Bidirectional TVS device with asymmetric mesa
The non-symmetric dual-directional TVS device with angled grooves and coatings addresses protection instability and leakage issues, achieving robust overvoltage protection and efficient slicing.
Patent Information
- Application Number
- CN202421649343.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-12
- Publication Date
- 2025-07-15
- Estimated Expiration
- 2034-07-12
AI Technical Summary
The protection capabilities of existing TVS devices are not stable enough, and there is a risk of leakage. In subsequent lobe operation, the edge blocking capacity is lower than the in vivo blocking capacity, resulting in breakdown voltage deviation and high leakage current problems.
A bidirectional TVS device with an asymmetrical mesa is designed, and a PNP or NPN structure is formed by forming a first doped layer and a second doped layer on the upper and lower surfaces of the substrate, and an asymmetric first and second trench are formed on the upper and lower portions of the substrate, with the edge of the groove close to 90°, and the protection performance and stability are improved in combination with the passivation layer.
The bidirectional protection function is realized, the edge blocking ability is comparable to the in vivo blocking ability, the pressure resistance is good, the overpressure protection performance is stable, and the risk of glass cracks is reduced during the scribing process, which improves the environmental protection of production.
Smart Images
Figure CN223110409U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to semiconductor devices, in particular to an asymmetrical mesa bidirectional TVS device. Background Art
[0002] A transient voltage suppressor (TVS) is an electronic component used to protect circuits. Its main function is to divert excessive transient voltages in the circuit to the ground wire or power line when the transient voltage in the circuit is too high, so as to protect other components in the circuit from damage. However, the protection ability of existing TVS devices is not stable enough, and there is a risk of leakage. On the other hand, during subsequent dicing operations, due to the edge blocking ability of existing TVS devices being lower than the in-body blocking ability, problems such as breakdown voltage deviation and high leakage current are likely to occur. Therefore, how to provide a TVS device with good protection ability and reliable performance has become an objective need. Summary of the Utility Model
[0003] The utility model provides an asymmetrical mesa bidirectional TVS device to solve problems such as poor protection function and unstable performance of existing TVS devices.
[0004] The utility model also provides a manufacturing method for an asymmetrical mesa bidirectional TVS device.
[0005] To achieve the purpose of the utility model, the utility model provides an asymmetrical mesa bidirectional TVS device, which includes a substrate, a first doping layer and a second doping layer respectively provided on the upper surface and the lower surface of the substrate, a first electrode provided on the upper surface of the first doping layer, and a second electrode provided on the lower surface of the second doping layer. Two first trenches are formed in the upper part of the substrate, and the two first trenches are respectively provided at both ends of the upper part of the substrate; two second trenches are formed at the lower edge of the substrate, and the two second trenches are respectively provided at both ends of the lower edge of the substrate;
[0006] The cross-section of the first trench is "U"-shaped, one side of which is close to the edge of the substrate, and the other side extends to the edge of the first doping layer; the cross-section of the second trench is "C"-shaped, and the side far from the edge of the substrate extends to the edge of the second doping layer.
[0007] The beneficial effects of the utility model are as follows:
[0008] 1) By forming a first doping layer and a second doping layer on the upper surface and the lower surface of the substrate respectively to form a PNP or NPN structure, a bidirectional protection function can be achieved.
[0009] 2) By setting the thickness of the substrate to 250 - 350 microns, the thicknesses of the first doping layer and the second doping layer to 15 - 20 microns respectively, and the groove depths of the first groove and the second groove to 60 - 80 microns respectively, it can ensure that the TVS device has good overvoltage protection function and is not easily broken down, with good stability.
[0010] 3) Forming asymmetric first and second grooves on the substrate. When the PN - junction space - charge region expands, since the shapes of the edges of the first groove and the second groove are close to 90°, the PN - junction region at the edges is reduced, and the electric - field region is distributed towards the center of the TVS tube body structure. Thus, the edges can get rid of the high electric field, and the blocking ability of the edge terminal is equivalent to that of the body, and 95% - 98% of the body blocking ability can be obtained, realizing good overvoltage protection performance. In addition, both the first PN - junction and the second PN - junction are bevel - terminal structures close to 90°, and the first doping layer and the second doping layer are diffused simultaneously, which can control the breakdown - voltage difference between the first PN - junction and the second PN - junction within ±0.5%. Thereby, it ensures the breakdown - voltage consistency of the first PN - junction and the second PN - junction, further improves the overvoltage protection performance, and has good stability.
