Discharge tube structure and method of manufacturing the same

Abstract

The application discloses a discharge tube structure and a preparation method thereof. The discharge tube structure comprises an N-type substrate, a first N+ doped region and a second N+ doped region, a P-doped region, a first metal layer and a second metal layer. The first N+ doped region and the second N+ doped region are respectively located on the first side and the second side of the N-type substrate, the projection of the first N+ doped region on the N-type substrate does not overlap with the projection of the second N+ doped region on the N-type substrate, the P-doped region is located on the side of the first N+ doped region away from the N-type substrate, and the P-doped region covers the first N+ doped region, the P doped region is located on the side of the P-doped region away from the N-type substrate, the projection of the P doped region on the N-type substrate at least partially overlaps with the projection of the first N+ doped region on the N-type substrate, the first metal layer is located on the outer side of the P doped region away from the N-type substrate, and the second metal layer is located on the outer side of the second N+ doped region away from the N-type substrate. The application reduces the capacitance and working voltage of the discharge tube.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a discharge tube structure and its fabrication method. Background Technology

[0002] The discharge tube is a switching overvoltage protection element connected in parallel across the protected circuit. Normally, the discharge tube operates at high resistance, approximating an open circuit. However, when encountering high-voltage conditions such as lightning strikes or surges, it quickly conducts, forming a low-resistance path to discharge surge current, limit voltage, and protect downstream circuits. It is one of the core components of current high-voltage, high-reliability protection circuits.

[0003] However, when current discharge tubes are used in low-voltage protected circuits, they generally have the characteristics of low voltage and large capacitance, which results in significant distortion when the discharge tubes transmit signals. Summary of the Invention

[0004] This invention provides a discharge tube structure and its fabrication method to solve the problem that discharge tubes cannot simultaneously meet the characteristics of low voltage and small capacitance.

[0005] According to one aspect of the present invention, a discharge tube structure is provided, comprising: An N-type substrate, comprising a first side and a second side disposed opposite to each other; The first N+ doped region and the second N+ doped region are located on the first side and the second side of the N-type substrate, respectively, and the projection of the first N+ doped region on the N-type substrate and the projection of the second N+ doped region on the N-type substrate do not overlap. The P-doped region is located on the side of the first N+ doped region away from the N-type substrate, and the P-doped region covers the first N+ doped region; The P-doped region is located on the side of the P-doped region away from the N-type substrate, and the projection of the P-doped region on the N-type substrate at least partially overlaps with the projection of the first N+ doped region on the N-type substrate. A first metal layer and a second metal layer, wherein the first metal layer is located on the outside of the P-doped region away from the N-type substrate, and the second metal layer is located on the outside of the second N+ doped region away from the N-type substrate.

[0006] Optionally, the thickness of the N-type substrate is within a first preset range; The thicknesses of both the first N+ doped region and the second N+ doped region are within a second preset range; the first preset range is generally larger than the second preset range. The thickness of the P-doped region is within a third preset range, and the third preset range is generally greater than or equal to the second preset range. The thickness of the P-doped region is within a fourth preset range, and the fourth preset range is generally less than or equal to the second preset range.

[0007] Optionally, both the first metal layer and the second metal layer comprise a four-layer alloy structure of aluminum, titanium, nickel, and silver.

[0008] Optionally, the discharge tube structure further includes: A first P+ doped region and a second P+ doped region, wherein the first P+ doped region is located on the side of the N-type substrate closer to the P-doped region, and the second P+ doped region is located on the second side of the N-type substrate; The projection of the first P+ doped region onto the N-type substrate at least partially overlaps with the projection of the second N+ doped region onto the N-type substrate, and the projection of the second P+ doped region onto the N-type substrate at least partially overlaps with the projection of the first N+ doped region onto the N-type substrate.

[0009] Optionally, the discharge tube structure further includes: A first N++ doped region and a second N++ doped region, wherein the first N++ doped region is located on the side of the P-doped region away from the N-type substrate, and the second N++ doped region is located on the side of the second N+ doped region away from the N-type substrate; The first N++ doped region surrounds the P doped region, and the projection of the first N++ doped region onto the N-type substrate does not overlap with the projection of the first N+ doped region onto the N-type substrate.

[0010] Optionally, the discharge tube structure further includes: A passivation ring is located on the outer side of the P-doped region away from the N-type substrate. The passivation ring surrounds the edge of the first side of the N-type substrate and covers part of the P-doped region. The passivation ring comprises a three-layer structure consisting of semi-insulating polycrystalline silicon, silicon nitride, and silicon phosphosilicate glass sequentially filled.

