A bidirectional transient voltage suppressor structure with body region conductance modulation as the dominant conduction point

Abstract

This invention discloses a bidirectional transient voltage suppressor structure with body region conductivity modulation-dominated conduction, comprising a semiconductor structure, a first electrode, and a second electrode. Along the direction from the first electrode to the second electrode, the semiconductor structure includes a first emitter region, a first base region, a body region, a second base region, and a second emitter region. The first electrode and the second electrode are electrically connected to the first emitter region and the second emitter region, respectively. The body region has a thickness of 30 μm to 60 μm and a doping concentration of 5 × 10⁻⁶. 14 cm ‑3 ~5×10 15 cm ‑3 Under overvoltage conditions, a dominant conduction region is formed in the bulk region through dual-sided carrier injection, generating a conductance modulation effect. This extends the conduction path from local PN junction conduction to bulk region conduction, thereby reducing the dynamic resistance as the conduction current increases and maintaining a low clamping voltage under high current conditions. This structure suppresses parasitic positive feedback conduction paths, allowing the device to return to a high-resistance state after the transient state ends. Furthermore, multi-voltage series designs can be achieved by adjusting the bulk region parameters.

Description

Technical Field

[0001] This invention relates to the field of semiconductor overvoltage protection device technology, and in particular to a bidirectional transient voltage suppressor structure with body region conductivity modulation as the dominant conduction. Background Technology

[0002] Transient voltage suppressors (TVS) are widely used in communication interfaces, power systems, industrial control, and automotive electronics to absorb electrostatic discharge and surge energy and protect downstream circuits from overvoltage damage. With the increasing reliability and power density of electronic systems, especially in automotive electronics systems where power networks, battery management systems, and in-vehicle communication interfaces are widely used, higher demands are placed on transient voltage suppressors, including lower dynamic resistance, more stable conduction characteristics, and the ability to design multi-voltage level series platforms.

[0003] Existing TVS devices based on the PN junction avalanche conduction mechanism have the following drawbacks in high-performance protection scenarios: Because the conduction current is limited to the vicinity of the junction depletion region, it cannot extend to the main body of the device under high current, resulting in high dynamic resistance and high clamping voltage. Furthermore, these devices typically require changes in layout size to achieve different breakdown voltage levels, making it difficult to cover multiple voltage levels on the same structural platform, leading to high serialization costs. TVS devices with SCR (Silicon Controlled Rectifier) ​​structures exhibit deep snapback characteristics, meaning they may not be able to recover to a high-resistance state after a transient event, posing a latch-up risk and affecting system reliability.

[0004] Therefore, there is an urgent need for a bidirectional transient voltage suppressor structure that achieves low dynamic resistance, bidirectional symmetrical conduction, and supports serialized design of multiple voltage levels under the same structural platform, in order to meet the application requirements of high-reliability transient protection scenarios, reduce device development costs, and improve process compatibility. Summary of the Invention

[0005] This invention provides a bidirectional transient voltage suppressor structure with body region conductivity modulation-dominated conduction. This bidirectional transient voltage suppressor structure can be used for electrostatic discharge (ESD) and surge protection, and can achieve bidirectional overvoltage protection. By forming a body region dominated by conduction and generating a conductivity modulation effect in the body region, the dynamic resistance is reduced, the transient current carrying capacity and thermal stability are improved, and the device structure is different from the SCR structure, and does not exhibit negative differential resistance characteristics, which can reduce the risk of latch-up. In addition, it can also support serialized designs with different breakdown voltage levels under the same structural platform by adjusting the main body parameters, which can meet the application requirements of high reliability transient protection scenarios, reduce device development costs, and improve process compatibility.

[0006] The bidirectional transient voltage suppressor structure provided by this invention includes: A semiconductor structure includes a body region, a first base region, a second base region, a first emitter region, and a second emitter region. The body region has a first conductivity type. The first base region and the second base region are located on opposite sides of the body region and both have a second conductivity type. The first emitter region is located on the side of the first base region away from the body region. The second emitter region is located on the side of the second base region away from the body region. Both the first emitter region and the second emitter region have the first conductivity type, and their doping concentration is greater than that of the body region. The first electrode is located on the side of the first emitter region away from the first base region and is electrically connected to the first emitter region; The second electrode is located on the side of the second emitter region away from the second base region and is electrically connected to the second emitter region; The first base region and the second base region, as well as the first launch region and the second launch region, are symmetrically arranged about the central plane of the body region. Furthermore, the thickness of the bulk region is 30 μm to 60 μm; the doping concentration of the bulk region is 5 × 10⁻⁶. 14 cm -3 ~5×10 15 cm -3 ; The bidirectional transient voltage suppressor structure is configured such that during the transient conduction period after avalanche conduction, the first base region and the second base region inject bipolar carriers into the body region, forming a body region-dominated conduction region and generating a conductance modulation effect. This causes the conduction current to change from PN junction conduction to body region-dominated conduction and to extend and propagate within the body region. As a result, the device exhibits a conduction characteristic in which the dynamic resistance decreases with the increase of the conduction current during conduction, and does not exhibit negative differential resistance characteristics.

