Multi-laminated high-voltage-resistance high-heat-conduction photoconductive switching device and preparation method thereof

Abstract

The invention discloses a multi-laminated high-voltage-resistant high-heat-conduction photoconductive switch device and a preparation method thereof, and mainly solves the problem of thermal failure of a photoconductive switch device in the prior art. The device comprises a plurality of semi-insulating substrates (1), metal electrodes (2), connecting electrodes (3) and external connecting electrodes (4), wherein the metal electrodes are distributed in the centers of the upper surface and the lower surface of each semi-insulating substrate; the connecting electrode is respectively connected with the metal electrode and the external connecting electrode; the upper and lower parts of each semi-insulating substrate are provided with boron nitride sheets (5) close to the semi-insulating substrate to form a multi-layer laminated structure; the center of each boron nitride sheet is provided with a through hole having the same shape and size as the connecting electrode, and the connecting electrode passes through the through hole of the boron nitride sheet and is connected with the metal electrodes on the two adjacent semi-insulating substrates. The problem of thermal failure in a photoconductive switching device is solved, the inter-stage capacitance of the device is reduced, the voltage resistance and frequency response capability of the device are improved, and the device can be used for an ultra-wideband electromagnetic pulse generator and a solid-state compact pulse power supply.

Description

Technical Field

[0001] The invention belongs to the field of microelectronic technology, and in particular relates to a photoconductive switch device which can be used for an ultra-wideband electromagnetic pulse generator and a solid-state compact pulse power supply. Background Art

[0002] Photoconductive switches have the characteristics of small jitter time, fast response and adjustable frequency. They have broad application prospects in the fields of high-power pulse generation and high-power microwave generation. Compared with the single frequency and large device size of traditional electric vacuum generation, photoconductive switches have the advantages of adjustable frequency and miniaturization. Photoconductive switches are devices that convert low-power energy accumulated over a long period of time into high-power energy in a short period of time, and transmit high-power electromagnetic pulses to the load. With the continuous in-depth research on photoconductive switches, the requirements for the performance of photoconductive switches in terms of ultrafast frequency, ultra-high power and stability are also increasing. Among them, an inevitable central problem encountered by photoconductive switches is the life of photoconductive switch devices. The life of photoconductive switch devices is related to the thermal failure of the device, and its thermal failure mainly comes from three aspects: 1) Ultra-high density current filaments formed during the conduction of the photoconductive switch, avalanche collision ionization occurs in the current filaments, and Joule heat is generated. 2) When the photoconductive switch device is irradiated by a high-energy laser beam, a large amount of light energy will be lost in the form of heat. At the same time, a single laser beam to trigger the photoconductive switch will produce a single high-density charge carrier filament. 3) The leakage current of the photoconductive switch in the dark state will also generate heat loss, and a large amount of heat accumulation will damage the switch.

[0003] Zhao Yue et al. designed a microchannel heat sink for heat dissipation in "Design and Test of Silicon Microchannel Heat Sink for High-Power Photoconductive Switch". Its basic structure is divided into two parts: the heat sink body and the cover plate. The heat sink body is provided with a shunt groove and a confluence groove. The shunt groove and the confluence groove form a microgroove array through MEMS technology. The cover plate uses a semiconductor etching process to form a through-hole structure. The heat sink body and the cover plate are connected by a bonding process to form a closed fluid channel. The photoconductive switch is bonded to the diamond sheet using epoxy resin, and the diamond sheet is bonded to the microchannel heat sink using thermal conductive silicone grease. The heat sink is fixed to a ceramic sheet with a through hole by bonding to increase the mechanical thickness. The fluid enters the shunt groove through the water inlet to complete the diversion, evenly enters the microgroove, takes away the heat on the device through surface convection, and enters the water outlet after being collected through the confluence groove. However, due to the small geometric dimensions of this microgroove structure and the through hole itself, it is easily affected by surface roughness, and the surface roughness not only has a great influence on the flow characteristics of the liquid, but also causes microfluid circulation in the microchannel, which is not conducive to heat dissipation.

[0004] The patent document with application number CN201911368860.X discloses a GaAs photoconductive switch with a heterogeneous structure based on a graphene interface layer and its preparation process. It transfers high-quality graphene to the target substrate, and then plates metal on the surface to form a composite structure of substrate-graphene-metal, homogenizes the electric field, makes the current not concentrated, and generates relatively less heat, which plays a great role in extending the life of the device. However, preparing the graphene film between the metal electrode and the substrate material will affect the adhesion between the metal electrode and the substrate material, causing the metal electrode to fall off. At the same time, the thin layer structure of graphene makes it very difficult to process and integrate into other materials, and requires precise control. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned technology and provide a multi-layer high-voltage and high-thermal conductivity photoconductive switch device and a preparation method, so as to effectively improve the heat dissipation performance of the device, reduce the inter-stage capacitance of the device, and improve the voltage resistance of the device.