[0011] According to another aspect of the present invention, a method for preparing a discharge tube structure is provided, applicable to the discharge tube structure described in any embodiment of the present invention, the method for preparing the discharge tube structure comprising: The first and second sides of the N-type substrate are doped to form the first N+ doped region and the second N+ doped region located on the first and second sides of the N-type substrate, respectively. A portion of the first N+ doped region is doped, while the middle portion of the first N+ doped region is retained, forming a structure in which the P- doped region covers the retained first N+ doped region. A portion of the P-doped region is doped to form the P-doped region; the projection of the P-doped region onto the N-type substrate at least partially overlaps with the projection of the first N+ doped region onto the N-type substrate. The first metal layer and the second metal layer are respectively fabricated on the first side and the second side of the N-type substrate.

[0012] Optionally, after doping the first and second sides of the N-type substrate to form the first N+ doped region and the second N+ doped region located on the first and second sides of the N-type substrate, respectively, the method further includes: The first and second sides of the N-type substrate are doped to form a first P+ doped region and a second P+ doped region located on the first and second sides of the N-type substrate, respectively; the projection of the first P+ doped region on the N-type substrate and the projection of the second N+ doped region on the N-type substrate at least partially overlap, and the projection of the second P+ doped region on the N-type substrate and the projection of the first N+ doped region on the N-type substrate at least partially overlap.

[0013] Optionally, after doping a portion of the P-doped region to form the P-doped region, the process further includes: Partial regions of the P-doped region and partial regions of the second N+ doped region are doped to form a first N++ doped region located on a first side of the N-type substrate and a second N++ doped region located on a second side of the N-type substrate, respectively; the first N++ doped region surrounds the P-doped region, and the projection of the first N++ doped region on the N-type substrate does not overlap with the projection of the first N+ doped region on the N-type substrate; the second N++ doped region is located within the second N+ doped region.

[0014] Optionally, before fabricating the first metal layer and the second metal layer on the first and second sides of the N-type substrate, respectively, the method further includes: Remove the oxide layer on the first side of the N-type substrate and prepare a full-surface passivation protective layer on the first side of the N-type substrate; The entire passivation protective layer is patterned, and the central rectangular region of the entire passivation protective layer is removed to form a passivation ring; the passivation ring surrounds the edge of the first side of the N-type substrate and covers part of the P-doped region.

[0015] The technical solution provided by this invention reduces the operating voltage of the discharge tube by setting adjacent first N+ doped regions and P- doped regions, making it suitable for overvoltage protection in low-voltage circuits. Furthermore, by setting adjacent P- doped regions and an N-type substrate, the capacitance of the discharge tube is effectively reduced, ensuring the reliability of the discharge tube during signal transmission. Therefore, this invention avoids the increase in capacitance caused by voltage reduction, improving the applicability and reliability of the discharge tube.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of a discharge tube structure provided according to an embodiment of the present invention; Figure 2 This is a top view of a partial region of an N-type substrate provided according to an embodiment of the present invention; Figure 3 This is a flowchart of a method for preparing a discharge tube structure according to an embodiment of the present invention; Figure 4 This is a flowchart of another method for preparing a discharge tube structure according to an embodiment of the present invention; Figure 5 This is a flowchart of another method for preparing a discharge tube structure according to an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] This invention provides a discharge tube structure. Figure 1 This is a cross-sectional view of a discharge tube structure provided in an embodiment of the present invention. (Reference) Figure 1 The discharge tube structure includes: an N-type substrate 1, a first N+ doped region 21, a second N+ doped region 22, a P-doped region 31, a P-doped region 32, a first metal layer 41, and a second metal layer 42. The N-type substrate 1 includes a first side and a second side disposed opposite to each other. The first N+ doped region 21 and the second N+ doped region 22 are located on the first side and the second side of the N-type substrate 1, respectively, and the projections of the first N+ doped region 21 and the second N+ doped region 21 on the N-type substrate 1 do not overlap. The P-doped region 31 is located on the side of the first N+ doped region 21 away from the N-type substrate 1, and the P-doped region 31 covers the first N+ doped region 21. The P-doped region 32 is located on the side of the P-doped region 31 away from the N-type substrate 1, and the projection of the P-doped region 32 on the N-type substrate 1 at least partially overlaps with the projection of the first N+ doped region 21 on the N-type substrate 1. The first metal layer 41 is located on the outside of the P-doped region 32 away from the N-type substrate 1, and the second metal layer 42 is located on the outside of the second N+ doped region 22 away from the N-type substrate 1.

