Schottky barrier diode integrated with groove and N-type suspension junction and preparation method of Schottky barrier diode

Abstract

The invention provides a Schottky barrier diode integrated with a groove and an N-type suspension junction and a preparation method, the Schottky barrier diode comprises an epitaxial layer arranged on a substrate, a P-type injection structure arranged in a drift region of the epitaxial layer, a first doping structure arranged in the drift region of the epitaxial layer and a Schottky contact, the first doping structure is arranged below the P-type injection structure, and the Schottky contact is arranged below the P-type injection structure. The doping concentration of the Schottky contact region is increased; the Schottky contact is arranged on the epitaxial layer drift region and extends into the epitaxial layer drift region so as to increase the area of the Schottky contact. The invention has the beneficial effects that a novel Schottky barrier technology and a novel P-type region injection layout structure are combined, Schottky contact is of a groove structure, and the P-type injection region adopts a mode of combining the main injection region and the compensation injection region, so that the break-over voltage of the device is reduced under the condition that the breakdown voltage of the device is not reduced, and the device reliability is improved. Or the breakdown voltage of the device is improved under the condition that the conduction voltage is not increased.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor devices, and in particular relates to a Schottky barrier diode with integrated trench and N-type suspension junction and a preparation method thereof. Background Art

[0002] SIC JBS (Silicon Carbide Junction Barrier Schottky Diode) is a low-power, high-current, ultra-high-speed semiconductor device. In the current mainstream SIC JBS devices, when the device is forward-conducting, in order to reduce the forward on-resistance of the device, the area of ​​the P-type ion implantation doping region should be designed to be the minimum value according to the process capability, and in order to effectively reduce the influence of the curvature effect on the reverse breakdown voltage of the device, the Schottky barrier region should be designed as a circle, regular hexagon or regular octagon, and accordingly, the P+ region, as the region that blocks the current from passing, is mostly designed as a strip, square, regular hexagon, etc.

[0003] Since the SiC PN junction does not open at low voltage, the conduction of the device is mainly completed by the Schottky contact part. If you want to reduce the on-resistance and forward conduction voltage, you need to increase the area of ​​the Schottky contact in the active area. As the Schottky contact area increases, the reverse withstand voltage of the device will decrease. Therefore, the forward on-resistance and reverse breakdown voltage of the device restrict each other. How to design the device structure so that it has lower on-resistance and voltage while ensuring the reverse characteristics has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of the above problems, the present invention provides a Schottky barrier diode with integrated trench and N-type suspended junction and a preparation method thereof to solve the above or other former problems existing in the prior art.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a Schottky barrier diode with integrated trench and N-type suspended junction, comprising an epitaxial layer arranged on a substrate, a P-type injection structure arranged in a drift region of the epitaxial layer, a first doping structure arranged in the drift region of the epitaxial layer, and a Schottky contact, wherein: The first doping structure is disposed below the P-type implantation structure to increase the doping concentration of the Schottky contact region; The Schottky contact is arranged on the drift region of the epitaxial layer and extends into the drift region of the epitaxial layer to increase the area of ​​the Schottky contact.

[0006] Furthermore, the doping type of the first doping structure is the same as the doping type of the drift region of the epitaxial layer.

[0007] Furthermore, the first doping structure corresponds to a Schottky contact region of the drift region of the epitaxial layer.

[0008] Furthermore, the first doping structure includes a plurality of suspended junctions, and the suspended junctions are formed by implanting first ions, and the first ions are nitrogen ions or phosphorus ions.

[0009] Furthermore, a plurality of Schottky contact trenches are provided in the Schottky contact region of the drift region of the epitaxial layer, and the cross-sectional shape of the bottom of the Schottky contact trench is an arc.

[0010] Furthermore, the cross-sectional shape of the Schottky contact groove is semicircular, the diameter of the Schottky contact groove is 1-5 μm, the depth of the Schottky contact groove is 0.1-0.2 μm, and the distance between adjacent Schottky contact grooves is 1.5-4 μm.

[0011] Furthermore, the Schottky contact includes a first contact portion and a second contact portion in contact with each other, the first contact portion is arranged in the Schottky contact trench, the second contact portion is arranged on the drift region of the epitaxial layer, and the second contact portion is in contact with the P-type implantation structure.

[0012] Furthermore, the Schottky contact is titanium, nickel or molybdenum, and the thickness of the second contact portion is 50-300 nm.

