Unidirectional TVS diode

Abstract

The invention discloses a unidirectional TVS diode, which comprises a P-type substrate, the P-type substrate comprises a first surface and a second surface which are oppositely arranged, a first N-type diffusion region is formed on the first surface of the P-type substrate, the second surface comprises a first region and a second region surrounding the outer side of the first region, the first N-type diffusion region is formed on the second surface of the P-type substrate, and the first N-type diffusion region is formed on the second surface of the P-type substrate; a second N-type diffusion region is formed on the second region; the electrode comprises a cathode metal layer arranged on the first surface of the P-type substrate and an anode metal layer arranged on the second surface of the P-type substrate; when the voltage difference between the cathode metal layer and the anode metal layer of the one-way TVS diode is larger than or equal to the breakdown voltage of the one-way TVS diode, electrons in the second N-type diffusion region enter the P-type substrate, and then conductance modulation is conducted on the P-type substrate. The one-way TVS diode is prepared by using the P-type substrate, so that a one-way voltage hysteresis function is realized, the clamping voltage of the one-way TVS diode is reduced, and the circuit is better protected.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular relates to a unidirectional TVS diode. Background Art

[0002] The unidirectional TVS diode is a commonly used, highly efficient circuit protection device. Its greatest characteristic is unidirectional conductivity. When a circuit is subjected to a transient high-energy impact, it can quickly change the high impedance between the two ends to a low impedance, absorbing the surge power and clamping the voltage at both ends to a fixed value, effectively protecting the precision components in the circuit from damage by the surge pulse.

[0003] In the prior art, unidirectional TVS diodes manufactured using a single crystal bipolar process have a single PN junction structure and a single conduction mechanism. Consequently, they are unable to produce a conductivity modulation effect during breakdown, resulting in a high clamping voltage when conducting current, severe heat generation, and limited current conduction capacity.

[0004] Therefore, in order to solve the above technical problems, it is necessary to provide a unidirectional TVS diode. Summary of the Invention

[0005] The present invention aims to provide a unidirectional TVS diode to reduce the clamping voltage and better protect the circuit.

[0006] In order to achieve the above-mentioned purpose, the technical solution provided by one embodiment of the present invention is as follows:

[0007] A unidirectional TVS diode, comprising:

[0008] A P-type substrate, the P-type substrate comprising a first surface and a second surface opposite to each other, a first N-type diffusion region formed on the first surface of the P-type substrate, the second surface comprising a first region and a second region surrounding the first region, a second N-type diffusion region formed on the second region;

[0009] The electrode comprises a cathode metal layer disposed on the first surface of the P-type substrate and an anode metal layer disposed on the second surface of the P-type substrate;

[0010] When the voltage difference between the cathode metal layer and the anode metal layer of the unidirectional TVS diode is greater than or equal to the breakdown voltage of the unidirectional TVS diode, electrons in the second N-type diffusion region enter the P-type substrate, thereby modulating the conductivity of the P-type substrate.

[0011] In one embodiment, the side length of the unidirectional TVS diode is 50 mil to 60 mil, and the area of ​​the first region is 0.002 mm. 2 ~0.051mm 2 .

[0012] In one embodiment, the second surface includes at least one first area, and the shape of the first area is circular or square.

[0013] In one embodiment, the first area is located in the middle of the second surface.

[0014] In one embodiment, the thickness of the P-type substrate is 180 μm to 250 μm.

[0015] In one embodiment, the operating voltage of the unidirectional TVS diode is 22V to 25V, and the breakdown voltage of the unidirectional TVS diode is greater than the operating voltage of the unidirectional TVS diode.

[0016] In one embodiment, the resistivity of the P-type substrate is 0.08 Ω·cm to 0.09 Ω·cm.

[0017] In one embodiment, the operating voltage of the unidirectional TVS diode is 13V to 16V, and the breakdown voltage of the unidirectional TVS diode is greater than the operating voltage of the unidirectional TVS diode.

