Bidirectional TVS diode chip

Abstract

The invention discloses a bidirectional TVS diode chip which comprises a P-type substrate, the P-type substrate comprises a first surface and a second surface which are oppositely arranged, and a first N-type diffusion region and a second N-type diffusion region are formed on the first surface and the second surface in a diffusion mode respectively. When the voltage applied to the two ends of the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, electrons in the first N-type diffusion region or the second N-type diffusion region enter the P-type substrate, and then conductance modulation is carried out on the P-type substrate. The P-type substrate is used for preparing the bidirectional TVS diode chip, when the voltage applied to the two ends of the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, conductivity modulation can be conducted on the P-type substrate, the clamping voltage of the bidirectional TVS diode chip is reduced, and the surge bearing capacity of the bidirectional TVS diode chip is improved.

Description

Technical Field

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

[0002] A bidirectional TVS diode is a commonly used, highly effective circuit protection device, often connected in parallel across the circuit being protected. When a transient pulse or surge current strikes the circuit, the diode rapidly changes its impedance from high to low, effectively conducting the circuit. This absorbs the transient and clamps the voltage across it to a predetermined value, protecting subsequent circuit components from the effects of the transient.

[0003] Existing bidirectional TVS diode chips are mostly manufactured using a single-crystal bipolar process, using an N-type substrate. The combined thickness of the N-type substrate, the first P-type diffusion region, and the second P-type diffusion region is over 300μm. Existing bidirectional TVS diode chips manufactured using an N-type substrate fail to produce a conductivity modulation effect when current is conducting, resulting in a high resistance during breakdown and a high clamping voltage. Furthermore, due to the high resistance during breakdown, these bidirectional TVS diode chips generate significant heat, which reduces their surge current handling capability.

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

[0005] The object of the present invention is to provide a bidirectional TVS diode chip.

[0006] In order to achieve the above object, a specific embodiment of the present invention provides the following technical solutions:

[0007] A bidirectional TVS diode chip includes a P-type substrate, the P-type substrate including a first surface and a second surface arranged opposite to each other, a first N-type diffusion region and a second N-type diffusion region diffusely formed on the first surface and the second surface, respectively. When the voltage applied to both ends of the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, electrons in the first N-type diffusion region or the second N-type diffusion region enter the P-type substrate, thereby modulating the conductivity of the P-type substrate.

[0008] In one embodiment, the sum of the thicknesses of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region is 180 μm to 250 μm.

[0009] In one embodiment, the total thickness of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region is 220 μm.

[0010] In one embodiment, the operating voltage of the bidirectional TVS diode chip is 12V to 15V, and the breakdown voltage of the bidirectional TVS diode chip is greater than the operating voltage of the bidirectional TVS diode chip.

[0011] In one embodiment, the bidirectional TVS diode chip is a mesa structure chip, and the resistivity of the P-type substrate is 0.045Ω·cm to 0.05Ω·cm.

[0012] In one embodiment, the bidirectional TVS diode chip is a planar structure chip, and the resistivity of the P-type substrate is 0.035Ω·cm to 0.04Ω·cm.

[0013] In one embodiment, the operating voltage of the bidirectional TVS diode chip is 22V to 25V, and the breakdown voltage of the bidirectional TVS diode chip is greater than the operating voltage of the bidirectional TVS diode chip.

[0014] In one embodiment, the resistivity of the P-type substrate is 0.08 Ω·cm to 0.09 Ω·cm.

[0015] In one embodiment, the bidirectional TVS diode chip further includes:

[0016] The electrodes include a first electrode disposed on a surface of the first N-type diffusion region and a second electrode disposed on a surface of the second N-type diffusion region;

[0017] 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.

[0018] In one embodiment, the first electrode and the second electrode are connected to the positive electrode and the negative electrode of an external power supply, respectively.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention uses a P-type substrate to prepare a bidirectional TVS diode chip. By reasonably controlling the total thickness of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region, as well as the doping concentration of the P-type substrate, the prepared bidirectional TVS diode chip can modulate the conductivity of the P-type substrate when avalanche breakdown occurs, resulting in voltage hysteresis, further reducing the clamping voltage of the bidirectional TVS diode chip, and improving the surge withstand capability of the bidirectional TVS diode chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] Figure 1 Schematic diagram of the structure of the bidirectional TVS diode chip in Example 1 of the present invention;

[0023] Figure 2 This is a comparison diagram of the clamping voltage of the bidirectional TVS diode chip in Comparative Example 1 and Example 1 of the present invention;

[0024] Figure 3 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.

[0025] Description of main reference numerals:

[0026] 10 - P-type substrate, 201 - first N-type diffusion region, 202 - second N-diffusion region, 301 - first passivation layer, 302 - second passivation layer, 401 - first electrode, 402 - second electrode. DETAILED DESCRIPTION

[0027] 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.

