Bimetal Schottky diode and preparation method thereof

Abstract

The invention discloses a bimetallic Schottky diode and a preparation method thereof, and belongs to the technical field of power device design, metal silicides with different potential barrier heights are formed at different temperatures, and then different potential barrier heights are formed through the combination of the metal silicides, namely, the Schottky diode with different leakage currents and different forward voltage drops is formed. According to the method, metal silicides with different potential barrier heights can be formed through annealing of two kinds of metal at different process temperatures, the situation that alloy target materials with different proportions need to be prepared for forming different silicides when the alloy target materials are adopted is avoided, process equipment is saved through different technological processes, and normalized management is achieved; the design method is simple in theory and easy to understand, different design technicians can adjust according to different products, results meeting product requirements can be obtained by following the method, and the application range is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of power device design, and specifically relates to a bimetallic Schottky diode and a preparation method thereof. Background Art

[0002] In existing technologies, although Schottky diodes as multi-substrate devices have shown unique advantages in the field of electronics, and the selection of Schottky contact metal is crucial to device performance, they still face a series of challenges and problems.

[0003] First, although metals such as Ni and Cr are widely used in the development of low-barrier Schottky devices due to their low barrier height and good thermal stability, these metals may be limited by material compatibility and process complexity in practical applications. For example, issues such as interface reaction with semiconductor materials, metal diffusion, and thermal stress during the process may affect the reliability and long-term stability of the device.

[0004] Secondly, for metals with high barrier heights such as Al and Pt, although their barrier heights are adjustable at different temperatures, providing more flexibility for device design, this adjustability also brings additional challenges. How to accurately control the barrier height to adapt to different application scenarios while maintaining stable device performance is a difficulty in current technology. In addition, the interface characteristics between high barrier metals and semiconductor materials, such as interface state density and interface recombination rate, also have an important impact on device performance, and the control and optimization of these factors is also one of the challenges facing current technology. Summary of the invention

[0005] The invention provides a bimetallic Schottky diode and a preparation method thereof, which solve the problems in the background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for preparing a bimetallic Schottky diode, comprising: The silicon epitaxial wafer is coated with photoresist, and exposure, development and etching are performed on the photoresist according to the layout structure to prepare an etched protection ring implantation pattern area; Ion implantation is performed in the guard ring implantation region, and implantation region push-up is performed to form a guard ring; The wafer is coated with photoresist, and exposure, development and etching are performed on the photoresist according to the layout structure to prepare the Schottky contact pattern area; Depositing a first metal layer on the surface of the wafer, then annealing to form a first metal silicide, and removing excess metal that has not formed silicide; Depositing a second metal layer on the surface of the wafer, then annealing to form a second metal silicide, and removing excess metal that has not formed silicide; Depositing multi-layer electrode metal on the first metal silicide and the second metal silicide, and performing annealing after patterning by photolithography; The back side of the wafer is thinned, and then the back electrode metal is evaporated on the back side of the wafer to obtain a bimetallic Schottky diode.

[0007] Preferably, the implanted element of the guard ring is boron, and the ion implantation dose is 1E14 / cm 3 ~1E16 cm 3 , the depth of the guard ring is 1.0μm~5.0μm.

[0008] Preferably, the first metal layer is made of Cr, Ni or Ti.

[0009] Preferably, the deposition thickness of the first metal layer is 50 nm-500 nm, and the annealing temperature is 400° C.-600° C.

[0010] Preferably, the second metal layer is made of Al or Pt Preferably, the deposition thickness of the second metal layer is 50 nm-500 nm, and the annealing temperature is 400° C.-500° C.

[0011] Preferably, the multilayer metal combination is Ti, Al or Ti, Ni, Ag, and annealing is performed after patterning, and the annealing temperature does not exceed 450°C.

[0012] Preferably, the back metal electrode is a combination of Ti, Ni and Ag or a combination of Cr, Ni and Ag.

