A graded-doped composite jte termination structure

Abstract

This application relates to the field of semiconductor technology and provides a gradient-doped composite JTE termination structure. The structure includes: a substrate; an epitaxial layer disposed on the substrate; an active region disposed in the epitaxial layer; and an edge protection zone disposed in the epitaxial layer and surrounding the active region. The edge protection zone includes multiple JTE regions and multiple reverse-doped regions. The multiple JTE regions are spaced apart in the epitaxial layer in a direction away from the active region, and the multiple reverse-doped regions are embedded within the JTE regions. The reverse-doped regions and the JTE regions are semiconductor materials with different conductivity types, and the doping concentration of the reverse-doped regions increases in a direction away from the active region. This application effectively flattens the surface electric field distribution by dividing the electric field spike at the main junction into multiple electric field peaks, thereby improving the device's breakdown voltage and tolerance to process variations.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to a gradient-doped composite JTE terminal structure. Background Technology

[0002] In high-voltage power semiconductor devices (especially wide-bandgap silicon carbide devices), junction termination extension (JTE) technology is a key means to alleviate the electric field concentration in the main junction and improve the device breakdown voltage (BVD). Traditional single-region or multi-region JTE structures laterally extend the depletion layer by injecting P-type doped regions around the main junction. However, this structure is extremely sensitive to the doping dose: too high a dose will cause the JTE region to not be completely depleted, leading to premature breakdown; too low a dose will not be able to effectively support the voltage, limiting the improvement of the device's breakdown voltage capability.

[0003] To overcome this challenge, Chinese invention patent CN106252385B discloses an anti-doped JTE structure. This structure introduces N-type anti-doped regions (such as CD1-CD4) into the P-type JTE region, utilizing the charge compensation effect to adjust the net doping concentration in a specific region to an ideal value, thereby optimizing the electric field distribution and improving terminal efficiency. Although this approach significantly improves the process sensitivity of traditional JTEs, its anti-doped regions are typically distributed as independent islands or blocks, leaving room for improvement in adjusting the uniformity of the lateral electric field distribution. Especially in ultra-high voltage (e.g., 3300V and above) applications, how to further smooth surface electric field spikes remains a pressing technical problem. Summary of the Invention

[0004] To help solve the above-mentioned technical problems, this application provides a gradient-doped composite JTE termination structure, which adopts the following technical solution: A gradient-doped composite JTE termination structure, comprising: A substrate having a semiconductor material of a first conductivity type; An epitaxial layer is disposed on the upper surface of the substrate and has a semiconductor material of the first conductivity type; An active region is disposed in the epitaxial layer; and An edge protection zone is set in the epitaxial layer and surrounds the active region; The edge protection zone includes: Multiple JTE regions are spaced apart in the epitaxial layer along a direction away from the active region, and the JTE regions are semiconductor materials of a second conductivity type. Multiple reverse-doped regions are embedded within the JTE region, and the reverse-doped regions have semiconductor materials of the first conductivity type; The doping concentration of the reverse doped region increases in the direction away from the active region.

[0005] The JTE region and the reverse doped region embedded therein constitute a plurality of PN junction units, and the plurality of PN junction units are arranged at intervals along a direction away from the active region.

[0006] The doping concentration of the reverse doped region increases in a stepwise or continuous manner along the direction away from the active region.

[0007] When the semiconductor material of the first conduction type is N-type, the semiconductor material of the second conduction type is P-type; when the semiconductor material of the first conduction type is P-type, the semiconductor material of the second conduction type is N-type.

[0008] The edge protection zone further includes at least one Pwell doped region, which is disposed between the active region and the JTE region, and the Pwell doped region is adjacent to the adjacent JTE region or the reverse doped region.

[0009] The edge protection zone further includes at least one P+ doped region, which is disposed between the active region and the Pwell doped region, and is adjacent to both the active region and the Pwell doped region.

[0010] The doping concentration of the JTE region is lower than that of the reverse doping region.

[0011] The width of the reverse doped region gradually increases in the direction away from the active region; and / or, the thickness of the reverse doped region gradually increases in the direction away from the active region.

[0012] The JTE region includes a first JTE region, a second JTE region, and a third JTE region arranged sequentially along the direction away from the active region; the reverse doping region includes a first reverse doping region, a second reverse doping region, a third reverse doping region, a fourth reverse doping region, a fifth reverse doping region, and a sixth reverse doping region; wherein, the first to fourth reverse doping regions are distributed at intervals within the first JTE region, the fifth reverse doping region is distributed within the second JTE region, and the sixth reverse doping region is distributed within the third JTE region.