[0007] Optionally, the ratio of the peak doping concentration of the first base region to the doping concentration of the bulk region is 10. 2 ~10 4 The ratio of the peak doping concentration in the second base region to the doping concentration in the bulk region is 10. 2 ~10 4This is achieved by limiting the parasitic positive feedback conduction path, preventing the device from forming a self-sustaining conduction state during transient conduction, and restoring it to a high-impedance state after the transient ends.

[0008] Optionally, the first electrode forms an ohmic contact with the first emitter region, and the second electrode forms an ohmic contact with the second emitter region.

[0009] Optionally, the doping concentrations of the first base region and the second base region are symmetrically set about the central plane of the body region, and the doping concentrations of the first emitter region and the second emitter region are symmetrically set about the central plane of the body region.

[0010] Optionally, the breakdown voltage of the bidirectional transient voltage suppressor structure is positively correlated with the thickness of the body region, and / or the breakdown voltage of the bidirectional transient voltage suppressor structure is negatively correlated with the doping concentration of the body region.

[0011] Optionally, the bidirectional transient voltage suppressor structure further includes an isolation structure; the isolation structure extends along the direction from the first electrode to the second electrode and is located at least within the body region.

[0012] Optionally, along the direction from the first electrode to the second electrode, the isolation structure penetrates the first emitter region, the first base region, the body region, and the second base region, and extends into the interior of the second emitter region.

[0013] Optionally, the isolation structure includes an isolation trench and a trench filling layer within the isolation trench, with a trench insulation layer spaced between the trench filling layer and the isolation trench, and the trench insulation layer contacting the inner wall and bottom surface of the isolation trench.

[0014] Optionally, the first conductivity type is N-type and the second conductivity type is P-type; or, the first conductivity type is P-type and the second conductivity type is N-type.

[0015] Optionally, the bidirectional transient voltage suppressor is a discrete device in a single package, or the bidirectional transient voltage suppressor is a single protection unit integrated in a multi-channel protection array.

[0016] The bidirectional transient voltage suppressor structure provided by this invention has the following beneficial effects: Firstly, by setting a first base region and a second base region, as well as a first emitter region and a second emitter region, on opposite sides of the body region of the semiconductor structure, with the first emitter region located on the side of the first base region away from the body region and the second emitter region located on the side of the second base region away from the body region, and by reasonably configuring the thickness and doping concentration of the body region, a body region-dominated conduction region is formed inside the body region during transient conduction, generating a conductivity modulation effect. This causes the conduction current to gradually extend from the local PN junction conduction to the body region, thereby reducing the equivalent resistance of the device conduction path. This results in a lower dynamic differential resistance under high current conditions, effectively reducing transient clamping voltage and improving the protection efficiency for the back-end circuits. Furthermore, the device structure is a non-SCR structure, which does not exhibit negative differential resistance characteristics, thus reducing the risk of latch-up.

[0017] Secondly, since the conduction current is mainly distributed within the bulk region and extends to the main body region, the conduction current is distributed over a larger semiconductor area, thereby reducing the local current density and reducing the heat concentration effect, which is beneficial to improving the transient current carrying capacity and thermal stability of the device under ESD and surge conditions.

[0018] Third, by adjusting parameters such as the doping concentration and thickness of the body region, different breakdown voltage levels can be achieved while maintaining the basic consistency of the base and emitter structures. This forms a unified structural platform that supports serial designs of multiple voltage levels, which helps reduce device development costs and improve process compatibility.

[0019] Fourth, through the symmetrical design of the first base region and the first emitter region with respect to the body region, the device can form basically consistent breakdown characteristics and conduction paths under both forward and reverse bias conditions, thereby achieving stable bidirectional overvoltage protection capability.

[0020] Fifth, by configuring the doping concentration of the base region and the body region and setting the electrode connection method, while achieving the low resistance characteristic of body region conductance modulation, the parasitic self-sustaining positive feedback effect is effectively suppressed, so that the device does not form a self-sustaining conduction state during conduction, and the voltage remains monotonically changing with the current. There is no negative differential resistance range, thereby avoiding the back-turn conduction behavior. After the transient overvoltage disappears, it can quickly return to the high resistance cutoff state, avoid latch-up failure of SCR-type structures, and effectively improve the system reliability.

