Longitudinal SCR type transient overvoltage protection device
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- APPLIED POWER MICROELECTRONICS CO INC
- Filing Date
- 2026-03-16
- Publication Date
- 2026-05-26
Smart Images
Figure CN121888620B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor transient overvoltage protection technology, specifically to an SCR (Silicon Controlled Rectifier) type transient overvoltage protection device, and more particularly to a transient overvoltage protection device with a vertical SCR (Vertical SCR) structure, suitable for high-speed communication lines, especially suitable for electrostatic discharge (ESD), electrical fast transient (EFT) and system-level transient overvoltage protection in automotive high-speed Ethernet interfaces. Background Technology
[0002] As in-vehicle electronic systems evolve towards higher speeds and networking, in-vehicle Ethernet is gradually becoming a core technology for in-vehicle communication. This type of high-speed communication line places more stringent comprehensive requirements on transient overvoltage protection devices: on the one hand, under normal operating conditions, transient overvoltage protection devices should have low parasitic parameters to avoid adversely affecting the integrity of high-speed differential signals; on the other hand, when a transient overvoltage event occurs, the device should be able to quickly trigger and form a low-resistance conduction path to effectively clamp the overvoltage, thereby protecting the safety of downstream circuits.
[0003] In existing technologies, while avalanche TVS devices possess a certain surge withstand capability, their overvoltage clamping primarily relies on the junction avalanche process, typically exhibiting high clamping voltage and large dynamic impedance. This makes it difficult to effectively limit the voltage of sensitive nodes in high-speed communication interfaces. Furthermore, their junction structure characteristics limit further optimization of parasitic parameters in high-speed applications. Traditional SCR-type transient overvoltage protection devices, while possessing strong transient current carrying capacity, typically have low trigger and sustaining voltages, and these are highly coupled. In high-speed automotive communication environments, this can easily lead to false triggering or false sustaining, potentially causing latch-up effects and affecting the stability and reliability of the communication system. Therefore, it is necessary to provide a transient overvoltage protection device structure that maintains the high transient protection capability of SCR-type devices while also considering low capacitance, high trigger voltage, and high sustaining voltage, to meet the dual requirements of signal integrity and system reliability in high-speed automotive communication systems. Summary of the Invention
[0004] To address at least one technical problem in the prior art, embodiments of the present invention provide a vertical SCR-type transient overvoltage protection device that maintains the high transient protection capability of SCR-type devices while also exhibiting low capacitance characteristics, high trigger voltage, and high sustaining voltage. To achieve the above technical objectives, the technical solution adopted by embodiments of the present invention is as follows:
[0005] This invention provides a longitudinal SCR-type transient overvoltage protection device, comprising:
[0006] First conductivity type heavily doped semiconductor substrate;
[0007] An epitaxial layer is disposed on a heavily doped semiconductor substrate of the first conductivity type; the epitaxial layer is a lightly doped high-resistivity epitaxial layer of the first conductivity type, including a lightly doped drift region of the first conductivity type located on the side close to the heavily doped semiconductor substrate of the first conductivity type;
[0008] A second conductivity type base region is formed in the epitaxial layer; the second conductivity type base region is located above the first conductivity type lightly doped drift region;
[0009] A first conductivity type base region is formed in the epitaxial layer; the first conductivity type base region is located above the second conductivity type base region;
[0010] A second conductivity type heavily doped contact region is formed in the near-surface region of the epitaxial layer; the second conductivity type heavily doped contact region is located above the first conductivity type base region;
[0011] A deep trench isolation structure is disposed at the lateral boundary of the device; the deep trench isolation structure extends downward from the surface of the epitaxial layer, penetrates the epitaxial layer and enters the first conductivity type heavily doped semiconductor substrate, forming a continuous electrical isolation boundary in the longitudinal direction of the device;
[0012] in,
[0013] A longitudinal body region is formed in the longitudinal direction of the device, which extends along the longitudinal direction of the device from the second conductivity type heavily doped contact region, the first conductivity type base region, the second conductivity type base region, the first conductivity type lightly doped drift region to the first conductivity type heavily doped semiconductor substrate.