[0013] Also includes: A P-type doped region is disposed in the epitaxial layer and ohmically contacts the JTE region; A first electrode is disposed on a portion of the P-type doped region; A second electrode is disposed on the lower surface of the substrate and is in ohmic contact with the substrate; An oxygen layer is disposed on the upper surface of the edge protection zone and covers at least a portion of the JTE region and the reverse doped region.

[0014] In summary, this application utilizes the charge balance principle further by constructing a periodically alternating PN-doped array as the JTE terminator, compared to traditional undoped JTEs. This structure optimizes the electric field distribution to be more uniform and smooth. Compared with existing technologies, this application has the following advantages: 1. In JTE, the PP ring and PW ring play a role in assisting depletion and clamping the peak electric field at the main junction, optimizing the electric field distribution, supporting the outward expansion of the depletion layer, which helps to reduce hot carrier injection and leakage current, and improves the long-term reliability of the device.

[0015] 2. In the alternating PN array, each PN junction unit participates in electric field modulation, which divides and flattens a single electric field peak into multiple smaller electric field peaks, resulting in a more uniform electric field distribution on the overall surface and improving the electric field distribution in the terminal region.

[0016] 3. Significantly improves the device's tolerance to process variations, thereby achieving higher breakdown voltage and more stable device performance with the same termination area. By adjusting the number, location, and doping concentration of the JTE region and the reverse doped region, it can be flexibly adapted to device designs of different voltage levels. Furthermore, this structure can be implemented using standard ion implantation processes, without the need for additional photomasks or complex process steps, making it easy to integrate and particularly suitable for the design and fabrication of high-voltage, high-power silicon carbide power devices. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an embodiment of a gradient-doped composite JTE terminal structure according to this application; Figure 2 for Figure 1 A schematic diagram of the first simulation result of the embodiment shown; Figure 3 for Figure 1 A schematic diagram of the second simulation results of the embodiment shown; Figure 4 for Figure 1 A schematic diagram of the measured results of the embodiment shown.

[0018] Reference numerals: 11-First electrode; 12-P-type doped region; 13-Epipolar layer; 14-Substrate; 15-Second electrode; 16-Field oxide layer; a1-First P+ doped region; a2-Second P+ doped region; b1-First Pwell doped region; b2-Second Pwell doped region; c1-First JTE region; c2-Second JTE region; c3-Third JTE region; d1-First reverse doped region; d2-Second reverse doped region; d3-Third reverse doped region; d4-Fourth reverse doped region; d5-Fifth reverse doped region; d6-Sixth reverse doped region. Detailed Implementation

[0019] The present application will be further described below with reference to the accompanying drawings. The principles of the present application are very clear to those skilled in the art. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

[0020] In traditional single P-type JTE regions, if the doping concentration is too high, the depletion layer cannot fully expand, leading to electric field concentration; if it is too low, it cannot effectively support the voltage. This application introduces P+ and Pwell doped regions within the P-type JTE region to assist depletion, effectively clamping the peak electric field at the main junction and supporting the outward expansion of the depletion region. Simultaneously, by introducing N-type reverse doped regions within the P-type JTE region, a precise net doping concentration gradient is formed in a localized region using the principle of PN mutual compensation. As the reverse doping concentration increases away from the active region, the net doping concentration exhibits a gradual distribution from low to high from the edge of the main junction outwards. This structural layout provides a basis for the smooth expansion of the depletion layer.

[0021] Under reverse bias, the depletion layer extends outward from the main junction (P+ / N- junction). This is because the concentration of the reverse-doped region increases progressively. Near the main junction region: The reverse doping concentration is low, the net doping concentration is low, and the depletion layer can easily extend here, effectively reducing the peak electric field at the edge of the main junction.

[0022] Far from the main junction region: The reverse doping concentration is higher, and the net doping concentration is correspondingly increased, which slows down the expansion rate of the depletion layer in this region and prevents the depletion layer from penetrating to the terminal edge too early.

[0023] This expansion method makes the relationship between the lateral width of the depletion layer and the reverse voltage more linear, avoiding electric field spikes caused by the sudden termination of the depletion layer in a certain region.

[0024] In the PN junction unit formed by the JTE region and the reverse-doped region embedded within it, each PN junction unit independently bears a portion of the voltage under reverse bias. Traditional single-junction terminations have only one main junction, where the electric field peak is concentrated. However, this scheme uses multiple spaced PN junction units to spatially decompose the single high electric field peak into multiple relatively lower electric field peaks. A local electric field peak is generated at each PN junction interface, but due to the gradient distribution of the overall net doping concentration, the amplitude of these peaks is effectively suppressed, resulting in a flatter electric field distribution curve on the termination surface.