[0021] Sixth, by forming a longitudinally extending isolation structure within the body region, the lateral diffusion of the conduction current within the body region can be limited, optimizing the internal current distribution and electric field distribution of the device, and improving the stability and reliability of the device under high-current transient conditions.

[0022] Seventh, while achieving low dynamic resistance and bidirectional conduction capability, this invention also possesses stable conduction and recovery characteristics, as well as good thermal stability and resistance to repeated impacts. It is suitable for scenarios with extremely high robustness requirements, such as overvoltage protection in automotive electronics (vehicle networking / control unit), high-performance power systems, and complex industrial control environments.

[0023] 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

[0024] 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.

[0025] Figure 1 This is a cross-sectional schematic diagram of a bidirectional transient voltage suppressor structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the working principle of the bidirectional transient voltage suppressor structure provided in this embodiment of the invention; Figure 3 This is a cross-sectional schematic diagram of another transient voltage suppressor provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the IV curves of TVS devices under different conduction mechanisms provided in the embodiments of the present invention; Figure 5 This is a schematic diagram of the breakdown voltage regulation of the bidirectional transient voltage suppressor structure provided in an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the relationship between breakdown voltage and body doping concentration provided in an embodiment of the present invention. Detailed Implementation

[0026] 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.

[0027] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the implementation methods provided in the embodiments of this application can be combined with each other without contradiction.

[0028] First, it should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "comprising" and similar terms mean that the element or object preceding the word encompasses the element or object listed after the word and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes. Furthermore, the shapes and sizes of the components in the accompanying drawings do not reflect actual proportions and are only intended to illustrate the content of this invention.

[0029] Figure 1 This is a cross-sectional schematic diagram of a bidirectional transient voltage suppressor structure provided in an embodiment of the present invention, as shown below. Figure 1As shown, the bidirectional transient voltage suppressor structure 100 provided in this embodiment of the invention includes a semiconductor structure 10, a first electrode 20, and a second electrode 30; the semiconductor structure 10 includes a body region 110, a first base region 121, a second base region 122, a first emitter region 131, and a second emitter region 132; the body region 110 has a first conductivity type; the first base region 121 and the second base region 122 are located on opposite sides of the body region 110, and both have a second conductivity type; the first emitter region 131 is located on the side of the first base region 121 away from the body region 110; the second emitter region 132 is located on the side of the second base region 122 away from the body region 110; the first emitter region 110... Both the first base region 121 and the second emitter region 132 have a first conductivity type and a doping concentration greater than that of the body region 110. The first electrode 20 is located on the side of the first emitter region 131 away from the first base region 121 and is electrically connected to the first emitter region 131. The second electrode 30 is located on the side of the second emitter region 132 away from the second base region 122 and is electrically connected to the second emitter region 132. The first base region 121 and the second base region 122, and the first emitter region 131 and the second emitter region 132 are symmetrically arranged about the central plane of the body region 110. The thickness of the body region 110 is 30 μm to 60 μm, and the doping concentration of the body region 110 is 5 × 10⁻⁶. 14 cm -3 ~5×10 15 cm -3 .

[0030] Wherein, semiconductor structure 10 refers to the structure corresponding to the semiconductor film layer in the bidirectional transient voltage suppressor structure. Body region 110, first base region 121, second base region 122, first emitter region 131 and second emitter region 132 refer to different functional regions in semiconductor structure 10. Two different functional regions can be located in the same film layer or in different film layers, and can be designed according to actual needs. This embodiment of the invention does not limit this.

[0031] Reference Figure 1 Optionally, the semiconductor structure 10 includes a semiconductor substrate 101, which is reused as a second emitter region 132. With this configuration, the semiconductor substrate 101 can simultaneously perform the mechanical support function of the substrate and the carrier injection function of the emitter region.

[0032] In addition, refer to Figure 1 The semiconductor structure 10 also includes a semiconductor epitaxial layer 102 located on the semiconductor substrate 101. The first emitter region 131, the first base region 121, the body region 110, and at least a portion of the second base region 122 are all located within the semiconductor epitaxial layer 102.

