Patent Application
20250072129
This application claims the benefit of Taiwan Patent Application Serial No. 112131309 filed on Aug. 21, 2023, which is hereby incorporated by reference in its entirety.
The present invention relates to a monolithic Opto-MOSFET relay and manufacturing method thereof. Specifically, the present invention uses identical semiconductor process to manufacture the elements of the monolithic Opto-MOSFET relay on the same low ion doping concentration silicon carbide (SiC) substrate.
Currently, most manufacturing processes for opto-MOS relays use silicon substrates. The light emitting end, which is the light emitting diode (LED), is produced using gallium arsenide (GaAs) processes. In contrast, the light receiving end, including the photodiode (PD) and the metal-oxide-semiconductor field effect transistor (MOSFET), is produced using silicon, serving as optical sensors and AC switches. Consequently, there is a need of two separate chips with two different semiconductor processes for manufacturing the PD and the MOSFET, and thus results in complex packaging and lower efficiency.
Furthermore, the withstand voltage capacity of traditional silicon optical gates at the output end is limited. Without additional silicon carbide components, the traditional silicon optical gates can withstand approximately the off-state voltage from 800 volts to 900 volts at most.
In view of above issues, the present invention provides an integrated silicon carbide Opto-MOSFET relay to enhance withstand voltage capabilities and simplify the manufacturing process.
An objective of the present disclosure is to provide a monolithic Opto-MOSFET relay and manufacturing method thereof. The monolithic Opto-MOSFET relay is manufactured by using a low ion doping concentration silicon carbide (SiC) substrate, and a light emitting element (i.e., light emitting diode) and a light receiving element (i.e., photodiode) that are needed to form the monolithic Opto-MOSFET relay are manufactured on the same SiC substrate to simplified manufacturing processes. Therefore, the withstand off-state voltage can be highly raised to 1700 volts without extra element, and thus reducing chip area and BOM cost.
To achieve the aforesaid objective, the present invention discloses a monolithic optoelectronic metal oxide semiconductor field effect transistor (Opto-MOSFET) relay which is connected to an input circuit and an output circuit, and includes a substrate, an epitaxial layer, an isolation layer, a light emitting diode (LED), a blue to ultraviolet light reflective film, a photodiode (PD), a first MOSFET, and a second MOSFET. The epitaxial layer is formed on the substrate. A groove is formed on the epitaxial layer to divide the epitaxial layer into a high voltage region and a low voltage region. The high voltage region and the low voltage region are electrically isolated from each other. The isolation layer is formed on the epitaxial layer. The LED is formed on the low voltage region of the epitaxial layer, and is configured to receive an input signal from the input circuit and generate an emission light in response to the input signal. The blue to ultraviolet light reflective film is configured to reflect the emission light and generate a reflection light. The PD is formed on the high voltage region of the epitaxial layer, and is configured to generate a sensing voltage in response to sensing the reflection light. The first MOSFET is formed on the high voltage region of the epitaxial layer and is electrically connected to the photodiode, and is configured to generate a first output current to the output circuit after being driven by the sensing voltage. The second MOSFET is formed on the high voltage region of the epitaxial layer and electrically connected to the photodiode, and is configured to generate a second output current to the output circuit after being driven by the sensing voltage. The LED, the PD, the first MOSFET and the second MOSFET are formed on the substrate.
In one embodiment, the substrate is made of silicon carbide (SiC) and is low ion doping concentration.
In one embodiment, the monolithic Opto-MOSFET relay is encapsulated by a molding compound after the blue to ultraviolet light reflective film is coated on the isolation layer. The blue to ultraviolet light reflective film reflects the emission light to the photodiode after the emission light is conducted to the blue to ultraviolet light reflective film through the isolation layer.
In one embodiment, the blue to ultraviolet light reflective film is coated on an outer face of a molding compound after the monolithic Opto-MOSFET relay is encapsulated by the molding compound. The blue to ultraviolet light reflective film reflects the emission light to the photodiode after the emission light is conducted to the blue to ultraviolet light reflective film through the molding compound.
In one embodiment, the blue to ultraviolet light reflective film is coated on an inner face of a metal case after the monolithic Opto-MOSFET relay is encapsulated by the metal case. The blue to ultraviolet light reflective film reflects the emission light to the photodiode after the emission light is conducted to the blue to ultraviolet light reflective film through an air inside the metal case.
In one embodiment, the epitaxial layer is N type doping.
In one embodiment, a wavelength of the emission light ranges from) 300 nanometers (nm) to 500 nm.
In one embodiment, the monolithic Opto-MOSFET relay includes a control circuit electrically connected to the PD, a first gate of the first MOSFET and a second gate of the second MOSFET, being configured to control a first voltage response time of the first MOSFET and a second voltage response time of the second MOSFET.