[0006] The technical solution of the present invention is achieved in this way:

[0007] 1. A multi-layer high-voltage and high-thermal-conductivity photoconductive switch device, comprising a plurality of semi-insulating substrates, metal electrodes, connecting electrodes and external connecting electrodes, wherein the metal electrodes are distributed at the center of the upper and lower surfaces of each semi-insulating substrate, and the connecting electrodes are respectively connected to the metal electrodes and the external connecting electrodes, characterized in that:

[0008] A boron nitride sheet is arranged between each two adjacent semi-insulating substrates, forming a multi-layer structure;

[0009] A through hole having the same shape and size as the connecting electrode is arranged at the center of each boron nitride sheet. The connecting electrode passes through the through hole of the boron nitride sheet to connect two adjacent metal electrodes on the semi-insulating substrate.

[0010] Preferably, the boron nitride sheet is in the form of a cube with a thickness of 0.5 mm to 1 mm and a side length of 18 mm to 24 mm.

[0011] Preferably, each of the semi-insulating substrates is a cube with a side length of 6 mm to 14 mm and a thickness of 0.35 mm to 1 mm, and its material is one of silicon carbide, gallium nitride, gallium arsenide, gallium oxide, and diamond.

[0012] Preferably, the metal electrode is in ohmic contact with the semi-insulating substrate, and the material is one of a Ni / Ti / Pt / Au composite metal layer, a Ti / Pt / Au composite metal layer, a W / Ti / Au composite metal layer, a Ni / Ti / Au composite metal layer or a Ni / Au composite metal layer.

[0013] Preferably, the shape and size of the connecting electrode are consistent with those of the metal electrode, and the thickness is consistent with the thickness of the boron nitride sheet, and the material is copper metal.

[0014] Preferably, the external connection electrode is made of copper material, has a length greater than half the side length of the boron nitride sheet, a width of 2 mm to 6 mm, and a thickness of 0.05 mm to 0.1 mm.

[0015] 2. A method for preparing a multi-layer high-voltage and high-thermal-conductivity photoconductive switch device, characterized in that it comprises the following steps:

[0016] S1) Clean the semi-insulating substrate wafer and evenly apply photoresist on the front side thereof.

[0017] S2) Photolithography and development are performed on the front side of the semi-insulating substrate wafer coated with photoresist through a mask to form a plurality of groove areas in the shape of metal electrodes, and then magnetron sputtering is performed on the front side of the semi-insulating substrate wafer to form a metal layer.

[0018] S3) All metal outside the front electrode area of ​​the semi-insulating substrate wafer is stripped off and removed to form a front metal electrode.

[0019] S4) The back side of the semi-insulating substrate wafer with the front metal electrode is cleaned again, and photoresist is evenly applied on the cleaned back side.

[0020] S5) Photolithography and development are performed on the back side of the semi-insulating substrate wafer coated with photoresist through a mask to form a plurality of groove areas in the shape of metal electrodes, and then magnetron sputtering is performed on the back side of the semi-insulating substrate to form a back metal layer.

[0021] S6) All metal outside the metal electrode area on the back side of the semi-insulating substrate wafer is stripped off and removed to form a back side metal electrode.

[0022] S7) The semi-insulating substrate wafer is attached to the blue film and diced and split in sequence to prepare a number of individual photoconductive switches, and each photoconductive switch has a metal electrode on the upper and lower surfaces.

[0023] S8) Select several cubic boron nitride sheets, and use laser cutting or plasma cutting to cut a through hole with the same size as the electrode in the center of each boron nitride sheet.

[0024] S9) Select several connecting electrodes, first place them in the corresponding through holes of several boron nitride sheets, and then arrange and stack them in order from top to bottom in the order of boron nitride sheet, photoconductive switch, boron nitride sheet, photoconductive switch, ..., boron nitride sheet to form a stacked structure, and align the connecting electrodes with the metal electrodes of the photoconductive switch, and then use eutectic welding to connect each connecting electrode in the stacked structure to the adjacent metal electrode.

[0025] S10) selecting two external connection electrodes, and connecting them respectively to the connection electrode in the first through hole of the boron nitride sheet and the connection electrode in the last through hole of the boron nitride sheet in the stacked structure.

[0026] S11) Using a packaging mold, the prepared stacked structure is encapsulated by glue filling to completely cover the plurality of photoconductive switches and expose the edge of each boron nitride sheet outside the packaging material, thereby completing the device manufacturing.