[0013] Furthermore, the P-type injection structure is arranged in the P-type injection region, the P-type injection region includes multiple first injection regions and multiple second injection regions, the area of ​​the second injection region is smaller than that of the first injection region, and the second injection region is arranged in the gap between adjacent first injection regions.

[0014] Furthermore, the cross-sectional shape of the first injection region is circular, and the cross-sectional shape of the second injection region is circular.

[0015] Furthermore, it also includes a cathode disposed on the substrate, an anode disposed on the Schottky contact, and an oxide layer disposed on the epitaxial layer, wherein: The cathode is nickel, titanium or silver, and the thickness of the cathode is 80nm-2μm; The anode is aluminum, and the thickness of the anode is 400nm-5μm; The oxide layer is arranged on both sides of the Schottky contact, the oxide layer is silicon dioxide, and the thickness of the oxide layer is 50 nm-4 μm.

[0016] Furthermore, the substrate is silicon carbide, and the doping concentration of the substrate is 1×10 19 -3×10 19 cm -3 ; The epitaxial layer is N-type silicon carbide, and the doping concentration of the epitaxial layer is 1×10 16 -3×10 16 cm -3 , the thickness of the epitaxial layer is 5-30μm.

[0017] A method for preparing a Schottky barrier diode with integrated trench and N-type suspended junction comprises the following steps: preparing an epitaxial layer on a substrate; preparing a P-type implantation structure in the drift region of the epitaxial layer; preparing a first doping structure in the drift region of the epitaxial layer; Preparation of Schottky contacts.

[0018] Furthermore, the step of preparing a P-type implantation structure in the drift region of the epitaxial layer includes: A first mask is prepared on the epitaxial layer, and the first mask is photolithographically etched according to the P-type implantation region layout to form an opening of the P-type implantation region; A second ion implantation is performed to form a P-type implantation structure.

[0019] Furthermore, the opening of the P-type injection region includes an opening of a first injection region and an opening of a second injection region, and the opening of the second injection region is arranged at a gap between the openings of the adjacent first injection regions.

[0020] Furthermore, the second ion is aluminum ion, the implantation energy of aluminum ion is 30-550 keV, and the dose is 1×10 13 -2×10 15 cm -2 .

[0021] Furthermore, the step of preparing a first doping structure in the drift region of the epitaxial layer includes: Performing photolithography etching on the first mask to form an opening in the Schottky contact region; Performing a first ion implantation to form a first doping structure under the Schottky contact region, wherein the first doping structure is located below the P-type implantation structure; An annealing process is performed to activate the implanted first ions and second ions.

[0022] Furthermore, the first ion is a nitrogen ion or a phosphorus ion, the implantation energy of the first ion is 200-1000 keV, and the dose is 1E12-1E16cm -2 .

[0023] Furthermore, when the device is annealed in an inert gas atmosphere, the annealing temperature is 1500-1900° C. and the annealing time is 10-30 minutes.

[0024] Furthermore, the first mask is silicon dioxide, and the inert gas is argon.

[0025] Furthermore, the step of preparing the Schottky contact includes: A second mask is prepared on the surface of the epitaxial layer, and the second mask is photoetched to form a Schottky contact opening; Etching the epitaxial layer at the Schottky contact opening to form a Schottky contact trench; Performing a first metal deposition at the Schottky contact opening to form a Schottky contact; Schottky annealing is performed to form a stable Schottky contact.

[0026] Furthermore, chemical vapor deposition is used to deposit the second mask, and the second mask is silicon dioxide.

[0027] Furthermore, the epitaxial layer at the Schottky contact opening is etched by dry etching.

[0028] Furthermore, the first metal is deposited by evaporation or sputtering, and the first metal is titanium, nickel or molybdenum.

[0029] Furthermore, a Schottky annealing treatment is performed in a first gas atmosphere, the annealing temperature is 400-600° C., the annealing time is 10-30 min, and the first gas is nitrogen.

[0030] Furthermore, it also includes preparing a cathode, depositing a second metal on the back of the substrate by sputtering, and performing cathode annealing to form a cathode, wherein the second metal is nickel, titanium or silver, the cathode annealing temperature is 900-1000°C, and the cathode annealing time is 2-5 minutes.

[0031] Furthermore, it also includes preparing an anode, depositing a third metal on the Schottky contact by evaporation or sputtering to form an anode, wherein the third metal is aluminum.

