Zener diode
By adopting a longitudinal structural design in the voltage-regulating diode, a voltage-regulating PN junction is formed along the longitudinal direction, which solves the problem of large area and low design density of the voltage-regulating diode device in the prior art, and achieves higher design density and greater overcurrent capability.
Patent Information
- Application Number
- CN202411916891.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-03-28
AI Technical Summary
The existing lateral voltage-regulating diode devices have a large area, resulting in a low design density, and the reverse withstand voltage is mainly determined by the length of the P-type base region, resulting in a further increase in the device area.
The voltage-regulating diode design adopts a longitudinal structure, in which the key voltage-regulating PN junction is formed along the longitudinal direction of the device, avoiding the influence of device length and functional area depth on the overcurrent capability of the PN junction. The design includes a P-type substrate, an N-type epitaxial, a P+-type ion-doped region, an N-well and an N-type ion-doped region, and a contact surface between the P+-type ion-doped region and an N-well forms a voltage-regulated PN junction.
It realizes the dynamic resistance of the reverse operation of the device while ensuring voltage stabilization accuracy, expands the device's overcurrent capability, and can provide a device area smaller than the prior art, thereby increasing the design density of semiconductor devices.
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Figure CN119730262A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of semiconductor devices, and in particular to a voltage stabilizing diode. Background Art
[0002] Zener diodes, also known as Zener diodes, use the characteristics of PN junctions that the current can vary over a wide range while the voltage can remain basically unchanged in the reverse breakdown state to stabilize the voltage in the circuit.
[0003] refer to Figure 1 , is a schematic diagram of a device cross section of a lateral voltage regulator diode provided in an existing bipolar process. Figure 1 As shown, an N-type epitaxy 13 is formed on a P-type substrate 11. A P-type base region 15 and an N+ type ion doping region 17 are formed in the N-type epitaxy 13. The P-type base region 15 and the N+ type ion doping region 17 overlap each other in the lateral direction of the N-type epitaxy 13 to form a key component of the Zener diode, a PN junction A that plays a voltage stabilizing role. The reverse operating current of the lateral Zener diode is mainly determined by the longitudinal section area of the overlapping surface of the N+ type ion doping region 17 and the P-type base region 15, that is, the product of the junction depth of the N+ type ion doping region 17 and the width of the N+ type ion doping region 17. The larger the longitudinal section area, the greater the operating current that the Zener diode can withstand.
[0004] The above-mentioned Zener diode is a lateral structure, so the area of its PN junction A is greatly affected by the junction depth and width of the N+ type ion doping region 17. The N+ type ion doping region 17 is usually high in concentration and low in junction depth, so in order to increase its junction area, the general practice is to increase its width, which leads to an increase in the device area of the lateral Zener diode. At the same time, due to the high concentration of the N+ type ion doping region 17, the PN junction A of the lateral Zener diode is an approximate abrupt junction, and its reverse withstand voltage is mainly determined by the length of the P-type base region 15. The higher the withstand voltage, the longer the length of the P-type base region 15 is required, which further leads to an increase in the device area of the lateral Zener diode. Summary of the invention
[0005] In order to reduce the device area of the voltage zener diode in the prior art, the present application provides a voltage zener diode.
[0006] The technical solution of the present invention provides a voltage stabilizing diode, comprising: a P-type substrate; an N-type epitaxial layer formed on a surface of one side of the P-type substrate; A stacked contact P+ type ion doping region and an N well are provided in the N type epitaxy, the P+ type ion doping region extends to the surface of the N type epitaxy to be electrically connected to an external circuit, a projection of the P+ type ion doping region in the thickness direction of the N type epitaxy completely covers the N well, and a contact surface between the P+ type ion doping region and the N well forms a PN junction for voltage stabilization; An N+ type ion doping region is also formed in the N type epitaxy, the N+ type ion doping region is not in contact with the P+ type ion doping region, and the N+ type ion doping region extends to the surface of the N type epitaxy to be electrically connected to an external circuit.
[0007] Preferably, in the N-type epitaxy, a P-type ion doping region is formed at the contact interface between the P+ type ion doping region and the N-type epitaxy, and the doping concentration of the P-type ion doping region is lower than the doping concentration of the P+ type ion doping region.