[0033] It should be noted that the number of semiconductor epitaxial layers is not limited in the embodiments of the present invention. For example, refer to... Figure 1In one embodiment, the second base region 122 may be formed by epitaxial growth, while the first base region 121 and the first emitter region 131 may be formed by ion implantation. Accordingly, the semiconductor structure 10 may include two semiconductor epitaxial layers 102. From bottom to top, the first semiconductor epitaxial layer 102 forms the second base region 122, and the thicker second semiconductor epitaxial layer 102, after its growth is completed, forms the first base region 121 and the first emitter region 131 above it through ion implantation. In other embodiments, the second base region 122 may also be implemented by buried layer implantation, for example, by ion implantation into the semiconductor substrate. In this case, the semiconductor structure includes a semiconductor epitaxial layer. During the growth process, the bottom of the semiconductor epitaxial layer forms the second base region 122 due to ion diffusion in the buried layer. After thermal propulsion, part of the second base region diffuses into the semiconductor substrate, and another part of the second base region diffuses into the semiconductor epitaxial layer. The first base region 121 and the first emitter region 131 can still be formed by ion implantation.

[0034] The first electrode 20 serves as the top metal contact layer, and the second electrode 30 serves as the bottom back metal layer, used to introduce or release transient current.

[0035] Figure 2 This is a schematic diagram illustrating the working principle of the bidirectional transient voltage suppressor structure provided in this embodiment of the invention. (Refer to...) Figure 2 In this embodiment, base regions (first base region 121 and second base region 122) and emitter regions (first emitter region 131 and second emitter region 132) are symmetrically arranged on opposite sides of the body region 110, and the thickness and doping concentration of the body region are reasonably configured. When the device enters avalanche conduction under overvoltage conditions and withstands transient large current, the first base region 121 and the second base region 122 respectively inject non-equilibrium carriers into the body region 110. Thus, under the bipolar carrier injection, a body-dominated conduction region 111 is formed inside the body region 110, and a conductivity modulation effect is generated in this region. Under this conductivity modulation effect, the equivalent carrier concentration in the body region 110 is significantly increased, which reduces the equivalent resistivity of the body region 110, thereby reducing the dynamic differential resistance of the device in the conduction state. As the conduction current increases, the conduction path gradually expands from the local PN junction to the body region 110, causing the conduction current to distribute within the body region 110 and expand laterally. The current density tends to be uniformly distributed within the body region, thereby increasing the effective conduction volume and reducing the local current density. Therefore, under high-current transient conditions, the bidirectional transient voltage suppressor structure provided in this embodiment exhibits a conduction characteristic where the dynamic differential resistance gradually decreases with increasing conduction current, thus achieving a low dynamic resistance conduction state, effectively reducing transient clamping voltage, and meeting the application requirements of high-reliability transient protection scenarios. This device is a non-SCR structure (PNPN type structure), therefore it does not exhibit negative differential resistance characteristics, which can reduce the risk of latch-up.

[0036] In summary, in this embodiment of the invention, the bidirectional transient voltage suppressor structure is configured such that, during the transient conduction period after avalanche conduction, the first base region and the second base region inject bipolar carriers into the body region, forming a body region-dominated conduction region within the body region and generating a conductance modulation effect. This causes the conduction current to change from PN junction partial conduction to body region-dominated conduction and to extend and propagate within the body region. As a result, the device exhibits a conduction characteristic during conduction where the dynamic resistance decreases with the increase of the conduction current, and does not exhibit negative differential resistance characteristics. This achieves low dynamic resistance and low clamping voltage, and reduces latch-up risk.

[0037] Optionally, the first conductivity type is N-type and the second conductivity type is P-type; or, the first conductivity type is P-type and the second conductivity type is N-type. In this way, the first base region 121 and the body region 110 form a PN junction, and the second base region 122 and the body region 110 form a symmetrical PN junction. These junctions, in conjunction with the first emitter region 131 and the second emitter region 132, induce a conductivity modulation effect, giving the device bidirectional symmetrical electrical characteristics. It has a conduction path under both forward and reverse bias conditions, thus achieving bidirectional overvoltage protection.

[0038] As described above, optionally, the first base region 121 and the second base region 122 are symmetrically arranged about the central plane of the body region 110, and the first emitter region 131 and the second emitter region 132 are symmetrically arranged about the central plane of the body region 110. Specifically, "symmetrical arrangement" at least means that the doping concentrations of the first base region 121 and the second base region 122 are symmetrical (basically consistent, allowing for a certain error), and the doping concentrations of the first emitter region 131 and the second emitter region 132 are symmetrical (basically consistent, allowing for a certain error). The thicknesses of the first base region 121 and the second base region 122 can also be symmetrically arranged. When the second emitter region 132 reuses the semiconductor substrate 101, the thickness of the second emitter region 132 is usually greater than the thickness of the first emitter region 131, and their doping concentrations are symmetrically arranged. In this way, the device can have basically consistent breakdown characteristics and conduction paths under forward and reverse bias conditions, such as basically consistent trigger voltage, conduction voltage, and clamping characteristics under forward and reverse transient conditions, thereby achieving stable bidirectional overvoltage protection.