[0011] 4) Forming a first passivation layer in the first groove and a second passivation layer in the second groove, which not only ensures the passivation ability but also ensures the reliability of scribing. Description of the Drawings
[0012] Figure 1 is a schematic structural diagram of the present utility model.
[0013] Figure 2 is Figure 1 an enlarged view of part A of
[0014] Figure 3 is Figure 1 an enlarged view of part B of
[0015] Figure 4 is the current - voltage curve graph of the over - voltage performance test of Embodiment 1 of the present utility model.
[0016] Figure 5 is the method flow chart of the present utility model.
[0017] In the figure, 10 is the substrate, 11 is the first PN - junction, 12 is the second PN - junction, 20 is the first doping layer, 30 is the second doping layer, 40 is the first electrode, 50 is the second electrode, 60 is the first groove, 70 is the second groove, 80 is the first passivation layer, 81 is the first semi - insulating polysilicon film, 82 is the first glass passivation film, 83 is the first low - temperature oxidation film, 90 is the second passivation layer, 91 is the second semi - insulating polysilicon film, 92 is the second glass passivation film, 93 is the second low - temperature oxidation film. Detailed Embodiments
[0018] The technical solution of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of them. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present utility model.
[0019] Embodiment 1
[0020] Please refer to Figure 1 , a bidirectional TVS device with an asymmetric mesa provided by the present utility model includes a substrate 10, a first doping layer 20, a second doping layer 30, a first electrode 40, a second electrode 50, a first trench 60, a second trench 70, a first passivation layer 80 and a second passivation layer 90. Among them, the first doping layer 20 and the second doping layer 30 are respectively provided on the upper and lower surfaces of the substrate 10, the first electrode 40 is provided on the upper surface of the first doping layer 20, the second electrode 50 is provided on the lower surface of the second doping layer 60, the first trench 60 is provided in the substrate 10, and the second trench 70 is provided at the edge of the substrate 10. The TVS device of the present utility model can be used for various circuit protection components.
[0021] As Figure 1 shown, the substrate 10 can be a <111> crystal orientation single crystal wafer of P-type or N-type, with a thickness of 250 - 350 μm and a resistivity of 0.002 - 3.0 Ω·cm. Doping can be carried out by doping phosphorus or boron inside the substrate 10. When doping phosphorus, it is N-type doping, and when doping boron, it is P-type doping.
[0022] As Figure 1 shown, a first doping layer 20 is provided on the upper surface of the substrate 10, and a second doping layer 30 is provided on the lower surface of the substrate 10. Among them, the first doping layer 20 partially covers the upper surface of the substrate 10, with a thickness of 15 - 20 microns, and the second doping layer 30 partially covers the lower surface of the substrate 10, with a thickness of 15 - 20 microns. Specifically, the first doping layer 20 is P-type doping or N-type doping, the second doping layer 30 is P-type doping or N-type doping, and the doping types of the first doping layer 20 and the second doping layer 30 are the same, so that a PNP or NPN-type structure is formed between the first doping layer 20, the substrate 10 and the second doping layer 30. A first PN junction 11 is formed between the first doping layer 20 and the substrate 10, and a second PN junction 12 is formed between the second doping layer 30 and the substrate 10. Utilizing the reverse cut-off characteristic of the PN junction, the substrate 10 forms a PNP or NPN structure with the first doping layer 20 and the second doping layer 30, thereby realizing a bidirectional protection function.
[0023] As Figure 1As shown, a first electrode 40 is provided on the upper surface of the first doping layer 20, and a second electrode 50 is provided on the lower surface of the second doping layer 30. Both the first electrode 40 and the second electrode 50 are metal electrodes, and a layer of metal titanium nickel silver, tin copper alloy or nickel gold alloy can be respectively covered on the first doping layer 20 and the second doping layer 30 by PVD, electroplating or electroless plating to form the first electrode 40 and the second electrode 50. In this embodiment, the first electrode 40 partially covers the upper surface of the first doping layer 20, and the second electrode 50 partially covers the lower surface of the second doping layer 30.
