Monolithic photo-MOS relay and manufacturing method thereof

Abstract

To provide a monolithic photo-MOS relay and a manufacturing method thereof.SOLUTION: A method for manufacturing a monolithic photo-MOS relay uses a lightly doped substrate and forms a first P-N structure, a second P-N structure, and an N-P-N structure on an epitaxial layer. The epitaxial layer is divided into electrically isolated high-voltage and low-voltage regions by dry etching. An isolation layer is then deposited on the epitaxial layer, and a number of patterns are formed by photomask etching. A metal layer is then deposited to form a light-emitting diode in the first P-N structure, a photodiode in the second P-N structure, and at least one metal oxide semiconductor field effect transistor in the N-P-N structure on the basis of the patterns.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a monolithic opto-mosfet relay and a method for its manufacture. Specifically, the present invention uses the same process and the same lightly doped silicon carbide substrate to fabricate the components of a monolithic opto-mosfet relay. [Background technology]

[0002] At present, silicon substrates are often used to manufacture photoMOS relays. The light-emitting end, i.e. light-emitting diode (LED), is manufactured using a gallium arsenide (GaAs) process. The light-receiving end, i.e. photodiode (PD) and metal-oxide-semiconductor field-effect transistor (MOSFET), are light sensors and AC switches made of silicon. Therefore, two separate wafers must be used and two different processes must be carried out, which makes packaging complicated and inefficient.

[0003] However, the output terminal of a conventional silicon photogate has a limited voltage resistance, which is only about 800 to 900 volts at most unless a silicon carbide element is added.

[0004] In view of the above circumstances, the present invention provides a silicon carbide photoelectric relay that can improve the withstand voltage and simplify the manufacturing process. Summary of the Invention

[0005] The object of the present invention is to provide a monolithic photoMOS relay and a manufacturing method thereof. The monolithic photoMOS relay uses a low-doped silicon carbide substrate, and the light-emitting element (light-emitting diode) and light-receiving element (photodiode) required for the monolithic photoMOS relay are fabricated on the same silicon carbide substrate, thereby simplifying the manufacturing process. This makes it possible to significantly increase the withstand voltage of the AC switch to 1700 volts without adding any components, reduce the chip area, and lower the cost of the module.

[0006] In order to achieve the above object, the present invention provides a monolithic photoMOS relay connected to an input circuit and an output circuit. The monolithic photoMOS relay includes a substrate, an epitaxial layer, an isolation layer, a light emitting diode (LED), a blue ultraviolet reflective film, a photodiode (PD), a first metal oxide semiconductor field effect transistor (MOSFET), and a second metal oxide semiconductor field effect transistor. The epitaxial layer is formed on the substrate. A trench is formed in the epitaxial layer, dividing the epitaxial layer into a high voltage region and a low voltage region. The high voltage region and the low voltage region are electrically insulated. The isolation layer is formed on the epitaxial layer. The light emitting diode is formed in the low voltage region of the epitaxial layer, receives an input signal from the input circuit, and generates light in response to the input signal. The blue ultraviolet reflective film reflects light to form a reflected light. The photodiode is formed in the high voltage region of the epitaxial layer and detects reflected light to generate a detection voltage. The first metal oxide semiconductor field effect transistor is formed in the high voltage region of the epitaxial layer, electrically connected to the photodiode, and driven in response to the detection voltage to generate a first output current and output it to the output circuit. The second metal oxide semiconductor field effect transistor is formed in the high voltage region of the epitaxial layer, electrically connected to the photodiode, and driven in response to the detection voltage to generate a second output current and output it to the output circuit. The light emitting diode, the photodiode, the first metal oxide semiconductor field effect transistor, and the second metal oxide semiconductor field effect transistor are formed adjacent to each other on a substrate.

[0007] In an embodiment of the invention, the substrate is made of silicon carbide (SiC) and is lightly doped with ions.

[0008] In an embodiment of the present invention, after the blue ultraviolet reflective film is coated on the isolation layer, the monolithic photoMOS relay is encapsulated with an encapsulant. The light passes through the isolation layer, reaches the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

[0009] In an embodiment of the present invention, the monolithic photoMOS relay is encapsulated with an encapsulant, and the blue ultraviolet reflective film is coated on the outer surface of the encapsulant, and the light passes through the encapsulant to reach the blue ultraviolet reflective film and is reflected by the blue ultraviolet reflective film to the photodiode.

