Based on a triangular, rounded-corner optical guide switch device and its fabrication and packaging method

Abstract

This invention discloses a triangular, rounded-corner photoconductive switch device and its fabrication and packaging method, mainly addressing the problem of low light energy utilization in existing photoconductive switch devices. It includes a semi-insulating substrate (1), a reflector (2), a metal electrode (3), an external connecting electrode (4), and a packaging material (5). The semi-insulating substrate has a triangular, rounded-corner shape, with an angle α between its side and the reflector. The reflector's length is only half the side length of the triangular substrate and is located on either the left or right half of the substrate, with the other half serving as the light-incident surface. The triangular substrate performs total internal reflection on the incoming trigger light, and the reflected light is then reflected back to the substrate for a second total internal reflection. The metal electrode is located on the semi-insulating substrate and connected to the external connecting electrode. The packaging material is poured onto the exterior of the entire device. This invention improves the utilization rate of light energy and has a simple structure, making it suitable for ultra-wideband electromagnetic pulse generators and solid-state compact pulse power supplies.

Description

Technical Field

[0001] This invention belongs to the field of microelectronics technology, and specifically relates to a photoconductive switching device that can be used in ultra-wideband electromagnetic pulse generators and solid-state compact pulse power supplies. Background Technology

[0002] Photoconductive switching devices are novel devices that use laser pulses of a specific wavelength to excite a large number of photogenerated carriers within a semiconductor device, controlling the material's conductivity to achieve on / off switching. Photoconductive switches offer advantages such as fast closing time, short jitter time, high repetition frequency, immunity to electromagnetic interference, and miniaturization. However, a key challenge currently facing photoconductive switching devices is the low utilization rate of laser energy. Due to the limited absorption of light energy by the substrate material, a significant portion of the light energy is lost through the device, resulting in low energy utilization. Improving the utilization rate of trigger laser energy in photoconductive switching devices can enhance photoelectric conversion efficiency, generate more photogenerated carriers, increase conduction current, and thus improve the output power of the photoconductive switching device.

[0003] Patent application number 202310744520.2 discloses an optical structure for improving the light energy utilization of a gallium arsenide photoconductive switch. It employs various optical lenses and mirrors to enhance the light energy utilization of the photoconductive switch. The optical structure consists of a photoconductive switch, a cylindrical lens, four mirrors, and a plano-concave cylindrical mirror. The first mirror, cylindrical lens, photoconductive switch, and second mirror are arranged horizontally from top to bottom, with their centers facing each other. The left end face of the cylindrical lens is bonded to the reflecting surface of the third mirror, and the right end face is bonded to the reflecting surface of the fourth mirror. The axis passes through the center of the third and fourth mirrors. A plano-concave cylindrical mirror is placed inside a circular through-hole in the middle of the first mirror. The gallium arsenide photoconductive switch, the third mirror, the first mirror, the plano-concave cylindrical mirror, and the fourth mirror constitute a sealed space containing the cylindrical lens. This structural design allows the incident pulsed laser to be reflected multiple times through the substrate material, increasing the optical path of the trigger laser within the device. This ensures that the trigger laser is fully absorbed by the photoconductive substrate, improving the utilization rate of pulsed laser energy and reducing the on-resistance of the photoconductive switch. While this structure can improve the light energy utilization rate of the photoconductive switch and achieve high photoelectric conversion efficiency to a certain extent, the structure is relatively cumbersome and complex, and the optical path is difficult to align. Even a slight misalignment between the relative positions of the lens and the via will have a significant impact on the output. Furthermore, this structure increases the size of the device, hindering the compactness and integration of photoconductive switches.

[0004] Patent application CN202310681018.1 discloses a high-efficiency photoconductive switch optical system based on a grating structure. It employs a grating structure to improve the light energy utilization of the photoconductive switch. By fabricating a grating structure composed of a series of parallel microgrooves in the incident light region, the absorption of laser light is enhanced by the reflection effect of the grating. Furthermore, the photoelectric conversion efficiency can be further improved by changing parameters such as the grating period. Although this system can improve the photoelectric conversion efficiency of the photoconductive switch device, the design and fabrication of its grating structure are quite demanding, easily leading to increased light scattering and reflection, thus reducing the photoconductive switch's light energy utilization.

