009] A first metal contact layer and a second metal contact layer are disposed on the semiconductor buffer epitaxial layer; wherein, an opening region for receiving the light to be detected is provided between the first metal contact layer and the second metal contact layer; the first metal contact layer, the semiconductor buffer epitaxial layer corresponding to the opening region, and the second metal contact layer constitute an MSM structural unit;

[0010] An LED-PN junction unit is disposed on the semiconductor buffer epitaxial layer; the LED-PN junction unit includes a lower semiconductor and an upper semiconductor; a third metal contact layer is disposed on the step surface of the lower semiconductor, and a first metal layer is electrically connected between the second metal contact layer and the third metal contact layer; a first insulating layer is disposed between the first metal layer and the lower semiconductor.

[0011] A fourth contact layer is disposed on the upper semiconductor of the LED-PN junction unit;

[0012] The first metal contact layer, the semiconductor buffer epitaxial layer corresponding to the opening region, the second metal contact layer, the first metal layer, and the LED-PN junction unit are sequentially connected to form an electrical path with the external drive based on the light received by the opening region.

[0013] In one specific embodiment, the lower semiconductor and the upper semiconductor are mutually exclusive N-type semiconductor layers or P-type semiconductor layers; wherein, when the upper semiconductor is a P-type semiconductor layer, the fourth contact layer is the anode of the homogeneous integrated structure, and the first metal contact layer is the cathode of the homogeneous integrated structure; when the upper semiconductor is an N-type semiconductor layer, the fourth contact layer is the cathode of the homogeneous integrated structure, and the first metal contact layer is the anode of the homogeneous integrated structure.

[0014] In one specific embodiment, the lower semiconductor and the upper semiconductor are mutually exclusive N-type gallium nitride layers or P-type gallium nitride layers, and the lower semiconductor and the upper semiconductor are further provided with quantum well layers.

[0015] In one specific embodiment, the main light-emitting direction of the LED-PN junction unit is towards the side where the fourth contact layer is located, and the first metal layer is also used to block the residual light of the LED-PN junction unit relative to the opening area. The technical problem to be solved in this solution is that when the LED-PN junction unit leaks light, it illuminates the MSM device area, causing changes in the measured light and resulting in errors. Therefore, the first metal layer is used for blocking.

[0016] In one specific embodiment, a second insulating layer and a second metal layer are further disposed on the step surface between the upper semiconductor and the lower semiconductor. The second metal layer is used to block the residual light of the LED-PN junction unit relative to the opening region. The technical problem to be solved in this solution is that when light leakage occurs in the LED-PN junction unit, it will illuminate the MSM device area, causing changes in the measured light and resulting in errors. Therefore, a second metal layer is used for blocking. Compared to blocking with a first metal layer, the blocking effect of the second metal layer is better.

[0017] In one specific embodiment, the second metal contact layer, the third metal contact layer, and the first metal layer are a single coating.

[0018] In addition, the fourth contact layer can also be a metal electrode, in which case it can be coated once with the second metal contact layer, the third metal contact layer and the first metal layer; it is worth mentioning that the transmittance can be improved by setting a narrower size or a hollow design.

[0019] In one specific embodiment, the first insulating layer is made of silicon nitride.

[0020] In a second aspect of the present invention, a method for fabricating a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode is provided, characterized by comprising the following steps:

[0021] S1: Deposit a semiconductor buffer epitaxial layer on the substrate surface, and deposit the lower semiconductor and upper semiconductor corresponding to the LED-PN junction unit on the semiconductor buffer epitaxial layer;

[0022] S2: Etching removes part of the upper semiconductor layer;

[0023] S3: Etching away part of the lower semiconductor layer to create an MSM surface on the semiconductor buffer epitaxial layer; wherein, the amount of etching of the lower semiconductor layer on the MSM surface side retains a step surface of the lower semiconductor layer relative to the upper semiconductor layer;

[0024] S4: Deposit and fabricate a first insulating layer, and etch the first insulating layer to retain it in the interface region between the MSM surface and the step surface of the underlying semiconductor.