[0022] In this invention, N-type substrate 1 can be formed by repeatedly doping the N-type substrate 1. + -N - -N + -P - In the -P discharge tube structure, when the potential of the first metal layer 41 is greater than the potential of the second metal layer 42, the PN junction formed between the P-doped region 31 and the first N+ doped region 21 is in a reverse cutoff state, and the discharge tube does not conduct.

[0023] When the potential of the first metal layer 41 is less than the potential of the second metal layer 42, the discharge tube can be turned on, and the current flows through the second metal layer 42, the second N+ doped region 21, the N-type substrate 1, the first N+ doped region 21, the P- doped region 31, the P- doped region 32, and out through the first metal layer 41.

[0024] Because the first N+ doped region 21 is a heavily doped region and the P- doped region 31 is a lightly doped region, and the first N+ doped region 21 and the P- doped region 31 are adjacent, they form a PN junction. The depletion layer of this PN junction mainly extends towards the lightly doped P- doped region 31. By adjusting the doping concentration of the P- doped region 31, the electric field within the depletion layer can reach the avalanche critical electric field at a lower reverse voltage, thus obtaining a lower avalanche breakover voltage to match the surge protection requirements of low-voltage lines. Simultaneously, the charge carriers generated by avalanche excitation in this structure ensure that the discharge tube obtains sufficient current gain, ensuring that the discharge tube can be in a stable conducting state and realizing the discharge of surge current. For example, the operating voltage of the discharge tube can be 10-50V, meaning the discharge tube can be applied to protected circuits with a voltage range of 10-50V.

[0025] Furthermore, because the present invention includes adjacent P-doped regions 31 and N-type substrate 1, both of which are lightly doped regions, a bilaterally graded PN junction can be formed. The depletion layer can extend bidirectionally to both the P-side and N-side simultaneously, significantly increasing the total width of the depletion layer. According to the depletion layer capacitance model, capacitance is inversely proportional to the depletion layer width. A larger depletion layer width effectively reduces the parasitic capacitance of the discharge tube, thereby reducing distortion during signal transmission. For example, compared to a scheme without P-doped regions 31 and N-type substrate 1, the present invention can reduce capacitance by 15%.

[0026] The technical solution provided by this invention reduces the operating voltage of the discharge tube by setting adjacent first N+ doped regions and P- doped regions, making it suitable for overvoltage protection in low-voltage circuits. Furthermore, by setting adjacent P- doped regions and an N-type substrate, the capacitance of the discharge tube is effectively reduced, ensuring the reliability of the discharge tube during signal transmission. Therefore, this invention avoids the increase in capacitance caused by voltage reduction, improving the applicability and reliability of the discharge tube.

[0027] Continue to refer to Figure 1Based on the above embodiments, optionally, the thickness of the N-type substrate 1 is within a first preset range. The thicknesses of the first N+ doped region 21 and the second N+ doped region 22 are both within a second preset range; the first preset range is generally larger than the second preset range. The thickness of the P- doped region 31 is within a third preset range, and the third preset range is generally larger than or equal to the second preset range. The thickness of the P- doped region 32 is within a fourth preset range, and the fourth preset range is generally smaller than or equal to the second preset range.

[0028] The first preset range can be 200-300 μm, and the resistivity of the N-type substrate is 3080 Ω·cm. The second preset range can be 20-30 μm, and the sheet resistance of both the first N+ doped region 21 and the second N+ doped region 22 can be 5-15 Ω·cm. The third preset range can be 3050 μm, and the sheet resistance of the P-doped region 31 can be 20-40 Ω·cm. The fourth preset range can be 1520 μm, and the sheet resistance of the P-doped region 32 can be 6-11 Ω·cm.

[0029] Continue to refer to Figure 1 Based on the above embodiments, optionally, the first metal layer 41 and the second metal layer 42 both include a four-layer alloy structure of aluminum, titanium, nickel and silver.

[0030] For example, the aluminum thickness is 1 μm, the titanium thickness is 800 Å, the nickel thickness is 5000 Å, and the silver thickness is 7500 Å. Finally, the alloy is placed in a furnace at a temperature of 470-530°C and held for 25-45 minutes.

[0031] Because the four-layer alloy structure of aluminum, titanium, nickel and silver has good electrical conductivity, it can form a good ohmic contact with the N-type substrate 1, thereby achieving a better current conduction effect.