[0024] As Figure 1 shown, a first trench 60 is formed in the upper part of the substrate 10. The cross-section of the first trench 60 is "U"-shaped, one side of which is close to the edge of the substrate 10, and the other side extends to the edge of the first doping layer 20. As Figure 1 shown in the embodiment, two first trenches 60 are provided in the upper part of the substrate 10, and the two first trenches are respectively provided at both ends of the upper part of the substrate 10. The first doping layer 20 is located between the two first trenches 60. The cross-section of the first trench 60 is "U"-shaped, and its edge is close to 90°. Since the edge of the first trench 60 is close to 90°, when the space charge region of the first PN junction 11 expands, the edge of the TVS can get rid of the high electric field, and the blocking ability at the edge is equivalent to the blocking ability in the body, and a blocking ability of 95% - 98% in the body can be obtained.
[0025] As Figure 1As shown, a first passivation layer 80 is provided on the upper surface of the first trench 60 for providing high-reliability passivation protection to the first PN junction 11. The first passivation layer 80 includes a first semi-insulating polysilicon film 81, a first glass passivation film 82, and a first low-temperature oxidation film 83. Among them, the first semi-insulating polysilicon film 81 covers the inner wall of the first trench 60, and its thickness is 0.4 to 0.6 microns. The first semi-insulating polysilicon film 81 can not only reduce the high-temperature leakage of the first PN junction 11, but also reduce the stress effect of the first glass passivation film 82 on the substrate 10, thereby reducing the risk of cracking of the substrate 10. The first glass passivation film 82 covers the first semi-insulating polysilicon film 81, and the thickness of the first glass passivation film 82 is 10 - 40 microns. The negative ion centers in the first glass passivation film 82 can effectively capture metal ions to avoid the contamination of the first PN junction 11 by metal ions, thereby reducing leakage and making the high-temperature performance of the TVS device more stable. The first low-temperature oxidation film 83 covers the upper surface edge of the substrate 10, the first glass passivation film 82, and part of the first doping layer 20, and its thickness is 4000 ± 2000 Å. The first low-temperature oxidation film 83 can effectively avoid the effect of thermal expansion and contraction on the glass during the solidification of the solder in the welding process. In this embodiment, since the first trench 60 is completely wrapped inside the substrate 10, only the first low-temperature oxidation film 83 exists on the surface of the scribe lane reserved at the edge of the substrate 10, and there is no glass on the scribe lane. Therefore, when scribing, the blade is in direct contact with the silicon, avoiding the risk of the blade cutting the glass and causing glass cracks.
[0026] As Figure 1 shown, a second trench 70 is formed at the lower edge of the substrate 10, which is used to form a scribing track for facilitating subsequent die separation operations. The cross-section of the second trench 70 is in a "C" shape, and the side thereof away from the edge of the substrate 10 extends to the edge of the second doping layer 30. As Figure 1 shown in the embodiment, the number of the second trenches 70 is two, and the two second trenches 70 are respectively provided at the lower ends of both edges of the substrate 10, and the second doping layer 30 is located between the two second trenches 70. Since the cross-section of the second trench 70 is in a "C" shape, its edge is close to 90°. Since the edge of the second trench 70 is close to 90°, when the space charge region of the second PN junction 12 expands, the TVS edge can get rid of the high electric field, and the blocking ability at the edge is equivalent to the in-body blocking ability, and 95% - 98% of the in-body blocking ability can be obtained.
[0027] As Figure 2 , Figure 3As shown in the figure, the connection part of the first PN junction 11 and the first groove 60 is a bevel terminal structure, and its bevel angle α1 is 80° - 88°. The connection part of the second PN junction 12 and the second groove 70 is a bevel terminal structure, and its bevel angle α2 is 80° - 88°. Since both α1 and α2 are less than 90°, the first PN junction 11 and the second PN junction 12 are both bevel terminal structures close to 90°, which reduces the PN junction area at the edge and distributes the electric field region towards the center of the TVS tube body structure. As a result, the edge can get rid of the high electric field, and the blocking ability of the edge terminal is equivalent to that of the body, enabling a body blocking ability of 95% - 98% and achieving good overvoltage protection performance. In addition, both the first PN junction and the second PN junction are bevel terminal structures close to 90°, and the first doping layer and the second doping layer are diffused simultaneously, which can control the withstand voltage difference between the first PN junction and the second PN junction within ±0.5%, thus ensuring the withstand voltage consistency of the first PN junction and the second PN junction, further improving the overvoltage protection performance and having good stability.