[0027] 3. A mold for packaging a photoconductive switch device, made of Teflon material, characterized by comprising a plurality of boron nitride sheet grooves, a plurality of substrate grooves and an external connection electrode groove;

[0028] The depth of each boron nitride groove is 0.75 to 1 times the side length of the boron nitride sheet;

[0029] The depth of each substrate groove is 0.5 to 1 times the side length of the boron nitride sheet;

[0030] The length and width of each external connection electrode groove are respectively consistent with the width and thickness of the external connection electrode, and the depth is greater than the length of the external connection electrode.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] Firstly, since the present invention provides a boron nitride sheet between the photoconductive switches, it can not only utilize the high thermal conductivity of the boron nitride material to timely dissipate the heat during the operation of the photoconductive switch and reduce the thermal damage of the photoconductive switch device; it can also act as a field plate to homogenize the electric field distribution at the metal electrode and improve the voltage resistance of the device.

[0033] Secondly, the present invention connects multiple photoconductive switches by using connecting electrodes in the through holes of the boron nitride sheet to form a stacked structure, which can increase the withstand voltage of the device, reduce the inter-stage capacitance of the device, and help improve the cutoff frequency and response capability of the device.

[0034] Thirdly, the present invention exposes the edge of the boron nitride sheet outside the packaging material during packaging, and utilizes the high thermal conductivity of the boron nitride material to effectively solve the problem of heat accumulation of the device when the photoconductive switch is working, thereby extending the working life of the photoconductive switch device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Device structure diagram of the present invention;

[0036] Figure 2 Preparation of the present invention Figure 1 Device implementation flow chart;

[0037] Figure 3 The present invention encapsulates Figure 1 Diagram of the mold structure used in the device. Specific implementation methods

[0039] The specific examples of the present invention are described in detail below with reference to the accompanying drawings.

[0040] Embodiment 1, based on multi-layer high voltage resistance and high thermal conductivity photoconductive switch device structure

[0041] Reference Figure 1 This example is based on a multi-layer high-voltage and high-thermal-conductivity photoconductive switch device structure, including a semi-insulating substrate 1, a metal electrode 2, a connecting electrode 3, an external connecting electrode 4 and a boron nitride sheet 5, wherein:

[0042] The semi-insulating substrate 1 is provided in several pieces, each with a side length of 6 mm to 14 mm and a thickness of 0.35 mm to 1 mm, and the material is one of silicon carbide, gallium nitride, gallium arsenide, gallium oxide, and diamond.

[0043] The metal electrode 2 is located at the center of the upper and lower surfaces of each semi-insulating substrate, and the material is one of Ni / Ti / Pt / Au composite metal layer, Ti / Pt / Au composite metal layer, W / Ti / Au composite metal layer, Ni / Ti / Au composite metal layer or Ni / Au composite metal layer.

[0044] The boron nitride 5 has a side length of 18 mm to 24 mm and a thickness of 0.5 mm to 1 mm. A through hole with the same shape and size as the metal electrode 2 is provided in the center. It is located above each adjacent semi-insulating substrate 1 and is close to it, forming a stacked structure in which boron nitride sheets and semi-insulating substrates are alternately arranged from top to bottom.

[0045] The connecting electrode 3 is located in the through hole of the boron nitride 5, connected to the metal electrode on the adjacent semi-insulating substrate 1, has the same shape and size as the metal electrode 2, and the same height as the thickness of the boron nitride sheet, and is made of copper.

[0046] The external connection electrodes 4 are set as two, each with a length of 15mm~20mm, a width of 2mm~6mm, a thickness of 0.05mm~0.1mm, and a material of copper. They are respectively located on the top and bottom connection electrodes of the stacked structure, one of which is welded to the connection electrode in the through hole of the first boron nitride sheet in the stacked structure and is located in the left half of the connection electrode; the other is welded to the connection electrode in the through hole of the last boron nitride sheet in the stacked structure and is located in the right half of the connection electrode.

[0047] Reference Figure 2 ,The present invention provides three embodiments for manufacturing the above-mentioned device.

[0048] Example 2: A photoconductive switching device having a three-layer stacked structure of a silicon carbide semi-insulating substrate with a side length of 8 mm and a thickness of 1 mm and a boron nitride substrate with a side length of 18 mm and a thickness of 0.5 mm is manufactured.

[0049] Step 1: clean the silicon carbide semi-insulating substrate and apply glue, as shown in 2a.

[0050] The silicon carbide semi-insulating substrate wafer was sequentially placed in BOE solution, deionized water, acetone, isopropanol, and deionized water for ultrasonic cleaning for 120 s, 180 s, 600 s, 180 s, and 180 s, respectively, and then photoresist was evenly applied on the front side thereof.

[0051] Step 2, preparing a metal layer on the front side of the cleaned silicon carbide semi-insulating wafer, as shown in 2b.