[0013] Preferably, the thinning thickness is 150 μm to 300 μm.

[0014] A method for preparing a bimetallic Schottky diode is based on a method for preparing a bimetallic Schottky diode.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a method for preparing a bimetallic Schottky diode, forming metal silicides with different barrier heights at different temperatures, and then forming different barrier heights by combining metal silicides, that is, forming Schottky diodes with different leakage currents and different forward voltage drops. The present invention can form metal silicides with different barrier heights by annealing two metals at different process temperatures, avoiding the need to prepare alloy targets of different proportions to form different silicides when alloy targets are used, saving process equipment through different process processes, and realizing normalized management; the design method is simple in theory and easy to understand, and different design technicians can make adjustments according to different products. Following this method, results that meet product requirements can be obtained, and the application range is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A bimetallic Schottky diode and a preparation method thereof according to the present invention; Figure 2 This is a structural diagram of a bimetallic Schottky diode of the present invention; In the figure, 1-first metal silicide, 2-electrode metal, 3-second metal silicide, 4-oxide layer, 5-guard ring, 6-N - Epitaxial layer, 7-N + Substrate. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the present invention provides a bimetallic Schottky diode and a method for preparing the same, comprising: S101: coating the silicon epitaxial wafer with photoresist, performing exposure, development and etching on the photoresist according to the layout structure, and preparing an etched protection ring injection pattern area; S102: performing ion implantation in the guard ring implantation region and performing push-up in the implantation region to form a guard ring; S103: coating the wafer with photoresist, performing exposure, development and etching on the photoresist according to the layout structure, and preparing a Schottky contact pattern area; S104 deposits a first metal layer on the surface of the wafer, then performs annealing to form a first metal silicide, and removes excess metal that has not formed silicide; S105 deposits a second metal layer on the surface of the wafer, then performs annealing to form a second metal silicide, and removes excess metal that has not formed silicide; S106: depositing a multilayer electrode metal on the first metal silicide and the second metal silicide, and performing annealing after patterning by photolithography; S107 thins the back side of the wafer, and then evaporates the back electrode metal on the back side of the wafer to obtain a bimetallic Schottky diode.

[0022] The implantation element of the guard ring is boron, and the ion implantation dose is 1E14 / cm 3 ~1E16 cm 3 , the depth of the guard ring is 1.0μm~5.0μm.

[0023] By implanting boron to form a guard ring, edge breakdown can be effectively prevented, and the breakdown voltage and reliability of the device can be improved. Precise control of ion implantation dose and depth ensures the effectiveness of the guard ring and the stability of device performance.

[0024] The deposition thickness of the first metal layer is 50nm-500nm, the first metal layer is Cr, Ni or Ti, and the annealing temperature is 400℃-600℃.

[0025] Cr, Ni or Ti is selected as the material of the first metal layer. These metals have low barrier height and good thermal stability, and are suitable for constructing low barrier Schottky diodes, thereby improving the current conduction capability and temperature stability of the device. Precise control of the deposition thickness and annealing temperature of the first metal layer helps to optimize the contact characteristics between the metal and the semiconductor, and improve the conductivity and stability of the device.

[0026] The deposition thickness of the second metal layer is 50nm-500nm, the second metal layer is Al or Pt, and the annealing temperature is 400℃-500℃.

[0027] Al or Pt is selected as the material of the second metal layer. These metals have adjustable barrier heights, providing more flexibility for device design. At the same time, they also have good conductivity and stability. The precise control of the deposition thickness and annealing temperature of the second metal layer helps to further optimize the contact characteristics between the metal and the semiconductor and ensure the stable performance of the device.

[0028] The multilayer metal combination is Ti, Al or Ti, Ni, Ag, and the annealing temperature does not exceed 450°C.

[0029] The introduction of multi-layer metal combinations (such as Ti, Al or Ti, Ni, Ag) can make full use of the characteristics of different metals to achieve more complex device structures and performance optimization. Precise control of annealing temperature helps ensure good contact between multi-layer metals and device stability.

