Groove Schottky diode with composite P + structure and manufacturing method thereof

Abstract

The invention discloses a groove Schottky diode of a composite P + structure and a manufacturing method of the groove Schottky diode, and belongs to the technical field of semiconductors. The epitaxial layer is located on the surface of one side of the substrate; the epitaxial layer comprises a wave-shaped groove and a plurality of P + columns; the depth of the wave-shaped groove is gradually reduced from the center of the cellular structure to the periphery, and the plurality of P + columns are uniformly distributed around the wave-shaped groove; an anode metal; schottky metal is deposited on the inner surface of the wave-shaped groove, the Schottky metal and the epitaxial layer form wave-shaped Schottky contact, and the anode metal is located in the wave-shaped groove covered by the Schottky metal and covers the surface of the side, away from the substrate, of the epitaxial layer. The cathode metal is located on the surface of the side, away from the epitaxial layer, of the substrate. According to the trench Schottky diode, the contradiction between the breakdown voltage and the break-over voltage of the trench Schottky diode in high-voltage and high-frequency application is solved, and the anti-surge capability of the device under the limiting condition can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a trench Schottky diode with a composite P+ structure and a manufacturing method thereof. Background Art

[0002] As power electronics systems evolve toward high frequency, high voltage, and high power density, traditional Schottky diodes face significant challenges in terms of reverse recovery loss, high-temperature leakage current, and voltage withstand capability. Planar Schottky diodes have limited breakdown voltage due to electric field concentration. While conventional trench Schottky diodes offer improved breakdown voltage, they still suffer from high reverse recovery charge and electric field spikes at the bottom of the trench. This is particularly true in applications such as new energy vehicle (OBC) and photovoltaic inverters, where excessive reverse recovery charge under high-frequency switching conditions can lead to significant switching losses, while high-temperature leakage currents threaten system reliability.

[0003] While existing solutions such as field plate structures and composite dielectric layers can optimize electric field distribution to a certain extent, they still struggle to simultaneously achieve high breakdown voltage (BV), low forward voltage (VF), low reverse leakage current (IR), and high surge protection. Therefore, there is an urgent need for a Schottky diode with a novel trench structure that can improve withstand voltage while ensuring low forward voltage and high surge protection. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a composite P+ structure trench Schottky diode and a method for manufacturing the same. The technical problem to be solved by the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a trench Schottky diode with a composite P+ structure, wherein the cell structure of the trench Schottky diode comprises: substrate; An epitaxial layer located on one surface of the substrate; the epitaxial layer includes a wavy groove and a plurality of P+ columns; the depth of the wavy groove gradually decreases from the center of the cell structure to the periphery, and the plurality of P+ columns are evenly distributed around the wavy groove; Anode metal; a Schottky metal is deposited on the inner surface of the wavy groove, the Schottky metal forms a wavy Schottky contact with the epitaxial layer, and the anode metal is located in the wavy groove covered by the Schottky metal and covers the surface of the epitaxial layer away from the substrate; The cathode metal is located on the surface of the substrate away from the epitaxial layer.

[0005] In one embodiment of the present invention, the epitaxial layer further includes a deep trench extending along a first direction, the deep trench being located at the center of the bottom of the wavy trench, and the first direction is perpendicular to the plane of the substrate and pointing from the epitaxial layer to the substrate.

[0006] In one embodiment of the present invention, a gate oxide layer is deposited on the outer surface of the deep trench.

[0007] In one embodiment of the present invention, a polysilicon layer is deposited inside the deep trench, wherein the Schottky metal forms an ohmic contact with the polysilicon layer.

[0008] In one embodiment of the present invention, in a direction perpendicular to the plane of the substrate, the orthographic projection of the wavy groove is a circle; The epitaxial layer includes four P+ columns, and the four P+ columns are equidistant from the circle.

[0009] In one embodiment of the present invention, the Schottky metal includes titanium, molybdenum, chromium or platinum.

[0010] In one embodiment of the present invention, the material of the epitaxial layer includes silicon.

