Composite termination structure for power devices

Abstract

The application discloses a kind of composite terminal structures of power device, including active region and the semiconductor substrate of terminal area located in the periphery of active region, junction terminal extension area located in terminal area and multiple columnar injection areas formed in the inside of junction terminal extension area.Columnar injection area invades first JTE injection area and second JTE injection area in junction terminal extension area, so that the electric field distribution of junction terminal extension area is more uniform, improves JTE efficiency.Meanwhile, by columnar injection area compensation electric field distribution, so that the equivalent doping concentration of junction terminal extension area has self-adapting adjustment ability, reduces the sensitive degree of injection dose deviation, facilitate to expand process window.

Description

Technical Field

[0001] This invention relates to the field of semiconductor power device technology, and more specifically, to a composite termination structure for a power device. Background Technology

[0002] Silicon carbide (SiC), as a wide-bandgap semiconductor material, has broad application prospects in high-voltage, high-frequency, and high-temperature power devices due to its excellent properties such as high critical breakdown electric field, high thermal conductivity, and high saturated electron drift velocity. In the design and fabrication of SiC power devices, effectively reducing the junction edge electric field and improving the device's breakdown voltage is one of the core challenges in device structure design.

[0003] Currently, the commonly used termination technologies in the industry mainly include field limiting ring (FLR), junction termination extension (JTE), and field plate (FP). Among them, JTE technology extends the depletion layer by introducing one or more lightly doped regions with the opposite conductivity type to the main junction at the edge of the main junction, effectively reducing the peak surface electric field. It is one of the most commonly used and efficient termination solutions for high-voltage SiC devices.

[0004] However, traditional JTE structures have a significant drawback: they require extremely high precision in the implantation dose. The optimal doping concentration in the JTE region depends on precise charge balance. When the implantation dose deviates from the ideal value, the electric field distribution deteriorates sharply, leading to a significant drop in breakdown voltage. This extremely narrow process window places stringent demands on equipment stability and process control capabilities in actual production, increasing manufacturing costs and development cycles.

[0005] To improve the performance of JTEs, various improvement schemes have been proposed in existing technologies. For example, multi-stage JTEs (such as JTE1, JTE2) structures are used to expand the process window through a stepped concentration distribution; or JTEs are combined with FLRs, field plates, etc. However, multi-stage JTEs still cannot completely eliminate the sensitivity to implantation accuracy, and the composite structure of FLR and JTE often requires additional photolithography alignment steps, increasing process complexity. In addition, some schemes have proposed inserting P+ guard rings in the JTE region, but this scheme only uses a single guard ring located between two JTE segments, which cannot effectively adjust the electric field distribution globally, and fails to solve the problem of non-uniformity of electric field peaks in the JTE region.

[0006] Therefore, there is an urgent need in this field for a new terminal structure that can maintain the high efficiency of JTE while significantly reducing the requirements for injection dose accuracy, and should also have the advantages of simple process, easy integration and small terminal area. Summary of the Invention

[0007] The purpose of this invention is to provide a composite terminal structure for power devices and its fabrication method, in order to solve the problems of low JTE efficiency and excessively high injection dose accuracy requirements.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This application provides a composite termination structure for a power device, including: A semiconductor substrate, the semiconductor substrate including an active region and a terminal region located around the active region; The junction terminal extension region is located within the terminal region, and the junction terminal extension region includes a first JTE injection region and a second JTE injection region; And multiple columnar injection zones formed within the terminal extension region of the junction.

[0009] The aforementioned composite termination structure of the power device includes an active region and a semiconductor substrate with a termination region surrounding the active region, a junction termination extension region located within the termination region, and multiple columnar implantation regions formed within the junction termination extension region. The columnar implantation regions penetrate the first and second JTE implantation regions within the junction termination extension region, resulting in a more uniform electric field distribution in the junction termination extension region and improving JTE efficiency. Simultaneously, by compensating for the electric field distribution through the columnar implantation regions, the equivalent doping concentration of the junction termination extension region possesses adaptive adjustment capability, reducing sensitivity to implantation dose deviations and facilitating the expansion of the process window.

[0010] As one optional embodiment, the injection elements of the columnar injection region are the inverse of the corresponding EPI.

[0011] As one alternative embodiment, the columnar injection regions are arranged periodically within the junction terminal extension region.

[0012] As one optional embodiment, the width of the columnar injection region gradually decreases along the direction from the active region to the terminal region.