[0018] In one embodiment, the structure of the unidirectional TVS diode is a mesa structure, and the resistivity of the P-type substrate is 0.045Ω·cm to 0.05Ω·cm; or,

[0019] The structure of the unidirectional TVS diode is a planar structure, and the resistivity of the P-type substrate is 0.035Ω·cm to 0.04Ω·cm.

[0020] In one embodiment, the unidirectional TVS diode further includes:

[0021] The passivation layer includes a first passivation layer disposed on the periphery of the first N-type diffusion region and a second passivation layer disposed on the periphery of the second N-type diffusion region.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention uses a P-type substrate to prepare a unidirectional TVS diode. By reasonably controlling the thickness and doping concentration of the P-type substrate, performing N-type diffusion only on the first surface and the second region of the second surface of the P-type substrate, and providing short-circuit holes, a unidirectional voltage hysteresis function is achieved, further reducing the clamping voltage of the unidirectional TVS diode, improving the surge withstand capability of the unidirectional TVS diode, and better protecting the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the structure of the unidirectional TVS diode in Example 1 of the present invention;

[0026] Figure 2 Schematic diagram of the working principle of the unidirectional TVS diode in Example 1 of the present invention;

[0027] Figure 3 Schematic diagram of the structure of the unidirectional TVS diode in Comparative Example 1 of the present invention;

[0028] Figure 4 1 is a comparison diagram of the clamping voltage of the unidirectional TVS diode in Comparative Example 1 and Example 1 of the present invention;

[0029] Figure 5 This is a comparison diagram of the minority carrier lifetime and minority carrier diffusion length in the N-type substrate and the P-type substrate in the present invention as a function of doping concentration.

[0030] Description of main reference numerals:

[0031] 111 - first P-type base region, 112 - second P-type base region, 121 - first N-type diffusion region, 122 - second N-type diffusion region, 131 - cathode metal layer, 132 - anode metal layer, 141 - first passivation layer, 142 - second passivation layer, 21 - N-type base region, 22 - P-type diffusion region, 231 - cathode, 232 - anode. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0033] The present invention discloses a unidirectional TVS diode, comprising:

[0034] A P-type substrate, the P-type substrate comprising a first surface and a second surface opposite to each other, a first N-type diffusion region formed on the first surface of the P-type substrate, and a second surface comprising a first region and a second region surrounding the first region, a second N-type diffusion region formed on the second region;

[0035] The electrode comprises a cathode metal layer disposed on the first surface of the P-type substrate and an anode metal layer disposed on the second surface of the P-type substrate;

[0036] When the voltage difference between the cathode metal layer and the anode metal layer of the unidirectional TVS diode is greater than or equal to the breakdown voltage of the unidirectional TVS diode, electrons in the second N-type diffusion region enter the P-type substrate, thereby modulating the conductivity of the P-type substrate.

[0037] Specifically, when the voltage difference between the cathode metal layer and the anode metal layer of the unidirectional TVS diode is greater than or equal to the breakdown voltage of the unidirectional TVS diode, the unidirectional TVS diode undergoes avalanche breakdown. Under the action of the electric field, a large number of electrons in the second N-type diffusion region are injected into the P-type substrate. Since the internal structure of the unidirectional TVS diode needs to maintain electrical neutrality, the same number and concentration of holes will accumulate in the P-type substrate. When the electron injection reaches a level equal to the hole concentration of the P-type substrate, the additional accumulated hole concentration is equivalent to the hole doping concentration of the P-type substrate, resulting in a decrease in the resistance of the P-type substrate and a significant increase in conductivity.

[0038] Specifically, to achieve the conductivity modulation of a P-type substrate in the present invention, it is necessary to ensure that the accumulated minority carrier (i.e., electron) concentration in the P-type substrate reaches a certain value. The accumulation of minority carriers is directly related to the minority carrier lifetime and the time it takes for minority carriers to drift through the P-type substrate. Therefore, to stimulate the conductivity modulation effect of the P-type substrate under the action of an electric field, it is necessary to increase the minority carrier lifetime in the P-type substrate and simultaneously reduce the time it takes for minority carriers to drift through the P-type substrate. The specific control method is as follows:

[0039] 1. By reducing the doping concentration of the P-type substrate, that is, controlling the resistivity of the P-type substrate, the number of recombination centers of minority carriers in the P-type substrate can be controlled. The fewer the number of recombination centers, the longer the minority carrier lifetime.