[0028] As Figure 1 shown in the figure, a second passivation layer 90 is provided on the lower surface of the second groove 70 for providing highly reliable passivation protection to the edge of the second PN junction 12. The second passivation layer 90 includes a second semi-insulating polysilicon film 91, a second glass passivation film 92, and a second low-temperature oxidation film 93. Among them, the second semi-insulating polysilicon film 91 covers the inner wall of the second groove 70, and its thickness is 0.4 - 0.6 microns. This second semi-insulating polysilicon film 91 can not only reduce the high-temperature leakage current of the second PN junction 12 but also reduce the stress effect of the second glass passivation film 92 on the substrate 10, thereby reducing the risk of substrate 10 cracking. The second glass passivation film 92 covers the first semi-insulating polysilicon film 91, and the thickness of the second glass passivation film 92 is 10 - 40 microns. The negative ion centers in this second glass passivation film 92 can effectively capture metal ions to avoid the pollution of the second PN junction 12 by metal ions, thereby reducing leakage current and making the high-temperature performance of the TVS device more stable. The second low-temperature oxidation film 93 covers the second glass passivation film 92 and part of the second doping layer 30, and its thickness is 4000 ± 2000 Å. This second low-temperature oxidation film 93 can effectively avoid the thermal expansion and contraction effect on the glass during the solidification of the solder during the welding process. In this embodiment, since the second groove 70 is provided at the edge of the substrate 10, a half-cut process is adopted during dicing, and after half-cutting, a fully automatic dicing machine is used, which can effectively improve the dicing speed, reduce the generation of wastewater in production, and improve the environmental protection of the production process. The asymmetric groove structure of this embodiment not only ensures the passivation ability but also ensures the reliability of dicing.
[0029] The overvoltage performance of the TVS device of this embodiment is tested, and the test results are as Figure 4 shown in the figure, and from Figure 4From the test results, it can be seen that the TVS device has good overvoltage protection ability in the voltage environment of -30~30V, and its performance is stable, which can be applied to most circuit protection components.
[0030] Example 2
[0031] Refer to Figure 5 , the manufacturing method of the asymmetrical mesa bidirectional TVS device in this embodiment includes the following steps:
[0032] S10. Provide a substrate.
[0033] In this step, the substrate 10 can be a <111>-oriented single crystal wafer of P-type or N-type, with a thickness of 250~350μm and a resistivity of 0.002~3.0Ω·cm. Doping can be carried out by doping phosphorus or boron inside the substrate 10. When doping phosphorus, it is N-type doping, and when doping boron, it is P-type doping.
[0034] S20. Form a first doping layer on the upper surface of the substrate and a second doping layer on the lower surface of the substrate.
[0035] In this step, through the method of boron diffusion or phosphorus diffusion, a first doping layer 20 is formed on the upper surface of the substrate 10, and a second doping layer 30 is formed on the lower surface of the substrate 10. Among them, the diffusion temperature is 1260°C, the diffusion time is 15~25 hours, the diffusion sheet junction depth is 15~20μm, and the sheet resistance R is 20 - 50 ohms / sq. Specifically, when the substrate 10 is P-type doped, the first doping layer 20 is formed as an N-type doping layer by the method of phosphorus diffusion, and the second doping layer 30 is formed as an N-type doping layer by the method of phosphorus diffusion; when the substrate 10 is N-type doped, the first doping layer 20 is formed as a P-type doping layer by the method of boron diffusion, and the second doping layer 30 is formed as a P-type doping layer by the method of boron diffusion. So that a PNP-type structure or an NPN-type structure is formed between the first doping layer 20, the substrate 10 and the second doping layer 30, and a first PN junction 11 is formed between the first doping layer 20 and the substrate 10, and a second PN junction 12 is formed between the second doping layer 30 and the substrate 10. Utilizing the reverse cut-off characteristics of the first PN junction 11 and the second PN junction 12, diffusion on both sides of the substrate 10 can achieve the bidirectional protection function. At the same time, the first doping layer 20 and the second doping layer 30 are diffused simultaneously, which can control the withstand voltage difference between the first PN junction 11 and the second PN junction 12 within ±0.5%, thus ensuring the withstand voltage consistency of the first PN junction 11 and the second PN junction 12.