[0014] Furthermore, the doping concentration of the base region of the second conductivity type is higher than the doping concentration of the lightly doped drift region of the first conductivity type, and the difference between the two is at least two orders of magnitude.
[0015] Furthermore, the resistivity of the first conductivity type heavily doped semiconductor substrate is less than 0.01 Ω•cm.
[0016] Furthermore, the thickness of the epitaxial layer is in the range of 10 μm to 30 μm; the thickness of the lightly doped drift region of the first conductivity type is in the range of 5 μm to 28 μm.
[0017] Furthermore, the resistivity of the lightly doped drift region of the first conductivity type is in the range of 80 Ω•cm to 200 Ω•cm.
[0018] Furthermore, the peak doping concentration of the base region of the second conductivity type is located at 1x10⁻⁶. 16 cm -3~5x10 17 cm -3 Within this range, the junction depth of the base region of the second conductivity type is in the range of 1 μm to 5 μm.
[0019] Furthermore, the peak doping concentration of the base region of the first conductivity type is located at 5x10⁻⁶. 16 cm -3 ~1x10 18 cm -3 Within this range, the junction depth of the base region of the first conductivity type is in the range of 0.5 μm to 2 μm.
[0020] Furthermore, the junction depth of the first conductivity type base region is smaller than the junction depth of the second conductivity type base region.
[0021] Furthermore, the peak doping concentration of the heavily doped contact region of the second conductivity type is located at 1x10⁻⁶. 18 cm -3 ~5x10 19 cm -3 Within the range.
[0022] Furthermore, the first conductivity type and the second conductivity type can be interchanged, so that the conduction polarity of the device is reversed accordingly.
[0023] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows:
[0024] 1) By using a high-resistivity epitaxial layer as the main depletion region, the device exhibits low capacitance characteristics under all normal operating conditions, making it suitable for high-speed communication lines that are highly sensitive to parasitic parameters.
[0025] 2) By rationally configuring the electrical characteristics of the drift region, the triggering condition of the longitudinal SCR structure is dominated by the depletion and electric field distribution characteristics of the drift region, thereby achieving a higher triggering voltage and avoiding false triggering under normal operating conditions.
[0026] 3) By adjusting the base structure and carrier positive feedback conditions, the sustaining voltage of the longitudinal SCR structure can be improved, enabling the device to exit the conduction state in a timely manner after the transient event ends, thus avoiding false holding and latch-up effects.
[0027] 4) By combining the longitudinal body region conduction path with the deep trench isolation structure, the formation of lateral parasitic SCR path is suppressed and the leakage current is reduced, thereby improving the stability and reliability of the device during transient protection.
[0028] 5) While meeting the above characteristics, maintain the inherent low dynamic impedance and good transient current carrying capacity of SCR type devices to achieve reliable transient overvoltage protection. Attached Figure Description
[0029] Figure 1 This is a schematic diagram of the longitudinal SCR type transient overvoltage protection device in an embodiment of the present invention.
[0030] Figure 2 This is a schematic diagram of the current-voltage characteristics of the longitudinal SCR type transient overvoltage protection device in an embodiment of the present invention. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0032] In the description of the embodiments of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0033] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.
[0034] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0035] In Example 1, the first conductivity type and the second conductivity type can be N-type and P-type conductivity types, respectively.
[0036] like Figure 1 As shown, this embodiment of the invention proposes a longitudinal SCR type transient overvoltage protection device (hereinafter referred to as the device), comprising:
[0037] First conductivity type heavily doped semiconductor substrate 1;
[0038] Epitaxial layer 2 is disposed on a heavily doped semiconductor substrate 1 of the first conductivity type; the epitaxial layer 2 is a lightly doped high-resistivity epitaxial layer of the first conductivity type, including a lightly doped drift region 201 of the first conductivity type located on the side close to the heavily doped semiconductor substrate 1 of the first conductivity type.