[0039] The thickness and doping concentration of the body region 110 are the main adjustment parameters for the device breakdown voltage. In this embodiment, by adjusting at least one of the thickness and doping concentration of the body region, it is possible to achieve a series of designs with different breakdown voltage levels while keeping the main structure of the device basically consistent and the structural parameters of the base region (first base region 121 and second base region 122) and the emitter region (first emitter region 131 and second emitter region 132) basically consistent. This is beneficial to reducing device development costs and improving process compatibility.

[0040] In some implementations, by reducing the doping concentration in the body region or appropriately increasing the thickness of the body region, the depletion region of the device can be further extended in the longitudinal direction, thereby reducing the local electric field concentration and increasing the breakdown voltage of the device.

[0041] For example, in one embodiment, the thickness of the body region 110 is approximately 40 μm, and the doping concentration is approximately 4 × 10⁻⁶. 15 cm -3 At this point, a breakdown voltage of approximately 30V can be achieved.

[0042] In another embodiment, with the thickness unchanged, a lower breakdown voltage, such as a breakdown voltage of about 24V, can be achieved by appropriately increasing the doping concentration of the body region 110, or a higher breakdown voltage, such as a breakdown voltage of 48V or 72V, can be achieved by appropriately decreasing the doping concentration of the body region 110, while maintaining the dominant conduction and conductance modulation characteristics of the body region and maintaining the dynamic resistance characteristics.

[0043] In other embodiments, a higher breakdown voltage can be achieved by increasing the thickness of the body region 110, or a lower breakdown voltage can be achieved by decreasing the thickness of the body region 110.

[0044] In other embodiments, the thickness and doping concentration of the body region 110 can also be adjusted simultaneously to achieve different levels of breakdown voltage. The specific adjustment method can be set as needed, and this embodiment of the invention does not limit this.

[0045] In summary, the embodiments of the present invention, by respectively setting a first base region and a second base region, a first emitter region and a second emitter region on opposite sides of the body region of the semiconductor structure, with the first emitter region located on the side of the first base region away from the body region and the second emitter region located on the side of the second base region away from the body region, and by reasonably configuring the thickness and doping concentration of the body region, achieve the following beneficial effects for the bidirectional transient voltage suppressor structure: Firstly, during transient conduction, a body-dominated conduction region is formed within the body region, generating a conductance modulation effect. This causes the conduction current to gradually extend from the local PN junction conduction to the body region, thereby reducing the equivalent resistance of the device's conduction path. This results in a lower dynamic differential resistance under high current conditions, effectively reducing the transient clamping voltage and improving performance. Firstly, it offers enhanced protection for back-end circuits, and its structure differs from that of SCRs, exhibiting no negative differential resistance, thus reducing latch-up risk. Secondly, since the conduction current is primarily distributed within the bulk region and extends towards the main body, it distributes the conduction current over a larger semiconductor area, thereby reducing local current density and heat concentration effects, which is beneficial for improving the device's transient current carrying capacity and thermal stability under ESD and surge conditions. Thirdly, by adjusting parameters such as the doping concentration and thickness of the bulk region, different breakdown voltage levels can be achieved while maintaining a basically consistent device structure, thus forming a unified structural platform that supports serial designs of multiple voltage levels, which helps reduce device development costs and improve process compatibility.

[0046] Optionally, the peak doping concentration of both the first emitter region 131 and the second emitter region 132 is greater than 1 x 10⁻⁶. 19 cm -3 The doping concentration of the first emitter region 131 is greater than that of the first base region 121, and the doping concentration of the second emitter region 132 is greater than that of the second base region 122.

[0047] Based on the above embodiments, optionally, the ratio of the peak doping concentration of the first base region to the doping concentration of the bulk region is 10. 2 ~10 4 The ratio of the peak doping concentration in the second base region to the doping concentration in the bulk region is 10. 2 ~10 4 This design limits the parasitic positive feedback conduction path, preventing the device from forming a self-sustaining conduction state during transient conduction and allowing it to return to a high-impedance state after the transient ends. Specifically, this configuration limits the current gain of the internal parasitic bipolar structure, suppresses the positive feedback effect of internal parasitic bipolar conduction, prevents the device from forming a self-sustaining conduction path during transient conduction, and allows the device to automatically return to a high-impedance cutoff state after the transient overvoltage ends, thereby avoiding latch-up phenomena similar to those in SCR structures.