[0005] To improve the utilization rate of light energy, a common solution is to introduce antireflective coatings and reflective coatings on the light-incident and back-light-out surfaces of the switch, respectively. This reduces the loss of laser light energy on the light-incident surface and allows unabsorbed laser light to pass through the conduction region a second time, increasing the optical path length within the device and thus improving light utilization. However, this approach has several problems: firstly, there is a lattice mismatch between the thin film material and the substrate.

[0006] Secondly, the testing of photoconductive switches involves multiple laser irradiations, which may damage the thin film material, directly affecting the reliability of the photoconductive switch and even causing it to fail.

[0007] Third, thermal stress is generated between the multilayer stacked structures, which causes the film to crack, reducing the antireflective and antireflective effects of the film. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of the prior art by providing a triangular rounded corner light-conducting switch device and its fabrication and packaging method, so as to simplify the device structure and improve the device's operational stability while increasing light energy utilization.

[0009] The key technology to achieve the purpose of this invention is: a triangular rounded corner substrate structure, which utilizes the total internal reflection of the substrate itself and an external reflector to improve the light energy utilization of the photoconductive switch; and the device structure is simplified by selecting simple and controllable optical components to improve the stability of the device operation.

[0010] The technical solution of this invention is implemented as follows:

[0011] 1. A photoconductive switch device based on a triangular shape with rounded corners, comprising a semi-insulating substrate, a reflector, a metal electrode, an external connecting electrode, and an encapsulation material, characterized in that:

[0012] The semi-insulating substrate has a triangular rounded corner shape, and its side is provided with an angle α between it and the reflector.

[0013] The reflector is only half the length of the side of the triangular substrate and is located on the left or right half of the triangular substrate. The other half serves as the light incident surface and its thickness is the same as that of the semi-insulating substrate.

[0014] The triangular substrate performs total internal reflection on the incoming trigger light. The light after total internal reflection is then reflected back to the substrate by a mirror for a second total internal reflection, thereby improving the device's utilization of light energy.

[0015] Preferably, the triangular substrate is any one of the semi-insulating materials such as silicon carbide, gallium nitride, gallium arsenide, gallium oxide, or diamond, with a thickness of 0.35mm-1mm, a side length of 6-14mm, and an angle α between the side and the reflector of 1° to 5°.

[0016] Preferably, the metal electrode is located at the center of the upper and lower surfaces of the semi-insulating substrate, and is a rounded triangle in shape. It is an ohmic contact and is made of one of the following materials: 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.

[0017] Preferably, the external connecting electrode is made of copper metal, and is shaped as a rectangular strip with a length of 6mm-10mm, a width of 2mm-4mm, and a thickness of 0.05mm-0.1mm, covering half of the metal electrode.

[0018] Preferably, the encapsulation material is made of epoxy resin, which tightly covers the entire surface of the device and is dense and air-free.

[0019] 2. A method for fabricating a photoconductive switch device based on a triangular shape with rounded corners, characterized by comprising the following steps:

[0020] S1: Cleaning of the semi-insulating substrate;

[0021] S2: Apply photoresist evenly to the front side of the cleaned semi-insulating substrate;

[0022] S3: Photolithography and development are performed on a semi-insulating substrate coated with photoresist using a mask to form several chamfered triangular electrode-shaped groove areas, and metal is evaporated, sputtered, and electroplated on the front side of the semi-insulating substrate to form a metal layer.

[0023] S4: Remove all metal outside the front electrode area of ​​the semi-insulating substrate to form a metal electrode;

[0024] S5: Clean the back side of the semi-insulating substrate again.

[0025] S6: Apply photoresist evenly to the back side of the cleaned semi-insulating substrate;

[0026] S7: Photolithography and development are performed on the back side of a semi-insulating substrate coated with photoresist using a mask to form a chamfered triangular electrode-shaped groove area, and metal is evaporated, sputtered, and electroplated on the back side of the semi-insulating substrate to form a metal layer.