[0025] S5: Using electron beam evaporation or sputtering technology and etching, a second metal contact layer, a third metal contact layer, a first metal layer, a fourth contact layer are formed on both sides of the first insulating layer, on the first insulating layer, on the semiconductor buffer epitaxial layer, and on the upper semiconductor layer, respectively; wherein, an opening area for receiving the light to be detected is provided between the first metal contact layer and the second metal contact layer.

[0026] In one specific embodiment, the lower semiconductor and the upper semiconductor are mutually exclusive N-type gallium nitride layers or P-type gallium nitride layers, and the lower semiconductor and the upper semiconductor are further provided with quantum well layers;

[0027] Step S1 includes: depositing an N-type gallium nitride layer, a quantum well layer, and a P-type gallium nitride layer on the semiconductor buffer epitaxial layer using a metal-organic chemical vapor deposition method, according to the specific semiconductor types of the lower semiconductor and the upper semiconductor.

[0028] In one specific embodiment, a second insulating layer and a second metal layer are further provided on the step surface between the upper semiconductor and the lower semiconductor. The second metal layer is used to block the residual light of the LED-PN junction unit relative to the opening region. The second insulating layer is generated in step S4, and the second metal layer is generated in step S5.

[0029] The beneficial effects of this invention are as follows: 1) This invention uses a buffer layer as an epitaxial layer to fabricate the MSM on the basis of the LED epitaxial layer, eliminating the need for additional MSM epitaxial fabrication and simplifying the process. This integration can reduce the connection resistance between devices, improve device performance and stability, and simplify the manufacturing process. 2) One aspect of this invention is to use a first metal layer to block the leakage light of the LED-PN junction unit, preventing LED light from illuminating the MSM device area and causing changes in the measured light, thus resulting in errors. 3) When the MSM device of this invention is powered on, it senses the intensity of external light, such as the intensity of ultraviolet radiation, and changes the electrical characteristics of the MSM device to increase the MSM device current, thereby driving the LED to illuminate and characterize the intensity of the measured light (ultraviolet radiation), realizing a homogeneous MSM-LED integrated structure. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode according to a specific embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the process flow for fabricating a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode according to a specific embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of LED light illumination with LED leakage blocking in a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode according to a specific embodiment of the present invention.

[0033] Figure 4This is a schematic diagram of an LED light leakage blocking structure of a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode, according to another specific embodiment of the present invention. Detailed Implementation

[0034] The embodiments of this patent are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.

[0035] In the description of this patent, it should be understood that the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this patent and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this patent.

[0036] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0037] like Figures 1-4 As shown, this embodiment of the invention provides a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode, the homogeneous integrated structure comprising:

[0038] Substrate 101;

[0039] Semiconductor buffer epitaxial layer 102;

[0040] A first metal contact layer 110 and a second metal contact layer 109 are disposed on the semiconductor buffer epitaxial layer 102; wherein, an opening region 114 for receiving the light to be detected is disposed between the first metal contact layer 110 and the second metal contact layer 109; the first metal contact layer 110, the semiconductor buffer epitaxial layer 102 corresponding to the opening region 114, and the second metal contact layer 109 constitute an MSM structure unit;

[0041] An LED-PN junction unit is disposed on the semiconductor buffer epitaxial layer 102; the LED-PN junction unit includes a lower semiconductor 103 and an upper semiconductor 105; a third metal contact layer 108 is disposed on the step surface of the lower semiconductor 103, and a first metal layer 111 is disposed between the second metal contact layer 109 and the third metal contact layer 108 for electrical connection; a first insulating layer 106 is disposed between the first metal layer 111 and the lower semiconductor 103;

[0042] The fourth contact layer 107 is disposed on the upper semiconductor 105 of the LED-PN junction unit;

[0043] The first metal contact layer 110, the semiconductor buffer epitaxial layer 102 corresponding to the opening region 114, the second metal contact layer 109, the first metal layer 111, and the LED-PN junction unit are sequentially connected to form an electrical path with the external drive according to the light received by the opening region 114.