[0036] S30. Form a first trench on the upper part of the substrate and a second trench on the lower edge of the substrate.
[0037] In this step, through a photolithography process, a first trench 60 is formed on the upper part of the substrate 10, and a second trench 70 is formed on the lower edge of the substrate 10. Among them, the cross-section of the first trench 60 is "U"-shaped, one side of which is close to the edge of the substrate 10, and the other side extends to the edge of the first doping layer 20. In this embodiment, two first trenches 60 are provided on the upper part of the substrate 10, and the two first trenches are respectively arranged at both ends of the upper part of the substrate 10, and the first doping layer 20 is located between the two first trenches 60. The cross-section of the second trench 70 is "C"-shaped, and the side away from the edge of the substrate 10 extends to the edge of the second doping layer 30. In this embodiment, the number of the second trenches 70 is two, and the two second trenches 70 are respectively arranged at both ends of the lower edge of the substrate 10, and the second doping layer 30 is located between the two second trenches 70. Specifically, a negative photoresist is used, the etching solution is kept at -5°C, and etched for 8 to 15 minutes, while forming two first trenches 60 and two second trenches 70 with a groove depth of 60 to 80 μm. Among them, the components of the etching solution are: hydrofluoric acid: glacial acetic acid: nitric acid: sulfuric acid = 9:9:12:4. Since the edges of the first trench 60 and the second trench 70 are close to 90°, when the space charge regions of the first PN junction 11 and the second PN junction 12 expand, the edge of the TVS can get rid of the high electric field, and the blocking ability at the edge is equivalent to the in-body blocking ability, and 95% to 98% of the in-body blocking ability can be obtained.
[0038] S40. A first passivation layer is formed on the upper surface of the first trench, and a second passivation layer is formed on the lower surface of the second trench.
[0039] In this step, the first passivation layer 80 includes a first semi-insulating polysilicon film 81, a first glass passivation film 82, and a first low-temperature oxidation film 83. Among them, the first semi-insulating polysilicon film 81 covers the inner wall of the first trench 60 by means of low-pressure chemical vapor deposition. The reaction source gases are silane: nitrous oxide = 5:1, the deposition time is 30 - 50 minutes, and the film thickness of the first semi-insulating polysilicon film 81 is 0.4 - 0.6 um. The first glass passivation film 82 is formed by glass passivation and sintering through a knife scraping glass process. It covers the upper surface of the first semi-insulating polysilicon film 81. Its main component is glass paste. The glass powder model in the glass paste is GP200S or GP200 / W020, and the glass paste ratio is: butyl carbitol: ethyl cellulose: glass powder = 1:0.05:1.25. The glass sintering temperature is 820 ± 10 °C, the sintering time is 15 - 25 minutes, and the whole sintering process is protected by oxygen. The first low-temperature oxidation film 83 is formed by low-pressure chemical vapor deposition. It covers the upper surface edge of the substrate 10, the first glass passivation film 82, and part of the first doped layer 20. Among them, the reaction temperature is 450 ± 50 °C, the reaction time is 20 - 40 minutes, the reaction source gases are: silane: oxygen ratio 2:1, and the film thickness of the first low-temperature oxidation film 83 is 4000 ± 2000 Å. In this embodiment, since the first trench 60 is wrapped inside the substrate, and the first glass passivation film 82 is inside the first trench 60, and the first low-temperature oxidation film 83 covers the edge of the substrate 10, only the first low-temperature oxidation film 83 exists on the surface of the scribing lane reserved at the edge of the substrate 10, and there is no glass on the scribing lane. Therefore, when scribing, the blade directly contacts the silicon, avoiding the risk of glass cracks caused by the blade cutting the glass.