[0052] The front side of the silicon carbide semi-insulating substrate wafer coated with photoresist is photoetched and developed by preparing a mask plate with a circular electrode pattern with a front diameter of 5 mm to form a plurality of groove areas in the shape of circular electrodes;

[0053] Then, the silicon carbide semi-insulating substrate wafer with the groove area is placed in the magnetron sputtering vacuum chamber, with the front side facing the target position, and the vacuum degree is 1×10 -5 Pa argon environment, set the temperature to 200 degrees Celsius, the magnetron sputtering pressure to 1Pa, and the sputtering power to 5W / cm 2 Under the process conditions, Ni, Ti, Pt and Au targets are used in sequence to deposit metal layers with thicknesses of 300nm / 200nm / 200nm / 2000nm respectively to form a front metal layer.

[0054] Step 3, making a metal electrode on the front side of the silicon carbide semi-insulating wafer, as shown in 2c.

[0055] The metal layer outside the groove area on the front side of the semi-insulating substrate wafer is completely peeled off and removed using a blue film peeling method and a stripping machine to form a Ni / Ti / Pt / Au front metal electrode.

[0056] Step 4, cleaning the back side of the silicon carbide semi-insulating wafer, as shown in 2d.

[0057] The back side of the semi-insulating substrate wafer with the front metal electrode was cleaned again, and ultrasonic cleaning was performed using BOE solution, deionized water, acetone, isopropanol, and deionized water for 120s, 180s, 600s, 180s, and 180s, respectively, and then photoresist was evenly applied on the back side.

[0058] Step 5, prepare a metal layer on the back side of the silicon carbide semi-insulating wafer, as shown in 2e.

[0059] The back side of the silicon carbide semi-insulating substrate wafer coated with photoresist is photoetched and developed by preparing a mask plate with a circular electrode pattern with a back side diameter of 5 mm to form a plurality of groove areas in the shape of circular electrodes;

[0060] Then, the silicon carbide semi-insulating substrate wafer with grooved area was placed in the magnetron sputtering vacuum chamber, with the back side facing the target position, and the vacuum degree was 1×10 -5 Pa argon environment, set the temperature to 200 degrees Celsius, the magnetron sputtering pressure to 1Pa, and the sputtering power to 5W / cm 2 Under the process conditions, Ni, Ti, Pt and Au targets were used in sequence to deposit metal layers with thicknesses of 300nm / 200nm / 200nm / 2000nm respectively.

[0061] Step 6, prepare a metal electrode on the back side of the silicon carbide semi-insulating wafer, as shown in 2f.

[0062] The metal layer outside the groove area on the back of the semi-insulating substrate wafer is completely peeled off and removed by tearing the blue film and using a stripping machine to form a Ni / Ti / Pt / Au back metal electrode.

[0063] Step 7, use the silicon carbide wafer with metal electrodes to slice and split to prepare a single photoconductive switch, as shown in 2g.

[0064] The blue film is attached to the front and back sides of the silicon carbide semi-insulating substrate wafer, and the silicon carbide wafer is first diced and then split to prepare several individual silicon carbide semi-insulating substrates with a side length of 8mm and a thickness of 1mm. Each silicon carbide semi-insulating substrate has a metal electrode at the center of the upper and lower surfaces.

[0065] Step 8, prepare through holes on the boron nitride sheet, as shown in 2h.

[0066] Four cubic boron nitride sheets with a side length of 18 mm and a thickness of 0.5 mm were selected, and a through hole with the same size as the electrode was cut in the center of each boron nitride sheet using laser cutting technology.

[0067] Step 9, prepare a boron nitride and silicon carbide substrate stacked structure, as shown in 2i.

[0068] Four cylindrical connecting electrodes with a diameter of 5 mm and a height of 0.5 mm are selected and first placed in the corresponding four through holes of the boron nitride sheet. Then the boron nitride is placed on the upper and lower surfaces of each silicon carbide semi-insulating substrate. From top to bottom, the boron nitride sheet, semi-insulating substrate, boron nitride sheet, semi-insulating substrate, boron nitride sheet, semi-insulating substrate, and boron nitride sheet are arranged and stacked in sequence to form a three-layer stacked structure. The connecting electrodes are aligned with the metal electrodes on the semi-insulating substrate, and then eutectic welding is used to connect each connecting electrode in the stacked structure to the adjacent metal electrode.

[0069] Step 10, welding external connection electrodes on the laminated structure, such as Figure 2 j shown.

[0070] Two external connection electrodes with a length of 14 mm, a width of 4 mm, and a thickness of 0.05 mm were selected, one of which was welded to the left half of the connection electrode in the through-hole of the first boron nitride sheet in the stacked structure; the other was welded to the right half of the connection electrode in the through-hole of the last boron nitride sheet in the stacked structure to complete the device preparation.