[0044] Optionally, the lower semiconductor 103 and the upper semiconductor 105 are mutually exclusive N-type semiconductor layers or P-type semiconductor layers; wherein, when the upper semiconductor 105 is a P-type semiconductor layer, the fourth contact layer 107 is the anode of the homogeneous integrated structure, and the first metal contact layer 110 is the cathode of the homogeneous integrated structure; when the upper semiconductor 105 is an N-type semiconductor layer, the fourth contact layer 107 is the cathode of the homogeneous integrated structure, and the first metal contact layer 110 is the anode of the homogeneous integrated structure.

[0045] In fact, this application does not limit the PN junction form of LED; the main focus of this invention is the homogeneous integration design of MSM-LED.

[0046] In this embodiment, the lower semiconductor 103 and the upper semiconductor 105 are mutually exclusive N-type gallium nitride layers or P-type gallium nitride layers, and the lower semiconductor 103 and the upper semiconductor 105 are also provided with quantum well layers 104.

[0047] To further address the issue of light leakage from the LED-PN junction unit relative to the MSM device, in this embodiment, the main light-emitting direction of the LED-PN junction unit is towards the side where the fourth contact layer 107 is located, and the first metal layer 111 is also used to block the residual light of the LED-PN junction unit relative to the opening region 114.

[0048] Furthermore, such as Figure 4As shown, in other optional embodiments, a second insulating layer 112 and a second metal layer 113 are further provided on the step surface between the upper semiconductor 105 and the lower semiconductor 103. The second metal layer 113 is used to block the residual light of the LED-PN junction unit relative to the opening region 114.

[0049] Optionally, the second metal contact layer 109, the third metal contact layer 108, and the first metal layer 111 are coated once.

[0050] In addition, the fourth contact layer 107 can also be a metal electrode, in which case it can be coated with the second metal contact layer 109, the third metal contact layer 108 and the first metal layer 111; it is worth mentioning that the transmittance can be improved by setting a narrower size or a hollow design.

[0051] In this embodiment, the first insulating layer 106 is made of silicon nitride.

[0052] Optionally, the third metal contact layer 108 and the fourth contact layer 107 are made of an aluminum-lanthanum alloy. In fact, the present invention does not limit the specific material of the electrodes; the above materials are illustrative. It is worth mentioning that the fourth contact layer 107 can also be made of a transparent conductive material, etc.

[0053] Optionally, the materials of the first metal contact layer 110 and the second metal contact layer 109 include, but are not limited to, molybdenum, tungsten, titanium, nickel, chromium, gold, silver, cadmium, and platinum. This invention does not limit the specific materials of the electrodes; the above materials are illustrative.

[0054] In addition, Figure 3 The light leakage path diagram is given in the figure. Figure 3 In this configuration, the light emitted by the LED can be effectively blocked by the first metal layer 111. Figure 4 In order to further prevent LED light leakage, a second insulating layer 112 and a second metal layer 113 are directly provided for shielding.

[0055] like Figure 2 as well as Figure 1 As shown, in the second embodiment of the present invention, a method for fabricating a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode is provided. The related device structure can be referred to in the first embodiment. Furthermore, the fabrication method in the second embodiment includes the following steps:

[0056] S1: A semiconductor buffer epitaxial layer 102 is deposited on the surface of substrate 101, and a lower semiconductor 103 and an upper semiconductor 105 corresponding to the LED-PN junction unit are deposited on the semiconductor buffer epitaxial layer 102; it is worth mentioning that, Figures 1-4In the middle, a quantum well layer 104 is also disposed between the lower semiconductor 103 and the upper semiconductor 105;

[0057] S2: Etching to remove part of the upper semiconductor 105;

[0058] S3: Etching away a portion of the lower semiconductor 103 to create an MSM surface on the semiconductor buffer epitaxial layer 102; wherein, the amount of etching of the lower semiconductor 103 on the MSM surface side retains a step surface of the lower semiconductor 103 relative to the upper semiconductor 105.