[0010] In an embodiment of the present invention, the monolithic photoMOS relay is sealed in a metal case, and the blue ultraviolet reflective film is coated on the inner surface of the metal case, and the light passes through the air in the metal case to reach the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

[0011] In an embodiment of the present invention, the epitaxial layer is doped N-type.

[0012] In an embodiment of the present invention, the light has a wavelength between 300 nanometers and 500 nanometers.

[0013] In an embodiment of the present invention, the monolithic photoMOS relay further includes a control circuit electrically connected to the photodiode, a first gate of the first metal oxide semiconductor field effect transistor, and a second gate of the second metal oxide semiconductor field effect transistor, the control circuit controlling a first voltage response time of the first metal oxide semiconductor field effect transistor and a second voltage response time of the second metal oxide semiconductor field effect transistor.

[0014] The present invention also provides a method for manufacturing a monolithic photoMOS relay, the method comprising the steps of forming an epitaxial layer on a substrate, injecting a plurality of ions into the epitaxial layer to form a first PN structure, a second PN structure, and an NPN structure in the epitaxial layer, performing dry etching to form a trench dividing the epitaxial layer into an electrically isolated high-voltage region and a low-voltage region, depositing an isolation layer on the epitaxial layer and the trench, performing photomask etching to form a plurality of patterns, and depositing a metal layer to form a light emitting diode (LED) in the first PN structure, a photodiode (PD) in the second PN structure, and a first metal oxide semiconductor field effect transistor (MOSFET) and a second metal oxide semiconductor field effect transistor in the NPN structure based on the patterns.

[0015] In an embodiment of the present invention, the method for manufacturing the monolithic photoMOS relay further includes coating the isolation layer with a blue ultraviolet reflective film, and sealing the monolithic photoMOS relay with a sealant.

[0016] In an embodiment of the present invention, light passes through the isolation layer to reach the blue ultraviolet reflective film and is reflected by the blue ultraviolet reflective film to the photodiode.

[0017] In an embodiment of the present invention, the method for manufacturing the monolithic photoMOS relay further includes the steps of encapsulating the monolithic photoMOS relay with an encapsulant, and coating an outer surface of the encapsulant with a blue ultraviolet reflective film.

[0018] In an embodiment of the present invention, light passes through the encapsulant to reach the blue UV reflective film and is reflected by the blue UV reflective film to the photodiode.

[0019] In an embodiment of the present invention, the method for manufacturing the monolithic photoMOS relay further includes the steps of sealing the monolithic photoMOS relay with a metal case, and coating an inner surface of the metal case with a blue ultraviolet reflective film.

[0020] In an embodiment of the present invention, light passes through the air inside the metal case to reach the blue ultraviolet reflective film and is reflected by the blue ultraviolet reflective film to the photodiode.

[0021] In an embodiment of the invention, the substrate is made of silicon carbide (SiC) and is lightly doped with ions.

[0022] In an embodiment of the present invention, the manufacturing method of the monolithic photoMOS relay further includes the steps of electrically connecting a control circuit to the photodiode, a first gate of the first metal oxide semiconductor field effect transistor, and a second gate of the second metal oxide semiconductor field effect transistor; and controlling a first voltage response time of the first metal oxide semiconductor field effect transistor and a second voltage response time of the second metal oxide semiconductor field effect transistor by the control circuit when the photodiode generates a detection voltage.

[0023] 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]

[0024] [Figure 1] FIG. 1 is a schematic diagram showing a circuit of a monolithic photoMOS relay according to the present invention. [Diagram 2] 1 is a cross-sectional view showing a manufacturing process of a monolithic photoMOS relay according to the present invention; [Diagram 3] 1 is a cross-sectional view showing a manufacturing process of a monolithic photoMOS relay according to the present invention; [Figure 4] 1 is a cross-sectional view showing a manufacturing process of a monolithic photoMOS relay according to the present invention; [Diagram 5] 1 is a cross-sectional view showing a manufacturing process of a monolithic photoMOS relay according to the present invention; [Figure 6] 1 is a cross-sectional view showing a manufacturing process of a monolithic photoMOS relay according to the present invention; [Figure 7] 1 is a cross-sectional view showing a manufacturing process of a monolithic photoMOS relay according to the present invention; [Figure 8] FIG. 1 is a top view showing a circuit layout of a monolithic photoMOS relay according to the present invention. [Figure 9] FIG. 1 is a cross-sectional view showing a monolithic photoMOS relay after packaging according to the present invention. [Figure 10] FIG. 1 is a cross-sectional view showing a monolithic photoMOS relay after packaging according to the present invention. [Figure 11] FIG. 1 is a cross-sectional view showing a monolithic photoMOS relay after packaging according to the present invention. [Figure 12] FIG. 1 is a schematic diagram showing a control circuit for a monolithic photoMOS relay according to the present invention; [Figure 13] A flow chart showing a method for manufacturing a monolithic photoMOS relay according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The contents of the present invention will be described below through examples. Note that the examples of the present invention are examples of embodiments, and are not intended to limit the present invention to the environments, applications, or specific aspects described in the examples. Therefore, the explanation of the examples is for explaining the present invention, but does not limit the present invention. Note that in the embodiments and drawings, components that are not directly related to the present invention are omitted and not shown. The dimensional relationship between the components in the drawings is for ease of understanding, and does not limit the actual dimensions.