[0071] Step 11, encapsulate the stacked structure to complete the preparation of the device, such as Figure 2 k shown.

[0072] The three-layer stacked structure with external connection electrodes welded to it is placed in a packaging mold. Epoxy resin glue is first poured into the packaging mold, and then the mold is placed in a vacuum chamber for evacuation to exhaust the air in the glue. After cooling and waiting for the epoxy resin glue to solidify, the device is taken out of the mold to complete the preparation of the device.

[0073] Example 3: A photoconductive switching device with a four-layer stacked structure is manufactured, wherein the gallium nitride semi-insulating substrate has a side length of 14 mm and a thickness of 0.35 mm, and the boron nitride has a side length of 24 mm and a thickness of 0.35 mm.

[0074] Step 1: Clean and spread the GaN semi-insulating substrate wafer, as shown in 2a.

[0075] The specific implementation of this step is the same as step 1 of Example 1.

[0076] Step 2: Prepare a metal layer on the front side of the gallium nitride semi-insulating wafer after cleaning and coating, as shown in 2b.

[0077] 2.1) Using a mask plate with a circular electrode pattern with a front diameter of 8 mm, photolithography and development are performed on the front side of a silicon carbide semi-insulating substrate wafer coated with photoresist to form a plurality of circular electrode-shaped groove areas;

[0078] 2.2) Place the silicon carbide semi-insulating substrate wafer with the groove area in the magnetron sputtering vacuum chamber, with the front side facing the target position, and place it in a vacuum chamber with a degree of vacuum of 1×10 -5 Pa argon environment, set the temperature to 200 degrees Celsius, the magnetron sputtering pressure to 0.8Pa, and the sputtering power to 5W / cm 2 Under the process conditions, Ni and Au targets are used in turn to deposit metal layers with a thickness of 300nm / 3000nm respectively to form a front metal layer.

[0079] Step three, make a metal electrode on the front side of the GaN semi-insulating wafer, as shown in 2c.

[0080] The metal layer outside the groove area on the front side of the semi-insulating substrate wafer is completely peeled off and removed by using a blue film peeling method and a stripping machine to form a Ni / Au front metal electrode.

[0081] Step 4: Clean the back side of the GaN semi-insulating substrate, as shown in 2d.

[0082] The specific implementation of this step is the same as step 4 of Example 1.

[0083] Step five, prepare a metal layer on the back of the gallium nitride wafer, as shown in 2e.

[0084] 5.1) Using a mask plate with a circular electrode pattern with a back diameter of 8 mm, the back side of the gallium nitride semi-insulating substrate wafer coated with photoresist is photolithographically processed and developed to form several groove areas in the shape of circular electrodes;

[0085] 5.2) Place the GaN semi-insulating substrate wafer with the grooved area in a magnetron sputtering vacuum chamber, with the back side facing the target position, and place it in a vacuum chamber with a degree of vacuum of 1×10 -5 Pa argon environment, at a temperature of 200 degrees Celsius, the magnetron sputtering pressure was 0.8 Pa, and the sputtering power was 5 W / cm 2 Under the process conditions, Ni and Au metals with thickness of 300nm / 3000nm are deposited in sequence to form a back metal layer.

[0086] Step six, make a metal electrode on the back of the silicon carbide semi-insulating wafer, as shown in 2f.

[0087] The metal layer outside the groove area on the back of the semi-insulating substrate wafer is completely peeled off and removed by using a blue film peeling method and a stripping machine to form a Ni / Au back metal electrode.

[0088] Step seven, scribe and split the GaN wafer to prepare a single photoconductive switch, as shown in 2g.

[0089] The blue film is attached to the front and back sides of the gallium nitride semi-insulating substrate wafer. The gallium nitride wafer is first diced and then split to prepare several individual gallium nitride semi-insulating substrates with a side length of 14mm and a thickness of 0.35mm. Each gallium nitride semi-insulating substrate has a metal electrode at the center of the upper and lower surfaces to form a single photoconductive switch.

[0090] Step eight, prepare through holes on the boron nitride sheet, as shown in 2h.

[0091] Five cubic boron nitride sheets with a side length of 24 mm and a thickness of 0.35 mm were selected, and a through hole with the same size as the electrode was cut in the center of each boron nitride sheet using laser cutting technology.

[0092] Step nine, prepare a boron nitride and gallium nitride substrate stacked structure, as shown in 2i.