[0013] As one optional embodiment, the columnar injection regions are arranged in an alternating pattern within the junction terminal extension region; The projections of two adjacent rows of columnar injection areas partially overlap in the direction perpendicular to the active area toward the terminal area.

[0014] As one optional embodiment, the first JTE injection region corresponds to the first JTE injection layer, and the second JTE injection region corresponds to the second JTE injection layer; The columnar injection region penetrates only the second JTE injection layer; Alternatively, the columnar injection region penetrates both the first JTE injection layer and the second JTE injection layer.

[0015] As one optional embodiment, the columnar injection area is a strip-shaped column, a circular column, or an elliptical column.

[0016] As one optional embodiment, the semiconductor substrate is a silicon carbide substrate.

[0017] As one optional embodiment, the doping concentration of the columnar implantation region is at least an order of magnitude higher than the doping concentration of the junction termination extension region.

[0018] As one optional embodiment, the terminal region further includes a stop ring located around the JTE region, the stop ring having the same conductivity type as the columnar implantation region but with a higher doping concentration. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings. Figure 1 A cross-sectional view of the composite terminal structure of a power device according to an embodiment of the application; Figure 2 This is a top view of the composite terminal structure of a power device according to an embodiment of the application; Figure 3 A top view of the composite terminal structure of a power device according to another embodiment of the application; Figure 4 This is a top view of the composite terminal structure of the power device according to another embodiment of the application; Figure 5 This is a simulation diagram of the electric field distribution at a traditional JTE terminal. Figure 6 This is a simulation diagram of the electric field distribution in this embodiment; Figure 7 This is a schematic diagram of the complete structure of the power device composite terminal. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] To facilitate understanding of the embodiments of this application, further explanation and description will be provided below with reference to the accompanying drawings and specific embodiments. These embodiments do not constitute a limitation on the embodiments of this application. In the drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than that described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of their description. Furthermore, the same reference numerals denote the same components.

[0022] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “(the)” are also intended to include the plural forms. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0023] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] This application provides a composite terminal structure for a power device.

[0025] Figure 1 This is a cross-sectional view of the composite terminal structure of a power device according to an embodiment of the application, as shown below. Figure 1 As shown, the composite termination structure of the power device in one embodiment of the application includes: A semiconductor substrate, the semiconductor substrate including an active region 100 and a terminal region 101 located around the active region; The junction terminal extension region is located within the terminal region 101, and the junction terminal extension region includes a first JTE injection region 102 and a second JTE injection region 103. And a plurality of columnar injection regions 104 formed within the junction terminal extension region.

[0026] In the embodiments of this application, "inner side" refers to the side closer to the main junction of the active region, and "outer side" refers to the direction away from the active region and towards the edge of the chip.

[0027] The semiconductor materials used in this invention include, but are not limited to, common semiconductor materials such as silicon carbide, gallium nitride, and diamond.

[0028] Preferably, in the columnar injection zone, such as Figure 1 As shown, the gap S between each columnar injection region gradually increases. An additional, geometrically gradient charge control layer is introduced within the conventional junction termination extension region. This columnar injection region and the junction termination extension region form a local PN junction. When the device is reverse biased, these PN junction depletion regions couple with each other, causing the transverse electric field to exhibit a smooth decreasing trend from the inside to the outside, avoiding the electric field spikes that occur in conventional single JTEs or uniform multi-stage JTEs under a certain dose deviation.

[0029] Preferably, with the gap S gradually increasing in each columnar injection region, the columnar injection region is not limited to a single row, but is arranged in two or three rows, with each row having a different gap change rate. For example, the first row (closest to the main junction) uses a faster gap increase rate (S: 0.1~0.5, 0.6~1.0, 1.2~1.8, 2.0~3.0), while the second row uses a slower gap increase rate (S: 0.1~0.9, 0.5~1.5, 0.7~2.1, 1.0~3.0). There is a certain overlap between the two rows of columns. This structure allows for more precise two-dimensional electric field control, and is particularly suitable for ultra-high voltage (above 6.5kV) devices. Preferably, the implanted element in the columnar implantation region is the inverse of the corresponding EPI. For example, when the EPI is P-type, the columnar implantation region uses N-type ion implantation; when the EPI is N-type, the columnar implantation region uses P-type ion implantation.

[0030] Preferably, Figure 2 This is a top view of the composite terminal structure of a power device according to an embodiment of the application, as shown below. Figure 2 As shown, the columnar injection regions are arranged periodically within the junction terminal extension region.