The present invention further discloses a monolithic opto metal oxide semiconductor field effect transistor (MOSFET) relay manufacturing method which includes growing an epitaxial layer on a substrate; implanting a plurality of ions to the epitaxial layer to form a first P-N structure, a second P-N structure and a N-P-N structure on the epitaxial layer; performing a dry etching to form a groove on the epitaxial layer, wherein the groove 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 isolated from each other; depositing an isolation layer on the epitaxial layer and the groove; performing a photolithograph process to generate a plurality of patterns; and depositing a metal layer to form a light emitting diode (LED) at the first P-N structure, form a photodiode (PD) at the second P-N structure, and form a first MOSFET and a second MOSFET at the N-P-N structure based on the patterns.
In one embodiment, the monolithic Opto-MOSFET relay manufacturing method further includes coating a blue to ultraviolet light reflective film on the isolation layer; and encapsulating the monolithic Opto-MOSFET relay by a molding compound.
In one embodiment, the blue to ultraviolet light reflective film reflects an emission light to the photodiode after the emission light is conducted to the blue to ultraviolet light reflective film through the isolation layer.
In one embodiment, the monolithic Opto-MOSFET relay manufacturing method further includes encapsulating the monolithic Opto-MOSFET relay by a molding compound; and coating a blue to ultraviolet light reflective film on an outer face of the molding compound.
In one embodiment, the blue to ultraviolet light reflective film reflects an emission light to the photodiode after the emission light is conducted to the blue to ultraviolet light reflective film through the molding compound.
In one embodiment, the monolithic Opto-MOSFET relay manufacturing method further includes encapsulating the monolithic Opto-MOSFET relay by a metal case and coating a blue to ultraviolet light reflective film on an inner face of the metal case.
In one embodiment, the blue to ultraviolet light reflective film reflects an emission light to the photodiode after the emission light is conducted to the blue to ultraviolet light reflective film through an air inside the metal case.
In one embodiment, the substrate is made of silicon carbide (SiC) and is low ion doping concentration.
In one embodiment, the monolithic Opto-MOSFET relay manufacturing method further includes electrically connecting a control circuit to the PD, a first gate of the first MOSFET and a second gate of the second MOSFET; and controlling a first voltage response time of the first MOSFET and a second voltage response time of the second MOSFET when the PD generates a sensing voltage.
The detailed technology and preferred embodiments implanted for the present invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention.
Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings, and are not intended to limit the present invention, applications or particular implementations described in these embodiments. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. It shall be appreciated that, in the following embodiments and the attached drawings, elements unrelated to the present invention are omitted from depiction; and dimensional relationships among individual elements in the attached drawings are provided only for ease of understanding, but not to limit the actual scale.
A first embodiment of the present invention is as shown in
The light emitting diode 110 receives an input signal from the input circuit 200 and generates an emission light 111 in response to the input signal. The emission light 111 is reflected to form a reflected light 113. The photodiode 130 generates a responsive current and consequently creates a voltage difference across its terminals when detecting the reflected light 113. The voltage difference is used to control the first gate 151 of the first MOSFET 150 and the second gate 171 of the second MOSFET 170.
Compared to the existing technology where photo-relays require manufacturing a light emitting diode on one chip and manufacturing a photodiode along with MOSFETs on another chip, the present technology offers a significant improvement. In other words, existing technology needs at least two separate chips to manufacture a photo-relay. Because the chip for manufacturing the LED is different from the chip for manufacturing the photodiode and MOSFETs, the manufacturing processes for these components are also different. Furthermore, conventional photo-relays manufactured on silicon substrates have limited voltage tolerance at the output end. Without additional silicon carbide (SiC) components, the maximum withstand voltage of conventional photo-relays are only 800 volts to 900 volts.
To simplify the manufacturing process, reduce overall costs, and enhance the off-state voltage tolerance, the present invention proposes manufacturing of the required light emitting element (i.e., light emitting diode) and light receiving element (i.e., photodiode) for the photo-relay on the same SiC substrate to simplify the manufacturing process. To be more specific, please refer to
The substrate 191 is manufactured using SiC with a low ion doping concentration, generally less than 1E15 (1/cm3). SiC exists in different crystalline structures, including hexagonal silicon carbide (6H-SiC), tetragonal silicon carbide (4H-SiC), and cubic silicon carbide (3C-SiC). SiC offers high temperature stability, high electron mobility, excellent voltage tolerance, and exceptional thermal conductivity. Therefore, compared to photo-relays manufactured with silicon substrates in existing technologies, using SiC in the manufacturing of the monolithic Opto-MOSFET relay 100 in the present invention significantly enhances its AC withstand voltage.
In this embodiment, the epitaxial layer 192 is N-type doping. Ions may involve either N-type ions or P-type ions. In detail, reference is made to
Next, reference is made to
After completing the dry etching process, an isolation layer 194 is deposited on both the epitaxial layer 192 and the groove 1924. Subsequently, a photolithography process is carried out to generate various patterns (not shown in the figures), and a metal layer 195 is deposited. Based on these patterns, the light emitting diode LED 110 is formed at the first P-N structure 1921, the photodiode 130 is formed at the second P-N structure 1922, and the first MOSFET 150 and the second MOSFET 170 are formed at the N-P-N structure 1923, as shown in
In this embodiment, the isolation layer 194 is manufactured by using deposition methods such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or sputtering during the manufacturing process. The materials used for manufacturing the isolation layer 194 may include silicon dioxide (SiO2) or silicon nitride (Si3N4). Both silicon dioxide and silicon nitride are insulating materials used primarily to prevent the flow of current between different regions, such as between the low voltage region 1925 and the high voltage region 1926.