[0028] The present invention discloses a bidirectional TVS diode chip, comprising a P-type substrate, wherein the P-type substrate comprises a first surface and a second surface arranged opposite to each other, wherein a first N-type diffusion region and a second N-type diffusion region are diffusely formed on the first surface and the second surface, respectively. When the voltage applied to both ends of the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, electrons in the first N-type diffusion region or the second N-type diffusion region enter the P-type substrate, thereby performing conductivity modulation on the P-type substrate.

[0029] When the voltage applied to the two ends of the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, the bidirectional diode chip undergoes avalanche breakdown. Under the action of the electric field, a large number of electrons in the first N-type diffusion region or the second N-type diffusion region are injected into the P-type substrate. Since the internal structure of the bidirectional TVS diode chip needs to maintain electrical neutrality, the same number and concentration of holes will accumulate in the P-type substrate. When the concentration of injected electrons reaches the same level as the hole concentration in the P-type substrate, the concentration of the additional accumulated holes is equivalent to the hole doping concentration in the P-type substrate, resulting in a decrease in the resistance of the P-type substrate and a significant increase in the conductivity.

[0030] 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:

[0031] 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.

[0032] 2. The time it takes for minority carriers to drift through the P-type substrate is reduced by thinning the sum of the thicknesses of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region.

[0033] The present invention will be further described below with reference to specific examples:

[0034] Example 1:

[0035] Ginseng Figure 1 As shown, the bidirectional TVS diode chip in this embodiment includes a P-type substrate 10, which includes a first surface and a second surface arranged opposite to each other. A first N-type diffusion region 201 and a second N-type diffusion region 202 are diffused on the first surface and the second surface, respectively. When the voltage applied to both ends of the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, under the action of the electric field directed from the first N-type diffusion region 201 to the second N-type diffusion region 202, electrons in the first N-type diffusion region 201 enter the P-type substrate 10, thereby modulating the conductivity of the P-type substrate 10.

[0036] Furthermore, the sum of the thicknesses of the P-type substrate 10 , the first N-type diffusion region 201 , and the second N-type diffusion region 201 is 180 μm to 250 μm.

[0037] As described above, by thinning the sum of the thicknesses of the P-type substrate 10 and the first N-type diffusion region 201 and the second N-type diffusion region 202 , the time for minority carriers to drift through the P-type substrate 10 can be reduced, thereby promoting the accumulation of minority carriers in the P-type substrate 10 and improving the conductivity modulation of the P-type substrate 10 .

[0038] It should be understood that the smaller the sum of the thicknesses of the P-type substrate 10 and the first N-type diffusion region 201 and the second N-type diffusion region 202, the easier it is to stimulate conductivity modulation of the P-type substrate. However, if the total thickness of the P-type substrate 10 and the first N-type diffusion region 201 and the second N-type diffusion region 202 is too thin, it is not conducive to the preparation of the bidirectional TVS diode chip and is prone to fragmentation during the production process.

[0039] Furthermore, the sum of the thicknesses of the P-type substrate 10 , the first N-type diffusion region 201 , and the second N-type diffusion region 202 is preferably 220 μm.

[0040] Preferably, the thickness of the first N-type diffusion region 201 is equal to the thickness of the second N-type diffusion region 202 , and the sum of the thicknesses of the first N-type diffusion region 201 and the second N-type diffusion region 202 is equal to the thickness of the P-type substrate.

[0041] Furthermore, the operating voltage of the bidirectional TVS diode chip is 22V to 25V, and the breakdown voltage of the bidirectional TVS diode chip is greater than the operating voltage of the bidirectional TVS diode chip.

[0042] Preferably, the operating voltage of the bidirectional TVS diode chip is 24V.

[0043] Furthermore, the resistivity of the P-type substrate 10 is 0.08-0.09 Ω·cm.

[0044] As described above, properly controlling the resistivity of the P-type substrate 10 and thereby the minority carrier lifetime within the P-type substrate 10 can promote minority carrier accumulation within the P-type substrate 10 and improve the conductivity modulation of the P-type substrate 10. When the bidirectional TVS diode chip operates at a voltage of 24V, the resistivity of the P-type substrate 10 can be set to a standard resistivity of 0.08-0.09Ω·cm. At this resistivity, the minority carrier lifetime within the P-type substrate 10 satisfies the requirements for the conductivity modulation effect.

[0045] Furthermore, the bidirectional TVS diode chip is a mesa structure chip.

[0046] Specifically, after diffusion, the mesa-structured bidirectional TVS diode chip retains only the PN junction and its essential portions. The unnecessary portions are etched away to form a trench, giving the bidirectional TVS diode chip a mesa-like shape. The junction of the mesa-structured bidirectional TVS diode chip terminates within the trench, minimizing the junction termination area.