[0032] Due to the adoption of the above technical solution, the silicon carbide junction barrier Schottky diode combines the new Schottky barrier technology and the new P-type region injection layout structure, the Schottky contact is a trench structure, and the P-type injection region adopts a combination of a main injection region and a compensation injection region, so that the device can reduce the on-voltage of the device while keeping the breakdown voltage unchanged, or increase the breakdown voltage of the device while keeping the on-voltage unchanged. A first doped region is provided in the drift region of the epitaxial layer below the Schottky contact region, and a plurality of suspended junctions are formed in the first doped region. The doping type of the suspended junction is the same as that of the drift region, thereby increasing the doping concentration of the Schottky contact region, reducing the on-resistance and voltage of the device, and alleviating the problem of mutual restriction between the Schottky contact area and the P-type region injection area; The Schottky contact is a trench structure that extends into the drift region of the epitaxial layer. The Schottky contact adopts a trench contact method, which increases the area of ​​the Schottky contact. The trench is semicircular, which can effectively alleviate the peak electric field at the corner compared to the traditional square trench, reduce the on-resistance of the device while maintaining the reverse characteristics of the device, and ensure the breakdown voltage of the device. The P-type injection region adopts the superposition method of the first injection region (main injection region) and the second injection region (compensation injection region), which helps to form a more uniform electric field distribution, reduce local electric field concentration, suppress the peak electric field and thus improve the voltage resistance of the device, increase the Schottky contact area and Schottky junction current, reduce manufacturing costs, protect weak areas of the depletion region, increase the reverse breakdown voltage of the diode, reduce power loss when working at high temperatures, and prevent the reverse breakdown voltage of the diode from decreasing after the Schottky area is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic structural diagram of a diode device according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the layout structure of a P-type implantation region according to an embodiment of the present invention.

[0034] In the figure: 1. substrate; 2. epitaxial layer; 3. P-type injection region; 4. first doped region; 5. Schottky contact; 6. oxide layer; 20. buffer region; 21. drift region; 30. P-type injection structure; 31. first injection region; 32. second injection region; 40. first doped structure; 50. Schottky contact trench; 7. cathode. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0036] Figure 1 A structural schematic diagram of an embodiment of the present invention is shown. This embodiment relates to a Schottky barrier diode with integrated trench and N-type suspended junction and a preparation method. The diode device has a first doping structure in the drift region of the epitaxial layer, the Schottky contact adopts a trench contact method, and adopts a P-type injection region layout structure combining a main injection region and a compensation injection region, so that the diode device can reduce the on-voltage of the device while keeping the breakdown voltage unchanged, or increase the breakdown voltage of the diode device while keeping the on-voltage unchanged.

[0037] A Schottky barrier diode with integrated trench and N-type floating junction, such as Figure 1 As shown, it includes an epitaxial layer 2 disposed on a substrate 1, a P-type injection structure 30 disposed in a drift region 21 of the epitaxial layer 2, a first doping structure 40 disposed in the drift region 21 of the epitaxial layer 2, and a Schottky contact 5, wherein the epitaxial layer 2 has a drift region 21 and a buffer region 20, the epitaxial layer 2 is disposed on a side surface of the substrate 1, the buffer region 20 is close to the substrate, the buffer region 20 is located between the drift region 21 and the substrate 1, and the first doping structure 40 and the P-type injection structure 30 are both located in the drift region 21; for the convenience of subsequent description, it is assumed that: the direction from the substrate 1 to the epitaxial layer 2 is the upper side, and the direction from the epitaxial layer 2 to the substrate 1 is the lower side; The first doping structure 40 is arranged below the P-type injection structure 30, and the first doping structure 40 is arranged below the Schottky contact region, and the first doping structure 40 is not directly connected to the electrode to increase the doping concentration of the Schottky contact region and reduce the on-resistance and voltage of the diode device; the first doping structure 40 is located in the first doping region 4, and the first doping region 4 is located below the Schottky contact region, the P-type injection structure 30 is located in the P-type injection region 3, the P-type injection region 3 and the Schottky contact region are arranged in parallel, and the P-type injection region 3 and the Schottky contact region are located in the same region on the upper surface of the drift region 21; The Schottky contact 5 is arranged on the drift region 21 of the epitaxial layer 2 and extends into the drift region 21 of the epitaxial layer 2. The Schottky contact 5 and the epitaxial layer 2 are in trench contact to increase the area of ​​the Schottky contact 5 and weaken the peak electric field at the corner, thereby ensuring the breakdown voltage of the device.