[0026] 1 to 8 are diagrams showing a first embodiment of the present invention. FIG. 1 is a schematic diagram showing a circuit of a monolithic photoMOS relay 100 according to the present invention. The monolithic photoMOS relay 100 is connected to an input circuit 200 and an output circuit 300. The monolithic photoMOS relay 100 includes a light emitting diode (LED) 110, a photodiode (PD) 130 in series, a first metal oxide semiconductor field effect transistor (MOSFET) 150, and a second metal oxide semiconductor field effect transistor 170. The first metal oxide semiconductor field effect transistor 150 has a first gate 151, a first source 153, and a first drain 155. The second metal oxide semiconductor field effect transistor 170 has a second gate 171, a second source 173, and a second drain 175.

[0027] The light emitting diode 110 receives an input signal from the input circuit 200 and generates light 111 in response to the input signal. The light 111 is reflected as reflected light 113. When the series photodiode 130 detects the reflected light 113, a response current is generated, creating a voltage difference across the series. This voltage difference is used to control the first gate 151 of the first metal oxide semiconductor field effect transistor 150 and the second gate 171 of the second metal oxide semiconductor field effect transistor 170.

[0028] In the conventional technology, a photoMOS relay requires a chip for making a light-emitting diode and another chip for making a photodiode and a metal oxide semiconductor field effect transistor. In other words, in the conventional technology, at least two chips must be used to make a photoMOS relay. The chip for making a light-emitting diode is different from the chip for making a photodiode and a metal oxide semiconductor field effect transistor, so the process for making a light-emitting diode is different from the process for making a photodiode and a metal oxide semiconductor field effect transistor. In addition, the output terminal of a conventional photoMOS relay using a silicon substrate has a limited withstand voltage, which is only about 800 to 900 volts at most unless a silicon carbide element is added.

[0029] In order to simplify the manufacturing process, reduce the cost of the product, and at the same time improve the off-state voltage, the present invention proposes to simplify the manufacturing process by manufacturing the light-emitting element (i.e., light-emitting diode) and the light-receiving element (i.e., photodiode) of the photoMOS relay on the same silicon carbide substrate. Specifically, the present invention will be described with reference to Figs. 2 to 8. Figs. 2 to 7 are cross-sectional views showing each stage of the manufacturing process of the monolithic photoMOS relay 100. Fig. 8 is a top view showing the circuit layout of the monolithic photoMOS relay 100. In the process of manufacturing the monolithic photoMOS relay 100 of the present invention, first, an epitaxial layer 192 is formed on a substrate 191. A plurality of ions are implanted into the epitaxial layer 192 to form a first PN structure 1921, a second PN structure 1922, and an NPN structure 1923 in the epitaxial layer 192, as shown in Figs. 2 and 3.

[0030] The substrate 191 is made of silicon carbide (SiC) doped with a low ion concentration, typically 1E15 (1 / cm 3) or less. Silicon carbide has various crystal structures, such as hexagonal silicon carbide (6H-SiC), tetragonal silicon carbide (4H-SiC), and cubic silicon carbide (3C-SiC). Silicon carbide has high temperature stability, high electron mobility, high voltage resistance, and excellent thermal conductivity. Therefore, compared with conventional photoMOS relays using silicon substrates, the present invention uses silicon carbide to fabricate the monolithic photoMOS relay 100, and therefore the withstand voltage of the AC switch can be significantly improved.