[0032] Continue to refer to Figure 1 Based on the above embodiments, optionally, the discharge tube structure further includes: a first P+ doped region 33 and a second P+ doped region 34. The first P+ doped region 33 is located on the side of the N-type substrate 1 closest to the P-doped region 31, and the second P+ doped region 34 is located on the second side of the N-type substrate 1. The projection of the first P+ doped region 33 onto the N-type substrate 1 at least partially overlaps with the projection of the second N+ doped region 22 onto the N-type substrate 1, and the projection of the second P+ doped region 34 onto the N-type substrate 1 at least partially overlaps with the projection of the first N+ doped region 21 onto the N-type substrate 1.

[0033] When the current flowing through the discharge tube is large, the second N+ doped region 21, the N-type substrate 1, the first N+ doped region 21, the P-doped region 31, and the P-doped region 32 remain conductive. Simultaneously, the second P+ doped region 34, the N-type substrate 1, the first N+ doped region 21, the P-doped region 31, and the P-doped region 32 also become conductive, effectively increasing the conductive path. For example, the second P+ doped region 34, the N-type substrate 1, the first P+ doped region 33, the P-doped region 31, and the P-doped region 32 can also become conductive.

[0034] For example, the sheet resistance of both the first P+ doped region 33 and the second P+ doped region 34 can be 1.5-3 Ω·cm. The thickness of the first P+ doped region 33 and the second P+ doped region 34 can be 80-120 μm. The thicker first P+ doped region 33 and the second P+ doped region 34 can improve the surge resistance and discharge capability of the discharge tube.

[0035] By setting a first P+ doped region and a second P+ doped region, the embodiments of the present invention increase the internal current path of the discharge tube under high current, so that the discharge tube can still maintain stable current discharge in a high current operating environment and reduce the short circuit phenomenon inside the discharge tube.

[0036] Figure 2 This is a top view of a partial region of an N-type substrate provided in an embodiment of the present invention. (In conjunction with...) Figure 1 and Figure 2 Based on the above embodiments, optionally, the discharge tube structure further includes: a first N++ doped region 23 and a second N++ doped region 24. The first N++ doped region 23 is located on the side of the P-doped region 31 away from the N-type substrate 1, and the second N++ doped region 24 is located on the side of the second N+ doped region 22 away from the N-type substrate 1. The first N++ doped region 23 surrounds the P-doped region 32, and the projection of the first N++ doped region 23 onto the N-type substrate 1 does not overlap with the projection of the first N+ doped region 21 onto the N-type substrate 1.

[0037] Among them, the first N++ doped region 23 and the second N++ doped region 24 are both ultra-heavily doped regions with sheet resistance as low as 0.5-2.5Ω·cm. Therefore, the first N++ doped region 23 and the second N++ doped region 24 have good current transport capability.

[0038] For example, when the discharge tube is struck by lightning, the discharge tube is turned on. If the current is small at this time, the second N++ doped region 24, the second N+ doped region 21, the N-type substrate 1, the first N+ doped region 21, the P- doped region 31, and the P doped region 32 are connected.

[0039] When the voltage and current increase and exceed the turn-on voltage between the second P+ doped region 34 and the N-type substrate 1, the second P+ doped region 34, the N-type substrate 1, the first N+ doped region 21, the P-doped region 31, and the P-doped region 32 also become connected.

[0040] If the current continues to increase, the second P+ doped region 34, the N-type substrate 1, the first N+ doped region 21, the P- doped region 31, and the first N++ doped region 23 will also be connected, and at this time, the current discharge capability is the maximum.

[0041] Correspondingly, the first N+ doped region 21 on one side of the N-type substrate 1 can also avoid the reduction in the ability to carry large currents due to an excessively large doping concentration gradient.

[0042] The embodiments of the present invention improve the current discharge capability of the discharge tube by setting a first N++ doped region and a second N++ doped region. Furthermore, the projections of the first N++ doped region and the first N+ doped region do not overlap. During the fabrication process, the probability of overlap between the first N++ doped region and the first N+ doped region is reduced, thereby improving the yield of the discharge tube.

[0043] Continue to refer to Figure 1 Based on the above embodiments, optionally, the discharge tube structure further includes a passivation ring located on the outer side of the P-doped region 32 away from the N-type substrate 1. The passivation ring surrounds the edge of the first side of the N-type substrate 1 and covers part of the P-doped region 31. The passivation ring comprises a three-layer structure sequentially filled with semi-insulating polycrystalline silicon 51 (SIPOS), silicon nitride 52 (SiN), and phosphosilicate glass 53 (PSG).

[0044] The passivation ring is arranged below the edge of the first metal layer 41 to prevent the step of the first metal layer 41 from breaking, and at the same time to prevent the first metal layer 41 from extending directly to the edge of the P-doped region, thus preventing the electric field from deteriorating at the edge of the PN junction.