[0038] The substrate 1 is silicon carbide, and the doping concentration of the substrate 1 is 1×10 19 -3×10 19 cm -3 In some feasible embodiments, the substrate 1 is an N+ 4H-SiC substrate.

[0039] The epitaxial layer 2 is N-type silicon carbide, and the doping concentration of the epitaxial layer 2 is 1×10 16 -3×10 16 cm -3 The thickness of the epitaxial layer 2 is 5-30 μm. In some feasible embodiments, the epitaxial layer 2 is an N-4H-SiC epitaxial layer.

[0040] The doping type of the first doping structure 40 is the same as the doping type of the drift region 21 of the epitaxial layer 2. The first doping structure 40 is located below the Schottky contact region. The first doping region 4 where the first doping structure 40 is located corresponds to the Schottky contact region of the drift region 21 of the epitaxial layer 2. The first doping structure 40 is formed in the drift region 21 of the epitaxial layer 2 through the Schottky contact region by ion implantation, and is located below the P-type implantation structure 30. There is a certain gap between the first doping structure 40 and the P-type implantation structure 30, and the two are not directly connected. The first doping structure 40 is not directly connected to the Schottky contact 5, which increases the doping concentration of the Schottky contact 5 region, thereby reducing the on-resistance and voltage of the device, and alleviating the problem of the mutual restriction between the area of ​​the Schottky contact 5 and the implantation area of ​​the P-type region.

[0041] The first doping structure 40 includes a plurality of suspended junctions 40, and the plurality of suspended junctions 40 are arranged in the drift region 21 of the epitaxial layer 2. The doping type of the suspended junction 40 is the same as the doping type of the drift region 21 of the epitaxial layer 2. The suspended junction 40 is arranged below the Schottky contact 5, and the suspended junction 40 is arranged below the P-type injection structure 30. The arrangement of the plurality of suspended junctions 40 is related to the arrangement of the Schottky contact region. During the formation of the suspended junction 40, the suspended junction 40 is formed by injecting a first ion. When the first ion injection is performed, the first ion injection is performed through the Schottky contact region to form the suspended junction 40 in the drift region 21 of the epitaxial layer 2 below the Schottky contact region. The first ion is a nitrogen ion or a phosphorus ion. When the first ion is injected, the injection energy is 20-1000 keV and the dose is 1E12-1E16cm -2 .

[0042] The Schottky contact region of the drift region 21 of the epitaxial layer 2 is provided with a plurality of Schottky contact grooves 50, and a portion of the Schottky contact 5 is located in the Schottky contact groove 50, so that the Schottky contact 5 is a groove structure, and the contact between the Schottky contact 5 and the epitaxial layer 2 is a groove contact, and the Schottky contact 5 extends to the inside of the epitaxial layer 2, increasing the area of ​​the Schottky contact 5. The cross-sectional shape of the bottom of the Schottky contact groove 50 is an arc shape, without a sharp corner, which can effectively alleviate the peak electric field at the sharp corner of the square groove and ensure the breakdown voltage of the diode device. The setting of the Schottky contact 5 of the groove structure reduces the on-resistance of the diode device while maintaining the reverse characteristics of the diode device. A plurality of Schottky contact grooves 50 and P-type injection structures 30 are alternately arranged, and a plurality of Schottky contact grooves 50 and P-type injection structures 30 are arranged in parallel, and are arranged according to design requirements, and are arranged in the drift region 21 of the epitaxial layer 2. The Schottky contact grooves 50 are formed by etching downward from the upper surface of the drift region 21 of the epitaxial layer 2. The P-type injection structure 30 is formed on the upper surface of the drift region 21 of the epitaxial layer 2 by ion implantation, and a P-type injection structure (P-well structure) is formed in the drift region 21 of the epitaxial layer 2, so that the Schottky contact 5 extends into the epitaxial layer 2 and the Schottky contact 5 contacts the P-type injection structure 30.

[0043] In some feasible embodiments, the cross-sectional shape of the Schottky contact groove 50 is semicircular, the diameter of the Schottky contact groove 50 is 1-5 μm, the depth of the Schottky contact groove 50 is 0.1-0.2 μm, and the spacing between adjacent Schottky contact grooves 50 is 1.5-4 μm.