[0011] In a second aspect, the present invention further provides a method for manufacturing a trench Schottky diode with a composite P+ structure, which is used to manufacture the trench Schottky diode with a composite P+ structure described in the first aspect; The method comprises: Providing a substrate and growing an epitaxial layer on the surface of the substrate; A plurality of windows arranged at intervals are formed on the surface of the epitaxial layer away from the substrate; the cross-section of the windows is an inverted trapezoid, and the opening width and depth of each window gradually decrease in a direction from the center of the cell structure to the periphery; Each window is rounded by wet isotropic etching to form a wavy groove; Etching a deep groove at the center of the bottom of the wavy groove; Using an ion implantation process, a plurality of P+ columns are formed around the wavy grooves and are evenly distributed. growing a gate oxide layer on an outer surface of the deep trench and depositing a polysilicon layer inside the deep trench; Depositing a Schottky metal on the inner surface of the wavy groove, wherein the Schottky metal forms a wavy Schottky contact with the epitaxial layer and an ohmic contact with the polysilicon layer; Anode metal is deposited on the surface of the epitaxial layer away from the substrate and in the wavy groove covered by Schottky metal, and cathode metal is deposited on the surface of the substrate away from the epitaxial layer to form an anode and a cathode respectively.

[0012] In one embodiment of the present invention, the step of forming a plurality of windows arranged at intervals on a surface of the epitaxial layer away from the substrate comprises: Depositing a silicon dioxide layer on the surface of the epitaxial layer away from the substrate as a hard mask; forming a photoresist pattern on the surface of the silicon dioxide layer, and transferring the photoresist pattern to the silicon dioxide layer by etching; The epitaxial layer is dry-etched using the patterned silicon dioxide layer as a mask to form a plurality of windows arranged at intervals.

[0013] In one embodiment of the present invention, the step of etching a deep trench at the center of the bottom of the wavy trench comprises: Forming a rectangular groove at the center of the bottom of the wavy groove by dry deep silicon etching; The rectangular groove is rounded by wet isotropic etching to form a deep groove.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a trench Schottky diode with a composite P+ structure and a method for manufacturing the same. The cell structure of the trench Schottky diode includes: a substrate and an epitaxial layer located on the surface of the substrate. The surface of the epitaxial layer away from the substrate includes a wavy groove, and the continuously changing curvature radius of the wavy groove can make the electric field diverge uniformly, avoid the formation of a local peak electric field, and thus improve the breakdown voltage of the device.

[0015] (2) The inner surface of the wavy groove is covered with Schottky metal, which can form a Schottky contact with the epitaxial layer. The wavy structure of the sidewall and bottom of the wavy groove can effectively expand the Schottky contact area, which is beneficial to reducing the current density at rated current and the forward conduction voltage of the device.

[0016] (3) The deep trench is located at the center of the bottom of the wavy trench, and a gate oxide layer is deposited on the outer surface, which can further increase the breakdown voltage of the device.

[0017] Therefore, the composite P+ structure trench Schottky diode and its manufacturing method provided in this application can solve the contradiction between the breakdown voltage and the conduction voltage of traditional trench Schottky diodes in high-voltage and high-frequency applications, while improving the device's surge resistance under extreme conditions.

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 is a top view of a cell structure of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 2is a cross-sectional view of a cellular structure provided by an embodiment of the present invention in the diagonal AA' direction; Figure 3 is a schematic diagram of the arrangement of multiple cellular structures provided by an embodiment of the present invention; Figure 4 This is a flow chart of a method for manufacturing a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 6 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 7 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 8 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 9 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 10 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 11 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention; Figure 12 This is a schematic diagram of a manufacturing process of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0021] Figure 1 1 is a top view of a cell structure of a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention. Figure 2 : is a cross-sectional view of the cell structure provided by an embodiment of the present invention in the diagonal AA' direction. Figures 1 and 2 As shown, an embodiment of the present invention provides a trench Schottky diode with a composite P+ structure, wherein the cell structure of the trench Schottky diode includes: Substrate 1; An epitaxial layer 2 is located on one side of the substrate 1; the epitaxial layer 2 includes a wavy groove 21 and a plurality of P+ pillars 22; the depth of the wavy groove 21 gradually decreases from the center of the cell structure to the periphery, and the plurality of P+ pillars 22 are evenly distributed around the wavy groove 21; Anode metal 3; a Schottky metal 23 is deposited on the inner surface of the wavy groove 21, and the Schottky metal 23 forms a wavy Schottky contact with the epitaxial layer 2. The anode metal 3 is located in the wavy groove 21 covered by the Schottky metal 23 and covers the surface of the epitaxial layer 2 away from the substrate 1; The cathode metal 4 is located on the surface of the substrate 1 away from the epitaxial layer 2 .