[0045] Specifically, the phosphosilicate glass 53 can be used to prevent external moisture, humidity, and impurities from penetrating into the discharge tube. The silicon nitride 52 can also be used to isolate moisture and protect the underlying semi-insulating polycrystalline silicon 51 from moisture absorption and failure. The semi-insulating polycrystalline silicon 51 utilizes its high resistance characteristics to achieve surface electric field homogenization, alleviate electric field concentration, and improve the breakdown voltage of the discharge tube.

[0046] The embodiments of the present invention improve the isolation and protection effect of the passivation ring by setting a multilayer passivation ring including semi-insulating polycrystalline silicon, silicon nitride and silicon phosphide glass, combining the advantages of different materials, thereby improving the reliability of the discharge tube.

[0047] This invention also provides a method for preparing a discharge tube structure, applicable to the discharge tube structure provided in any embodiment of this invention. Figure 3 This is a flowchart illustrating a method for fabricating a discharge tube structure according to an embodiment of the present invention. (See reference...) Figure 3 The methods for preparing the discharge tube structure include: S110, doping is performed on the first and second sides of the N-type substrate to form a first N+ doped region and a second N+ doped region located on the first and second sides of the N-type substrate, respectively.

[0048] Among them, an N-type silicon wafer with a resistivity of 30·80Ω·cm and a thickness of 200-300μm can be selected as the N-type substrate. Oxygen is introduced at 1140-1210℃ at a rate of 6L / min and hydrogen is introduced at a rate of 3L / min. An oxide layer with a thickness of 12μm is grown on the surface of the N-type substrate.

[0049] Subsequently, a double-sided N+ doped pattern region is patterned on the surface of the N-type substrate. The N+ doped pattern region is the surface of the N-type substrate and is not covered by an oxide layer. The N+ doped pattern region is doped with phosphorus to form a first N+ doped region and a second N+ doped region with a certain depth.

[0050] Specifically, phosphorus pre-expansion is performed in the N+ doped pattern region using a liquid phosphorus oxychloride (POCl3) source at 900-920℃ for 30 min, while nitrogen is introduced at a rate of 5-10 L / min, oxygen at a rate of 2-4 L / min, and nitrogen carrying phosphorus oxychloride at a rate of 1.5-3.5 L / min. Then, phosphorus re-expansion is performed at 1250-1270℃ for 40-100 h, while nitrogen is introduced at a rate of 5-10 L / min and oxygen at a rate of 2-3 L / min, resulting in a first and second N+ doped region thickness of 20-30 μm, i.e., an N+ junction depth of 20-30 μm. During this process, an oxide layer thickness of 1-2 μm is formed.

[0051] S120. A portion of the first N+ doped region is doped, while the middle portion of the first N+ doped region is retained, forming a structure in which the P- doped region covers the retained first N+ doped region.

[0052] Specifically, a P-doped pattern region is patterned and formed on the surface of an N-type substrate. The P-doped pattern region is the area on the surface of the N-type substrate that is not covered by an oxide layer. The P-doped pattern region is located in the middle part of the N-type substrate. The P-doped pattern region is doped with boron to form a P-doped region with a certain depth.

[0053] Specifically, boron pre-expansion is performed in the P-doped pattern region using a B30 liquid source at 920-940℃ for 50-60 min, while nitrogen gas is introduced at a rate of 5-10 L / min and oxygen gas at a rate of 100-300 L / min. The sheet resistance of the P-doped region is 20-40 Ω·cm. Then, boron re-expansion is performed at 1250-1270℃ for 20-30 h, with nitrogen gas introduced at a rate of 5-10 L / min and oxygen gas at a rate of 2-3 L / min during the boron re-expansion, resulting in a P-doped region thickness of 30-50 μm, i.e., a P-junction depth of 30-50 μm. The oxide layer thickness generated during this process is 1-1.5 μm.

[0054] In this process, only the middle part of the first N+ doped region is retained, and the part of the first N+ doped region near the first side of the N-type substrate is the P- doped region.

[0055] S130. A portion of the P-doped region is doped to form a P-doped region; the projection of the P-doped region onto the N-type substrate at least partially overlaps with the projection of the first N+ doped region onto the N-type substrate.

[0056] Specifically, a P-doped pattern region is patterned and formed on the surface of an N-type substrate. The P-doped pattern region is the surface of the N-type substrate and is not covered by an oxide layer. The P-doped pattern region is located above the first N+ doped region. The P-doped pattern region is doped with boron to form a P-doped region with a certain depth.