[0008] Preferably, the P-type ion doping region at least covers the corner region of the P+ type ion doping region; Alternatively, the P-type ion doping region covers the entire interface region where the P+-type ion doping region contacts the N-type epitaxy.
[0009] Preferably, an N-type buried layer is provided between the P-type substrate and the N-type epitaxy, and the N+-type ion-doped region is electrically connected to the N-type buried layer.
[0010] Preferably, a projection of the N-type buried layer in a thickness direction of the N-type epitaxial layer covers a portion of the P+ type ion doping region and the N+ type ion doping region.
[0011] Preferably, an N-type buried layer is provided between the P-type substrate and the N-type epitaxy, and the N+-type ion-doped region is electrically connected to the N-type buried layer.
[0012] Preferably, the N-type epitaxy forms a deep N-well electrically connecting the N-type buried layer and the N+-type ion-doped region.
[0013] Preferably, it further comprises a P-type isolation layer arranged around the N-type epitaxy, wherein the lower portion of the P-type isolation layer extends to contact the P-type substrate, and the upper portion extends to the surface of the N-type epitaxy.
[0014] Preferably, the P-type isolation layer comprises a P-type buried layer and a P-type upper isolation layer formed in stacked contact within the N-type epitaxy; The P-type buried layer extends to the P-type substrate, and the P-type upper isolation layer extends to the N-type epitaxial surface.
[0015] The present application provides a structural solution for a voltage stabilizing diode of a longitudinal structure, in which a PN junction that plays a key voltage stabilizing role is formed along the longitudinal direction of the device, thereby avoiding the influence of the device length and the depth of the functional area on the overcurrent capacity of the PN junction. While ensuring the voltage stabilizing accuracy of the device, reducing the dynamic resistance of the device working in reverse, and expanding the overcurrent capacity of the device, a device area smaller than that of the prior art can be provided, thereby improving the design density of the semiconductor device. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a longitudinal cross-sectional schematic diagram of a voltage zener diode in the prior art; Figure 2 A schematic longitudinal cross-sectional view of the voltage zener diode of the present application; Figure 3 A longitudinal cross-sectional schematic diagram of another embodiment of the voltage zener diode of the present application; Figure 4 A longitudinal cross-sectional schematic diagram of another embodiment of the voltage zener diode of the present application; Figure 5 A longitudinal cross-sectional schematic diagram of another embodiment of the voltage zener diode of the present application; Figure 6 Schematic diagram of other embodiments of the voltage zener diode of the present application; Figure 7 Schematic diagram of other embodiments of the voltage regulator diode of the present application.
[0017] In the figure: 11: P-type substrate; 13: N-type epitaxy; 15: P-type base region; 17: N+ type ion doping region; 21: P+ type ion doping region; 22: P type ion doping region; 23: N well; 25: N+ type ion doping region; 27: deep N well; 29: N-type buried layer; 31: P-type buried layer; 32: P-type upper isolation layer; A: PN junction; 3: P-type isolation layer. DETAILED DESCRIPTION
[0018] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. In this specification, the size ratios in the drawings do not represent the actual size ratios, but are only used to reflect the relative position relationship and connection relationship between the components. Components with the same name or the same number represent similar or identical structures and are only for illustrative purposes.
[0019] Figure 2The longitudinal cross-sectional schematic diagram of the voltage regulator diode of the present application. The voltage regulator diode has a longitudinal structure. It has a P-type substrate 11. An N-type epitaxy 13 is formed on one side surface of the P-type substrate 11. A stacked P+ type ion doping region 21 and a P-type ion doping region 22 are formed in the N-type epitaxy 13, wherein the P+ type ion doping region 21 extends to the surface of the N-type epitaxy 13 for electrical connection with an external circuit. Specifically, it can be electrically connected to the external circuit through a metal electrode formed on the surface of the N-type epitaxy 13. The projection area of the P+ type ion doping region 21 in the thickness direction completely covers the area where the N-well 23 is located, thereby forming a PN junction A between the overlapping interfaces between the P+ type ion doping region 21 and the N-well 23. The area of the PN junction A is determined by the contact area between the P+ type ion doping region 21 and the N-well 23, and obviously has a larger junction area than the lateral structure and a more convenient parameter control method (adjusting the doping state of the N-well 23). The PN junction A works in a breakdown state when it has a reverse bias to realize a voltage stabilization function. An N+ type ion doping region 25 is also formed independently in the N-type epitaxy 13 without contacting the P+ type ion doping region 21, and the N+ type ion doping region 25 extends to the surface of the N-type epitaxy 13 to be electrically connected to an external circuit. Preferably, the N+ type ion doping region 25 and the N well 23 do not contact each other. Specifically, the N+ type ion doping region 25 can also be electrically connected to an external circuit through a metal electrode formed on its surface.