[0025] The breakdown voltage is typically determined by the location where the electric field strength exceeds a critical value (approximately 3.0 MV / cm for silicon carbide in the prior art). By segmenting and smoothing the electric field as described above, the local electric field is prevented from reaching the critical value prematurely. This allows the entire termination region to make fuller use of the semiconductor material's withstand voltage capability. With the same termination width, it can withstand a higher reverse voltage, or with the same withstand voltage requirement, the termination size can be shortened.

[0026] It should be noted that in this application, when the semiconductor material of the first conduction type is N-type, the semiconductor material of the second conduction type is P-type; and when the semiconductor material of the first conduction type is P-type, the semiconductor material of the second conduction type is N-type. For ease of explanation, the following embodiments are described using N-type as the first conduction type and P-type as the second conduction type. Those skilled in the art will understand that the semiconductor structure of this application can also be constructed by reversing the polarity of all doping types.

[0027] Figure 1 A schematic diagram of an embodiment of a gradient-doped composite JTE terminal structure of this application is shown. The semiconductor structure includes: a substrate 14, an epitaxial layer 13, an active region, and an edge protection region.

[0028] The substrate 14 is an N+ type doped silicon carbide semiconductor substrate. The epitaxial layer 13 is disposed on the upper surface of the substrate 14 and is an N- type doped silicon carbide epitaxial layer.

[0029] An active region is disposed in the epitaxial layer 13, and its structure can be adjusted according to the device type. In this embodiment, the active region includes at least a P-type doped region 12 and a first electrode 11. The P-type doped region 12 is formed in the upper region of the epitaxial layer 13, and the first electrode 11 is disposed on a portion of the P-type doped region 12, serving as an anode. A second electrode 15 is disposed on the lower surface of the substrate 14 and is in ohmic contact with the substrate 14, serving as a cathode.

[0030] An edge protection zone is located in epitaxial layer 13 and surrounds the active region to improve the breakdown voltage of the device. This edge protection zone includes multiple JTE regions, multiple reverse-doped regions, a Pwell-doped region, and a P+-doped region.

[0031] Specifically, from the active region outwards, the regions are: a first P+ doped region a1, a second P+ doped region a2, a first Pwell doped region b1, a second Pwell doped region b2, and a first JTE region c1, a second JTE region c2, and a third JTE region c3, spaced apart from the inside out. The first P+ doped region a1 is adjacent to the P-type doped region 12 in the active region, and the second P+ doped region a2 is adjacent to the first P+ doped region a1. The P+ doped region has a high P-type doping concentration, used to assist in depletion and clamp the peak electric field at the main junction. The first Pwell doped region b1 is adjacent to the second P+ doped region a2, and the second Pwell doped region b2 is adjacent to the first Pwell doped region b1. The doping concentration of the Pwell doped region is lower than that of the P+ doped region, used to further optimize the electric field distribution. The first JTE region c1, the second JTE region c2, and the third JTE region c3 are sequentially arranged around the second Pwell doped region b2, and are all P-type doped regions. The first JTE region c1 is adjacent to the second Pwell doped region b2.

[0032] In this embodiment, multiple reverse doped regions are N-type doped regions embedded within the JTE region. Specifically, the first reverse doped region d1, the second reverse doped region d2, the third reverse doped region d3, and the fourth reverse doped region d4 are distributed alternately within the first JTE region c1; the fifth reverse doped region d5 is distributed within the second JTE region c2; and the sixth reverse doped region d6 is distributed within the third JTE region c3.

[0033] In this embodiment, the doping concentration of the N-type semiconductor material in the reverse doped region increases progressively away from the active region. In this embodiment, this concentration distribution increases in a stepwise manner. For example, the N-type doping concentration gradually increases from the first reverse doped region d1 closest to the active region to the sixth reverse doped region d6 furthest from the active region. Simultaneously, the width of the reverse doped region can also gradually increase away from the active region to synergistically achieve a gradient change in net doping concentration. The JTE region and the reverse doped regions embedded therein constitute multiple PN junction units, which are spaced apart along the direction away from the active region and arranged around the active region.

[0034] Furthermore, an oxide layer 16 is disposed on the upper surface of the edge protection zone, covering at least a portion of the JTE region and the reverse-doped region, serving as surface passivation and insulation. This embodiment, through the above structure, utilizes multiple PN junction units formed by the JTE region and the embedded reverse-doped region to segment the single electric field peak at the main junction into multiple smaller electric field peaks, thereby flattening the surface electric field distribution and significantly improving the device's breakdown voltage and tolerance to process variations.