[0027] S8: Remove all metal outside the metal electrode area on the back side of the semi-insulating substrate to form a metal electrode;

[0028] S9: External connecting electrodes are welded onto the metal electrodes on the upper and lower surfaces of the semi-insulating substrate, and the photoconductive switch device is fixed in the packaging mold through the external connecting electrodes. Then, the reflector is fixed by potting glue, and the entire device is packaged.

[0029] S10: Cool until the epoxy resin solidifies, open the encapsulation mold, and obtain the photoconductive switch device.

[0030] 3. A packaging method for a triangular, rounded-corner photoconductive switch device, characterized by the following implementation steps:

[0031] 1) Use Teflon material to prepare the mortise and tenon structure packaging mold, which has a glue-filling hole. The mold must be able to fit tightly to ensure no glue leakage.

[0032] 2) Fix the position of the photoconductive switch device by the external electrode that has been welded to the metal electrode, fix the photoconductive switch device in the center of the mold, and tightly fasten the mold together;

[0033] 3) Fill the mold with glue through the filling hole. When the glue can just completely immerse the device, place the reflector on the side closest to the device. At this time, the reflector and the surface of the flowing glue should be horizontal and at a slight angle to the device. Then fill a small amount of encapsulating glue to completely immerse the entire structure.

[0034] 4) Perform a vacuuming operation on the encapsulating adhesive and allow it to cool and solidify;

[0035] 5) Open the mold to obtain the packaged device.

[0036] 4. A mold for encapsulating a photoconductive switching device, comprising a bottom and a top part, which are tightly fitted together by protruding tenons and recessed mortises to form a mortise and tenon encapsulation structure, characterized in that:

[0037] The bottom is provided with a square groove with a depth of 1.5mm-2.0mm close to the bottom edge. On both sides of the groove, there are shallow inclined grooves with a depth of 0.05mm-0.1mm. Both shallow inclined grooves are at an angle α with the bottom edge so that the device and the reflector maintain an angle of 1° to 5°.

[0038] The top is provided with a square groove with a depth of 0.5mm-0.8mm close to the bottom edge, which corresponds to the square groove at the bottom.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] Firstly, this invention improves the light energy utilization rate of photoconductive switching devices by utilizing the total internal reflection of the rounded-corner triangular-shaped photoconductive opening substrate and the reflecting mirror.

[0041] Secondly, this invention improves the light energy utilization of the device by adding only an external reflector, which not only makes the process simple and controllable, but also improves the stability of the device operation.

[0042] Third, the present invention avoids the local electric field enhancement caused by the sharp edges and corners of the device through the rounded corner structure design, thereby reducing the risk of device breakdown.

[0043] Fourth, the present invention places the external electrode by designing a shallow groove in the packaging structure. The angle between the photoconductive switch device and the reflector can prevent the laser from being damaged by reflected light, and at the same time, it can make the trigger light uniformly distributed in the substrate. Attached Figure Description

[0044] Figure 1 Device structure diagram of the present invention;

[0045] Figure 2 Preparation of this invention Figure 1 Flowchart of the device;

[0046] Figure 3 This invention encapsulation Figure 1 Device flowchart;

[0047] Figure 4 A structural diagram of the mold used for packaging in this invention. Detailed Implementation

[0048] The following detailed description of specific examples of the present invention is provided in conjunction with the accompanying drawings.

[0049] Example 1: A photoconductive switch based on a triangular shape with rounded corners

[0050] Reference Figure 1 This example is based on a triangular, rounded-corner photoconductive switch, comprising a semi-insulating substrate 1, a reflector 2, a metal electrode 3, an external connecting electrode 4, and an encapsulation material 5, wherein:

[0051] The semi-insulating substrate 1 is made of silicon carbide material and is an equilateral triangle with a side length of 10 mm and a thickness of 1 mm. The three corners of the equilateral triangle are chamfered with a radius of 1 mm to form a rounded equilateral triangle shape.

[0052] The reflector 2 is a rectangle with a length and width of 5mm × 1mm. It is located on the left half of the side of the triangular substrate 1 and maintains a 2° angle with the side of the substrate to ensure that the two do not contact each other.