[0020] like Figure 2 As shown, when working, a reverse bias voltage is connected between the N+ type ion doping region 25 and the P+ type ion doping region 21, and when the PN junction A breaks down in the reverse direction, a circuit as shown in FIG. Figure 2 The current path shown is along the N+ type ion doping region 25, N type epitaxy 13, N well 23 to the P+ type ion doping region 21. At this time, the PN junction A is in a reverse breakdown state, and its volt-ampere characteristic curve shows that the voltage across its two ends can be relatively stable, achieving the expected function of the voltage stabilizing diode.
[0021] Figure 3 FIG. 1 is a schematic longitudinal cross-sectional view of a further embodiment of the present application. Figure 2As shown. When the breakdown voltage at the corner is close to the breakdown voltage of the PN junction A, and the process fluctuates or there are defects on the surface, the breakdown voltage at the corner will be less than the breakdown voltage of the PN junction A, so that the corner of the P+ ion implantation area 21 will be broken down first, affecting the target breakdown voltage of the Zener diode, that is, affecting the voltage regulation value of the Zener diode. In order to avoid the breakdown of the P+ type ion doping area 21 in the non-contact area with the N well 23, especially to avoid the breakdown at the corner of the P+ type ion doping area 21, it is preferred to form a P-type ion doping area 22 at the interface of the direct contact between the P+ type ion doping area 21 and the N-type epitaxy 13. The concentration of the P-type ion doping area 22 is lower than that of the P+ type ion doping area 21, so that it can be ensured that the breakdown does not occur at the corner of the P+ type ion doping area 21. The function of the P-type ion doping region 22 is to protect the electrical isolation of the boundary between the P+ type ion doping region 21 and the N-type epitaxy 13, so that the breakdown occurs first (and only the breakdown, because after the first breakdown, the pressure between the P+ type ion doping region 21 and the N-type epitaxy 13 is lost, and it is impossible to break down between the P+ type ion doping region 21 and the N-type epitaxy 13 later) at the PN junction A between the P+ type ion doping region 21 and the N well 23. Therefore, the P-type ion doping region 22 can further improve the voltage resistance and voltage resistance accuracy of the device. Considering that under the action of electric field stress, the breakdown between the N-type epitaxy 13 and the P+ type ion doping region 21 is more likely to occur at the corner of the P+ type ion doping region 21, the P-type ion doping region 22 should at least cover the corner area of the P+ type ion doping region 21, such as Figure 3 Preferably, the P-type ion doping region 22 covers the entire region where the P+-type ion doping region 21 contacts the N-type epitaxy 13 .
[0022] like Figure 4 As shown, the N+ type ion doping region 25 can be arbitrarily arranged around the P+ type ion doping region 21, as long as it satisfies the aforementioned condition of not contacting the P+ type ion doping region 21. The P+ type ion doping region 21 can be formed on one side of the P+ type ion doping region 21. Some sides or formed on the surrounding side of the P+ type ion doping region 21. Figure 4 as well as Figure 6 1 is one embodiment, and both figures are cross-sectional schematic diagrams of a voltage regulator diode device. It shows a device structure with spaced distribution, where the N+ type ion doping region 25 can be distributed on one side or two opposite sides of the P+ type ion doping region 21 and isolated from the N type epitaxy 13 in the N type epitaxy 13. Figure 7 The embodiment of the present invention provides a device with a ring structure. The N+ type ion doping region 25 is formed on the periphery of the P+ type ion doping region 21 and is connected to the P+ type ion doping region 21 through the N type epitaxy 13 .