[0047] Furthermore, the bidirectional TVS diode chip further includes:

[0048] Electrodes, including a first electrode 401 disposed on the surface of the first N-type diffusion region 201 and a second electrode 402 disposed on the surface of the second N-type diffusion region 202;

[0049] The passivation layer includes a first passivation layer 301 disposed on the periphery of the first N-type diffusion region 201 and a second passivation layer 302 disposed on the periphery of the second N-type diffusion region 202 .

[0050] Furthermore, the first electrode 401 and the second electrode 402 are connected to the positive electrode and the negative electrode of the external power supply respectively.

[0051] Specifically, in this embodiment, the first electrode is connected to the negative electrode of the external power supply, and the second electrode is connected to the positive electrode of the external power supply.

[0052] Specifically, the working principle of the bidirectional TVS diode chip in this embodiment is as follows:

[0053] When the bidirectional TVS diode chip in this embodiment is used for circuit protection, under normal circuit operation, the bidirectional TVS diode chip is in a cut-off state and does not affect the normal operation of the circuit. When an abnormal surge voltage occurs in the circuit and reaches the breakdown voltage of the bidirectional TVS diode chip, the bidirectional TVS diode chip undergoes avalanche breakdown. Under the action of the electric field directed from the second N-type diffusion region 202 to the first N-type diffusion region 201, electrons in the first N-type diffusion region 201 enter the P-type substrate 10 and accumulate in large quantities, thereby modulating the conductivity of the P-type substrate 10 and generating a conductivity modulation effect. Under the action of the conductivity modulation effect, voltage hysteresis occurs in the bidirectional TVS diode chip. As the current increases, the voltage will further drop, clamping the voltage of the protected circuit to a lower value, thereby better protecting the circuit.

[0054] The manufacturing process of the bidirectional TVS diode chip in this embodiment is a conventional bipolar process. The key lies in adjusting the total thickness of the P-type substrate 10, the first N-type diffusion region 201, and the second N-type diffusion region 202, as well as the resistivity of the P-type substrate 10 according to needs during production.

[0055] Example 2:

[0056] The structure of the bidirectional TVS diode chip in this embodiment is substantially the same as that in embodiment 1, except that the operating voltage of the bidirectional TVS diode chip is 12V to 15V, and the resistivity of the P-type substrate is 0.045 to 0.05Ω·cm.

[0057] The structure of the bidirectional TVS diode chip in this embodiment is a mesa structure.

[0058] Compared to Example 1, the operating voltage of the bidirectional TVS diode chip in this embodiment is lower, and therefore the breakdown voltage of the bidirectional TVS diode chip must be reduced accordingly. The breakdown voltage of a bidirectional TVS diode chip is closely related to the resistivity of the substrate; the lower the substrate resistivity, the lower the breakdown voltage.

[0059] It should be understood that when the operating voltage of the bidirectional TVS diode chip 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.

[0060] Example 3:

[0061] The structure of the bidirectional TVS diode chip in this embodiment is substantially the same as that in Embodiment 1, except that the operating voltage of the bidirectional TVS diode chip is 12V to 15V, the structure of the bidirectional TVS diode chip is planar, and the resistivity of the P-type substrate is 0.035 to 0.04Ω·cm.

[0062] Compared with Example 2, the structure of the bidirectional TVS diode chip in this embodiment is a planar structure. Since the junction depth and junction termination technology during the preparation of the bidirectional TVS diode chip with a planar structure are different from those of the mesa structure, the resistivity of its P-type substrate should also be adjusted accordingly.

[0063] Specifically, when manufacturing a bidirectional TVS diode chip with a planar structure, the first N-type diffusion region and the second N-type diffusion region are often formed on the first and second surfaces of the P-type substrate, respectively, using a secondary epitaxial growth method. This results in a shallow junction structure, and the junction termination technology used is either field plate technology or junction termination extension technology. When manufacturing a bidirectional TVS diode chip with a planar structure, no etching is required to form trenches. The surface of the bidirectional TVS diode chip is flat, and the junction terminates on the surface of the bidirectional TVS diode chip, resulting in a relatively large junction termination area. When the voltage applied across the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, the width of the P-type substrate that electrons must traverse under the action of the electric field is greater than that of a bidirectional TVS diode chip with a mesa structure. Therefore, to ensure that the clamping voltage of the bidirectional TVS diode chip with a planar structure is consistent with that of the bidirectional TVS diode chip with a mesa structure when the conductivity of the P-type substrate is modulated, the resistivity of the P-type single crystal substrate must be reduced.

[0064] Comparative Example 1:

[0065] The bidirectional TVS diode chip in this comparative example is a conventional bidirectional TVS diode chip, including an N-type substrate. The N-type substrate includes a first surface and a second surface arranged opposite to each other, and a first P-type diffusion region and a second P-type diffusion region are diffused on the first surface and the second surface, respectively. The sum of the thickness of the N-type substrate, the first P-type diffusion region, and the second P-type diffusion region is 360 μm.