[0031] In this embodiment, the epitaxial layer 192 is doped N-type. The ions are N-type ions or P-type ions. In detail, as shown in FIG. 3, the shaded areas in FIG. 3 are P-type doped areas, and the gray areas are N-type doped areas. The first PN structure 1921 is a PN structure consisting of a P-type doped region formed by injecting P-type ions into the N-type epitaxial layer by ion implantation, and an N-type epitaxial layer. The second PN structure 1922 is a PN structure formed by injecting N-type ions into the P-type doped region formed by injecting P-type ions into the N-type epitaxial layer by ion implantation, and then injecting N-type ions into two different areas of the P-type doped region by ion implantation. Similar to the second PN structure 1922, the NPN structure 1923 is a structure formed by injecting P-type ions into the N-type epitaxial layer by ion implantation to form a P-type doped region, and injecting N-type ions into two different areas of the P-type doped region by ion implantation.

[0032] Next, as shown in FIG. 4, dry etching is performed to form a trench 1924 in the epitaxial layer 192. Dry etching selectively removes material from the wafer surface with plasma. The trench 1924 divides the epitaxial layer 192 into a low voltage region 1925 and a high voltage region 1926. In order to electrically insulate the low voltage region 1925 and the high voltage region 1926, the dry etching needs to reach the substrate 191 and expose the surface of the substrate 191. In this case, the low voltage region 1925 and the high voltage region 1926 are connected only by the substrate 191. Since the substrate 191 is a substrate doped with a low ion concentration, the electrical resistance of the substrate 191 is high. That is, the substrate 191 can prevent electrical changes between the low voltage region 1925 and the high voltage region 1926 and completely electrically insulate the low voltage region 1925 and the high voltage region 1926.

[0033] After the dry etching is completed, an isolation layer 194 is deposited on the epitaxial layer 192 and the trench 1924. In addition, photomask etching is performed to form a number of patterns (not shown). Then, as shown in Figs. 5 and 6, a metal layer 195 is deposited to form a light emitting diode 110 in a first PN structure 1921, a photodiode 130 in a second PN structure 1922, and a first metal oxide semiconductor field effect transistor 150 and a second metal oxide semiconductor field effect transistor 170 in an NPN structure 1923 based on the patterns.

[0034] In this embodiment, the isolation layer 194 is formed by a deposition method such as chemical vapor deposition, physical vapor deposition, or sputtering. The material of the isolation layer 194 is silicon dioxide (SiO2) or silicon nitride (Si3N4). Silicon dioxide and silicon nitride are insulating materials and are used in the manufacture of the isolation layer 194 to prevent current flow between different crystal regions, for example, low voltage region 1925 and high voltage region 1926.

[0035] As shown in Fig. 6, the positions of the patterns formed by photomask etching correspond to a first PN structure 1921, a second PN structure 1922, and an NPN structure 1923. Therefore, after depositing the metal layer 195, the light emitting diode 110 is formed in the first PN structure 1921, the photodiode 130 is formed in the second PN structure 1922, and the first metal oxide semiconductor field effect transistor 150 and the second metal oxide semiconductor field effect transistor 170 are formed in the NPN structure 1923, as shown in Figs. 7 and 8.

[0036] The light emitting diode 110 is formed in the low voltage region 1925 of the epitaxial layer 192, receives an input signal from an input circuit, and generates light 111 in response to the input signal. The photodiode 130 is formed in the high voltage region 1926 of the epitaxial layer 192, detects the reflected light 113, and generates a detection voltage. The first metal oxide semiconductor field effect transistor 150 is formed in the high voltage region 1926 of the epitaxial layer 192, electrically connected to the photodiode 130, and driven in response to the detection voltage to generate a first output current and output it to the output circuit 300. The second metal oxide semiconductor field effect transistor 170 is formed in the high voltage region 1926 of the epitaxial layer 192, electrically connected to the photodiode 130, and driven in response to the detection voltage to generate a second output current and output it to the output circuit.

[0037] In this manner, the light emitting diode 110, the photodiode 130, the first metal oxide semiconductor field effect transistor 150, and the second metal oxide semiconductor field effect transistor 170 are fabricated on the same substrate 191 by the same process, and are formed adjacent to one another on the substrate 191. Therefore, the present invention makes it possible to significantly increase the withstand voltage of the AC switch to 1700 volts (V) or more, reduce the chip area, and lower the module cost (BOM cost) without adding any components.