[0048] Optionally, the first electrode 20 forms an ohmic contact with the first emitter region 131; the second electrode 30 forms an ohmic contact with the second emitter region 132. This electrical connection method allows for the formation of a base region resistance shunt path between the base region and the emitter region, thereby limiting the current gain of the parasitic bipolar structure within the device, suppressing self-sustaining positive feedback conduction, and improving the device's latch-up resistance.

[0049] It should be noted that, within the limits of this invention, the bulk thickness (30μm~60μm) and bulk doping concentration (5×10⁻⁶) are specified. 14 cm -3 ~5×10 15 cm -3 ) and the peak doping concentration ratio of the base region to the bulk region (10 2 ~10 4 Within the specified range, even if the first electrode only forms an ohmic contact with the first emitter region and the second electrode only forms an ohmic contact with the second emitter region, the current gain of the parasitic BJT is still effectively limited, and self-sustaining positive feedback conduction will not occur. After the transient overvoltage ends, the non-equilibrium carriers stored in the bulk region disappear rapidly through recombination, and the device can automatically return to a high-resistance state, thus achieving non-latch-up conduction characteristics while simplifying the electrode structure.

[0050] In summary, by rationally configuring the doping ratio of the base region and the body region, as well as the electrode connection method, the device can achieve body region conduction during transient conduction without generating a self-sustaining positive feedback conduction path. This avoids latch-up phenomena similar to those in SCR structures, allowing the device to recover to a high-resistance cutoff state after the transient overvoltage event, thus improving system reliability. Therefore, the bidirectional transient voltage suppressor structure provided by this invention maintains low dynamic resistance and bidirectional conduction capability while possessing stable recovery characteristics and resistance to repeated impacts. It can be applied to transient overvoltage protection scenarios with extremely high reliability / robustness requirements, and is suitable for applications such as automotive electronics, power systems, and industrial control.

[0051] Figure 3 This is a cross-sectional schematic diagram of another transient voltage suppressor provided in an embodiment of the present invention, as shown below. Figure 3 As shown, optionally, the bidirectional transient voltage suppressor structure 100 further includes an isolation structure 40; the isolation structure 40 extends along the direction from the first electrode 20 to the second electrode 30 and is located at least within the body region 110. By providing the isolation structure 40 within the body region 110 and extending it along the direction from the first electrode 20 to the second electrode 30, electrical isolation can be achieved. By limiting the diffusion region of current along a first direction parallel to the plane where the first electrode is located, i.e., limiting the lateral diffusion of current, the current density distribution in the body region is optimized, and the edge electric field control capability is enhanced.

[0052] Reference Figure 3In one embodiment, optionally, along the direction from the first electrode 20 to the second electrode 30, the isolation structure 40 penetrates the first emission region 131, the first base region 121, the body region 110, and the second base region 122, and extends into the interior of the second emission region 132. This arrangement can effectively ensure the isolation effect.

[0053] Reference Figure 3 Optionally, the isolation structure 40 includes an isolation trench 41 and a trench filling layer 42 in the isolation trench. A trench insulation layer 43 is spaced between the trench filling layer 42 and the isolation trench 41. The trench insulation layer 43 is in contact with the inner wall and bottom surface of the isolation trench 41.

[0054] Specifically, the isolation trench 41 has a trench insulation layer 43 on its sidewalls and bottom surface, and a trench filling layer 42 inside. The isolation trench 41 serves as an electrical isolation layer; the trench insulation layer 43 provides electrical insulation protection, prevents leakage current, and helps improve the electric field distribution at the edge of the mesa; the trench filling layer 42 can be made of polysilicon or other dielectric materials to support the trench structure and balance the local electric field, thereby improving device stability.

[0055] Optionally, the bidirectional transient voltage suppressor structure can be a discrete device in a single package, or it can be a single protection unit integrated into a multi-channel protection array. Specifically, in this embodiment, the bidirectional transient voltage suppressor structure can be a discrete device in a single package, in which case the bidirectional transient voltage suppressor structure has independent pins and a package structure. Alternatively, the bidirectional transient voltage suppressor structure can be a single protection unit integrated into a multi-channel protection array, in which case the bidirectional transient voltage suppressor structure shares a package structure and common pins with other protection units.