[0040] The second passivation layer 90 includes a second semi-insulating polysilicon film 91, a second glass passivation film 92, and a second low-temperature oxidation film 93. Among them, the second semi-insulating polysilicon film 91 is formed by low-pressure chemical vapor deposition. Among them, the reaction source gases are silane: nitrous oxide = 5:1, the deposition time is 30 - 50 minutes, and the film thickness of the second semi-insulating polysilicon film 91 is 0.4 - 0.6 um. The second glass passivation film 92 is formed by glass passivation and sintering through a knife scraping glass process. Its main component is glass paste. The glass powder model in the glass paste is GP200S or GP200 / W020. The glass paste ratio is: butyl carbitol: ethyl cellulose: glass powder = 1:0.05:1.25. The glass sintering temperature is 820 ± 10 °C, the sintering time is 15 - 25 minutes, and the whole sintering process is protected by oxygen. The second low-temperature oxidation film 93 is formed by low-pressure chemical vapor deposition. Among them, the reaction temperature is 450 ± 50 °C, the reaction time is 20 - 40 minutes, the reaction source gases are: silane: oxygen ratio 2:1, and the film thickness of the second low-temperature oxidation film 93 is 4000 ± 2000 Å. In this embodiment, since the second trench 70 is provided at the edge of the substrate 10, a half-cut process is used during dicing. After half-cutting, a full-automatic dicing machine is used, which can effectively improve the dicing speed, reduce the generation of wastewater in production, and improve the environmental protection of the production process. The first passivation layer 80 and the second passivation layer 90 are respectively disposed in the asymmetric first trench 60 and second trench 70, which not only provides composite high-reliability passivation protection for the first PN junction 11 and the second PN junction 12, but also ensures the reliability of dicing.
[0041] S50. A first electrode is formed on the upper surface of the first doping layer, and a second electrode is formed on the lower surface of the second doping layer.
[0042] In this step, a layer of metal titanium nickel silver, tin copper alloy, or nickel gold alloy is respectively coated on the first doping layer 20 and the second doping layer 30 by PVD, electroplating, or electroless plating to form the first electrode 40 and the second electrode 50. In some embodiments, before fabricating the first electrode 40 and the second electrode 50, lead holes can be formed through photoresist, and the residual first low-temperature oxidation film 83 and second low-temperature oxidation film 93 in the lead holes can be removed by wet etching.
[0043] In summary, the asymmetric mesa bidirectional TVS device of the present invention forms a PNP or NPN structure by respectively providing the first doping layer 20 and the second doping layer 30 on both sides of the substrate 10, can achieve bidirectional protection, and the protection performance is stable and reliable.
[0044] On the other hand, a first trench 60 is provided on the upper part of the substrate 10, and a second trench 70 is provided on the lower edge of the substrate 10 to form an asymmetric double mesa trench structure. The edges of the first trench 60 and the second trench 70 are close to 90°. When the space charge regions of the first PN junction 11 and the second PN junction 12 expand, the edge of the TVS can get rid of the high electric field, and the blocking ability at the edge is equivalent to the in-body blocking ability, and an in-body blocking ability of 95% - 98% can be obtained. At the same time, both the first PN junction 11 and the second PN junction 12 are beveled terminal structures close to 90°, and the first doping layer 20 and the second doping layer 30 are diffused simultaneously, so that the breakdown voltage difference between the first PN junction 11 and the second PN junction 12 can be controlled within ±0.5%, thereby ensuring the breakdown voltage consistency of the first PN junction 11 and the second PN junction 12.
[0045] In addition, a first passivation layer 80 is provided on the upper surface of the first trench 60, and a second passivation layer 90 is provided on the lower surface of the second trench 70, providing passivation protection with high reliability for the first PN junction 11 and the second PN junction 12. Among them, the negative ion centers in the glass material can effectively capture metal ions to avoid the pollution of the PN junction by metal ions, thereby reducing leakage current and making the high-temperature performance of the product more stable. At the same time, since the first trench 60 is completely wrapped inside the substrate 10, only the first low-temperature oxide film 83 exists on the surface of the scribing lane reserved at the edge of the substrate 10, and there is no glass on the scribing lane. Therefore, when scribing, the blade is in direct contact with the silicon, avoiding the risk of the blade cutting the glass and causing glass cracks. And the second trench 70 is provided at the edge of the substrate 10, so the semi-cut process is adopted during scribing. After semi-cutting, a fully automatic dicing saw is used, which can effectively improve the scribing speed, reduce the generation of waste water in production, and improve the environmental protection of the production process. Therefore, the asymmetric trench structure not only ensures the passivation ability but also ensures the reliability of scribing.