[0023] like Figure 5In the embodiment shown, the voltage-stabilizing diode can also form an N-type buried layer 29 between the P-type substrate 11 and the N-type epitaxial 13, and the N+ type ion doping region 25 is electrically connected to the N-type buried layer 29. At this time, the current first flows from the N+ type ion doping region 25 through the N-type buried layer 29, then enters the N well 23 from the N-type buried layer 29 through the N-type epitaxial 13, and finally enters the P+ type ion doping region 21 through the PN junction A. At this time, the current can be constrained to flow in the longitudinal direction, and the lateral diffusion can be completed in the low-resistance N-type buried layer 29.
[0024] Furthermore, if Figure 5 As shown, preferably, in order to optimize the reverse conductive characteristics of the device and optimize the conductive path design of the device, a deep N well 27 connecting the N+ type ion doped region 25 and the N type buried layer 29 is formed between the two. The deep N well 27 can further reduce the dynamic resistance of the device under this configuration, thereby avoiding the increase of the on-resistance due to the configuration change.
[0025] Figure 5 It is a schematic diagram of the Zener diode of the present application. On the basis of the above-mentioned embodiments, an isolation structure is preferably provided on the basis of the independent cells of the Zener diode to avoid leakage current between multiple common substrate devices arranged. Specifically, the isolation structure includes a P-type isolation layer 3 provided around the N-type epitaxy 13, the lower portion of the P-type isolation layer 3 extends to contact with the P-type substrate 11, and the upper portion extends to the surface of the N-type epitaxy 13. The P-type isolation layer 3 can be a single layer or a multi-layer, and the P-type isolation layer 3 preferably includes a P-type buried layer 31 and a P-type upper isolation layer 32 formed in stacked contact in the N-type epitaxy 13, wherein the P-type buried layer 31 extends to the P-type substrate 11, and the P-type upper isolation layer 32 extends to the surface of the N-type epitaxy 13. Single-layer isolation is also possible, and the advantage of double-layer isolation is that the lateral diffusion width of the isolation region can be reduced, thereby reducing the area of the device. As Figure 6 , 7 As shown, the P-type isolation layer electrically isolates a Zener diode structure from other surrounding devices.
[0026] Except for the need to add a layer of N-well 23, all the injection levels of the technical solution of the present application can be provided by the existing process platform, and the process compatibility is high; due to the addition of the additional N-well 23 level, the device structure can achieve any voltage resistance adjustment without increasing the chip area, and only needs to change the injection conditions of the N-well 23. For example, if you want to improve the voltage resistance of the Zener diode, you can reduce its injection dose, and conversely, increasing the injection dose can reduce its voltage resistance. The design of the N-well has the following specific features: reverse doping gradient distribution and adjustable junction depth. The reverse doping gradient distribution is characterized by a gradual decrease in concentration from the bottom of the N-well to the top of the N-well, or a high concentration is used at the bottom of the N-well and a low concentration is used at the top of the N-well. The top low-concentration N-well can ensure that the voltage resistance of the Zener diode meets the design requirements, and the high-concentration N-well can reduce the dynamic resistance of the Zener diode. By reducing the distance from the bottom of the N-well to the N-type buried layer 21 through high-energy injection to achieve a high junction depth, this can also further reduce the dynamic resistance of the Zener diode.
[0027] The cathode (N-well 23) of the vertical Zener diode is inside the body, and the anode (P+-type ion doping region 21) is on the surface of the device. In order to integrate the circuit and lead the cathode to the device surface, it is necessary to introduce an N+-type ion doping region 25 of the same type as the N-well 23 on the left and right sides or one side of the Zener diode structure as the cathode of the Zener diode, and the deep N-well 27 is connected to the N-type buried layer 29. The advantage of this is that when the Zener diode is working, the current can flow as much as possible in the vertical direction, through the low-resistance N-type buried layer 29 and the deep N-well 27 to the N+-type ion doping region 25, thereby further reducing the dynamic resistance of the Zener diode. Therefore, the projection of the N-type buried layer 29 in the thickness direction of the N-type epitaxy 13 preferably covers the P+-type ion doping region 21 and part of the N+-type ion doping region 25.