[0056] In summary, this invention provides a bidirectional symmetrical transient voltage suppressor structure. During the transient conduction period following avalanche triggering, this device forms a body-dominated conduction path and generates a conductance modulation effect within the body region under carrier injection, thereby reducing the device's dynamic resistance. Furthermore, by controlling the doping relationship between the base and body regions and forming a base region resistance shunt path, internal parasitic positive feedback conduction is suppressed, ensuring the device can recover to a high-resistance state after the transient ends, achieving non-latch-up conduction characteristics. Moreover, by adjusting the body region doping concentration, a series of designs with different breakdown voltage levels can be achieved while maintaining a basically consistent main structure, covering a voltage range of approximately 24V to 72V. Furthermore, by forming a vertically extending isolation structure, lateral current diffusion is restricted, the body region current density distribution is optimized, the edge electric field control capability is enhanced, and the device's performance reliability and stability are improved.

[0057] Table 1 below summarizes the internal structure and function of the bidirectional transient voltage suppressor structure provided in the embodiments of the present invention.

[0058] Table 1. Internal structure and function of the bidirectional transient voltage suppressor. Figure 4 This is a schematic diagram of the IV curves of TVS devices under different conduction mechanisms provided in the embodiments of the present invention. Figure 4 In the diagram, the horizontal axis represents voltage (V) and the vertical axis represents current (I). Taking a breakdown voltage (Breakdown Voltage (Vbr)) of 30V as an example, curve A represents the IV characteristic curve of a traditional transient voltage suppressor based on PN junction avalanche conduction. Its conduction current is mainly concentrated in the region near the junction. As the current increases, the voltage rises rapidly, exhibiting high dynamic resistance characteristics. Curve B represents the IV characteristic curve of an SCR-type transient voltage suppressor with snapback conduction characteristics. Such devices rely on positive feedback to reduce resistance, which carries a latch-up risk. Specifically, after triggering, such devices exhibit a snapback characteristic, where the voltage drops back and enters a low-voltage conduction region. In this conduction mode, the device has a self-sustaining conduction path and may not be able to return to a high-resistance state in time after the transient ends, thus posing a latch-up risk. Curve C represents the IV characteristic curve of the bidirectional transient voltage suppressor provided in this embodiment of the invention. Compared to curve A, the transient voltage suppressor structure provided in this embodiment of the invention, due to the formation of a body-dominant conduction region within the body region and the generation of conductance modulation effect, causes the dynamic differential resistance of the device to gradually decrease with the increase of conduction current, making the voltage change trend with the increase of current gradually more gradual, thus exhibiting lower dynamic resistance characteristics under high current conditions. Compared to curve B, the bidirectional transient voltage suppressor structure provided in this embodiment of the invention has no positive feedback, is not self-sustaining, and relies only on physical conductance modulation. During conduction, the device maintains a voltage that changes monotonically with current, and there is no negative differential resistance range, thereby avoiding foldback conduction behavior and eliminating latch-up risk. The device can recover to a high-resistance state after the transient overvoltage ends, resulting in higher system reliability.

[0059] Figure 5 This is a schematic diagram of the breakdown voltage regulation of the bidirectional transient voltage suppressor structure provided in an embodiment of the present invention, as shown below. Figure 5 As shown, the test results demonstrate that, with essentially the same device structure and conduction mechanism, a series of designs with different breakdown voltage levels can be achieved by adjusting at least one of the body region thickness and doping concentration. In some implementations, different breakdown voltage levels are implemented within the same layout structure, with voltage level configuration achieved solely through adjustment of the body region doping concentration. Specifically, a higher breakdown voltage level can be achieved by reducing the doping concentration. Figure 5The breakdown voltages corresponding to the four IV characteristic curves are 24V, 30V, 48V and 72V from left to right, and the corresponding doping concentrations gradually decrease from left to right.

[0060] In some implementations, different breakdown voltage levels can be achieved by adjusting the doping concentration of the body region while maintaining a substantially uniform body thickness. Examples are shown in Table 2 below: Table 2. Schematic diagram of the relationship between bulk doping concentration and breakdown voltage. It should be noted that the above correspondence is a schematic result under the condition that the thickness of the bulk region and the device structural parameters are basically consistent, and is used to illustrate the effect of bulk region doping concentration on breakdown voltage, and does not constitute a limitation on the scope of protection of this invention.

[0061] Overall, as the doping concentration in the body region decreases, the depletion layer in the body region can extend further in the vertical direction under reverse bias, thereby reducing the local electric field concentration and increasing the breakdown voltage of the device; conversely, as the doping concentration in the body region increases, the breakdown voltage decreases accordingly.

[0062] Under different voltage levels, the device can form a body region dominant conduction and generate a conductance modulation effect after avalanche triggering, so that the conduction current changes from local junction region conduction to body region extended conduction, thereby maintaining a consistent low dynamic resistance conduction characteristic under different breakdown voltage levels.