[0022] Specifically, the cell structure of the trench Schottky includes a substrate 1 and an epitaxial layer 2 located on the upper surface of the substrate 1. The surface of the epitaxial layer 2 away from the substrate 1 includes a wavy groove 21. Figure 1 From the perspective shown, the orthographic projection of the wavy groove 21 is a circle, while Figure 2 From the perspective shown, the bottom and sidewalls of the wavy groove 21 are wavy, and the depth in the vertical direction (the direction perpendicular to the plane of the substrate 1) gradually decreases from the center of the cell structure to the periphery. Figure 2 The cross section along the AA' direction is generally arc-shaped.

[0023] In related art, trench Schottky diodes typically use a vertical trench structure with a right-angled or V-shaped trench bottom. This design leads to electric field concentration at the bottom of the trench, especially at locations with geometrical changes (sudden changes in the radius of curvature). Furthermore, because the peak electric field at the bottom of the trench is much higher than the average field strength, it can easily lead to localized premature breakdown, limiting the reverse breakdown voltage of the device. In this embodiment, the introduction of the wavy trench 21 allows its continuously varying radius of curvature to evenly distribute the electric field, avoiding the formation of local peak electric fields and thereby increasing the breakdown voltage of the device.

[0024] Schottky metal 23 such as titanium, molybdenum, chromium, platinum, etc. is also deposited on the inner surface of the wavy groove 21. Silicon can be selectively used as the material of the epitaxial layer 2, so that the Schottky metal 23 can form a Schottky contact with the epitaxial layer 2. The wavy structure of the sidewalls and bottom of the wavy groove 21 can effectively expand the Schottky contact area, which is beneficial to reducing the current density under rated current and the forward conduction voltage of the device.

[0025] Please continue to see Figure 1-2 In the cellular structure, four P+ columns 22 are evenly distributed around the wavy groove 21. In the direction perpendicular to the plane of the substrate 1, the positive projection of the wavy groove is a circle, and the four P+ columns 22 are equidistant from the circle.

[0026] It should be understood that the cell structure is the smallest repeating unit of the trench Schottky diode. Figure 3 is a schematic diagram of the arrangement of multiple cellular structures provided by an embodiment of the present invention, such as Figure 3 As shown, the four cellular structures are arranged in an array. The P+ column 22 can not only improve the surge resistance of the device, but also solve the problem of insufficient depletion in the reverse direction due to the long distance between the wavy grooves 21 in the two adjacent cellular structures, making the reverse electric field distribution more uniform and avoiding premature breakdown.

[0027] The cell structure of the trench Schottky diode also includes an anode metal 3 and a cathode metal 4. The anode metal 3 is located in the wavy trench 21 covered by the Schottky metal 23 and covers the surface of the epitaxial layer 2 away from the substrate 1. The cathode metal 4 is located on the lower surface of the substrate 1.

[0028] In order to avoid the residual electric field concentration at the bottom of the wavy groove 21, the epitaxial layer 2 also includes a deep groove 24 extending along a first direction, and the first direction is: perpendicular to the plane of the substrate 1 and pointing from the epitaxial layer 2 to the substrate 1. Optionally, the deep groove 24 is located at the bottom center of the wavy groove 21. The deep groove 24 extends the residual electric field lines further downward by introducing an additional curvature radius mutation point, thereby avoiding the bottom center of the wavy groove from becoming a new electric field peak area. Based on the above analysis, it can be seen that the composite P+ structure trench Schottky diode provided in this application can solve the contradiction between the breakdown voltage and the conduction voltage of the traditional trench Schottky diode in high-voltage and high-frequency applications, while improving the surge resistance of the device under extreme conditions.

[0029] In addition, a gate oxide layer 25 is deposited on the outer surface of the deep trench 24. The material of the gate oxide layer 25 can be SiO2 with a thickness of 0.1 to 0.4 μm. It should be understood that thermally grown SiO2 is a high-quality insulator with a dense structure and relatively few defects. Its intrinsic breakdown electric field strength is very high, about 10 MV / cm, that is, it can withstand a voltage of about 10 million volts per centimeter of thickness. In this embodiment, the main function of the gate oxide layer 25 is to insulate and control the channel. The high-quality gate oxide layer 25 can provide reliable electrical isolation and avoid the low breakdown problem caused by direct contact between metal and semiconductor. In addition, the gate oxide layer 25, combined with the silicon surface state below it, helps to form a smoother and more controllable surface potential distribution. The good gate oxide / silicon interface quality (low interface state density, low fixed charge) can reduce the distortion or local enhancement of the electric field at the interface, avoid the generation of unexpected low breakdown points, thereby improving the breakdown voltage of the device.