[0031] Preferably, Figure 3 A top view of the composite terminal structure of a power device according to another application embodiment, as shown below. Figure 3 As shown, the width W of the columnar injection region gradually decreases along the direction from the inner side to the outer side. This combination of "increased gap and decreased width" further finely adjusts the equivalent doping concentration, thereby enhancing the depletion capability at the outer end and effectively suppressing the electric field at the inner end.

[0032] Preferably, the width W of the columnar implantation region gradually decreases from the inside out. Specifically, W1 = 0.6~3.0 μm, W2 = 0.5~2.8 μm, W3 = 0.4~2.6 μm, W4 = 0.3~2.4 μm, W5 = 0.2~2.2 μm; the gaps S1 = 0.1~2.0 μm, S2 = 0.2~2.2 μm, S3 = 0.3~2.8 μm, S4 = 0.4~3.6 μm, S5 = 0.5~5.0 μm. By simultaneously increasing the gap and decreasing the column width, the equivalent lateral P-type doping areal density exhibits a quadratic decreasing trend, more accurately matching the ideal linear variable doping distribution and further smoothing the electric field distribution. Simulation results show that this structure can still maintain a breakdown voltage >1100V when the implantation dose shifts by ±20%, while the termination width can be further reduced to 10~100 μm.

[0033] Preferably, Figure 4 This is a top view of the composite terminal structure of the power device according to another application embodiment, as shown below. Figure 4 As shown, the columnar injection regions are arranged in an alternating pattern within the junction terminal extension region, such that the projections of adjacent rows of columnar injection regions partially overlap in a direction perpendicular to the inner side and pointing outward. This alternating arrangement can further smooth the lateral electric field distribution curve and suppress inter-column leakage current channels.

[0034] Preferably, the columnar injection regions are not arranged in a single row of strips, but rather in a double-row staggered layout. That is, the first row of columnar injection regions and the second row are staggered by half a cycle in the direction perpendicular to the current propagation direction (i.e., parallel to the edge of the active region). This staggered layout allows the projection of the P-pillars in the lateral direction to form a continuous but gradually varying density region, effectively avoiding straight leakage paths that may exist between the strip-shaped columnar injection regions. Simultaneously, the staggered layout allows the electric field lines to more uniformly bypass the P-pillars, suppressing the local electric field enhancement effect at the pillar edges.

[0035] Preferably, the junction termination extension region includes a first JTE injection layer and a second JTE injection layer. That is, the first JTE injection region corresponds to the first JTE injection layer, and the second JTE injection region corresponds to the second JTE injection layer; the columnar injection region is located between the first JTE injection layer and the second JTE injection layer, or penetrates through the first JTE injection layer and the second JTE injection layer. By inserting the columnar injection region between the JTE layers, the longitudinal electric field distribution can be more flexibly controlled.

[0036] Preferably, the columnar injection region is a strip-shaped, circular, or elliptical columnar region, and its depth is greater than or equal to the depth of the junction termination extension region. A deeper columnar injection region helps to push the peak electric field into the semiconductor interior and reduce the surface electric field.

[0037] Preferably, the semiconductor substrate is a silicon carbide (SiC) substrate, the first conductivity type is N-type, the second conductivity type is P-type, and the implanted elements in the columnar implantation region are inversely related to the corresponding EPI.

[0038] Preferably, the doping concentration of the columnar implantation region is at least an order of magnitude higher than that of the JTE region. The higher P-type doping concentration ensures that the columnar implantation region is fully depleted under reverse bias, while providing a stable lateral depletion boundary for the junction termination extension region.

[0039] Preferably, the columnar injection region and the junction terminal extension region are activated by the same annealing process, and the injection energy of the columnar injection region is higher than that of the junction terminal extension region, so that the depth of the columnar injection region is greater than that of the junction terminal extension region.

[0040] For example, the depth of the columnar implantation region is greater than the depth of the junction termination extension region, reaching 1.5 μm, while the depths of the first JTE implantation layer and the second JTE implantation layer are 0.6 μm. To achieve deep column implantation, a combination of multiple implantations with different energies is used (e.g., 300 keV + 500 keV + 700 keV). Deep columns can further push the surface electric field peak into the bulk, improving the device's resistance to single-event burn-out, making it suitable for high-voltage SiC devices.

[0041] Furthermore, the injection step of the columnar injection region is performed after the injection step of forming the junction terminal extension region.

[0042] Alternatively, partial injection layers in the columnar injection region and the junction terminal extension region can be injected simultaneously—using a modified P+ mask for simultaneous injection.