[0063] In some implementations, devices with different breakdown voltage levels are implemented in the same layout structure, and the voltage level can be switched simply by adjusting the doping concentration in the body region.

[0064] For example, Figure 6 This is a schematic diagram illustrating the relationship between breakdown voltage and body doping concentration according to an embodiment of the present invention. It shows the relationship between body doping concentration and device breakdown voltage under the condition that the body thickness remains basically consistent. Figure 6 As shown, as the bulk doping concentration decreases, the depletion region expands longitudinally under reverse bias, and the electric field distribution tends to become more uniform, thereby gradually increasing the breakdown voltage. This relationship indicates that different breakdown voltage levels can be controlled by adjusting the bulk doping concentration.

[0065] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A bidirectional transient voltage suppressor structure with body region conductivity modulation-dominated conduction, characterized in that, include: A semiconductor structure includes a body region, a first base region, a second base region, a first emitter region, and a second emitter region; the body region has a first conductivity type; the first base region and the second base region are located on opposite sides of the body region and both have a second conductivity type; the first emitter region is located on the side of the first base region away from the body region; the second emitter region is located on the side of the second base region away from the body region; both the first emitter region and the second emitter region have the first conductivity type, and their doping concentration is greater than that of the body region. The first electrode is located on the side of the first emitter region away from the first base region and is electrically connected to the first emitter region; The second electrode is located on the side of the second emitter region away from the second base region and is electrically connected to the second emitter region; The first base region and the second base region, and the first emission region and the second emission region are symmetrically arranged about the central plane of the body region. And, the thickness of the body region is 30 μm~60 μm; the doping concentration of the body region is 5×10 14 cm -3 ~5×10 15 cm -3 ; The bidirectional transient voltage suppressor structure is configured such that, during the transient conduction period after avalanche conduction, the first base region and the second base region inject bipolar carriers into the body region, forming a body region-dominant conduction region and generating a conductance modulation effect, causing the conduction current to change from PN junction conduction to body region-dominant conduction, and to extend and propagate within the body region. This results in the device exhibiting a conduction characteristic where the dynamic resistance decreases with increasing conduction current during conduction, and does not exhibit negative differential resistance characteristics.

2. The bidirectional transient voltage suppressor structure according to claim 1, characterized in that, the ratio of the peak doping concentration of the first base region to the doping concentration of the body region is 10 2 ~10 4 the ratio of the peak doping concentration of the second base region to the doping concentration of the body region is 10 2 ~10 4 to prevent the device from forming a self-sustained on state during the transient on period by limiting the parasitic positive feedback conduction path and to return to a high impedance state after the transient is over.

3. The bidirectional transient voltage suppressor structure according to claim 1, characterized in that, The first electrode forms an ohmic contact with the first emitter region, and the second electrode forms an ohmic contact with the second emitter region.

4. The bidirectional transient voltage suppressor structure according to claim 1, characterized in that, The doping concentrations of the first base region and the second base region are symmetrically arranged about the central plane of the body region, and the doping concentrations of the first emitter region and the second emitter region are symmetrically arranged about the central plane of the body region.

5. The bidirectional transient voltage suppressor structure according to claim 1, characterized in that, The breakdown voltage of the bidirectional transient voltage suppressor structure is positively correlated with the thickness of the body region, and / or the breakdown voltage of the bidirectional transient voltage suppressor structure is negatively correlated with the doping concentration of the body region.

6. The bidirectional transient voltage suppressor structure according to claim 1, characterized in that, The bidirectional transient voltage suppressor structure further includes an isolation structure; the isolation structure extends along the direction from the first electrode to the second electrode and is located at least within the body region.

7. The bidirectional transient voltage suppressor structure according to claim 6, characterized in that, Along the direction from the first electrode to the second electrode, the isolation structure penetrates the first emitter region, the first base region, the body region and the second base region, and extends into the interior of the second emitter region.

8. The bidirectional transient voltage suppressor structure according to claim 6, characterized in that, The isolation structure includes an isolation trench and a trench filling layer within the isolation trench. A trench insulation layer is spaced between the trench filling layer and the isolation trench, and the trench insulation layer is in contact with the inner wall and bottom surface of the isolation trench.

9. The bidirectional transient voltage suppressor structure according to claim 1, characterized in that, The first conductivity type is N-type, and the second conductivity type is P-type; or, the first conductivity type is P-type, and the second conductivity type is N-type.

10. The bidirectional transient voltage suppressor structure according to claim 1, characterized in that, The bidirectional transient voltage suppressor structure is a discrete device in a single package, or the bidirectional transient voltage suppressor structure is a single protection unit integrated in a multi-channel protection array.

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