[0044] The above-mentioned Schottky contact 5 includes a first contact portion and a second contact portion that are in contact with each other. The first contact portion is arranged in the Schottky contact groove 50, and the second contact portion is arranged on the drift region 21 of the epitaxial layer 2. The second contact portion is in contact with the P-type injection structure 30. The second contact portion covers the first contact portion and the P-type injection structure 30 located in the Schottky contact groove 50. The second contact portion is in contact with the first contact portion and the P-type injection structure 30. The Schottky contact 5 is formed by evaporation or sputtering. The Schottky contact 5 is titanium, nickel or molybdenum. The first contact portion is located in the Schottky contact groove 50. The shape and size of the first contact portion are adapted to the shape and size of the Schottky contact groove 50. The thickness of the second contact portion is 50-300nm.

[0045] The above-mentioned P-type injection region 3 includes multiple first injection regions 31 and multiple second injection regions 32. The area of ​​the second injection region 32 is smaller than that of the first injection region 31. The second injection region 32 is arranged at the gap between the adjacent first injection regions 31. The P-type injection region 3 adopts the setting mode of the first injection region 31 and the second injection region 32. The first injection region 31 is used as the main P-type injection region, which can form a more uniform electric field distribution and reduce local electric field concentration. At the same time, the first injection region 31 increases the area of ​​the Schottky contact region and the Schottky junction current, reducing the manufacturing cost. The second injection region 32 is used as a compensation injection region, so that its depletion layer covers the contact between the adjacent first injection regions 31, suppresses the peak electric field, protects the weak places of the depletion region, improves the reverse breakdown voltage of the silicon carbide junction barrier Schottky diode, reduces the power loss when working at high temperature, and prevents the reduction of the reverse breakdown voltage after the increase of the diode Schottky region, thereby improving the withstand voltage capability of the diode device.

[0046] In some feasible embodiments, the cross-sectional shape of the first injection region 31 is circular, and the cross-sectional shape of the second injection region 32 is circular. When the multiple first injection regions 31 and the multiple second injection regions 32 are arranged, the multiple first injection regions 31 are arranged in multiple rows and columns along the first direction and the second direction of the epitaxial layer 2, and the first direction is perpendicular to the second direction. For example, the first direction can be the length direction of the epitaxial layer 2, and the second direction can be the width direction of the epitaxial layer 2. The multiple first injection regions 31 in two adjacent rows or columns are staggered so that the multiple first injection regions 31 are evenly arranged, and the second injection region 32 is arranged in the gap between any at least three adjacent first injection regions 31, such as Figure 2 As shown, a second injection region 32 can be set in the gap between any three adjacent first injection regions 31, and two second injection regions 32 can be set in the gap between any four adjacent first injection regions 31. The first injection regions 31 and the second injection regions 32 are set in this way, so as to protect the weak places of the depletion region.

[0047] By ion implantation, second ion implantation is performed in both the first implantation region 31 and the second implantation region 32 to form a P-type implantation region structure 30. The second ion is aluminum ion, the implantation energy is 30-550 keV, and the dose is 1×10 13 -2×10 15 cm -2 .

[0048] The Schottky contact 5 , the first doping structure 40 and the P-type implantation structure 30 are all located in the active region of the drift region 21 of the epitaxial layer 2 .

[0049] Further optimization scheme, the Schottky barrier diode also includes a cathode 7 arranged on the substrate 1, an anode arranged on the Schottky contact 5, and an oxide layer 6 arranged on the epitaxial layer 2, wherein the cathode 7 is arranged on the side of the substrate 1 where the epitaxial layer 2 is not arranged, and the cathode 7 is formed by sputtering to form an ohmic contact back electrode, and the cathode 7 is nickel, titanium or silver, and the thickness of the cathode is 80nm-2μm. The thickness of the cathode 7 is selected according to actual needs, and no specific requirements are made here. The anode is arranged on the surface of the Schottky contact 5, and the anode is formed by evaporation or sputtering. The anode is aluminum, and the thickness of the anode is 400nm-5μm. The thickness of the anode is selected according to actual needs, and no specific requirements are made here. The above-mentioned oxide layer 6 is arranged on both sides of the Schottky contact 5, that is, an oxide layer 6 is arranged in the area of ​​the upper surface of the epitaxial layer 2 not covered by the Schottky contact 5, and the oxide layer 6 is formed by chemical vapor deposition. The oxide layer 6 is silicon dioxide, and the thickness of the oxide layer 6 is 50nm-4μm. The thickness of the oxide layer 6 is selected according to actual needs, and no specific requirements are made here.