[0038] In the second embodiment of the present invention, FIG. 9 is a cross-sectional view showing a monolithic photoMOS relay 100. The second embodiment is an extension of the first embodiment. In this embodiment, a packaging method of the monolithic photoMOS relay 100 will be described in detail. Specifically, the monolithic photoMOS relay 100 is sealed with a blue-violet transparent encapsulant 400. The outer surface of the encapsulant 400 is coated with a blue ultraviolet reflective film 500. The blue ultraviolet reflective film 500 reflects the light 111 to form a reflected light 113. Thereby, the light 111 emitted by the light emitting diode 110 passes through the encapsulant 400 to reach the blue ultraviolet reflective film 500, and is reflected by the blue ultraviolet reflective film 500 to the photodiode 130. The light 111 emitted by the light emitting diode 110 is mainly blue to ultraviolet light. The light 111 has a wavelength of 300 nanometers to 500 nanometers.

[0039] In the third embodiment of the present invention, FIG. 10 is a cross-sectional view showing another embodiment of the monolithic photoMOS relay 100. The third embodiment is an extension of the first embodiment. Different from the second embodiment, in this embodiment, the blue ultraviolet reflective film 500 is first coated on the isolation layer 194, and then the monolithic photoMOS relay 100 is sealed with the encapsulant 400. Thereby, the light 111 emitted by the light emitting diode 110 passes through the isolation layer 194 to reach the blue ultraviolet reflective film 500, and is reflected by the blue ultraviolet reflective film 500 to the photodiode 130.

[0040] In the fourth embodiment of the present invention, FIG. 11 is a cross-sectional view showing a monolithic photoMOS relay 100. The fourth embodiment is an extension of the first embodiment. Different from the second and third embodiments, in this embodiment, the monolithic photoMOS relay 100 is sealed in a metal case 600, and then a blue ultraviolet ray reflective film 500 is coated on the inner surface of the metal case. No sealant is filled in the metal case. As a result, the light emitted by the light emitting diode passes through the air in the metal case to reach the blue ultraviolet ray reflective film, and is reflected by the blue ultraviolet ray reflective film to the photodiode.

[0041] In the fifth embodiment of the present invention, FIG. 12 is a schematic diagram showing a control circuit 700 of the monolithic photoMOS relay in the present invention. The fifth embodiment is an extension of the first embodiment. The control circuit 700 includes at least one metal oxide semiconductor field effect transistor 710, at least one resistor 730, and at least one diode 750. A schematic circuit of the control circuit 700 is shown in FIG. 12. The control circuit 700 is electrically connected to the photodiode 130, the first gate 151 of the first metal oxide semiconductor field effect transistor 150, and the second gate 171 of the second metal oxide semiconductor field effect transistor 170, and controls the first voltage response time of the first metal oxide semiconductor field effect transistor 150 and the second voltage response time of the second metal oxide semiconductor field effect transistor 170. In the manufacturing process, the control circuit 700, the light emitting diode 110, the photodiode 130, the first metal oxide semiconductor field effect transistor 150, and the second metal oxide semiconductor field effect transistor 170 are fabricated on the same silicon carbide substrate 191 in the same process.

[0042] 13 is a flow chart showing a method for manufacturing a monolithic photoMOS relay according to the sixth embodiment of the present invention. The method for manufacturing a monolithic photoMOS relay is applicable to the manufacture of the monolithic photoMOS relay 100 of the above-mentioned embodiments. The manufacture of a monolithic photoMOS relay uses semiconductor equipment such as, but not limited to, a deposition equipment, an ion implantation equipment, a photolithography equipment, an etching equipment, a cleaning equipment, a sputtering equipment, a test equipment, and a packaging equipment.

[0043] First, in step S1302, an epitaxial layer is formed on a substrate. For example, as shown in FIG. 2 to FIG. 7, an epitaxial layer 192 is formed on a substrate 191. The substrate is made of silicon carbide and is doped with a low ion concentration. In step S1304, a plurality of ions are implanted into the epitaxial layer to form a first PN structure, a second PN structure, and an NPN structure in the epitaxial layer. In step S1306, dry etching is performed to form a trench in the epitaxial layer. The trench divides the epitaxial layer into a high voltage region and a low voltage region. The high voltage region and the low voltage region are electrically insulated.

[0044] Then, in step S1308, an isolation layer is deposited on the epitaxial layer and the trench. In step S1310, photomask etching is performed to form a number of patterns. In step S1312, a metal layer is deposited to form a light emitting diode in a first PN structure, a photodiode in a second PN structure, and a first metal oxide semiconductor field effect transistor and a second metal oxide semiconductor field effect transistor in an NPN structure according to the patterns.