[0046] Although the present invention has been disclosed through the above embodiments, the protection scope of the present invention is not limited thereto. Without departing from the concept of the present invention, the deformations, substitutions, etc. made to the above components will all fall within the scope of the claims of the present invention.
Claims
1. An asymmetrical mesa bidirectional TVS device, characterized in that, The device includes a substrate, a first doping layer and a second doping layer respectively disposed on the upper surface and the lower surface of the substrate, a first electrode disposed on the upper surface of the first doping layer, and a second electrode disposed on the lower surface of the second doping layer. Two first trenches are formed in the upper part of the substrate, and the two first trenches are respectively disposed at both ends of the upper part of the substrate. Two second trenches are formed at the lower edge of the substrate, and the two second trenches are respectively disposed at both ends of the lower edge of the substrate. The cross-section of the first trench is in a "U" shape, one side of which is close to the edge of the substrate, and the other side extends to the edge of the first doping layer; the cross-section of the second trench is in a "C" shape, and the side away from the edge of the substrate extends to the edge of the second doping layer.
2. The bidirectional TVS device with an asymmetric mesa as claimed in claim 1, characterized in that, The substrate, the first doping layer and the second doping layer form a PNP-type structure or an NPN-type structure. A first PN junction is formed between the first doping layer and the substrate, and a second PN junction is formed between the second doping layer and the substrate.
3. The bidirectional TVS device with an asymmetric mesa as claimed in claim 2, wherein The thickness of the substrate is 250 - 350 microns, the thickness of the first doping layer is 15 - 20 microns, the thickness of the second doping layer is 15 - 20 microns, the groove depth of the first trench is 60 - 80 microns, and the groove depth of the second trench is 60 - 80 microns.
4. The bidirectional TVS device with an asymmetric mesa as claimed in claim 3, wherein The connection part between the first PN junction and the first trench is a bevel terminal structure, and the angle α1 of its bevel is 80 - 88°.
5. The bidirectional TVS device with an asymmetric mesa as claimed in claim 3, wherein The connection part between the second PN junction and the second trench is a bevel terminal structure, and the angle α2 of its bevel is 80 - 88°.
6. The bidirectional TVS device with an asymmetric mesa as claimed in claim 1, wherein A first passivation layer is disposed on the upper surface of the first trench, and a second passivation layer is disposed on the lower surface of the second trench.
7. The bidirectional TVS device with an asymmetric mesa as claimed in claim 6, wherein The first passivation layer includes a first semi-insulating polysilicon film, a first glass passivation film and a first low-temperature oxidation film. The first semi-insulating polysilicon film covers the inner wall of the first trench, the first glass passivation film covers the first semi-insulating polysilicon film, and the first low-temperature oxidation film covers part of the substrate, the first glass passivation film and part of the first doping layer.
8. The bidirectional TVS device with an asymmetric mesa according to claim 7, wherein, The thickness of the first semi-insulating polysilicon film is 0.4 - 0.6 microns; the thickness of the first glass passivation film is 10 - 40 microns; the thickness of the first low-temperature oxidation film is 4000 ± 2000 Å.
9. The bidirectional TVS device with an asymmetric mesa as claimed in claim 6, wherein, The second passivation layer includes a second semi-insulating polysilicon film, a second glass passivation film and a second low-temperature oxidation film. The second semi-insulating polysilicon film covers the inner wall of the second trench, the second glass passivation film covers the second semi-insulating polysilicon film, and the second low-temperature oxidation film covers part of the substrate, the second glass passivation film and part of the second doping layer.
10. The bidirectional TVS device with an asymmetric mesa according to claim 9, characterized in that, The thickness of the second semi-insulating polysilicon film is 0.4 - 0.6 microns; the thickness of the second glass passivation film is 10 - 40 microns; the thickness of the second low-temperature oxidation film is 4000 ± 2000 Å.