[0050] A method for preparing a Schottky barrier diode with integrated trench and N-type floating junction, for preparing the above-mentioned Schottky barrier diode with integrated trench and N-type floating junction, comprises the following steps: A substrate 1 is provided. The substrate 1 is silicon carbide and the doping concentration of the substrate 1 is 1×10 19 -3×10 19 cm -3 In some feasible embodiments, the substrate 1 is an N+ 4H-SiC substrate.

[0051] The epitaxial layer 2 is prepared on the substrate 1. The epitaxial layer 2 is formed by growing on the substrate 1. The epitaxial layer 2 is N-type silicon carbide. The doping concentration of the epitaxial layer 2 is 1×10 16 -1×10 16 cm -3 The thickness of the epitaxial layer 2 is 5-30 μm. In some feasible embodiments, the epitaxial layer 2 is an N-4H-SiC epitaxial layer.

[0052] The P-type implantation structure 30 is prepared in the drift region 21 of the epitaxial layer 2, comprising the following steps: A first mask is prepared on the epitaxial layer 2, and the first mask is photoetched according to the layout of the P-type implantation structure 30 to form an opening of the P-type implantation region 3. The layout of the P-type implantation region 3 is as follows: Figure 2 As shown, the openings of the P-type injection region 3 include a plurality of openings of the first injection region 31 and a plurality of openings of the second injection region 32, and the openings of the second injection region 32 are arranged at the gaps between the openings of the adjacent first injection regions 31; the first mask is silicon dioxide, and the thickness of the first mask is selected according to actual needs, and no specific requirements are made here; The second ion implantation is performed through the opening of the first implantation region 30 and the opening of the second implantation region 32 to form a P-type implantation structure 30. The second ion is aluminum ion. The implantation energy of aluminum ion is 30-550 keV and the dose is 1×10 13 -2×10 15 cm -2 .

[0053] The first doping structure 40 is prepared in the drift region 21 of the epitaxial layer 2, comprising the following steps: Performing photolithography etching on the first mask to form an opening in the Schottky contact region; A first ion implantation is performed through the opening of the Schottky contact region to form a first doping structure 40 under the Schottky contact region, that is, a suspended junction 40 is formed by doping. The first doping structure 40 is located below the P-type implantation structure 30. The first ion is a nitrogen ion or a phosphorus ion. The implantation energy of the first ion is 200-1000 keV and the dosage is 1E12-1E16cm -2 ; After the first ion implantation is completed, the device is annealed to activate the implanted first ions and second ions to form effective doping. During the annealing process, when the device is annealed in an inert gas atmosphere, the annealing temperature is 1500-1900°C. The annealing temperature is selected according to actual needs, and the inert gas is argon.

[0054] After the annealing treatment, the first mask that has not been etched is removed to prepare the Schottky contact 5, which includes the following steps: A second mask is prepared on the surface of the epitaxial layer 2, and the second mask is photoetched to form a Schottky contact opening. When preparing the second mask, chemical vapor deposition is used to deposit the second mask. The second mask is silicon dioxide, and the thickness of the second mask is 50nm-4μm. The thickness of the second mask is selected according to actual needs; The epitaxial layer 2 at the Schottky contact opening is etched to form a Schottky contact groove 50. The epitaxial layer 2 at the Schottky contact opening is etched by dry etching. The cross-sectional shape of the Schottky contact groove 50 is preferably semicircular, the diameter of the Schottky contact groove 50 is 1-5 μm, the depth of the Schottky contact groove 50 is 0.1-0.2 μm, and the distance between adjacent Schottky contact grooves 50 is 1.5-4 μm; After the Schottky contact trench 50 is formed, a first metal is deposited at the Schottky contact opening to form a Schottky contact 5. The first metal is deposited by evaporation or sputtering. The first metal is titanium, nickel or molybdenum. After the Schottky contact 5 is formed, the device is subjected to Schottky annealing treatment to form a stable Schottky contact 5. The Schottky annealing treatment is performed in a first gas atmosphere at a temperature of 400-600° C. for 10-30 minutes. The annealing temperature and annealing time are selected according to actual needs, and no specific requirements are made here. The first gas is nitrogen.

[0055] The second mask that is not removed by photolithography and etching is located on the epitaxial layer 2 and serves as an oxide layer 6 .

[0056] Prepare cathode 7, deposit a second metal on the substrate by sputtering, and after the second metal deposition is completed, perform cathode annealing on the device to form cathode 7, wherein the second metal is nickel, titanium or silver, the cathode annealing temperature is 900-1000°C, and the cathode annealing time is 2-5min. The cathode annealing temperature and cathode annealing time are selected according to actual needs, and no specific requirements are made here. The thickness of the cathode is 80nm-2μm.