[0057] Specifically, boron pre-expansion is first performed using a B30 liquid source at 1000-1020℃ for 60 min, while nitrogen gas is introduced at a rate of 5-10 L / min and oxygen gas at a rate of 100-300 L / min. The sheet resistance of the P-doped region is 6-11 Ω·cm. Then, boron re-expansion is performed at 1150-1180℃ for 3-5 h, while oxygen gas is introduced at a rate of 5-6 L / min and hydrogen gas at a rate of 2.5-3 L / min, resulting in a P-doped region thickness of 1520 μm, i.e., a P-junction depth of 1520 μm. During this process, an oxide layer thickness of 1-1.5 μm is formed.

[0058] Correspondingly, setting a P-doped region above the P-doped region can also prevent the ability to carry large currents from being reduced due to an excessively large doping concentration gradient.

[0059] S140. A first metal layer and a second metal layer are respectively prepared on the first side and the second side of the N-type substrate.

[0060] The first and second metal layers comprise a four-layer alloy structure of aluminum, titanium, nickel, and silver. For example, the aluminum has a thickness of 1 μm, the titanium has a thickness of 800 Å, the nickel has a thickness of 5000 Å, and the silver has a thickness of 7500 Å. The first and second metal layers are prepared by alloying aluminum, titanium, nickel, and silver in a furnace at a temperature of 470-530°C for 25-45 minutes.

[0061] The technical solution provided by this invention reduces the operating voltage of the discharge tube by setting adjacent first N+ doped regions and P- doped regions, making it suitable for overvoltage protection in low-voltage circuits. Furthermore, by setting adjacent P- doped regions and an N-type substrate, the capacitance of the discharge tube is effectively reduced, ensuring the reliability of the discharge tube during signal transmission. Therefore, this invention avoids the increase in capacitance caused by voltage reduction, improving the applicability and reliability of the discharge tube.

[0062] Figure 4 A flowchart illustrating another method for fabricating a discharge tube structure according to an embodiment of the present invention. (See reference...) Figure 4 Based on the above embodiments, optionally, after doping the first and second sides of the N-type substrate in S110 to form a first N+ doped region and a second N+ doped region located on the first and second sides of the N-type substrate, respectively, the method further includes: S150, doping is performed on the first and second sides of the N-type substrate to form a first P+ doped region and a second P+ doped region located on the first and second sides of the N-type substrate, respectively; the projection of the first P+ doped region onto the N-type substrate at least partially overlaps with the projection of the second N+ doped region onto the N-type substrate, and the projection of the second P+ doped region onto the N-type substrate at least partially overlaps with the projection of the first N+ doped region onto the N-type substrate.

[0063] In this process, patterning is performed on both sides of the N-type substrate to form a first P+ doped pattern region and a second P+ doped pattern region, respectively. The first P+ doped pattern region is the first side of the N-type substrate and is not covered by an oxide layer. The second P+ doped pattern region is the second side of the N-type substrate and is not covered by an oxide layer. The first P+ doped pattern region and the second P+ doped pattern region can be doped with boron to form a first P+ doped region and a second P+ doped region with a certain depth, respectively.

[0064] Specifically, boron pre-expansion is first performed using a B30 liquid source at 1160-1200℃ for 300 min, while nitrogen is introduced at a rate of 5-10 L / min and oxygen at a rate of 100-300 L / min. The sheet resistance of the first and second P+ doped regions is 1.5-3 Ω·cm. Then, boron re-expansion is performed at 1250-1270℃ for 70-130 h, while nitrogen is introduced at a rate of 5-10 L / min and oxygen at a rate of 2-3 L / min. This results in the thickness of the first and second P+ doped regions being 80-120 μm, i.e., the P+ junction depth being 80-120 μm. The oxide layer thickness generated during this process is 1.5-2.5 μm.

[0065] Because the sheet resistance of the first P+ doped region and the second P+ doped region is low, they have good current discharge capability. When the discharge tube is turned on and a large current flows through it, the first P+ doped region and the second P+ doped region can carry more current, so that the discharge tube can still maintain stable current discharge in a high current operating environment and reduce the short circuit phenomenon inside the discharge tube.