[0028] The embodiments of the present application are not only applicable to bipolar process platforms, but also to mainstream process platforms such as BiCMOS and BCD, and have a wide range of applications. In the voltage regulator diode of the present application, it is recommended to give priority to the injection process for the N well 23, because the injection can better control the distribution of the doped well, and the process accuracy is high, which is necessary for high-precision voltage regulators. The doping concentration range of the N well 23 is 1×10 16 cm -3 ~1×10 20 cm -3 The specific doping concentrations of other layers not described can be designed in accordance with the prior art.
[0029] The above content only describes the preferred implementation mode of the present invention, and does not limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solution of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.
Claims
1. A voltage zener diode, characterized in that: include: A P-type substrate (11); an N-type epitaxial layer (13) formed on a surface of one side of the P-type substrate (11); The N-type epitaxy (13) has a stacked contact P+ type ion doping region (21) and an N well (23), the P+ type ion doping region (21) extends to the surface of the N-type epitaxy (13) to be electrically connected to an external circuit, the projection of the P+ type ion doping region (21) in the thickness direction of the N-type epitaxy (13) completely covers the N well (23), and the contact surface between the P+ type ion doping region (21) and the N well (23) forms a PN junction (A) for voltage stabilization; An N+ type ion doping region (25) is also formed in the N type epitaxy (13), the N+ type ion doping region (25) is not in contact with the P+ type ion doping region (21), and the N+ type ion doping region (25) extends to the surface of the N type epitaxy (13) to be electrically connected to an external circuit.
2. The voltage zener diode according to claim 1, characterized in that: The doping concentration of the N-well (23) gradually decreases from the bottom of the N-well to the top of the N-well; Or, the doping concentration of the N well (23) is in the range of 1×10 16 cm -3 ~1×10 20 cm -3 .
3. The voltage zener diode according to claim 1, characterized in that: In the N-type epitaxy (13), a P-type ion doping region (22) is formed at the contact interface between the P+ type ion doping region (21) and the N-type epitaxy (13), and the doping concentration of the P-type ion doping region (22) is lower than the doping concentration of the P+ type ion doping region (21).
4. The voltage zener diode according to claim 3, characterized in that: The P-type ion doping region (22) at least covers the corner region of the P+-type ion doping region (21); Alternatively, the P-type ion doping region (22) covers the entire interface region where the P+-type ion doping region (21) contacts the N-type epitaxy (13).
5. The voltage zener diode according to claim 1, characterized in that: An N-type buried layer (29) is provided between the P-type substrate (11) and the N-type epitaxy (13), and the N+-type ion doped region (25) is electrically connected to the N-type buried layer (29).
6. The voltage zener diode according to claim 5, characterized in that: The projection of the N-type buried layer (29) in the thickness direction of the N-type epitaxy (13) covers a portion of the P+-type ion doping region (21) and the N+-type ion doping region (25).
7. The voltage zener diode according to claim 5, characterized in that: An N-type buried layer (29) is provided between the P-type substrate (11) and the N-type epitaxy (13), and the N+-type ion doped region (25) is electrically connected to the N-type buried layer (29).
8. The voltage zener diode according to claim 7, characterized in that: The N-type epitaxy (13) forms a deep N-well (27) electrically connecting the N-type buried layer (29) and the N+-type ion doped region (25).
9. The voltage zener diode according to claim 1, characterized in that: It also includes a P-type isolation layer (3) arranged around the N-type epitaxy (13), wherein the lower portion of the P-type isolation layer extends to contact the P-type substrate (11), and the upper portion extends to the surface of the N-type epitaxy (13).
10. The voltage zener diode according to claim 1, characterized in that: The P-type isolation layer (3) comprises a P-type buried layer (31) and a P-type upper isolation layer (32) formed in stacked contact in the N-type epitaxy (13); The P-type buried layer (31) extends to the P-type substrate (11), and the P-type upper isolation layer (32) extends to the surface of the N-type epitaxial layer (13).