[0053] The metal electrode 3 is located in the center of the substrate 1. It is a rounded equilateral triangle with a side length of 6 mm. The material is a Ni / Ti / Pt / Au composite metal layer, and the thickness of each layer is 300 nm / 200 nm / 200 nm / 2000 nm respectively.

[0054] The external connecting electrode 4 is made of copper. The external connecting electrode on the upper surface covers the right side of the upper surface metal electrode, and the external connecting electrode on the lower surface covers the left side of the lower surface metal electrode. The external connecting electrode is partially encapsulated in epoxy resin and partially exposed to the air.

[0055] The encapsulation material 5 is made of epoxy resin and covers the entire surface of the semi-insulating substrate, metal electrode and reflector.

[0056] Example 2: Fabrication of a triangular, rounded-corner light guide switch

[0057] Reference Figure 2 This example demonstrates a method for fabricating a triangular, rounded-corner light-guiding switch, which includes the following steps:

[0058] Step 1: Clean the semi-insulating substrate, such as... Figure 2 As shown in a.

[0059] The semi-insulating substrate wafer was sequentially immersed in BOE solution, deionized water, acetone, isopropanol, and deionized water for ultrasonic cleaning for 120s, 180s, 600s, 180s, and 180s, respectively.

[0060] Step 2: Apply uniform coating to the front side of the semi-insulating substrate, such as... Figure 2 As shown in b.

[0061] Photoresist is uniformly applied to the front side of the cleaned semi-insulating substrate.

[0062] Step 3: Fabricate a metal layer on the front side of the semi-insulating substrate, such as... Figure 2 As shown in c.

[0063] The front side of the coated semi-insulating substrate is photolithographically developed using a pre-prepared rounded triangular pattern mask to create the required electrode pattern area. Then, nickel metal is first evaporated and deposited on the front side of the semi-insulating substrate, followed by sputtering and depositing titanium, platinum, and gold. In this example, the thickness of the evaporated nickel deposit is set to 300 nm, and the thicknesses of the sputtered titanium, platinum, and gold deposits are 200 nm, 200 nm, and 2000 nm, respectively.

[0064] Step 4: Fabricate a metal electrode on the front side of the semi-insulating substrate, such as... Figure 2 As shown in d.

[0065] All metal layers outside the metal electrode area on the front side of the semi-insulating substrate are stripped away to form Ni / Ti / Pt / Au metal electrodes;

[0066] Step 5: Clean the back side of the semi-insulating substrate, such as... Figure 2 As shown in e.

[0067] The back side of the semi-insulating substrate was ultrasonically cleaned sequentially with BOE solution, deionized water, acetone, isopropanol, and deionized water. In this example, the cleaning times for each solution were set to, but not limited to, 120s, 180s, 600s, 180s, and 180s, respectively.

[0068] Step 6: Apply adhesive evenly to the back side of the semi-insulating substrate, such as... Figure 2 As shown in f.

[0069] Photoresist is evenly applied to the back side of the semi-insulating substrate after back cleaning;

[0070] Step 7: Fabricate a metal layer on the back side of the semi-insulating substrate, such as... Figure 2 As shown in g.

[0071] The back side of the coated semi-insulating substrate is photolithographically developed using a pre-prepared rounded triangular mask to create the desired electrode pattern area. Then, nickel metal is first evaporated and deposited on the back side of the semi-insulating substrate, followed by sputtering and depositing titanium, platinum, and gold. In this example, the thickness of the evaporated nickel deposit is set to 300 nm, and the thicknesses of the sputtered titanium, platinum, and gold deposits are 200 nm, 200 nm, and 2000 nm, respectively.

[0072] Step 8: Fabricate a metal electrode on the back side of the semi-insulating substrate, such as... Figure 2 As shown in h.

[0073] All metal outside the back metal electrode area of ​​the semi-insulating substrate is stripped away to form the back metal electrode;

[0074] Step 9: Fill the encapsulation mold with glue to fix the device structure, such as... Figure 2 As shown in i.