[0043] Based on this, traditional JTEs are extremely sensitive to implantation dose deviations. This application's embodiments introduce a geometrically gradient P-pillar array, enabling adaptive adjustment of the equivalent doping concentration in the junction termination extension region. Even if the implantation dose fluctuates within a certain range, the electric field distribution can be compensated by changes in the P-pillar spacing, thereby expanding the breakdown voltage process window by 30% to 50%. Due to the more uniform electric field distribution, the required total JTE width can be shortened by approximately 15% to 25% compared to traditional JTEs, thus increasing the effective active area within the same chip size and increasing the number of Gross dies on a single wafer by approximately 3%. The uniform electric field distribution avoids excessively high local electric field peaks, reducing the risk of long-term device degradation under high temperature and high pressure.

[0044] Meanwhile, the columnar injection region in this application embodiment only requires adding one photolithography and injection step to the existing JTE process flow (or achieving it through P+ mask modification), without the need to introduce special materials or complex etching, resulting in low development costs.

[0045] For example, when implanting the second JTE implantation layer, the same mask is used but the local pattern is changed so that the second JTE implantation region simultaneously receives N-type doping, while the columnar implantation region is achieved by additional P-type implantation. Alternatively, if the depth of the columnar implantation region is the same as that of a certain JTE layer, all N-type implantation can be completed with one mask first, and then P-type implantation can be completed with another mask, forming a composite structure after annealing.

[0046] Preferably, the columnar injection region can be adapted to various columnar layouts such as strips, circles, and staggered shapes, and is suitable for various power device structures such as planar gates and trench gates. In one embodiment, the top view shape of the columnar injection region is not a rectangular strip, but a circle or ellipse. The diameter of the circular pillars gradually decreases from the inside to the outside (from 0.6 μm to 0.3 μm), while the spacing between the pillar centers gradually increases (from 0.8 μm to 2.0 μm). The advantage of circular pillars is that the edge curvature is uniform, which can further reduce the electric field concentration effect at the pillar edges. This structure is suitable for devices with higher voltage levels (such as 3300V and above).

[0047] In one preferred embodiment, the device is based on a 4H-SiC substrate on which an N-type epitaxial layer is grown. The doping concentration of the epitaxial layer is 1×10^16 cm^-3, and the thickness is 10 μm. A power MOSFET cell structure is fabricated in the active region, with the main junction located at the boundary between the active region and the termination region.

[0048] Within the terminal region, a first JTE implantation layer and a second JTE implantation layer are formed through ion implantation. Both JTE1 and JTE2 are N-type doped, with JTE1 having a doping concentration of 2 × 10^17 cm^-3 and JTE2 having a doping concentration of 1 × 10^17 cm^-3. Between JTE1 and JTE2, multiple strip-shaped columnar implantation regions are formed through another P-type ion implantation. The doping concentration of the columnar implantation regions is 5 × 10^18 cm^-3, with a width W of 0.5 μm and a depth of 0.8 μm.

[0049] The gap S between adjacent columnar implantation regions gradually increases from the inside (near the active region) to the outside (near the chip edge). Specifically: the first gap S1 = 0.5 μm, the second gap S2 = 0.8 μm, the third gap S3 = 1.2 μm, the fourth gap S4 = 1.8 μm, and the fifth gap S5 = 2.5 μm. There are 6 columnar implantation regions.

[0050] like Figure 1 As shown, a cutoff ring 105 is also provided on the outermost side of the terminal area to isolate the interface charge at the edge of the chip.

[0051] like Figure 5 and 6As shown, when the device is subjected to reverse voltage, the depletion layer beneath the main junction extends towards the termination region. In a conventional JTE, the lateral extension of the depletion layer mainly depends on the charge of the first JTE injection layer (JTE1) and the second JTE injection layer (JTE2). In this embodiment, the P-type columnar injection region and the N-type JTE region form a series of PN junctions in series. Since the spacing S between the columnar injection regions gradually increases from the inside to the outside, the spacing between the inner columns is small, the coupling between the columnar depletion layers is strong, and the equivalent lateral resistance is large, which reduces the peak value of the electric field at the inner end; the spacing between the outer columns is large, the coupling between the columns is weak, and the depletion layer can extend further, thus significantly expanding the width of the depletion region at the end. Finally, the lateral electric field exhibits a gently decreasing trapezoidal distribution from the edge of the active region to the cutoff ring, eliminating the single-peak spike electric field in a conventional JTE.