[0066] Figure 5 A flowchart illustrating another method for fabricating a discharge tube structure according to an embodiment of the present invention. (See reference...) Figure 5 Based on the above embodiments, optionally, after doping a portion of the P-doped region in S130 to form the P-doped region, the method further includes: S160. Part of the P-doped region and part of the second N+ doped region are doped to form a first N++ doped region located on the first side of the N-type substrate and a second N++ doped region located on the second side of the N-type substrate, respectively; the first N++ doped region surrounds the P-doped region, and the projection of the first N++ doped region on the N-type substrate does not overlap with the projection of the first N+ doped region on the N-type substrate; the second N++ doped region is located in the second N+ doped region.

[0067] In this process, patterning is performed on both sides of the N-type substrate to form a first N++ doped pattern region and a second N++ doped pattern region, respectively. The first N++ doped pattern region is the first side of the N-type substrate and is not covered by an oxide layer. The first N++ doped pattern region surrounds the P-doped region. The second N++ doped pattern region is the second side of the N-type substrate and is not covered by an oxide layer. The first N++ doped pattern region and the second N++ doped pattern region can be doped with phosphorus to form a first N++ doped region and a second N++ doped region with a certain depth, respectively.

[0068] Specifically, phosphorus pre-diffusion is performed in the first N++ doped pattern region and the second N++ doped pattern region using a liquid phosphorus oxychloride (POCl3) source at 1150-1190℃ for 70-80 min, with a sheet resistance of 0.5-2.5 Ω·cm. Then, diffusion is performed at 1190-1200℃ for 400-600 min to form the first N++ doped region and the second N++ doped region with a thickness of 15-20 μm.

[0069] Because the sheet resistance of the first N++ doped region and the second N++ doped region is low, the first N++ doped region and the second N++ doped region have good current discharge capability.

[0070] Furthermore, during the fabrication of the first N++ doped region, the first N++ doped region and the first N+ doped region are not adjacent, and are separated by a P- doped region and a P doped region. This can reduce the possibility of overlap between the homogeneous first N++ doped region and the first N+ doped region during fabrication, thereby improving the yield of the discharge tube.

[0071] Continue to refer to Figure 5 Based on the above embodiments, optionally, before S140, when the first metal layer and the second metal layer are formed on the first side and the second side of the N-type substrate respectively, the method further includes: S170. Remove the oxide layer on the first side of the N-type substrate and prepare a full-surface passivation protective layer on the first side of the N-type substrate.

[0072] In this process, the oxide layer on the entire surface of the first side of the N-type substrate can be removed by a wet process, and semi-insulating polycrystalline silicon (SIPOS), silicon nitride (SiN) and silicon phosphosilicate glass (PSG) can be deposited sequentially on the entire surface of the first side of the N-type substrate to form a passivation protective layer.

[0073] For example, semi-insulating polycrystalline silicon (SIPOS), silicon nitride (SiN), and silicon phosphosilicate glass (PSG) can be deposited using low-pressure chemical vapor deposition.

[0074] S180, patterned full-surface passivation protective layer, remove the central rectangular area of ​​the full-surface passivation protective layer to form a passivation ring; the passivation ring surrounds the edge of the first side of the N-type substrate and covers part of the P-doped region.

[0075] In this process, the entire passivation protective layer is patterned so that the formed passivation ring can extend from the edge of the first side of the N-type substrate to the inner side of the P-doped region edge by 100-200 μm.

[0076] Optionally, after S140, steps such as testing, film application, grinding with a grinding wheel, and vacuum packaging may be included to package the discharge tube into a finished product that is easy to transport.

[0077] It should be noted that, in the embodiments of the present invention, the acquisition, storage and / or processing of the data and its quality elements, quality inspection classifications, and changes involved comply with the relevant provisions of national laws and regulations and do not violate public order and good morals.

[0078] In various embodiments of the pixel circuit, specific descriptions of driving methods are provided for different pixel circuits. These driving methods can all be considered as driving methods for the pixel circuits provided in the embodiments of the present invention, and repeated content will not be described here.

[0079] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0080] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A discharge tube structure, characterized in that, include: An N-type substrate, comprising a first side and a second side disposed opposite to each other; The first N+ doped region and the second N+ doped region are located on the first side and the second side of the N-type substrate, respectively, and the projection of the first N+ doped region on the N-type substrate and the projection of the second N+ doped region on the N-type substrate do not overlap. The P-doped region is located on the side of the first N+ doped region away from the N-type substrate, and the P-doped region covers the first N+ doped region; The P-doped region is located on the side of the P-doped region away from the N-type substrate, and the projection of the P-doped region on the N-type substrate at least partially overlaps with the projection of the first N+ doped region on the N-type substrate. A first metal layer and a second metal layer, wherein the first metal layer is located on the outside of the P-doped region away from the N-type substrate, and the second metal layer is located on the outside of the second N+ doped region away from the N-type substrate.