[0040] 2. Reduce the time it takes for minority carriers to drift through the P-type substrate by reducing the thickness of the P-type substrate.

[0041] The present invention will be further described below with reference to specific examples:

[0042] Example 1:

[0043] Ginseng Figure 1 As shown, the unidirectional TVS diode in this embodiment includes:

[0044] A P-type substrate, the P-type substrate including a first surface and a second surface opposite to each other, a first N-type diffusion region 121 being formed on the first surface of the P-type substrate, and a second surface including a first region and a second region surrounding the first region, a second N-type diffusion region 122 being formed on the second region;

[0045] The electrode comprises a cathode metal layer 131 disposed on the first surface of the P-type substrate, and an anode metal layer 132 disposed on the second surface of the P-type substrate;

[0046] When the voltage difference between the cathode metal layer 131 and the anode metal layer 132 of the unidirectional TVS diode is greater than or equal to the breakdown voltage of the unidirectional TVS diode, electrons in the second N-type diffusion region 122 enter the P-type substrate, thereby modulating the conductivity of the P-type substrate.

[0047] Specifically, after the first N-type diffusion region 121 and the second N-type diffusion region 122 are formed on the P-type substrate, the remaining area is a P-type base region, including a first P-type base region 111 located between the first N-type diffusion region 121 and the second N-type diffusion region 122, and a second P-type base region 112 located in the first area of ​​the second surface, and the second P-type base region 112 is connected to the first P-type base region 111.

[0048] Furthermore, the thickness of the P-type substrate is 180 μm to 250 μm. Preferably, the thickness of the P-type substrate is 220 μm.

[0049] As mentioned above, by reducing the thickness of the P-type substrate, the time for minority carriers to drift through the P-type base region can be reduced, thereby promoting the accumulation of minority carriers in the P-type base region and achieving conductivity modulation of the P-type base region.

[0050] It should be understood that the smaller the thickness of the P-type substrate, the easier it is to stimulate the conductivity modulation of the P-type base region. However, if the thickness of the P-type substrate is too thin, it is not conducive to the preparation of the unidirectional TVS diode and is prone to fragmentation during the production process.

[0051] Furthermore, the operating voltage of the unidirectional TVS diode is 22V to 25V, and the breakdown voltage of the unidirectional TVS diode is greater than the operating voltage of the unidirectional TVS diode.

[0052] Preferably, the operating voltage of the unidirectional TVS diode is 24V.

[0053] Furthermore, the resistivity of the P-type substrate is 0.08-0.09 Ω·cm.

[0054] As mentioned above, properly controlling the resistivity of the P-type substrate, and thereby the minority carrier lifetime within the P-type substrate, can promote the accumulation of minority carriers in the P-type base region, thereby modulating the conductivity of the P-type base region. When the operating voltage of a unidirectional TVS diode is 24V, the P-type substrate resistivity can be set to a standard value of 0.08 to 0.09Ω·cm. At this resistivity, the minority carrier lifetime in the P-type substrate satisfies the conditions for the conductivity modulation effect.

[0055] Furthermore, the structure of the unidirectional TVS diode is a mesa structure.

[0056] Specifically, after diffusion, the mesa-structured unidirectional TVS diode retains only the PN junction and its essential portion. The unnecessary portion is etched away to form a trench, giving the unidirectional TVS diode a mesa-like shape. The junction of the mesa-structured unidirectional TVS diode terminates within the trench, minimizing the junction termination area.

[0057] In this embodiment, the side length of the unidirectional TVS diode is 50 mil to 60 mil, and the area of ​​the first region is 0.002 mm. 2 ~0.051mm 2 .