[0052] like Figure 5 and 6 As shown, simulation results indicate that, under the same breakdown voltage target (1200V), the traditional JTE terminal can maintain a breakdown voltage >1100V within a process window of ±5% of the injected dose; while the terminal structure of this embodiment can still maintain a breakdown voltage >1100V within a range of ±15% of the injected dose offset, thus expanding the process window by 3 times. Simultaneously, the total width of the terminal region is reduced from the traditional 80μm to 65μm, increasing the effective chip area by approximately 3.1%.

[0053] Preferably, the embodiments of this application are also applicable to other wide bandgap semiconductor power devices. For example, in GaN materials, due to the strong polarization effect, the JTE termination itself has certain limitations. The columnar injection region gradient gap structure of the embodiments of this application helps to compensate for the electric field distortion caused by the non-uniformity of polarization charge.

[0054] Preferably, such as Figure 7 The complete structural diagram of the power device composite terminal structure is shown in the figure. Figure 7 Based on the structure shown, a metal field plate is fabricated above the termination region. This field plate is electrically connected to the source and extends to cover part of the junction termination extension region and the columnar injection region. The field plate and the P-pillars in the junction termination extension region work synergistically to further suppress surface charge effects and improve long-term stability. This structure is suitable for harsh environmental applications.

[0055] The composite termination structure of the power device in any of the above embodiments includes an active region and a semiconductor substrate with a termination region located around the active region, a junction termination extension region located within the termination region, and a plurality of columnar implantation regions formed within the junction termination extension region. The columnar implantation regions penetrate the first JTE implantation region and the second JTE implantation region within the junction termination extension region, resulting in a more uniform electric field distribution in the junction termination extension region and improving JTE efficiency. Simultaneously, by compensating for the electric field distribution through the columnar implantation regions, the equivalent doping concentration of the junction termination extension region possesses adaptive adjustment capability, reducing sensitivity to implantation dose deviation and facilitating the expansion of the process window.

[0056] The following points should be noted regarding this application: (1) The accompanying drawings of the embodiments of this application only involve the structures involved in the embodiments of this application. Other structures can be referred to the general design.

[0057] (2) For clarity, the thickness and dimensions of layers or structures are enlarged in the accompanying drawings used to describe embodiments of the invention. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “above” or “below” another element, the element may be “directly” located “above” or “below” the other element, or there may be intermediate elements present.

[0058] (3) Where there is no conflict, the embodiments and features in the embodiments of this application can be combined with each other to obtain new embodiments. The above are only specific implementations of this application, but the protection scope of this application is not limited thereto, and the protection scope of this application shall be determined by the protection scope of the claims.

[0059] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0061] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A composite termination structure for a power device, characterized in that, include: A semiconductor substrate, the semiconductor substrate including an active region and a terminal region located around the active region; The junction terminal extension region is located within the terminal region, and the junction terminal extension region includes a first JTE injection region and a second JTE injection region; And multiple columnar injection zones formed within the terminal extension region of the junction.

2. The composite termination structure of the power device according to claim 1, characterized in that, The injected elements in the columnar injection region are the inverse of the corresponding EPI.

3. The composite terminal structure of the power device according to claim 1, characterized in that, The columnar injection regions are arranged periodically within the terminal extension region of the junction.

4. The composite termination structure of the power device according to claim 3, characterized in that, The width of the columnar injection region gradually decreases along the direction from the active region to the terminal region.

5. The composite terminal structure of the power device according to claim 1, characterized in that, The columnar injection zones are arranged in an alternating pattern within the terminal extension zone of the junction; The projections of two adjacent rows of columnar injection areas partially overlap in the direction perpendicular to the active area toward the terminal area.

6. The composite termination structure of the power device according to claim 1, characterized in that, The first JTE injection region corresponds to the first JTE injection layer, and the second JTE injection region corresponds to the second JTE injection layer; The columnar injection region penetrates only the second JTE injection layer; Alternatively, the columnar injection region penetrates both the first JTE injection layer and the second JTE injection layer.

7. The composite termination structure of the power device according to claim 1, characterized in that, The columnar injection area can be a strip-shaped column, a circular column, or an elliptical column.

8. The composite termination structure of the power device according to claim 1, characterized in that, The doping concentration of the columnar implantation region is at least one order of magnitude higher than the doping concentration of the junction termination extension region.

9. The composite termination structure of the power device according to claim 1, characterized in that, The semiconductor substrate is a silicon carbide substrate, a gallium nitride substrate, or a diamond substrate.

10. The composite termination structure of the power device according to claim 1, characterized in that, The terminal region also includes a stop ring located around the JTE region. The stop ring has the same conductivity type as the columnar implantation region but with a higher doping concentration.

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