2. The discharge tube structure according to claim 1, characterized in that, The thickness of the N-type substrate is within a first preset range; The thicknesses of both the first N+ doped region and the second N+ doped region are within a second preset range; the first preset range is generally larger than the second preset range. The thickness of the P-doped region is within a third preset range, and the third preset range is generally greater than or equal to the second preset range. The thickness of the P-doped region is within a fourth preset range, and the fourth preset range is generally less than or equal to the second preset range.

3. The discharge tube structure according to claim 1, characterized in that, Both the first metal layer and the second metal layer comprise a four-layer alloy structure of aluminum, titanium, nickel, and silver.

4. The discharge tube structure according to claim 1, characterized in that, The discharge tube structure also includes: A first P+ doped region and a second P+ doped region, wherein the first P+ doped region is located on the side of the N-type substrate closer to the P-doped region, and the second P+ doped region is located on the second side of the N-type substrate; The projection of the first P+ doped region onto the N-type substrate at least partially overlaps with the projection of the second N+ doped region onto the N-type substrate, and the projection of the second P+ doped region onto the N-type substrate at least partially overlaps with the projection of the first N+ doped region onto the N-type substrate.

5. The discharge tube structure according to claim 1, characterized in that, The discharge tube structure also includes: A first N++ doped region and a second N++ doped region, wherein the first N++ doped region is located on the side of the P-doped region away from the N-type substrate, and the second N++ doped region is located on the side of the second N+ doped region away from the N-type substrate; The first N++ doped region surrounds the P doped region, and the projection of the first N++ doped region onto the N-type substrate does not overlap with the projection of the first N+ doped region onto the N-type substrate.

6. The discharge tube structure according to claim 1, characterized in that, The discharge tube structure also includes: A passivation ring is located on the outer side of the P-doped region away from the N-type substrate. The passivation ring surrounds the edge of the first side of the N-type substrate and covers part of the P-doped region. The passivation ring comprises a three-layer structure consisting of semi-insulating polycrystalline silicon, silicon nitride, and silicon phosphosilicate glass sequentially filled.

7. A method for preparing a discharge tube structure, characterized in that, The discharge tube structure described in any one of claims 1-6 is applied, wherein the method for preparing the discharge tube structure comprises: The first and second sides of the N-type substrate are doped to form the first N+ doped region and the second N+ doped region located on the first and second sides of the N-type substrate, respectively. A portion of the first N+ doped region is doped, while the middle portion of the first N+ doped region is retained, forming a structure in which the P- doped region covers the retained first N+ doped region. A portion of the P-doped region is doped to form the P-doped region; the projection of the P-doped region onto the N-type substrate at least partially overlaps with the projection of the first N+ doped region onto the N-type substrate. The first metal layer and the second metal layer are respectively fabricated on the first side and the second side of the N-type substrate.

8. The method for preparing the discharge tube structure according to claim 7, characterized in that, After doping the first and second sides of the N-type substrate to form the first N+ doped region and the second N+ doped region located on the first and second sides of the N-type substrate, respectively, the method further includes: The first and second sides of the N-type substrate are doped to form a first P+ doped region and a second P+ doped region located on the first and second sides of the N-type substrate, respectively; the projection of the first P+ doped region on the N-type substrate and the projection of the second N+ doped region on the N-type substrate at least partially overlap, and the projection of the second P+ doped region on the N-type substrate and the projection of the first N+ doped region on the N-type substrate at least partially overlap.

9. The method for preparing the discharge tube structure according to claim 7, characterized in that, After doping a portion of the P-doped region to form the P-doped region, the process further includes: Partial regions of the P-doped region and partial regions of the second N+ doped region are doped to form a first N++ doped region located on a first side of the N-type substrate and a second N++ doped region located on a second side of the N-type substrate, respectively; the first N++ doped region surrounds the P-doped region, and the projection of the first N++ doped region on the N-type substrate does not overlap with the projection of the first N+ doped region on the N-type substrate; the second N++ doped region is located within the second N+ doped region.

10. The method for preparing the discharge tube structure according to claim 7, characterized in that, Before fabricating the first metal layer and the second metal layer on the first and second sides of the N-type substrate, respectively, the method further includes: Remove the oxide layer on the first side of the N-type substrate and prepare a full-surface passivation protective layer on the first side of the N-type substrate; The entire passivation protective layer is patterned, and the central rectangular region of the entire passivation protective layer is removed to form a passivation ring; the passivation ring surrounds the edge of the first side of the N-type substrate and covers part of the P-doped region.

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