[0058] For example, the side length of the unidirectional TVS diode in this embodiment is 55 mil, the shape of the first region is circular with a diameter of 4 mil, and the first region is located in the middle of the second surface with an area of ​​about 0.008 mm. 2 .

[0059] Exemplarily, the shape of the first area may also be a square.

[0060] For example, in other embodiments, the second surface of the P-type substrate may also include a plurality of discretely distributed first regions, and it is only necessary to ensure that the total area of ​​the first regions is 0.002 mm 2 ~0.051mm 2 .

[0061] Furthermore, the unidirectional TVS diode further includes:

[0062] The passivation layer includes a first passivation layer 141 disposed on the periphery of the first N-type diffusion region 121 and a second passivation layer 142 disposed on the periphery of the second N-type diffusion region 122 .

[0063] Specifically, refer to Figure 2 As shown, the working principle of the unidirectional TVS diode in this embodiment is as follows:

[0064] In the circuit, the anode metal layer 132 is connected to the negative electrode of the external power supply, and the cathode metal layer 131 is connected to the positive electrode of the external power supply;

[0065] Under normal conditions, the unidirectional TVS diode is in the cut-off state;

[0066] When a forward surge occurs in the circuit and the voltage difference between the cathode metal layer 131 and the anode metal layer 132 is greater than or equal to the breakdown voltage of the unidirectional TVS diode, electrons in the second N-type diffusion region 122 enter the first P-type base region 111, modulating the conductivity of the P-type base region. The resistivity of the unidirectional TVS diode decreases, and the unidirectional TVS diode is turned on. Under the action of the conductivity modulation effect, a lower clamping voltage is achieved, thereby better protecting the circuit.

[0067] When a reverse surge occurs in the circuit, the unidirectional TVS diode conducts, acting as a wire to conduct the surge.

[0068] Specifically, when a reverse surge occurs in the circuit, since the resistance of the second region is much greater than that of the first region, almost all the current passes through the first region. That is, the current limit of the unidirectional TVS diode at this time depends on the area of ​​the first region.

[0069] It should be understood that for the unidirectional TVS diode of the present invention, there is a balanced antagonistic relationship between its forward and reverse surge current carrying capacity. A large short-circuit hole provides a strong reverse surge current carrying capacity for the unidirectional TVS diode, but the conductivity modulation effect is not significant, and the forward surge current carrying capacity is weak. A small short-circuit hole provides a strong conductivity modulation effect, resulting in a strong forward surge current carrying capacity but a weak reverse surge current carrying capacity. However, in most application scenarios, the reverse surge current carrying capacity of the unidirectional TVS diode is not required.

[0070] Example 2:

[0071] The structure of the unidirectional TVS diode in this embodiment is substantially the same as that in embodiment 1, except that the operating voltage of the unidirectional TVS diode is 13V to 16V, and the resistivity of the P-type substrate is 0.045 to 0.05Ω·cm.

[0072] The structure of the unidirectional TVS diode in this embodiment is a mesa structure.

[0073] Compared to Example 1, the operating voltage of the unidirectional TVS diode in this embodiment is lower, and therefore the breakdown voltage of the unidirectional TVS diode must be reduced accordingly. The breakdown voltage of a unidirectional TVS diode is closely related to the resistivity of the substrate; the lower the resistivity of the substrate, the lower the breakdown voltage.

[0074] It should be understood that when the operating voltage of the unidirectional TVS diode used is relatively lower or higher than that of Example 1, the resistivity of the P-type substrate should be adjusted accordingly to meet the needs of the protected circuit.

[0075] Example 3:

[0076] The structure of the unidirectional TVS diode in this embodiment is substantially the same as that in embodiment 1, except that the operating voltage of the unidirectional TVS diode is 12V to 15V, the structure of the unidirectional TVS diode is planar, and the resistivity of the P-type substrate is 0.035 to 0.04Ω·cm.