[0059] S4: Deposit and fabricate a first insulating layer 106, and etch the first insulating layer 106 to retain it in the interface region between the MSM surface and the step surface of the lower semiconductor 103.

[0060] S5: Using electron beam evaporation or sputtering technology and etching, a second metal contact layer 109, a third metal contact layer 108, a first metal layer 111, a first metal contact layer 110, and a fourth contact layer 107 are formed on both sides of the first insulating layer 106, on the first insulating layer 106, on the semiconductor buffer epitaxial layer 102, and on the upper semiconductor layer 105, respectively; wherein, an opening region 114 for receiving the light to be detected is provided between the first metal contact layer 110 and the second metal contact layer 109.

[0061] Typical coating processes include electron beam evaporation or sputtering techniques.

[0062] Typically, wet etching can be used to remove part of the metal layer. For semiconductor materials, both wet etching and ICP dry etching can be used. In fact, this invention does not limit the etching method.

[0063] Specifically, optionally, the lower semiconductor 103 and the upper semiconductor 105 are mutually exclusive N-type gallium nitride layers or P-type gallium nitride layers, and the lower semiconductor 103 and the upper semiconductor 105 are further provided with quantum well layers 104.

[0064] Step S1 includes: depositing an N-type gallium nitride layer, a quantum well layer 104, and a P-type gallium nitride layer on the semiconductor buffer epitaxial layer 102 using a metal-organic chemical vapor deposition method, according to the specific semiconductor types of the lower semiconductor 103 and the upper semiconductor 105.

[0065] Optional, such as Figure 1 As shown, the lower semiconductor 103 is N-type gallium nitride, the upper semiconductor 105 is P-type gallium nitride, and the quantum well layer 104 is between the two.

[0066] Optionally, in this embodiment, the main light-emitting direction of the LED-PN junction unit is towards the side where the fourth contact layer 107 is located, and the first metal layer 111 is also used to block the residual light of the LED-PN junction unit relative to the opening region 114. Specifically, the film thickness and metal layer structure can be designed according to actual blocking needs.

[0067] Furthermore, such as Figure 4 As shown, in other optional embodiments, a second insulating layer 112 and a second metal layer 113 are further provided on the step surface between the upper semiconductor 105 and the lower semiconductor 103. The second metal layer 113 is used to block the residual light of the LED-PN junction unit relative to the opening region 114.

[0068] The second insulating layer 112 is generated in step S4; the second metal layer 113 is generated in step S5.

[0069] In addition, the fourth contact layer 107 can also be a metal electrode, in which case it can be coated with the second metal contact layer 109, the third metal contact layer 108 and the first metal layer 111; it is worth mentioning that the transmittance can be improved by setting a narrower size or a hollow design.

[0070] Optionally, the first insulating layer 106 and the second insulating layer 112 are made of silicon nitride.