The patterns generated through photolithography are positioned to correspond to the first P-N structure 1921, the second P-N structure 1922, and the N-P-N structure 1923, as shown in
The light emitting diode 110 is formed at the low voltage region 1925 of the epitaxial layer 192. The light emitting diode 110 may receive an input signal from the input circuit and generate the emission light 111 in response to the input signal. The photodiode 130 is formed at the high voltage region 1926 of the epitaxial layer 192. The photodiode 130 may sense the reflected light 113 and generate a sensing voltage. The first MOSFET 150 is formed at the high voltage region 1926 of the epitaxial layer 192 and is electrically connected to the photodiode 130. The first MOSFET 150 may generate a first output current and transmit the first output current to the output circuit 300 after being driven by the sensing voltage. The second MOSFET 170 is formed at the high voltage region 1926 of the epitaxial layer 192 and is electrically connected to the photodiode 130. The second MOSFET 170 may generate a second output current and transmit the second output current to the output circuit after being driven by the sensing voltage.
As a result, the light emitting diode 110, the photodiode 130, the first MOSFET 150, and the second MOSFET 170 are manufactured using the same process on the same substrate 191, and are formed adjacent to each other on the substrate 191. Therefore, in the present invention, it is possible to significantly increase the AC withstand voltage to above 1700 volts (V) without additional components. This not only reduces chip area but also reduce Bill of Materials (BOM) cost.
A second embodiment of the present invention is as shown in
A third embodiment of the present invention is as shown in
A fourth embodiment of the present invention is as shown in
A fifth embodiment of the present invention is as shown in
A sixth embodiment of the present invention is as shown in
First, in step S1302, an epitaxial layer is grown on a substrate, as illustrated, for example, in
Then, in step S1308, an isolation layer is deposited on both the epitaxial layer and the groove. In step S1310, photolithography is performed to generate a plurality of patterns. In step S1312, a metal layer is deposited to form a light emitting diode at the first P-N structure, a photodiode at the second P-N structure, and a first MOSFET and a second MOSFET at the N-P-N structure based on the patterns.
In one embodiment, the monolithic Opto-MOSFET relay is encapsulated by a molding compound, and a blue to ultraviolet light reflective film is coated on an outer surface of the molding compound. The emission light is conducted through the molding compound to the blue to ultraviolet light reflective film and is reflected by the blue to ultraviolet light reflective film to the photodiode, as described in the second embodiment and as shown in
In other embodiments, the blue to ultraviolet light reflective film is coated on the isolation layer, and then the monolithic Opto-MOSFET relay is encapsulated by the molding compound. In this case, the emission light is conducted through the isolation layer to the blue to ultraviolet light reflective film and is reflected by the blue to ultraviolet light reflective film to the photodiode, as described in the third embodiment and as shown in
In other embodiments, the monolithic Opto-MOSFET relay is encapsulated by a metal case, and then the blue to ultraviolet light reflective film is coated on an inner surface of the metal case. In this case, the emission light is conducted through the air inside the metal case to the blue to ultraviolet light reflective film and is reflected by the blue to ultraviolet light reflective film to the photodiode, as described in the fourth embodiment and shown in
Furthermore, in other embodiments, the monolithic Opto-MOSFET relay manufacturing method of the present invention may further electrically connects a control circuit to the photodiode and to the first gate of the first MOSFET and the second gate of the second MOSFET. When the photodiode generates a sensing voltage, the control circuit controls the first voltage response time of the first MOSFET and the second voltage response time of the second MOSFET.
In addition to the aforesaid steps, the monolithic Opto-MOSFET relay manufacturing method of the present invention can also execute all the operations described in the aforesaid embodiments and have all the corresponding functions, and how this embodiment executes these operations and has these functions based on the aforesaid embodiments shall be readily appreciated by those of ordinary skill in the art, and thus will not be further described herein.
According to the above descriptions, the monolithic Opto-MOSFET relay of the present invention is manufactured on a low ion doping concentration silicon carbide substrate. Compared to silicon substrates used in existing technologies, silicon carbide has an electrical breakdown strength ten times that of silicon and can simultaneously be used to produce light emitting components and light-receiving components. Therefore, in the present invention, after growing an epitaxial layer and ion implantation on a silicon carbide substrate, the epitaxial layer is divided into two parts through dry etching. An isolation layer is deposited, followed by photolithographic etching, and finally, a metal layer is deposited. This process simultaneously forms a light-emitting diode, a photodiode, and a metal-oxide-semiconductor field-effect transistor (MOSFET) in the two parts of the epitaxial layer. Consequently, the present invention manufactures all the components of the monolithic Opto-MOSFET relay on the same substrate using a single process, eliminating the need for additional components, significantly increasing the AC voltage withstand capability, reducing chip size, and lowering module costs.
Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 112131309 | Aug 2023 | TW | national |