[0077] Compared with Example 2, the structure of the unidirectional TVS diode in this embodiment is a planar structure. Since the junction depth and junction termination technology during the preparation of the planar structure unidirectional TVS diode are different from those of the mesa structure, the resistivity of its P-type substrate should also be adjusted accordingly.

[0078] Specifically, the planar unidirectional TVS diode has a shallow junction structure, and the junction termination technology used is field plate technology or junction termination extension technology. When preparing the planar unidirectional TVS diode, there is no need to etch to form grooves. The surface of the unidirectional TVS diode is flat, and the junction is terminated on the surface of the unidirectional TVS diode. The junction termination occupies a large area. When the voltage applied to the two ends of the unidirectional TVS diode reaches the breakdown voltage of the unidirectional TVS diode, under the action of the electric field, the width of the P-type base region that electrons need to pass through is larger than that of the unidirectional TVS diode with a table structure. Therefore, in order to ensure that the clamping voltage of the planar unidirectional TVS diode is consistent with that of the unidirectional TVS diode with a table structure when the conductivity of the P-type base region is modulated, the resistivity of the P-type substrate needs to be reduced.

[0079] Comparative Example 1:

[0080] Ginseng Figure 3 As shown, the unidirectional TVS diode in this comparative example is a unidirectional TVS diode of conventional structure, including an N-type substrate, and the N-type substrate includes an N-type base region 21 and a P-type diffusion region 22 .

[0081] In this comparative example, the operating voltage of the unidirectional TVS diode is 24 V, the thickness of the N-type substrate is 360 μm, and the resistivity of the N-type substrate is 0.08 to 0.09 Ω·cm.

[0082] The conventional unidirectional TVS diode further includes a cathode 231 located on the surface of the N-type base region 21 and an anode 232 located on the surface of the P-type diffusion region 22 .

[0083] In the circuit, the cathode 231 of the unidirectional TVS diode is connected to the positive electrode of the external power supply, and the anode 232 is connected to the negative electrode of the external power supply or the ground.

[0084] Compared with Example 1, the unidirectional TVS diode with a conventional structure cannot produce a conductivity modulation effect, so the clamping voltage is higher.

[0085] Ginseng Figure 4The figure shows a comparison of the clamping voltages of Comparative Example 1 and Example 1 under the same test waveform. When avalanche breakdown occurs, the unidirectional TVS diode in Comparative Example 1 cannot produce a conductivity modulation effect, and no voltage hysteresis phenomenon occurs. When avalanche breakdown occurs, the unidirectional TVS diode in Example 1 can achieve conductivity modulation of the P-type base region in the unidirectional TVS diode, and voltage hysteresis phenomenon occurs, resulting in a lower clamping voltage.

[0086] Table 1: Maximum peak current and clamping voltage at different test voltages

[0087]

[0088] The test results of the unidirectional TVS diodes in Example 1 and Comparative Example 1 at different test voltages are shown in Table 1. The surge test waveform is an 8 / 20 μs waveform, and the measured parameters are the maximum peak current (I PP ) and clamping voltage (V C ).

[0089] As shown in Table 1, when the test voltage is the same, the unidirectional TVS diode in Example 1 has a lower clamping voltage and can withstand a higher maximum reverse peak current than that in Comparative Example 1. Furthermore, because the unidirectional TVS diode in Comparative Example 1 cannot produce a conductivity modulation effect when conducting, its resistance is relatively large during breakdown, resulting in severe heat generation and low surge withstand capability. When the test voltage exceeds 350V, the unidirectional TVS diode in Comparative Example 1 fails. However, the unidirectional TVS diode in Example 1 still operates normally when subjected to a test voltage of 510V, and the clamping voltage at this time is comparable to the clamping voltage measured for the unidirectional TVS diode in Comparative Example 1 at a test voltage of 200V.

[0090] Compared with Example 1, in Comparative Example 1, the thickness of the N-type substrate in the conventional unidirectional TVS diode is 360 μm, which is much larger than the thickness of the P-type substrate in Example 1, and thus cannot produce the conductivity modulation effect.