[0093] 9.1) Select five cylindrical connection electrodes with a diameter of 8 mm and a height of 0.35 mm and place them in the corresponding five through holes of the boron nitride sheet;

[0094] 9.2) Place boron nitride on the upper and lower surfaces of each gallium nitride semi-insulating substrate, and stack them in the order of boron nitride sheet, semi-insulating substrate, boron nitride sheet, semi-insulating substrate, boron nitride sheet, semi-insulating substrate, boron nitride sheet, semi-insulating substrate, and boron nitride sheet from top to bottom to form a four-layer stacked structure, and align the connecting electrodes with the metal electrodes on the semi-insulating substrate;

[0095] 9.3) Use eutectic welding to connect each connecting electrode in the stacked structure to the adjacent metal electrode.

[0096] Step 10: Weld external connection electrodes on the laminated structure, such as Figure 2 j shown.

[0097] Two external connection electrodes with a length of 20 mm, a width of 6 mm, and a thickness of 0.05 mm were selected, one of which was welded to the left half of the connection electrode in the through-hole of the first boron nitride sheet in the stacked structure; the other was welded to the right half of the connection electrode in the through-hole of the last boron nitride sheet in the stacked structure to complete the device preparation.

[0098] Step 11: encapsulate the stacked structure to complete the device preparation, such as Figure 2 k shown.

[0099] The four-layer stacked structure with external connection electrodes welded is placed in a packaging mold. Epoxy resin glue is first poured into the packaging mold, and then the mold is placed in a vacuum chamber for vacuuming to exhaust the air in the glue. After cooling and waiting for the epoxy resin glue to solidify, the device is taken out of the mold to complete the preparation of the device.

[0100] Example 4: A photoconductive switch device with a two-layer stacked structure is manufactured, wherein the gallium arsenide semi-insulating substrate has a side length of 10 mm and a thickness of 0.5 mm, and the boron nitride has a side length of 20 mm and a thickness of 0.5 mm.

[0101] Step A, clean the GaAs semi-insulating substrate and spread the glue, as shown in 2a.

[0102] The specific implementation of this step is the same as step 1 of Example 1.

[0103] Step B, preparing a metal layer on the front side of the GaAs wafer, as shown in 2b.

[0104] B1 uses a mask plate with a circular electrode pattern with a front diameter of 7 mm to perform photolithography and development on the front side of a gallium arsenide semi-insulating substrate wafer coated with photoresist to form several groove areas in the shape of circular electrodes;

[0105] B2 Place the GaAs semi-insulating substrate wafer with grooved area in the magnetron sputtering vacuum chamber, with the front side facing the target position, and place it in a vacuum of 1×10 -5 Pa argon environment, set the temperature to 200 degrees Celsius, the magnetron sputtering pressure to 1.2 Pa, and the sputtering power to 5 W / cm 2 Under the process conditions, Ni, Ti and Au targets are used in sequence to deposit metal layers with thicknesses of 300nm / 500nm / 3000nm respectively to form a front metal layer.

[0106] Step C, making a metal electrode on the front side of the GaAs semi-insulating wafer, as shown in 2c.

[0107] The blue film is peeled off and a stripping machine is used to completely remove the metal layer outside the front electrode area of ​​the gallium arsenide semi-insulating substrate wafer to form a Ni / Ti / Au front metal electrode.

[0108] Step D, cleaning the back side of the GaAs semi-insulating wafer, as shown in 2d.

[0109] The specific implementation of this step is the same as step 4 of Example 1.

[0110] Step E, preparing a metal layer on the back side of the GaAs wafer, as shown in 2e.

[0111] E1) using a mask plate with a circular electrode pattern having a back diameter of 7 mm, photolithography and development are performed on the back side of a gallium arsenide semi-insulating substrate wafer coated with photoresist to form a plurality of groove areas in the shape of circular electrodes;

[0112] E2) Place the GaAs semi-insulating substrate wafer with the grooved area in a magnetron sputtering vacuum chamber, with the back side facing the target position, and place it in a vacuum chamber of 1×10 -5 Pa argon environment, temperature is 200 degrees Celsius, magnetron sputtering pressure is 1.2Pa, sputtering power is 5W / cm 2 Under the process conditions, Ni, Ti, and Au targets are used in sequence to deposit metal layers with thicknesses of 300nm / 500nm / 3000nm respectively to form the back metal layer.

[0113] Step F, prepare a metal electrode on the back side of the GaAs wafer, as shown in 2f.

[0114] The blue film is peeled off and a stripping machine is used to completely strip off the metal layer outside the back electrode area of ​​the gallium arsenide semi-insulating substrate wafer to form a Ni / Ti / Au back metal electrode.

[0115] Step G, slicing and splitting the GaAs wafer to prepare a single photoconductive switch, as shown in 2g.

[0116] The blue film is attached to the front and back sides of the gallium arsenide semi-insulating substrate wafer. The gallium arsenide wafer is first diced and then split to prepare several individual gallium arsenide semi-insulating substrates with a side length of 10 mm and a thickness of 0.5 mm. Each gallium arsenide semi-insulating substrate has a metal electrode at the center of the upper and lower surfaces to form a single photoconductive switch.