[0039] A second conductivity type base region 202 is formed in the epitaxial layer 2; the second conductivity type base region 202 is located above the first conductivity type lightly doped drift region 201;
[0040] A first conductivity type base region 203 is formed in the epitaxial layer 2; the first conductivity type base region 203 is located above the second conductivity type base region 202;
[0041] A second conductivity type heavily doped contact region 204 is formed in the near-surface region of epitaxial layer 2; the second conductivity type heavily doped contact region 204 is located above the first conductivity type base region 203;
[0042] A deep trench isolation structure 3 is disposed at the lateral boundary of the device; the deep trench isolation structure 3 extends downward from the surface of the epitaxial layer 2, penetrates the epitaxial layer 2 and enters the heavily doped semiconductor substrate 1 of the first conductivity type, forming a continuous electrical isolation boundary in the longitudinal direction of the device;
[0043] in,
[0044] A longitudinal body region is formed in the longitudinal direction of the device. The longitudinal body region extends from the second conductivity type heavily doped contact region 204, the first conductivity type base region 203, the second conductivity type base region 202, the first conductivity type lightly doped drift region 201 to the first conductivity type heavily doped semiconductor substrate 1 in the longitudinal direction of the device; thereby, a PNPN type longitudinal SCR structure can be formed in the longitudinal direction of the device.
[0045] The present invention provides a longitudinal SCR-type transient overvoltage protection device that may further include:
[0046] A dielectric layer 4 is disposed on the epitaxial layer 2;
[0047] A front metal layer 5 is disposed on the dielectric layer 4, and the front metal layer 5 is electrically connected to the second conductivity type heavily doped contact region 204 through contact hole 401.
[0048] A passivation layer 6 is disposed on the front metal layer 5, and the passivation layer 6 has an opening to expose the pad area;
[0049] A back metal layer disposed on the back side of a heavily doped semiconductor substrate 1 of the first conductivity type.
[0050] The aforementioned device employs a PNPN-type vertical SCR structure. The second conductivity type heavily doped contact region 204, the first conductivity type base region 203, the second conductivity type base region 202, the first conductivity type lightly doped drift region 201, and the first conductivity type heavily doped semiconductor substrate 1 are arranged sequentially in the vertical bulk region direction, forming a PNPN-type vertical SCR structure. After triggering conduction, the conduction current mainly flows along the vertical bulk region conduction path of the device. By introducing a high-resistivity epitaxial layer as the main depletion region, combined with the synergistic configuration of the base region structure, the device exhibits low capacitance characteristics under normal operating conditions. Simultaneously, the deep trench isolation structure 3 effectively suppresses the formation of lateral parasitic SCR paths and reduces leakage current, thereby synergistically regulating the device's triggering and sustaining characteristics. Based on the above structural design, the device can quickly exit the conduction state after a transient overvoltage event, effectively avoiding latch-up effects.
[0051] The structure and principle of the longitudinal SCR type transient overvoltage protection device proposed in this application are described in detail below.
[0052] (a) Substrate and Epitaxial Structure
[0053] The resistivity of the first conductivity type heavily doped semiconductor substrate 1 is less than 0.01 Ω•cm, which is used to form a low-resistivity body conduction path for the vertical SCR structure.
[0054] In one embodiment, the resistivity of the heavily doped semiconductor substrate 1 of the first conductivity type is in the range of 0.002 Ω•cm to 0.01 Ω•cm.
[0055] Epitaxial layer 2 is grown on a heavily doped semiconductor substrate 1 of the first conductivity type. The thickness of epitaxial layer 2 is in the range of 10 μm to 30 μm, for example, 10 μm, 20 μm or 30 μm. Epitaxial layer 2 is a lightly doped high-resistivity epitaxial layer of the first conductivity type. The resistivity of epitaxial layer 2 is in the range of 80 Ω•cm to 200 Ω•cm. Therefore, the resistivity of the lightly doped drift region 201 of the first conductivity type in epitaxial layer 2 is in the range of 80 Ω•cm to 200 Ω•cm, for example, 80 Ω•cm, 100 Ω•cm, 120 Ω•cm, 140 Ω•cm, 160 Ω•cm or 200 Ω•cm. The thickness of the lightly doped drift region 201 of the first conductivity type is in the range of 5 μm to 28 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm or 28 μm.
[0056] By using a high-resistivity epitaxial layer structure, the device forms a depletion region dominated by the high-resistivity epitaxial layer under normal operating conditions, thereby reducing capacitance and providing a basis for the electric field distribution for the regulation of triggering characteristics.