[0030] The thinning thickness is 150μm ~300μm, and the back metal electrode is a TiNiAg combination or a CrNiAg combination.

[0031] The back metal electrode uses a combination of Ti, Ni and Ag or a combination of Cr, Ni and Ag. These metals have good conductivity and adhesion, which helps to reduce contact resistance and improve device reliability. Through the thinning process, the thickness of the device can be reduced, thereby improving its response speed and heat dissipation performance. At the same time, the thinned device is also easier to package and integrate.

[0032] Example 1 A method for preparing a bimetallic Schottky diode comprises coating a silicon epitaxial wafer with photoresist, and performing exposure, development and etching on the photoresist according to a layout structure to prepare an etched protection ring injection pattern area.

[0033] Boron ion implantation is performed in the guard ring implantation area with an ion implantation dose of 1E15 / cm³, and the implantation area is pushed open to form a guard ring with a depth of 2.5μm.

[0034] The wafer is coated with photoresist, and exposure, development and etching are performed on the photoresist according to the layout structure to prepare the Schottky contact pattern area.

[0035] Cr metal is deposited in the Schottky contact pattern region with a deposition thickness of 200 nm, and then annealed at a temperature of 500° C. to form a first metal silicide, and excess metal that has not formed silicide is removed.

[0036] Al metal is deposited on the first metal silicide with a deposition thickness of 300 nm, and then annealed at a temperature of 450° C. to form a second metal silicide, and excess metal that has not formed silicide is removed.

[0037] Deposition of Ti, Ni, Ag multilayer electrode metal is performed on the second metal silicide, and annealing is performed after patterning with an annealing temperature of 400°C.

[0038] The back side of the wafer is thinned to 200 μm, and then Ti, Ni, and Ag combined back electrode metal is evaporated on the back side of the wafer.

[0039] After the above steps, a bimetallic Schottky diode is obtained.

[0040] Example 2 A method for preparing a bimetallic Schottky diode Steps 1 and 2 of Example 1 were followed, except that the depth of the guard ring was adjusted to 4.0 μm.

[0041] Proceed according to step 3 of Example 1.

[0042] Ni metal is deposited in the Schottky contact pattern region with a deposition thickness of 400 nm, and then annealed at a temperature of 450° C. to form a first metal silicide, and excess metal that has not formed silicide is removed.

[0043] Pt metal is deposited on the first metal silicide with a deposition thickness of 250 nm, and then annealed at a temperature of 480° C. to form a second metal silicide, and excess metal that has not formed silicide is removed.

[0044] Ti and Al multilayer electrode metals are deposited on the second metal silicide, and annealing is performed after patterning with an annealing temperature of 420°C.

[0045] The back side of the wafer is thinned to 180 μm, and then a Cr, Ni, and Ag combination back electrode metal is evaporated on the back side of the wafer.

[0046] After the above steps, another bimetallic Schottky diode is obtained.

[0047] Example 3 A method for preparing a bimetallic Schottky diode The steps 1 and 2 of Example 1 were followed, but the ion implantation dose was adjusted to 5E14 / cm³.

[0048] Proceed according to step 3 of Example 1.

[0049] Ti metal is deposited in the Schottky contact pattern region with a deposition thickness of 100 nm, and then annealed at a temperature of 600° C. to form a first metal silicide, and excess metal that has not formed silicide is removed.

[0050] Al metal is deposited on the first metal silicide with a deposition thickness of 500 nm, and then annealed at a temperature of 500° C. to form a second metal silicide, and excess metal that has not formed silicide is removed.

[0051] Ti and Ni multilayer electrode metals are deposited on the second metal silicide, and annealing is performed after patterning with an annealing temperature of 450°C.

[0052] The back side of the wafer is thinned to 300 μm, and then Ti and Ni combined back electrode metal is evaporated on the back side of the wafer.