[0075] External connecting electrodes are soldered to the right side of the upper surface metal electrode and the left side of the lower surface metal electrode of the semi-insulating substrate. The device is then fixed in the packaging mold through the external connecting electrodes. When the epoxy resin just covers the semi-insulating substrate, a reflector is placed on the left side of the semi-insulating substrate, and encapsulation glue is poured in to cover the entire device structure.

[0076] Step 10: After the mold has been filled with glue and cooled to solidify, open the mold to obtain the photoconductive switch device, such as... Figure 2 As shown in j.

[0077] Example 3: Triangular rounded corner photoconductive switch package

[0078] Reference Figure 3 The method for encapsulating a triangular, rounded-corner photoconductive switch in this example includes the following steps:

[0079] The first step is to use a mortise and tenon encapsulation mold made of Teflon material. The mold is divided into a top and a bottom, and a potting hole is prepared on the side of the encapsulation mold. The top and bottom of the mold can fit together tightly without leakage.

[0080] The second step is to fix the photoconductive switch device in the center of the bottom groove of the mold using the external electrode of the photoconductive switch device, and then cover the bottom with the top and fasten the mold together tightly using the tenon and mortise structure.

[0081] The third step is to place the mold on a horizontal plane and pour the epoxy resin through the potting hole of the mold to ensure that the liquid level of the epoxy resin is kept horizontal. When the resin can just completely immerse the device, place the reflector on the left side of the semi-insulating substrate, adjust the position of the reflector so that the reflector is facing the left half of the semi-insulating substrate, and then pour in a small amount of encapsulating resin to completely immerse the entire structure.

[0082] The fourth step is to place the entire mold after potting in a sealed environment, use a vacuum pump to extract the gas from the environment and remove the air from the encapsulating adhesive, and then cool it until the epoxy resin solidifies.

[0083] The fifth step is to open the mold to obtain the packaged device.

[0084] Example 4: Mold for encapsulating a triangular, rounded-corner photoconductive switch

[0085] Reference Figure 4 The mold used to encapsulate the triangular rounded corner light guide switch in this example includes a bottom 1 and a top 2, and is made of Teflon material.

[0086] The bottom 1 has a square groove 12 close to the bottom edge; the groove has a depth of 1.5mm, and there are shallow inclined grooves 11 with a depth of 0.05mm on both sides. Both shallow inclined grooves 11 have an angle of 2° with the bottom edge so that the device and the reflector maintain an angle of 2°. Tenons are also provided at the four top corners of the bottom 1.

[0087] The top 2 is provided with a square groove 21 close to the bottom edge of the top, the groove has a depth of 0.5mm, and it corresponds to the square groove 12 at the bottom. The four corners of the top 2 are also provided with mortises corresponding to the tenons at the bottom.

[0088] In use, first fix the photoconductive switch device to the bottom 1 using the external electrode, then snap the tenon of the bottom 1 and the mortise of the top 2 together, and then perform subsequent potting.

[0089] The above descriptions are merely a few specific examples of the present invention and do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure 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 photoconductive switch device based on a triangular rounded corner shape, comprising a semi-insulating substrate (1), a reflector (2), a metal electrode (3), an external connecting electrode (4), and an encapsulation material (5), characterized in that: The semi-insulating substrate (1) is triangular with rounded corners, and its side is provided with an angle α between it and the reflector, and the angle α is 1° to 5°. The reflector (2) is only half the length of the side of the triangular substrate and is located on the left or right half of the triangular substrate. The other half serves as the light incident surface and its thickness is the same as that of the semi-insulating substrate. The metal electrode (3) is located in the middle of the upper and lower surfaces of the semi-insulating substrate, and is a rounded triangle in shape, which is an ohmic contact. The external connecting electrode (4) covers half of the metal electrode; The triangular substrate performs total internal reflection on the incoming trigger light. The light after total internal reflection is then reflected back to the substrate by a mirror for a second total internal reflection, thereby improving the device's utilization of light energy.