[0057] (ii) Base region structure and doping concentration range
[0058] 1. Second conductivity type base region 202
[0059] The second conductivity type base region 202 is formed in the epitaxial layer 2, and its peak doping concentration is located at 1x10⁻⁶. 16 cm -3 ~5x10 17 cm -3 Within this range, the junction depth of the second conductivity type base region 202 is in the range of 1 μm to 5 μm; preferably 1.5 μm to 3.5 μm.
[0060] 2. Base region 203 of the first conductivity type
[0061] The first conductivity type base region 203 is located above the second conductivity type base region 202, and its peak doping concentration is 5x10. 16 cm -3 ~1x10 18 cm -3 Within this range, the junction depth of the first conductivity type base region 203 is in the range of 0.5 μm to 2 μm;
[0062] The junction depth of the base region 203 of the first conductivity type is smaller than the junction depth of the base region 202 of the second conductivity type, thus forming a controlled longitudinal PN junction coupling relationship between the two.
[0063] 3. Heavy doped contact region 204 of the second conductivity type
[0064] The second conductivity type heavily doped contact region 204 is formed on the first conductivity type base region 203; its peak doping concentration is 1x10⁻⁶. 18 cm -3 ~5x10 19 cm -3 Within this range, the region is used to form a low-resistivity cathode contact region and serves as the emitter region of the vertical SCR structure. The carrier injection efficiency can be adjusted by regulating its doping concentration and spatial distribution.
[0065] (III) The mechanism by which doping gradient modulates triggering and sustaining characteristics
[0066] The vertical SCR structure can be equivalently represented as a four-layer (PNPN) positive feedback system formed by coupling PNP and NPN bipolar transistors. Its conduction and sustaining depend on the superposition of the current gains of the two equivalent transistors. In this embodiment, the doping concentration of the base region 202 of the second conductivity type is higher than that of the lightly doped drift region 201 of the first conductivity type, and the difference between the two is at least two orders of magnitude. This doping difference causes the depletion region to mainly extend into the drift region under reverse bias, making the triggering behavior dominated by the electric field distribution of the drift region, thereby achieving a higher trigger voltage. At the same time, this doping configuration reduces the current gain of the equivalent bipolar transistor, limiting the positive feedback enhancement condition and making it difficult for the SCR to maintain a strong injection state when the conduction current decreases. Therefore, the device can reliably trigger and enter the conduction state under transient overvoltage conditions, and automatically exit the conduction state when the conduction current decreases, thereby improving the sustaining voltage and suppressing the latch-up effect.
[0067] (iv) The synergistic mechanism between the drift region and the base region
[0068] The drift region is responsible for regulating the triggering characteristics. Due to its light doping and relatively large vertical thickness, it forms the main depletion region under overpressure stress conditions, making the triggering behavior determined by the electric field distribution within the drift region. The second conductivity type base region 202 is responsible for regulating the sustaining characteristics. By controlling its doping concentration, junction depth, and the ratio of its vertical junction depth to that of the first conductivity type base region 203, as well as its lateral coverage relationship, the carrier positive feedback loop becomes difficult to maintain when the current decreases. Thus, decoupled regulation of triggering and sustaining characteristics is achieved.
[0069] (V) Longitudinal body region conduction mechanism
[0070] When an electrostatic discharge or transient overvoltage event occurs, the longitudinal SCR structure is triggered to enter the conduction state. After triggering, charge carriers diffuse and flow in the longitudinal direction in the epitaxial layer and substrate, forming a longitudinal bulk conduction path, which makes the device exhibit low dynamic impedance and effectively clamps the transient overvoltage.
[0071] like Figure 2 As shown, under transient overvoltage conditions, the device is triggered to enter the conduction state at a higher voltage level and forms a conduction behavior with flyback characteristics, so that the overvoltage current is released along the conduction path of the longitudinal body region of the device. Figure 2 In this context, Vtrigger is the trigger voltage, and Vhold is the holding voltage.