[0071] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode, characterized in that, The homogeneous integrated structure includes: Substrate; Semiconductor buffer epitaxial layer; A first metal contact layer and a second metal contact layer are disposed on the semiconductor buffer epitaxial layer; wherein, an opening region for receiving the light to be detected is provided between the first metal contact layer and the second metal contact layer; the first metal contact layer, the semiconductor buffer epitaxial layer corresponding to the opening region, and the second metal contact layer constitute an MSM structural unit; An LED-PN junction unit is disposed on the semiconductor buffer epitaxial layer; the LED-PN junction unit includes a lower semiconductor and an upper semiconductor; a third metal contact layer is disposed on the step surface of the lower semiconductor, and a first metal layer is electrically connected between the second metal contact layer and the third metal contact layer; a first insulating layer is disposed between the first metal layer and the lower semiconductor. A fourth contact layer is disposed on the upper semiconductor of the LED-PN junction unit; The first metal contact layer, the semiconductor buffer epitaxial layer corresponding to the opening region, the second metal contact layer, the first metal layer, and the LED-PN junction unit are sequentially connected to form an electrical path with the external drive according to the light received by the opening region. The lower semiconductor and the upper semiconductor are mutually exclusive N-type semiconductor layers or P-type semiconductor layers, respectively; wherein, when the upper semiconductor is a P-type semiconductor layer, the fourth contact layer is the anode of the homogeneous integrated structure, and the first metal contact layer is the cathode of the homogeneous integrated structure; when the upper semiconductor is an N-type semiconductor layer, the fourth contact layer is the cathode of the homogeneous integrated structure, and the first metal contact layer is the anode of the homogeneous integrated structure. The lower semiconductor and the upper semiconductor are mutually exclusive N-type gallium nitride layers or P-type gallium nitride layers, and the lower semiconductor and the upper semiconductor are further provided with quantum well layers; The step surface between the upper semiconductor and the lower semiconductor is further provided with a second insulating layer and a second metal layer, the second metal layer being used to block the residual light of the LED-PN junction unit relative to the opening region.

2. The homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode as described in claim 1, characterized in that, The main light emission direction of the LED-PN junction unit is towards the side where the fourth contact layer is located, and the first metal layer is also used to block the residual light of the LED-PN junction unit relative to the opening area.

3. The homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode as described in claim 1, characterized in that, The second metal contact layer, the third metal contact layer, and the first metal layer are a single coating.

4. The homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode as described in claim 1, characterized in that, The first insulating layer is made of silicon nitride.

5. A method for fabricating a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode, the method being used to fabricate the homogeneous integrated structure according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Deposit a semiconductor buffer epitaxial layer on the substrate surface, and deposit the lower semiconductor and upper semiconductor corresponding to the LED-PN junction unit on the semiconductor buffer epitaxial layer; S2: Etching removes part of the upper semiconductor layer; S3: Etching away part of the lower semiconductor layer to create an MSM surface on the semiconductor buffer epitaxial layer; wherein, the amount of etching of the lower semiconductor layer on the MSM surface side retains a step surface of the lower semiconductor layer relative to the upper semiconductor layer; S4: Deposit and fabricate a first insulating layer, and etch the first insulating layer to retain it in the interface region between the MSM surface and the step surface of the underlying semiconductor. S5: Using electron beam evaporation or sputtering technology and etching, a second metal contact layer, a third metal contact layer, a first metal layer, a fourth contact layer are formed on both sides of the first insulating layer, on the first insulating layer, on the semiconductor buffer epitaxial layer, and on the upper semiconductor layer, respectively; wherein, an opening area for receiving the light to be detected is provided between the first metal contact layer and the second metal contact layer.

6. The method for fabricating a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode as described in claim 5, characterized in that, The lower semiconductor and the upper semiconductor are mutually exclusive N-type gallium nitride layers or P-type gallium nitride layers, and the lower semiconductor and the upper semiconductor are further provided with quantum well layers; Step S1 includes: depositing an N-type gallium nitride layer, a quantum well layer, and a P-type gallium nitride layer on the semiconductor buffer epitaxial layer using a metal-organic chemical vapor deposition method, according to the specific semiconductor types of the lower semiconductor and the upper semiconductor.

7. The method for fabricating a homogeneous integrated structure of a metal-semiconductor-metal photodetector and a light-emitting diode as described in claim 5, characterized in that, The step surface between the upper semiconductor and the lower semiconductor is further provided with a second insulating layer and a second metal layer. The second metal layer is used to block the residual light of the LED-PN junction unit relative to the opening region. The second insulating layer is generated in step S4, and the second metal layer is generated in step S5.

Images