2. The device according to claim 1, characterized in that, The semi-insulating substrate (1) is any one of the semi-insulating materials such as silicon carbide, gallium nitride, gallium arsenide, gallium oxide or diamond, with a thickness of 0.35mm-1mm and a side length of 6-14mm.

3. The device according to claim 1, characterized in that, The metal electrode (3) is made of one of the following materials: 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.

4. The device according to claim 1, characterized in that, The external connecting electrode (4) is made of copper metal and is designed as a rectangular strip with a length of 6mm-10mm, a width of 2mm-4mm, and a thickness of 0.05mm-0.1mm.

5. The device according to claim 1, characterized in that, The encapsulation material (5) is epoxy resin, which tightly covers the entire surface of the device and is dense without air inside.

6. A method for manufacturing the device according to claim 1, characterized in that, Includes the following steps: S1: Cleaning of the semi-insulating substrate; S2: Apply photoresist evenly to the front side of the cleaned semi-insulating substrate; S3: Photolithography and development are performed on a semi-insulating substrate coated with photoresist using a mask to form several chamfered triangular electrode-shaped groove areas, and metal is evaporated, sputtered, and electroplated on the front side of the semi-insulating substrate to form a metal layer. S4: Remove all metal outside the front electrode area of ​​the semi-insulating substrate to form a metal electrode; S5: Clean the back side of the semi-insulating substrate again; S6: Apply photoresist evenly to the back side of the cleaned semi-insulating substrate; S7: Photolithography and development are performed on the back side of a semi-insulating substrate coated with photoresist using a mask to form a chamfered triangular electrode-shaped groove area, and metal is evaporated, sputtered, and electroplated on the back side of the semi-insulating substrate to form a metal layer. S8: Remove all metal outside the metal electrode area on the back side of the semi-insulating substrate to form a metal electrode; S9: External connecting electrodes are welded onto the metal electrodes on the upper and lower surfaces of the semi-insulating substrate, and the photoconductive switch device is fixed in the packaging mold through the external connecting electrodes. Then, the reflector is fixed by potting glue and the entire device is packaged. S10: Cool until the epoxy resin solidifies, open the encapsulation mold, and obtain the photoconductive switch device.

7. The method according to claim 6, characterized in that, The cleaning of the semi-insulating substrate wafer involves sequentially immersing the semi-insulating substrate wafer in BOE solution, deionized water, acetone, isopropanol, and deionized water for ultrasonic cleaning for 120s, 180s, 600s, 180s, and 180s, respectively.

8. The method according to claim 6, characterized in that, The mask is made of quartz and chromium, where chromium is the opaque area and quartz is the translucent area, which is a beveled triangular shape.

9. A packaging method for the device according to claim 1, characterized in that, The implementation steps include the following: (1) Use Teflon material to prepare a mortise and tenon structure packaging mold with a glue-filling hole. The mold must be able to fit tightly to ensure no glue leakage. (2) Fix the position of the photoconductive switch device by the external electrode that has been welded to the metal electrode of the device, fix the photoconductive switch device in the center of the mold, and tightly fasten the mold together; (3) Fill the mold with glue through the filling hole. When the glue can just completely immerse the device, place the reflector on the side closest to the device. At this time, the reflector and the surface of the flowing glue should be horizontal and at a slight angle to the device. Then fill a small amount of encapsulating glue to completely immerse the entire structure. (4) Vacuum the encapsulating adhesive and let it cool and solidify; (5) Open the mold to obtain the packaged device.

10. A mold for encapsulating the device of claim 1, comprising a bottom (1) and a top (2) thereof, which are tightly fitted together by a protruding tenon (11) and a recessed mortise (21) to form a mortise and tenon encapsulation structure, characterized in that: The bottom (1) is provided with a square groove (12) with a depth of 1.5mm-2.0mm close to the bottom edge. On both sides of the groove, there are inclined shallow grooves (13) with a depth of 0.05mm-0.1mm. Both of these inclined shallow grooves are at an angle α with the bottom edge so that the device and the reflector maintain an angle of 1° to 5°. The top (2) is provided with a square groove (22) with a depth of 0.5mm-0.8mm close to the bottom edge, which corresponds to the square groove at the bottom.

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