[0072] When the transient overvoltage event ends and the device conduction current drops below a certain level, due to the limitation of the positive feedback condition of the base region on the carriers, the device can exit the conduction state under conditions higher than the normal operating voltage of the protected line, thereby avoiding false holding and suppressing the occurrence of latch-up effect.
[0073] (vi) Deep trench isolation structure
[0074] The deep trench isolation structure 3 extends downward from the surface of the epitaxial layer 2, penetrates the epitaxial layer 2, and enters the heavily doped semiconductor substrate 1 of the first conductivity type; forming a continuous electrical isolation boundary in the longitudinal direction. This isolation structure cuts off the lateral carrier diffusion path, suppresses the formation of lateral parasitic SCR pathways, and reduces the leakage current caused by lateral coupling.
[0075] (vii) Interchangeable conductivity type implementation methods
[0076] The first conductivity type and the second conductivity type can be interchanged, and the conductivity types of the functional areas are configured in reverse accordingly, so that the triggering and conduction mechanisms of the vertical SCR structure remain consistent, with only the conduction polarity of the device being reversed.
[0077] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A longitudinal SCR type transient overvoltage protection device, characterized in that, include: First conductivity type heavily doped semiconductor substrate (1); An epitaxial layer (2) disposed on a heavily doped semiconductor substrate (1) of the first conductivity type; The epitaxial layer (2) is a lightly doped high-resistivity epitaxial layer of the first conductivity type, including a lightly doped drift region (201) of the first conductivity type located on the side close to the heavily doped semiconductor substrate (1) of the first conductivity type; A second conductivity type base region (202) is formed in the epitaxial layer (2); the second conductivity type base region (202) is located above the first conductivity type lightly doped drift region (201); A first conductivity type base region (203) is formed in the epitaxial layer (2); the first conductivity type base region (203) is located above the second conductivity type base region (202); A second conductivity type heavily doped contact region (204) is formed in the near-surface region of the epitaxial layer (2); the second conductivity type heavily doped contact region (204) is located above the first conductivity type base region (203); A deep trench isolation structure (3) is provided at the lateral boundary of the device; the deep trench isolation structure (3) extends downward from the surface of the epitaxial layer (2), penetrates the epitaxial layer (2) and enters the first conductivity type heavily doped semiconductor substrate (1), forming a continuous electrical isolation boundary in the longitudinal direction of the device; in, A longitudinal body region is formed in the longitudinal direction of the device, which extends along the longitudinal direction of the device from the second conductivity type heavily doped contact region (204), the first conductivity type base region (203), the second conductivity type base region (202), the first conductivity type lightly doped drift region (201) to the first conductivity type heavily doped semiconductor substrate (1).
2. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The doping concentration of the base region (202) of the second conductivity type is higher than that of the lightly doped drift region (201) of the first conductivity type, and the difference between the two is at least two orders of magnitude.
3. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The resistivity of the first conductivity type heavily doped semiconductor substrate (1) is less than 0.01 Ω•cm.
4. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The thickness of the epitaxial layer (2) is in the range of 10 μm to 30 μm; the thickness of the first conductivity type lightly doped drift region (201) is in the range of 5 μm to 28 μm.
5. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The resistivity of the first conductivity type lightly doped drift region (201) is in the range of 80 Ω•cm to 200 Ω•cm.
6. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The peak doping concentration of the base region (202) of the second conductivity type is located at 1x10. 16 cm -3 ~5x10 17 cm -3 Within this range, the junction depth of the second conductivity type base region (202) is in the range of 1 μm to 5 μm.
7. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The peak doping concentration of the base region (203) of the first conductivity type is located at 5 x 10⁻⁶. 16 cm -3 ~1x10 18 cm -3 Within the range, the junction depth of the first conductivity type base region (203) is in the range of 0.5 μm to 2 μm.
8. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The junction depth of the first conductivity type base region (203) is smaller than the junction depth of the second conductivity type base region (202).
9. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The peak doping concentration of the heavily doped contact region (204) of the second conductivity type is located at 1x10. 18 cm -3 ~5x10 19 cm -3 Within the range.
10. The longitudinal SCR type transient overvoltage protection device as described in claim 1, characterized in that, The first conductivity type and the second conductivity type can be interchanged, so that the conduction polarity of the device is reversed accordingly.