[0066] The operating voltage of the bidirectional TVS diode chip in this comparative example is 24V.

[0067] Compared with Example 1, the conventional bidirectional TVS diode chip cannot produce the conductivity modulation effect, so the clamping voltage is higher.

[0068] Ginseng Figure 2 The 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 bidirectional TVS diode chip in Comparative Example 1 cannot produce a conductivity modulation effect, and no voltage hysteresis phenomenon occurs. When avalanche breakdown occurs, the bidirectional TVS diode chip in Example 1 can achieve conductivity modulation of the P-type substrate, and voltage hysteresis phenomenon occurs, and the clamping voltage is lower.

[0069] The test results of the bidirectional TVS diode chips 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 ).

[0070] Table 1: Maximum peak current and clamping voltage at different test voltages

[0071]

[0072] As shown in Table 1, when the test voltage is the same, the bidirectional 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. At the same time, because the bidirectional 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 bidirectional TVS diode in Comparative Example 1 fails. However, the bidirectional 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 bidirectional TVS diode in Comparative Example 1 when the test voltage is 200V.

[0073] Compared with Example 1, in Comparative Example 1, the sum of the thickness of the N-type substrate, the first P-type diffusion region, and the second P-type diffusion region of the conventional bidirectional TVS diode chip is 360 μm, which is much larger than the total thickness of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region of the bidirectional TVS diode chip in Example 1. The time required for minority carriers to drift through the N-type substrate is long, and minority carriers cannot accumulate in the N-type substrate, and no conductivity modulation effect can be produced.

[0074] Ginseng Figure 3 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.

[0075] Specifically, the operating voltage of the bidirectional TVS diode chips 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 -3 As described above, the resistivity of the N-type substrate in Comparative Example 1 is the same as that of the P-type substrate in Example 1, both being 0.08-0.09 Ω·cm. At this time, only the P-type substrate can ensure sufficiently long minority carrier lifetime and diffusion length.

[0076] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0077] The present invention uses a P-type substrate to prepare a bidirectional TVS diode chip. By reasonably controlling the total thickness of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region, as well as the doping concentration of the P-type substrate, the prepared bidirectional TVS diode chip can modulate the conductivity of the P-type substrate when avalanche breakdown occurs, resulting in voltage hysteresis, further reducing the clamping voltage of the bidirectional TVS diode chip, and improving the surge withstand capability of the bidirectional TVS diode chip.

[0078] 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.

[0079] 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 bidirectional TVS diode chip, characterized in that: The bidirectional TVS diode chip includes a P-type substrate, which includes a first surface and a second surface arranged opposite to each other. A first N-type diffusion region and a second N-type diffusion region are diffused on the first surface and the second surface, respectively. When the voltage applied to both ends of the bidirectional TVS diode chip reaches the breakdown voltage of the bidirectional TVS diode chip, electrons in the first N-type diffusion region or the second N-type diffusion region enter the P-type substrate, thereby modulating the conductivity of the P-type substrate.

2. The bidirectional TVS diode chip according to claim 1, characterized in that: The sum of the thicknesses of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region is 180 μm to 250 μm.

3. The bidirectional TVS diode chip according to claim 1, characterized in that: The total thickness of the P-type substrate, the first N-type diffusion region, and the second N-type diffusion region is 220 μm.

4. The bidirectional TVS diode chip according to claim 1, characterized in that: The operating voltage of the bidirectional TVS diode chip is 12V to 15V, and the breakdown voltage of the bidirectional TVS diode chip is greater than the operating voltage of the bidirectional TVS diode chip.

5. The bidirectional TVS diode chip according to claim 4, characterized in that: The bidirectional TVS diode chip is a table structure chip, and the resistivity of the P-type substrate is 0.045Ω·cm to 0.05Ω·cm.

6. The bidirectional TVS diode chip according to claim 4, characterized in that: The bidirectional TVS diode chip is a planar structure chip, and the resistivity of the P-type substrate is 0.035Ω·cm to 0.04Ω·cm.

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

8. The bidirectional TVS diode chip according to claim 8, characterized in that: The resistivity of the P-type substrate is 0.08Ω·cm to 0.09Ω·cm.

9. The bidirectional TVS diode chip according to claim 1, characterized in that: The bidirectional TVS diode chip further includes: The electrodes include a first electrode disposed on a surface of the first N-type diffusion region and a second electrode disposed on a surface of the second N-type diffusion region; 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.

10. The bidirectional TVS diode chip according to claim 9, characterized in that: The first electrode and the second electrode are connected to the positive electrode and the negative electrode of the external power supply respectively.

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