[0091] Ginseng Figure 5 The figure shows a comparison of the minority carrier lifetime and minority carrier diffusion length in N-type and P-type substrates. Compared with N-type substrates, P-type substrates have obvious advantages. Under the same doping concentration, the minority carrier lifetime and minority carrier diffusion length in P-type substrates are significantly better than those in N-type substrates.

[0092] Specifically, the operating voltage of the unidirectional TVS diodes in Example 1 and Comparative Example 1 is 24V. Under this operating voltage, in order to meet the surge current carrying capacity requirements of the device and reduce the loss of the device, the doping concentration of the substrate must reach 10 18 cm -3As described above, the resistivity of the N-type substrate of the unidirectional TVS diode in Comparative Example 1 is the same as the resistivity of the P-type substrate of the unidirectional TVS diode in Example 1, both of which are 0.08-0.09 Ω·cm. At this time, only the P-type substrate can ensure a sufficiently long minority carrier lifetime and diffusion length.

[0093] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0094] The present invention uses a P-type substrate to prepare a unidirectional TVS diode. By reasonably controlling the thickness and doping concentration of the P-type substrate, performing N-type diffusion only on the first surface and the second region of the second surface of the P-type substrate, and providing short-circuit holes, a unidirectional voltage hysteresis function is achieved, further reducing the clamping voltage of the unidirectional TVS diode, improving the surge withstand capability of the unidirectional TVS diode, and better protecting the circuit.

[0095] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0096] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A unidirectional TVS diode, characterized in that: The unidirectional TVS diode comprises: A P-type substrate, the P-type substrate comprising a first surface and a second surface opposite to each other, a first N-type diffusion region formed on the first surface of the P-type substrate, the second surface comprising a first region and a second region surrounding the first region, a second N-type diffusion region formed on the second region; The electrode comprises a cathode metal layer disposed on the first surface of the P-type substrate and an anode metal layer disposed on the second surface of the P-type substrate; When the voltage difference between the cathode metal layer and the anode metal layer of the unidirectional TVS diode is greater than or equal to the breakdown voltage of the unidirectional TVS diode, electrons in the second N-type diffusion region enter the P-type substrate, thereby modulating the conductivity of the P-type substrate.

2. The unidirectional TVS diode according to claim 1, characterized in that: The side length of the unidirectional TVS diode is 50mil to 60mil, and the area of ​​the first region is 0.002mm 2 ~0.051mm 2 .

3. The unidirectional TVS diode according to claim 1, characterized in that: The second surface includes at least one first area, and the shape of the first area is circular or square.

4. The unidirectional TVS diode according to claim 3, characterized in that: The first area is located in the middle of the second surface.

5. The unidirectional TVS diode according to claim 1, characterized in that: The thickness of the P-type substrate is 180 μm to 250 μm.

6. The unidirectional TVS diode according to claim 1, characterized in that: The operating voltage of the unidirectional TVS diode is 22V to 25V, and the breakdown voltage of the unidirectional TVS diode is greater than the operating voltage of the unidirectional TVS diode.

7. The unidirectional TVS diode according to claim 6, characterized in that: The resistivity of the P-type substrate is 0.08Ω·cm to 0.09Ω·cm.

8. The unidirectional TVS diode according to claim 1, wherein: The operating voltage of the unidirectional TVS diode is 13V to 16V, and the breakdown voltage of the unidirectional TVS diode is greater than the operating voltage of the unidirectional TVS diode.

9. The unidirectional TVS diode according to claim 8, characterized in that: The structure of the unidirectional TVS diode is a mesa structure, and the resistivity of the P-type substrate is 0.045Ω·cm to 0.05Ω·cm; or, The structure of the unidirectional TVS diode is a planar structure, and the resistivity of the P-type substrate is 0.035Ω·cm to 0.04Ω·cm.

10. The unidirectional TVS diode according to claim 1, wherein: The unidirectional TVS diode further includes: The passivation layer includes a first passivation layer disposed on the periphery of the first N-type diffusion region and a second passivation layer disposed on the periphery of the second N-type diffusion region.

Images