[0117] Step H, prepare through holes on the boron nitride sheet, as shown in 2h.

[0118] Three cubic boron nitride sheets with a side length of 20 mm and a thickness of 0.5 mm were selected, and a through hole with the same size as the electrode was cut in the center of each boron nitride sheet using laser cutting technology.

[0119] Step I, prepare a boron nitride and gallium arsenide semi-insulating substrate stacked structure, as shown in 2i.

[0120] I1) Select three cylindrical connection electrodes with a diameter of 7 mm and a height of 0.5 mm and place them in the corresponding three through holes of the boron nitride sheet;

[0121] I2) placing boron nitride on the upper and lower surfaces of each gallium arsenide semi-insulating substrate, and then arranging and stacking them in the order of boron nitride sheet, gallium arsenide semi-insulating substrate, boron nitride sheet, gallium arsenide semi-insulating substrate, and boron nitride sheet from top to bottom to form a two-layer stacked structure, and aligning the connecting electrode with the metal electrode of the photoconductive switch;

[0122] I3) Each connecting electrode in the stacked structure is connected to an adjacent metal electrode using eutectic welding.

[0123] Step J, welding external connection electrodes on the laminated structure, such as Figure 2 k shown.

[0124] Two external connection electrodes with a length of 15 mm, a width of 6 mm and a thickness of 0.05 mm are selected, and one of them is welded to the left half of the connecting electrode in the through hole of the first boron nitride sheet in the laminated structure; the other is welded to the right half of the connecting electrode in the through hole of the last boron nitride sheet in the laminated structure.

[0125] Step K, encapsulating the stacked structure to complete the preparation of the device, such as Figure 2 k shown.

[0126] Place the two-layer stacked structure with external connection electrodes welded to it in a packaging mold. First, fill the packaging mold with epoxy resin glue, then place the mold in a vacuum chamber to evacuate the air in the glue, cool it and wait for the epoxy resin glue to solidify, then take the device out of the mold to complete the device preparation.

[0127] Embodiment 5: Multi-layer high-voltage-resistant and high-thermal-conductivity photoconductive switch device packaging mold structure

[0128] Reference Figure 3 , this example is used for packaging a mold of a multi-layer high-voltage and high-thermal-conductivity photoconductive switch device, using Teflon material, and including several deep grooves I, several shallow grooves II and metal electrode grooves III, wherein:

[0129] The several deep grooves I are of the same shape and size, the depth of each groove is set to 0.75 to 1 times the side length of the boron nitride sheet, and the length and width are respectively consistent with the side length and thickness of the boron nitride sheet;

[0130] The several shallow grooves II have the same shape and size, the depth of each groove is set to 1.4 to 2 times the side length of the semi-insulating substrate sheet, the length is 1.2 to 1.8 times the side length of the semi-insulating substrate sheet, and the width is consistent with the thickness of the semi-insulating substrate sheet. The shallow grooves are located on the upper and lower sides of each deep groove, and are arranged in order of shallow groove, deep groove, shallow groove, deep groove, ..., shallow groove to form a laminated structure.

[0131] The external connection electrode groove III is located in the middle of the bottom of the top shallow groove in the stacked structure. Its length and width are consistent with the width and thickness of the external connection electrode respectively, and its depth is greater than the length of the external connection electrode.

[0132] The deep groove I, shallow groove II and metal electrode groove III of the packaging mold can be adjusted according to the size of the actual laminated structure to be packaged.

[0133] The above descriptions are only a few specific examples of the present invention and do not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, they may make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A multi-layer high-voltage-withstand and high-thermal-conductivity photoconductive switch device, comprising a plurality of semi-insulating substrates (1), metal electrodes (2), connecting electrodes (3) and external connecting electrodes (4), wherein the metal electrodes (2) are distributed at the center of the upper and lower surfaces of each semi-insulating substrate (1), and the connecting electrodes (3) are respectively connected to the metal electrodes (2) and the external connecting electrodes (4), characterized in that: A boron nitride sheet (5) is arranged between each two adjacent semi-insulating substrates, and is close to the substrates, so as to form a multi-layer structure; A through hole having the same shape and size as the connecting electrode (3) is provided at the center of each boron nitride sheet (5); the connecting electrode passes through the through hole of the boron nitride sheet to connect two adjacent metal electrodes (2) on the semi-insulating substrate.

2. The device according to claim 1, characterized in that The boron nitride sheet (5) is in the form of a cube with a thickness of 0.5 mm to 1 mm and a side length of 18 mm to 24 mm.