[0045] In the embodiment of the present invention, the monolithic photoMOS relay is encapsulated with an encapsulant, and a blue ultraviolet reflective film is coated on the outer surface of the encapsulant. As described in the second embodiment and shown in Figure 9, light passes through the encapsulant to reach the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

[0046] In another embodiment, the blue UV reflective film is first coated on the isolation layer, and then the monolithic photoMOS relay is encapsulated with an encapsulant, in which case light passes through the isolation layer to the blue UV reflective film and is reflected by the blue UV reflective film to the photodiode, as described in the third embodiment and shown in FIG.

[0047] In another embodiment, the monolithic photoMOS relay is sealed in a metal case, and a blue ultraviolet reflective film is coated on the inner surface of the metal case, so that the light passes through the air in the metal case to reach the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode, as described in the fourth embodiment and shown in FIG.

[0048] In addition, in another embodiment, the method for manufacturing a monolithic photoMOS relay of the present invention includes electrically connecting a control circuit to the photodiode, the first gate of the first metal oxide semiconductor field effect transistor, and the second gate of the second metal oxide semiconductor field effect transistor, and when the photodiode generates a detection voltage, the first voltage response time of the first metal oxide semiconductor field effect transistor and the second voltage response time of the second metal oxide semiconductor field effect transistor are controlled by the control circuit.

[0049] In addition to the steps described above, the method for manufacturing the monolithic photoMOS relay in this embodiment can carry out the steps described in the previous embodiment to achieve the same functions. Based on the above embodiment, those skilled in the art can easily understand how to carry out these steps and functions, so the description will be omitted.

[0050] As described above, the monolithic photoMOS relay of the present invention uses a low-doped silicon carbide substrate, and compared with the conventional one using a silicon substrate, the dielectric breakdown strength of silicon carbide is 10 times that of silicon. The silicon carbide substrate is applicable to the manufacture of both light-emitting elements and light-receiving elements. Therefore, in the present invention, an epitaxial layer is formed on a silicon carbide substrate, ions are implanted, the epitaxial layer is divided into two parts by dry etching, an isolation layer is deposited, photomask etching is performed, and finally a metal layer is deposited, so that light-emitting diodes, photodiodes, and metal oxide semiconductor field effect transistors are simultaneously formed in the two parts of the epitaxial layer. In this way, the present invention uses the same process and the same substrate to fabricate all the components of the monolithic photoMOS relay. It is possible to significantly increase the withstand voltage of the AC switch without adding any parts, reduce the chip area, and reduce the cost of the module.

[0051] The above examples are for explaining the embodiments of the present invention and for explaining the characteristic configuration of the present invention. The present invention is not limited to the above examples. 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 is based on the claims. [Explanation of symbols]

[0052] 100 Monolithic PhotoMOS Relay 110 Light Emitting Diode 111 light 113 Reflected light 130 Photodiode 150 First metal oxide semiconductor field effect transistor 151 Gate 1 153 First Source 155 First Drain 170 Second Metal Oxide Semiconductor Field Effect Transistor 171 Gate 2 173 Second Source 175 Second Drain 191 Substrate 192 Epitaxial Layer 1921 First PN structure 1922 Second PN structure 1923 NPN structure 1924 Trench 1925 High Voltage Area 1926 Low voltage area 194 Isolation layer 195 Metal layer 200 Input circuit 300 Output circuit 400 Sealant 500 Blue UV Reflective Film 600 Metal Case 700 Control circuit S1302~S1314 Steps

Claims

1. A monolithic photoMOS relay connected to an input circuit and an output circuit, A substrate; an epitaxial layer divided into high voltage and low voltage regions that are electrically isolated by a trench; an isolation layer formed on the epitaxial layer; a light emitting diode formed in the low voltage region of the epitaxial layer, the light emitting diode receiving an input signal from the input circuit and emitting light in response to the input signal; a blue ultraviolet reflective film that reflects the light to form a reflected light; a photodiode formed in the high voltage region of the epitaxial layer for detecting the reflected light and generating a detection voltage; a first metal oxide semiconductor field effect transistor formed in the high voltage region of the epitaxial layer, electrically connected to the photodiode, and driven in response to the detection voltage to generate a first output current and output the first output current to the output circuit; a second metal oxide semiconductor field effect transistor formed in the high voltage region of the epitaxial layer, electrically connected to the photodiode, and driven in response to the detection voltage to generate a second output current and output the second output current to the output circuit; the light emitting diode, the photodiode, the first metal oxide semiconductor field effect transistor, and the second metal oxide semiconductor field effect transistor are formed adjacent to one another on the substrate, forming a monolithic photoMOS relay.