[0030] Optionally, a polysilicon layer 26 is deposited inside the deep trench 24 , wherein the Schottky metal 23 forms an ohmic contact with the polysilicon layer 26 .

[0031] Figure 4This is a flow chart of a method for manufacturing a trench Schottky diode with a composite P+ structure provided by an embodiment of the present invention. Figure 5-12 FIG. 1 is a schematic diagram of the manufacturing process of the composite P+ structure trench Schottky diode provided by an embodiment of the present invention. Figure 2-12 As shown, an embodiment of the present invention provides a method for manufacturing a trench Schottky diode with a composite P+ structure, which is used to manufacture a trench Schottky diode with a composite P+ structure; The above methods include: S1, such as Figure 5 As shown, a substrate 1 is provided, and an epitaxial layer 2 is grown on the surface of the substrate 1 .

[0032] S2. A plurality of spaced windows are formed on the surface of the epitaxial layer 2 away from the substrate 1. The cross section of the windows is an inverted trapezoid, and the opening width and depth of each window gradually decrease from the center of the cell structure to the periphery.

[0033] For example, see Figure 6-7 , step S2 includes: S201, depositing a silicon dioxide layer on the surface of the epitaxial layer 2 away from the substrate 1 as a hard mask; S202, forming a photoresist pattern on the surface of the silicon dioxide layer, and transferring the photoresist pattern to the silicon dioxide layer by etching; S203 , using the patterned silicon dioxide layer as a mask, dry-etching the epitaxial layer 2 to form a plurality of windows arranged at intervals.

[0034] It should be noted that the number and size of the windows should be flexibly adjusted according to the required curvature radius and depth of the wavy groove, and this application does not impose any restrictions on this.

[0035] S3, such as Figure 8 As shown, each window is rounded by wet isotropic etching to form a wavy groove 21.

[0036] S4. Etching to form a deep trench 24 at the center of the bottom of the wavy trench 21.

[0037] Specifically, if Figure 9-10 As shown, firstly, a rectangular trench is formed at the center of the bottom of the wavy trench 21 by dry deep silicon etching, and then the rectangular trench is rounded by wet isotropic etching to form a deep trench 24.

[0038] S5, see Figure 11 , using an ion implantation process, a plurality of P+ columns 22 are evenly distributed around the wavy groove 21 .

[0039] S6 , growing a gate oxide layer 25 on the outer surface of the deep trench 24 , and depositing a polysilicon layer 26 inside the deep trench 24 .

[0040] In this step, after the gate oxide layer 25 is grown on the outer surface of the deep trench 24 , a polysilicon layer 26 is deposited on the upper surface of the cell structure, and then the polysilicon layer 26 is etched, leaving only the polysilicon layer 26 inside the deep trench 24 .

[0041] S7 . Depositing a Schottky metal 23 on the inner surface of the wavy groove 21 . The Schottky metal 23 forms a wavy Schottky contact with the epitaxial layer 2 and an ohmic contact with the polysilicon layer 26 .

[0042] S8, depositing anode metal 3 on the surface of the epitaxial layer 2 away from the substrate 1 and in the wavy groove 21 covered by the Schottky metal 23, and depositing cathode metal 4 on the surface of the substrate 1 away from the epitaxial layer 2 to form an anode and a cathode respectively, to obtain Figure 2 The trench Schottky diode with a composite P+ structure is shown.

[0043] It can be seen from the above embodiments that the beneficial effects of the present invention are: (1) The present invention provides a trench Schottky diode with a composite P+ structure and a method for manufacturing the same. The cell structure of the trench Schottky diode includes: a substrate and an epitaxial layer located on the surface of the substrate. The surface of the epitaxial layer away from the substrate includes a wavy groove, and the continuously changing curvature radius of the wavy groove can make the electric field diverge uniformly, avoid the formation of a local peak electric field, and thus improve the breakdown voltage of the device.

[0044] (2) The inner surface of the wavy groove is covered with Schottky metal, which can form a Schottky contact with the epitaxial layer. The wavy structure of the sidewall and bottom of the wavy groove can effectively expand the Schottky contact area, which is beneficial to reducing the current density at rated current and the forward conduction voltage of the device.

[0045] (3) The deep trench is located at the center of the bottom of the wavy trench, and a gate oxide layer is deposited on the outer surface, which can further increase the breakdown voltage of the device.