3. The device according to claim 1, characterized in that Each semi-insulating substrate (1) is a cube with a side length of 6 mm to 14 mm and a thickness of 0.35 mm to 1 mm, and its material is one of silicon carbide, gallium nitride, gallium arsenide, gallium oxide, and diamond.

4. The device according to claim 1, characterized in that The metal electrode (2) is in ohmic contact with the semi-insulating substrate, and the material is one of a Ni / Ti / Pt / Au composite metal layer, a Ti / Pt / Au composite metal layer, a W / Ti / Au composite metal layer, a Ni / Ti / Au composite metal layer or a Ni / Au composite metal layer.

5. The device according to claim 1, characterized in that The shape and size of the connecting electrode (3) are consistent with those of the metal electrode, and its thickness is consistent with that of the boron nitride sheet, and the material used is copper metal.

6. The device according to claim 1, characterized in that The external connection electrode (4) is made of copper material, has a length greater than half the side length of the boron nitride sheet (5), a width of 2 mm to 6 mm, and a thickness of 0.05 mm to 0.1 mm.

7. A method for preparing a multi-layer high-voltage and high-thermal-conductivity photoconductive switch device, characterized in that: The steps include: S1) cleaning the semi-insulating substrate wafer and evenly applying photoresist on the front side thereof; S2) performing photolithography and development on the front side of the semi-insulating substrate wafer coated with photoresist through a mask to form a plurality of groove areas in the shape of metal electrodes, and then magnetron sputtering is performed on the front side of the semi-insulating substrate wafer to form a metal layer; S3) removing all the metal outside the front electrode area of ​​the semi-insulating substrate wafer to form a front metal electrode; S4) cleaning the back side of the semi-insulating substrate wafer with the front metal electrode again, and evenly applying photoresist on the cleaned back side; S5) performing photolithography and development on the back side of the semi-insulating substrate wafer coated with photoresist through a mask to form a plurality of groove areas in the shape of metal electrodes, and then performing magnetron sputtering on the back side of the semi-insulating substrate to form a back side metal layer; S6) removing all the metal outside the metal electrode region on the back side of the semi-insulating substrate wafer to form a back side metal electrode; S7) attaching the semi-insulating substrate wafer to the blue film and sequentially scribing and splitting the wafer to prepare a plurality of individual photoconductive switches, each of which has a metal electrode on the upper and lower surfaces; S8) selecting several cubic boron nitride sheets, and cutting a through hole having the same size as the electrode in the center of each boron nitride sheet by laser cutting or plasma cutting; S9) Selecting a plurality of connection electrodes, placing them in the corresponding through holes of the boron nitride sheets, and then stacking them in the order of boron nitride sheet, photoconductive switch, boron nitride sheet, photoconductive switch, ..., boron nitride sheet from top to bottom to form a stacked structure, aligning the connection electrodes with the metal electrodes of the photoconductive switch, and then connecting each connection electrode in the stacked structure with the adjacent metal electrode by eutectic welding; S10) selecting two external connection electrodes, and connecting them respectively to the connection electrode in the first through hole of the boron nitride sheet and the connection electrode in the last through hole of the boron nitride sheet in the stacked structure; S11) Using a packaging mold, the prepared stacked structure is encapsulated by glue filling to completely cover the plurality of photoconductive switches and expose the edge of each boron nitride sheet outside the packaging material, thereby completing the device manufacturing.

8. The method according to claim 7, characterized in that The semi-insulating substrate wafer is cleaned by sequentially placing the semi-insulating substrate wafer into BOE solution, deionized water, acetone, isopropanol, and deionized water for ultrasonic cleaning for 120s, 180s, 600s, 180s, and 180s, respectively.

9. The method according to claim 7, characterized in that: The semi-insulating substrate magnetron sputtering is to place the semi-insulating substrate wafer in a vacuum chamber filled with argon gas with a vacuum degree better than 5×10 -4 Pa environment, the magnetron sputtering pressure is set to 0.5Pa-1.5Pa, and the sputtering power is 5W / cm 2 , the target materials Ni / Ti / Pt / Au are sputtered in sequence.

10. A mold for packaging a photoconductive switch device, made of Teflon material, characterized in that: It includes several deep grooves I, several shallow grooves II and external connection electrode grooves III; The depth of each deep groove I is 0.75 to 1 times the side length of the boron nitride sheet, and the length and width are consistent with the side length and thickness of the boron nitride sheet respectively; The depth of each shallow groove II is 1.4 to 2 times the side length of the semi-insulating substrate sheet, the length is 1.2 to 1.8 times the side length of the semi-insulating substrate sheet, and the width is consistent with the thickness of the semi-insulating substrate sheet; The length and width of each external connection electrode groove III are respectively consistent with the width and thickness of the external connection electrode, and the depth is greater than the length of the external connection electrode.

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