[0035] Figure 2 and Figure 3for Figure 1 A schematic diagram of simulation results for the illustrated embodiment. From... Figure 2 As can be seen from the data, compared with the existing structure, the optimized structure of this application significantly reduces the electric field at the SiC / field oxygen layer interface after adjusting the dose and related dimensions of the reverse doping region, thus avoiding the generation of peak electric field. Figure 3 This demonstrates that the P+ doped region and the Pwell doped region can effectively clamp the peak electric field at the main junction and support the expansion of the depletion region to the outer ring. Figure 4 The measured breakdown voltage results verify that the terminal structure proposed in this application can achieve excellent withstand voltage performance. Figures 2 to 4 In the diagram, red represents the results of the cited documents in the background art, and green represents the results of the above embodiments of this application. It should be noted that... Figure 2 To simulate the JTE structure, the electric field distribution at the field oxygen layer interface is represented, with the horizontal axis representing the terminal distance (µm) and the vertical axis representing the electric field magnitude (MV / cm). Figure 3 To simulate the JTE structure, the electric field distribution at the bottom of the JTE is represented by the horizontal axis representing the terminal distance (µm) and the vertical axis representing the electric field magnitude (MV / cm). Figure 4 The breakdown voltage-current characteristic curves are shown, where the horizontal axis represents the drain-source voltage (V) and the vertical axis represents the zero-gate-voltage drain current (A).

[0036] In summary, this application achieves a more uniform and smooth electric field distribution by setting multiple JTE regions and embedding reverse-doped regions within them, with the doping concentration of the reverse-doped regions increasing away from the active region. This structure not only improves the device's breakdown voltage but also enhances its tolerance to process variations. Furthermore, it can be implemented using standard ion implantation processes, is easy to integrate, and is particularly suitable for the design and fabrication of high-voltage, high-power silicon carbide power devices.

[0037] The technical scope of this application is not limited to the contents of the above specification. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this application, and all such modifications and variations should fall within the scope of this application.

Claims

1. A gradient-doped composite JTE termination structure, characterized in that, include: A substrate having a semiconductor material of a first conductivity type; An epitaxial layer is disposed on the upper surface of the substrate and has a semiconductor material of the first conductivity type; An active region is disposed in the epitaxial layer; as well as An edge protection zone is set in the epitaxial layer and surrounds the active region; The edge protection zone includes: Multiple JTE regions are spaced apart in the epitaxial layer along a direction away from the active region, and the JTE regions are semiconductor materials of a second conductivity type. Multiple reverse-doped regions are embedded within the JTE region, and the reverse-doped regions have semiconductor materials of the first conductivity type; The doping concentration of the reverse doped region increases in a direction away from the active region. The edge protection zone further includes at least one Pwell doped region, which is disposed between the active region and the JTE region, and the Pwell doped region is adjacent to the adjacent JTE region or the reverse doped region.

2. The gradient-doped composite JTE termination structure according to claim 1, characterized in that, The JTE region and the reverse doped region embedded therein constitute a plurality of PN junction units, and the plurality of PN junction units are arranged at intervals along a direction away from the active region.

3. The gradient-doped composite JTE termination structure according to claim 1, characterized in that, The doping concentration of the reverse doped region increases in a stepwise or continuous manner along the direction away from the active region.

4. The gradient-doped composite JTE termination structure according to claim 1, characterized in that, When the semiconductor material of the first conduction type is N-type, the semiconductor material of the second conduction type is P-type; when the semiconductor material of the first conduction type is P-type, the semiconductor material of the second conduction type is N-type.

5. The gradient-doped composite JTE termination structure according to claim 1, characterized in that, The edge protection zone further includes at least one P+ doped region, which is disposed between the active region and the Pwell doped region, and is adjacent to both the active region and the Pwell doped region.

6. The gradient-doped composite JTE termination structure according to claim 1, characterized in that, The doping concentration of the JTE region is lower than that of the reverse doping region.

7. The gradient-doped composite JTE termination structure according to claim 1, characterized in that, The width of the reverse doped region gradually increases in the direction away from the active region; and / or, the thickness of the reverse doped region gradually increases in the direction away from the active region.

8. The gradient-doped composite JTE termination structure according to claim 1, characterized in that, The JTE region includes a first JTE region, a second JTE region, and a third JTE region arranged sequentially along the direction away from the active region; the reverse doping region includes a first reverse doping region, a second reverse doping region, a third reverse doping region, a fourth reverse doping region, a fifth reverse doping region, and a sixth reverse doping region; wherein, the first to fourth reverse doping regions are distributed at intervals within the first JTE region, the fifth reverse doping region is distributed within the second JTE region, and the sixth reverse doping region is distributed within the third JTE region.

9. The gradient-doped composite JTE termination structure according to any one of claims 1 to 8, characterized in that, Also includes: A P-type doped region is disposed in the epitaxial layer and ohmically contacts the JTE region; A first electrode is disposed on a portion of the P-type doped region; A second electrode is disposed on the lower surface of the substrate and is in ohmic contact with the substrate; An oxygen layer is disposed on the upper surface of the edge protection zone and covers at least a portion of the JTE region and the reverse doped region.

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