[0057] Prepare the anode, and deposit the third metal on the Schottky contact 5 by evaporation or sputtering to form the anode, wherein the third metal is aluminum, and the thickness of the anode is 400nm-5μm.

[0058] The preparation is completed and a silicon carbide junction barrier Schottky diode device is obtained.

[0059] Due to the adoption of the above technical scheme, the silicon carbide junction barrier Schottky diode combines the new Schottky barrier technology and the new P-type region injection layout structure, the Schottky contact is a trench structure, and the P-type injection region adopts a combination of a main injection region and a compensation injection region, so that the device can reduce the on-voltage of the device while keeping the breakdown voltage unchanged, or increase the breakdown voltage of the device while keeping the on-voltage unchanged; a first doped region is set in the drift region of the epitaxial layer below the Schottky contact region, and a plurality of suspended junctions are formed in the first doped region. The doping type of the suspended junction is the same as that of the drift region, which increases the doping concentration of the Schottky contact region, reduces the on-resistance and voltage of the device, and alleviates the problem of mutual restriction between the Schottky contact area and the P-type region injection area; the Schottky contact is a trench structure extending to the outside Inside the drift region of the extended layer, the Schottky contact adopts a trench contact method, which increases the area of ​​the Schottky contact. The groove is semicircular, which can effectively alleviate the peak electric field at the corner compared to the traditional square groove, reduce the on-resistance of the device while maintaining the reverse characteristics of the device, and ensure the breakdown voltage of the device; the P-type injection area adopts the superposition method of the first injection area (main injection area) and the second injection area (compensation injection area), which helps to form a more uniform electric field distribution, reduce local electric field concentration, suppress the peak electric field and thus improve the voltage resistance of the device, increase the Schottky contact area area and Schottky junction current, reduce manufacturing costs, protect the weak areas of the depletion region, increase the reverse breakdown voltage of the diode, reduce the power loss when working at high temperature, and prevent the reduction of the reverse breakdown voltage of the diode after the increase of the Schottky area.

[0060] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A Schottky barrier diode with integrated trench and N-type floating junction, characterized in that: It includes an epitaxial layer disposed on a substrate, a P-type implantation structure disposed in a drift region of the epitaxial layer, a first doping structure disposed in the drift region of the epitaxial layer, and a Schottky contact, wherein: The first doping structure is disposed below the P-type implantation structure to increase the doping concentration of the Schottky contact region; The Schottky contact is arranged on the epitaxial layer drift region and extends into the epitaxial layer drift region to increase the area of ​​the Schottky contact.

2. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 1, characterized in that: The doping type of the first doping structure is the same as the doping type of the epitaxial layer drift region.

3. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 2, characterized in that: The first doping structure corresponds to a Schottky contact region of the epitaxial layer drift region.

4. The Schottky barrier diode with integrated trench and N-type floating junction according to any one of claims 1 to 3, characterized in that: The first doping structure includes a plurality of suspended junctions, and the suspended junctions are formed by implanting first ions, wherein the first ions are nitrogen ions or phosphorus ions.

5. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 4, characterized in that: The Schottky contact region of the epitaxial layer drift region is provided with a plurality of Schottky contact grooves, and the cross-sectional shape of the bottom of the Schottky contact groove is an arc shape.

6. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 5, characterized in that: The cross-sectional shape of the Schottky contact groove is semicircular, the diameter of the Schottky contact groove is 1-5 μm, the depth of the Schottky contact groove is 0.1-0.2 μm, and the distance between adjacent Schottky contact grooves is 1.5-4 μm.

7. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 5 or 6, characterized in that: The Schottky contact includes a first contact portion and a second contact portion in contact with each other, wherein the first contact portion is disposed in the Schottky contact trench, the second contact portion is disposed on the epitaxial layer drift region, and the second contact portion is in contact with the P-type implantation structure.

8. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 7, characterized in that: The Schottky contact is made of titanium, nickel or molybdenum, and the thickness of the second contact portion is 50-300 nm.

9. The Schottky barrier diode with integrated trench and N-type floating junction according to any one of claims 1 to 3, 5 to 6 and 8, characterized in that: The P-type injection structure is arranged in a P-type injection region, and the P-type injection region includes multiple first injection regions and multiple second injection regions, the area of ​​the second injection region is smaller than that of the first injection region, and the second injection region is arranged in the gap between adjacent first injection regions.

10. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 9, characterized in that: The cross-sectional shape of the first injection region is circular, and the cross-sectional shape of the second injection region is circular.

11. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 1, characterized in that: It also includes a cathode disposed on the substrate, an anode disposed on the Schottky contact, and an oxide layer disposed on the epitaxial layer, wherein: The cathode is nickel, titanium or silver, and the thickness of the cathode is 80nm-2μm; The anode is aluminum, and the thickness of the anode is 400nm-5μm; The oxide layer is arranged on both sides of the Schottky contact, the oxide layer is silicon dioxide, and the thickness of the oxide layer is 50nm-4μm.

12. The Schottky barrier diode with integrated trench and N-type floating junction according to claim 1 or 11, characterized in that: The substrate is silicon carbide, and the doping concentration of the substrate is 1×10 19 -3×10 19 cm -3 The epitaxial layer is N-type silicon carbide, and the doping concentration of the epitaxial layer is 1×10 16 -3×10 16 cm -3 , the thickness of the epitaxial layer is 5-30 μm.

13. A method for preparing a Schottky barrier diode with integrated trench and N-type floating junction, characterized in that: The following steps are involved: preparing an epitaxial layer on a substrate; Preparing a P-type implantation structure in the drift region of the epitaxial layer; Preparing a first doping structure in the drift region of the epitaxial layer; Preparation of Schottky contacts.

14. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 13, characterized in that: The step of preparing a P-type implantation structure in the drift region of the epitaxial layer includes: Preparing a first mask on the epitaxial layer, and performing photolithography etching on the first mask according to the P-type implantation region layout to form an opening of the P-type implantation region; A second ion implantation is performed to form the P-type implantation structure.

15. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 14, characterized in that: The opening of the P-type injection region includes an opening of a first injection region and an opening of a second injection region, and the opening of the second injection region is arranged at a gap between the openings of the first injection region arranged adjacent to each other.

16. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 15, characterized in that: The second ion is aluminum ion, the implantation energy of the aluminum ion is 30-550 keV, and the dose is 1×10 13 -2×10 15 cm -2 .

17. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to any one of claims 14 to 16, characterized in that: The step of preparing a first doping structure in the drift region of the epitaxial layer includes: Performing photolithography etching on the first mask to form an opening in the Schottky contact region; Performing a first ion implantation to form the first doping structure under the Schottky contact region, wherein the first doping structure is located below the P-type implantation structure; An annealing process is performed to activate the implanted first ions and the second ions.

18. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 17, characterized in that: The first ion is a nitrogen ion or a phosphorus ion, and the implantation energy of the first ion is 200-1000 keV, and the dose is 1E12-1E16cm -2 .

19. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 18, characterized in that: When the device is annealed in an inert gas atmosphere, the annealing temperature is 1500-1900° C. and the annealing time is 10-30 minutes.

20. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 19, characterized in that: The first mask is silicon dioxide, and the inert gas is argon.

21. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to any one of claims 14-16 and 18-20, characterized in that: The step of preparing the Schottky contact comprises: Preparing a second mask on the surface of the epitaxial layer, and photolithographically etching the second mask to form a Schottky contact opening; Etching the epitaxial layer at the Schottky contact opening to form a Schottky contact groove; Performing a first metal deposition at the Schottky contact opening to form the Schottky contact; Schottky annealing is performed to form a stable Schottky contact.

22. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 21, characterized in that: The second mask is deposited by chemical vapor deposition, and the second mask is silicon dioxide.

23. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 22, characterized in that: The epitaxial layer at the Schottky contact opening is etched by dry etching.

24. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 22 or 23, characterized in that: The first metal is deposited by evaporation or sputtering, and the first metal is titanium, nickel or molybdenum.

25. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 24, characterized in that: The Schottky annealing treatment is performed in a first gas atmosphere, the annealing temperature is 400-600° C., the annealing time is 10-30 minutes, and the first gas is nitrogen.

26. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 13, characterized in that: The method also includes preparing a cathode, depositing a second metal on the back of the substrate by sputtering, and performing cathode annealing to form a cathode, wherein the second metal is nickel, titanium or silver, the cathode annealing temperature is 900-1000°C, and the cathode annealing time is 2-5 minutes.

27. The method for preparing a Schottky barrier diode with integrated trench and N-type floating junction according to claim 26, characterized in that: The method also includes preparing an anode, depositing a third metal on the Schottky contact by evaporation or sputtering to form an anode, wherein the third metal is aluminum.

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