2. 2. A monolithic photoMOS relay as claimed in claim 1, wherein said substrate is made of silicon carbide (SiC) and is lightly doped with ions.

3. 2. The monolithic photoMOS relay of claim 1, wherein the blue ultraviolet reflective film is coated on the isolation layer, and the monolithic photoMOS relay is encapsulated with an encapsulant.

4. 4. The monolithic photoMOS relay of claim 3, wherein the light passes through the isolation layer, reaches the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

5. 2. The monolithic photoMOS relay according to claim 1, wherein the monolithic photoMOS relay is sealed with a sealant, and the blue ultraviolet reflective film is coated on an outer surface of the sealant.

6. 6. The monolithic photoMOS relay of claim 5, wherein the light passes through the encapsulant, reaches the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

7. 2. The monolithic photoMOS relay according to claim 1, wherein the monolithic photoMOS relay is sealed in a metal case, and the blue ultraviolet reflective film is coated on an inner surface of the metal case.

8. 8. The monolithic photoMOS relay according to claim 7, wherein the light passes through the air in the metal case, reaches the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

9. 2. A monolithic photoMOS relay as claimed in claim 1, wherein said epitaxial layer is doped N-type.

10. 2. A monolithic photoMOS relay according to claim 1, wherein said light has a wavelength of 300 nanometers to 500 nanometers.

11. 2. The monolithic photoMOS relay of claim 1, further comprising a control circuit electrically connected to the photodiode, a first gate of the first metal oxide semiconductor field effect transistor, and a second gate of the second metal oxide semiconductor field effect transistor, for controlling a first voltage response time of the first metal oxide semiconductor field effect transistor and a second voltage response time of the second metal oxide semiconductor field effect transistor.

12. A method for manufacturing a monolithic photoMOS relay, comprising the steps of: forming an epitaxial layer on a substrate; implanting a plurality of ions into the epitaxial layer to form a first PN structure, a second PN structure, and an NPN structure in the epitaxial layer; performing a dry etch to form a trench dividing the epitaxial layer into electrically isolated high voltage and low voltage regions; depositing an isolation layer on the epitaxial layer and on the trench; performing photomask etching to form a plurality of patterns; and forming a light emitting diode in the first P-N structure, a photodiode in the second P-N structure, and a first metal oxide semiconductor field effect transistor and a second metal oxide semiconductor field effect transistor in the N-P-N structure based on the pattern by evaporating a metal layer.

13. coating the isolation layer with a blue ultraviolet reflective film; 13. The method of claim 12, further comprising the step of sealing the monolithic photoMOS relay with a sealant.

14. 14. The method for manufacturing a monolithic photoMOS relay according to claim 13, wherein light passes through the isolation layer, reaches the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

15. encapsulating the monolithic photoMOS relay with an encapsulant; 13. The method of claim 12, further comprising the step of: coating an outer surface of the encapsulant with a blue ultraviolet reflective film.

16. 16. The method for manufacturing a monolithic photoMOS relay according to claim 15, wherein light passes through the encapsulant, reaches the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

17. encapsulating the monolithic photoMOS relay in a metal case; 13. The method of claim 12, further comprising the step of coating an inner surface of the metal case with a blue ultraviolet reflective film.

18. 18. The method for manufacturing a monolithic photoMOS relay according to claim 17, wherein light passes through the air in the metal case, reaches the blue ultraviolet reflective film, and is reflected by the blue ultraviolet reflective film to the photodiode.

19. 13. The method of claim 12, wherein the substrate is made of silicon carbide (SiC) and is doped with a low ion concentration.

20. electrically connecting a control circuit to the photodiode, a first gate of the first metal oxide semiconductor field effect transistor, and a second gate of the second metal oxide semiconductor field effect transistor; 13. The method of claim 12, further comprising the step of controlling a first voltage response time of the first metal-oxide-semiconductor field effect transistor and a second voltage response time of the second metal-oxide-semiconductor field effect transistor by the control circuit when the photodiode generates a detection voltage.

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