[0053] After the above steps, another bimetallic Schottky diode is obtained.

[0054] Example 4 A method for preparing a bimetallic Schottky diode This embodiment is based on Embodiment 1, but differs in the selection of the metal layer and the deposition thickness.

[0055] Follow steps 1-3 of Example 1.

[0056] Ni metal is deposited in the Schottky contact pattern region with a deposition thickness of 50 nm, and then annealed at a temperature of 400° C. to form a first metal silicide, and excess metal that has not formed silicide is removed.

[0057] Pt metal is deposited on the first metal silicide with a deposition thickness of 100 nm, and then annealed at a temperature of 400° C. to form a second metal silicide, and excess metal that has not formed silicide is removed.

[0058] The subsequent steps are performed according to steps 6-8 of Example 1, but the multilayer electrode metal is selected as a combination of Ti and Al, and the back electrode metal is selected as a combination of Cr, Ni, and Ag.

[0059] After the above steps, another bimetallic Schottky diode with different metal combinations and deposition thicknesses is obtained.

[0060] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative and instructive, rather than restrictive. Under the guidance of the specification, a person skilled in the art can make many forms without departing from the scope of protection of the claims of the present invention, all of which belong to the scope of protection of the present invention.

Claims

1. A method for preparing a bimetallic Schottky diode, characterized in that: include: The silicon epitaxial wafer is coated with photoresist, and exposure, development and etching are performed on the photoresist according to the layout structure to prepare an etched protection ring implantation pattern area; Ion implantation is performed in the guard ring implantation region to form an implantation region, and a push-up is performed in the implantation region to form a guard ring; The wafer is coated with photoresist, and exposure, development and etching are performed on the photoresist according to the layout structure to prepare the Schottky contact pattern area; Depositing a first metal layer on the surface of the wafer, then annealing to form a first metal silicide, and removing excess metal that has not formed silicide; Depositing a second metal layer on the surface of the wafer, then annealing to form a second metal silicide, and removing excess metal that has not formed silicide; Depositing multi-layer electrode metal on the first metal silicide and the second metal silicide, and performing annealing after patterning by photolithography; The back side of the wafer is thinned, and then the back electrode metal is evaporated on the back side of the wafer to obtain a bimetallic Schottky diode.

2. The method for preparing a bimetallic Schottky diode according to claim 1, characterized in that: The implantation element of the guard ring is boron, and the ion implantation dose is 1E14 / cm 3 ~1E16 cm 3 , the depth of the guard ring is 1.0μm~5.0μm.

3. The method for preparing a bimetallic Schottky diode according to claim 1, characterized in that: The first metal layer uses metal such as Cr, Ni or Ti.

4. The method for preparing a bimetallic Schottky diode according to claim 4, characterized in that: The deposition thickness of the first metal layer is 50nm~500nm, and the annealing temperature is 400℃~600℃.

5. The method for preparing a bimetallic Schottky diode according to claim 1, characterized in that: The second metal layer uses Al or Pt as the metal.

6. The method for preparing a bimetallic Schottky diode according to claim 5, characterized in that: The deposition thickness of the second metal layer is 50nm~500nm, and the annealing temperature is 400℃~500℃.

7. The method for preparing a bimetallic Schottky diode according to claim 1, characterized in that: The multilayer metal combination is Ti, Al or Ti, Ni, Ag, and annealing is performed after photolithography, and the annealing temperature does not exceed 450°C.

8. The method for preparing a bimetallic Schottky diode according to claim 1, characterized in that: The back metal electrode is a combination of Ti, Ni and Ag or a combination of Cr, Ni and Ag.

9. The method for preparing a bimetallic Schottky diode according to claim 8, characterized in that: The thinning thickness is 150μm ~300μm.

10. A method for preparing a bimetallic Schottky diode, characterized in that: The invention is prepared based on the preparation method of a bimetallic Schottky diode according to any one of claims 1 to 9.

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