[0046] Therefore, the composite P+ structure trench Schottky diode and its manufacturing method provided in this application can solve the contradiction between the breakdown voltage and the conduction voltage of traditional trench Schottky diodes in high-voltage and high-frequency applications, while improving the device's surge resistance under extreme conditions.

[0047] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0048] Descriptions with reference to the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0049] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A trench Schottky diode with a composite P+ structure, characterized in that: The cell structure of the trench Schottky diode includes: substrate; An epitaxial layer located on one surface of the substrate; the epitaxial layer includes a wavy groove and a plurality of P+ columns; the depth of the wavy groove gradually decreases from the center of the cell structure to the periphery, and the plurality of P+ columns are evenly distributed around the wavy groove; Anode metal; a Schottky metal is deposited on the inner surface of the wavy groove, the Schottky metal forms a wavy Schottky contact with the epitaxial layer, and the anode metal is located in the wavy groove covered by the Schottky metal and covers the surface of the epitaxial layer away from the substrate; The cathode metal is located on the surface of the substrate away from the epitaxial layer.

2. The trench Schottky diode of the composite P+ structure according to claim 1, characterized in that: The epitaxial layer further includes a deep trench extending along a first direction, the deep trench being located at the center of the bottom of the wavy trench. The first direction is perpendicular to the plane of the substrate and pointing from the epitaxial layer to the substrate.

3. The trench Schottky diode of the composite P+ structure according to claim 2, characterized in that: A gate oxide layer is deposited on the outer surface of the deep trench.

4. The trench Schottky diode of the composite P+ structure according to claim 3, characterized in that: A polysilicon layer is deposited inside the deep trench, wherein the Schottky metal forms an ohmic contact with the polysilicon layer.

5. The trench Schottky diode of the composite P+ structure according to claim 1, characterized in that: In a direction perpendicular to the plane of the substrate, the orthographic projection of the wavy groove is a circle; The epitaxial layer includes four P+ columns, and the four P+ columns are equidistant from the circle.

6. The trench Schottky diode of the composite P+ structure according to claim 1, characterized in that: The Schottky metal includes titanium, molybdenum, chromium or platinum.

7. The trench Schottky diode of the composite P+ structure according to claim 1, characterized in that: The material of the epitaxial layer includes silicon.

8. A method for manufacturing a trench Schottky diode with a composite P+ structure, characterized in that: Used to manufacture the composite P+ structure trench Schottky diode according to any one of claims 1 to 7; The method comprises: Providing a substrate and growing an epitaxial layer on the surface of the substrate; A plurality of windows arranged at intervals are formed on the surface of the epitaxial layer away from the substrate; the cross-section of the windows is an inverted trapezoid, and the opening width and depth of each window gradually decrease in a direction from the center of the cell structure to the periphery; Each window is rounded by wet isotropic etching to form a wavy groove; Etching a deep groove at the center of the bottom of the wavy groove; Using an ion implantation process, a plurality of P+ columns are formed around the wavy grooves and are evenly distributed. growing a gate oxide layer on an outer surface of the deep trench and depositing a polysilicon layer inside the deep trench; Depositing a Schottky metal on the inner surface of the wavy groove, wherein the Schottky metal forms a wavy Schottky contact with the epitaxial layer and an ohmic contact with the polysilicon layer; Anode metal is deposited on the surface of the epitaxial layer away from the substrate and in the wavy groove covered by Schottky metal, and cathode metal is deposited on the surface of the substrate away from the epitaxial layer to form an anode and a cathode respectively.

9. The method for manufacturing a trench Schottky diode with a composite P+ structure according to claim 8, characterized in that: The step of forming a plurality of windows arranged at intervals on a surface of the epitaxial layer away from the substrate comprises: Depositing a silicon dioxide layer on the surface of the epitaxial layer away from the substrate as a hard mask; forming a photoresist pattern on the surface of the silicon dioxide layer, and transferring the photoresist pattern to the silicon dioxide layer by etching; The epitaxial layer is dry-etched using the patterned silicon dioxide layer as a mask to form a plurality of windows arranged at intervals.

10. The method for manufacturing a trench Schottky diode with a composite P+ structure according to claim 8, characterized in that: The step of etching a deep groove at the center of the bottom of the wavy groove comprises: Forming a rectangular groove at the center of the bottom of the wavy groove by dry deep silicon etching; The rectangular groove is rounded by wet isotropic etching to form a deep groove.

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