A sub-vertical structure gallium nitride Schottky barrier diode and a manufacturing method thereof

Abstract

The invention discloses a sub-vertical structure gallium nitride Schottky barrier diode and a manufacturing method thereof, comprising a substrate (1), a buffer layer (2), and a n + ‑GaN epitaxial layer (3a), n ‑ ‑GaN epitaxial layer (3b), n ‑ The upper surface of the GaN epitaxial layer (3b) is a Schottky electrode setting area (13b), n + The locally exposed portion of the upper surface of the GaN epitaxial layer (3a) is an ohmic electrode setting region (13a); the first insulating protection layer (6a) covers the ohmic electrode setting region (13a) and the Schottky electrode setting region (13b), and also covers the n- + ‑GaN epitaxial layer (3a) and n ‑ On the step side wall surface formed by the GaN epitaxial layer (3b), the first insulating protective layer (6a) is provided with an ohmic electrode (4) in a window formed on the ohmic electrode setting area (13a), and the first insulating protective layer (6a) is provided with a Schottky electrode (5) in a window formed on the Schottky electrode setting area (13b). The Schottky barrier diode of the present invention increases the forward current and improves the reverse breakdown voltage.

Description

Technical Field

[0001] The present invention relates to the technical field of third-generation semiconductor materials and devices, and in particular to the structure of a sub-vertical gallium nitride Schottky barrier diode and a manufacturing method thereof. Background Art

[0002] Schottky barrier diode (SBD) is a key device in the rectifier circuit. It uses the unidirectional conductivity of the device to change the physical properties of the circuit such as voltage, current, frequency, and conduction state to achieve functions such as power switching and power conversion. In the process of industrial electronic upgrading, it has been increasingly valued and applied. It is a core device in China's industrial processing, automobile manufacturing, wireless communication, consumer electronics, power transmission and transformation, and new energy applications. Therefore, higher requirements are placed on its forward current characteristics, reverse withstand voltage characteristics, and working characteristics under high-frequency conditions.

[0003] Schottky barrier diodes manufactured using traditional technology have technical problems such as large reverse leakage current, low reverse withstand voltage and insufficient stability. Therefore, it is an urgent market requirement to manufacture diodes with small reverse leakage current, high reverse withstand voltage and good stability.

[0004] In order to solve the above problems, the present invention is proposed. Summary of the invention

[0005] Gallium nitride (GaN)-based materials have the characteristics of high electron mobility and high electron saturation velocity, wide bandgap width, high breakdown field, etc. Therefore, SBD devices made of semiconductor GaN materials have received widespread attention as devices that can work stably in more harsh working environments.

[0006] A first aspect of the present invention provides a sub-vertical structure gallium nitride Schottky barrier diode, comprising:

[0007] A substrate 1 and a buffer layer 2, n arranged in sequence from bottom to top on the upper surface of the substrate 1 + -GaN epitaxial layers 3a and n - -GaN epitaxial layer 3b, the n - -GaN epitaxial layer 3b has a Schottky electrode setting area 13b on its upper surface. + - The upper surface of the GaN epitaxial layer 3a is partially exposed, and the exposed portion is the ohmic electrode setting area 13a;

[0008] The first insulating protective layer 6a covers the ohmic electrode setting area 13a and the Schottky electrode setting area 13b, and the first insulating protective layer 6a also covers the n + -GaN epitaxial layer 3a and n -- On the step sidewall surface formed by the GaN epitaxial layer 3b, the first insulating protection layer 6a is respectively formed with windows on the upper surfaces of the ohmic electrode setting area 13a and the Schottky electrode setting area 13b;

[0009] A Schottky electrode 5, which is arranged in the window portion of the Schottky electrode arrangement region 13b, and the edge of the Schottky electrode 5 covers the first insulating protection layer 6a to form a field plate structure;

[0010] The ohmic electrode 4 is arranged in the window of the ohmic electrode arrangement area 13a.

[0011] Among them, the n - -GaN epitaxial layer 3b is used as the drift layer of the subvertical structure gallium nitride Schottky barrier diode of the present invention, regulating n - The thickness of the GaN epitaxial layer 3b can conveniently achieve the required reverse breakdown voltage of the Schottky barrier diode.

[0012] Preferably, the diode further includes a second insulating protection layer 6 b disposed on the first insulating protection layer 6 a , a partial region of the Schottky electrode 5 , and a partial region of the ohmic electrode 4 .

[0013] The substrate 1 used in the present invention is based on the epitaxial layer (i.e., n - -GaN epitaxial layers 3b and n + -GaN epitaxial layer 3a) and its preparation method, availability and price are appropriately selected. The present invention takes into account factors such as the lattice and thermal expansion coefficient matching of the epitaxial layer and cost, and preferably selects sapphire as the substrate. In addition, other substrates may also be selected, such as silicon carbide, silicon, germanium, oxides (zinc oxide, lithium aluminum oxide, magnesium oxide, LiGaO2, etc.), III-V compounds in the periodic table (GaN, GaAs, AlN, AlGaN, etc.), borides (AlInN), etc.

[0014] In order to obtain a good epitaxial material, it is necessary to consider the lattice and thermal expansion coefficient matching between the substrate 1 and the epitaxial material. Usually, a buffer layer 2 is used as a transition layer between the substrate 1 and the epitaxial layer. When selecting the material of the buffer layer 2, it is necessary to consider the lattice and thermal expansion coefficient matching between the substrate 1 and the epitaxial material, as well as the composition, structure and formation method of each layer of the epitaxial device layer material on the buffer layer 2. In the present invention, a low-temperature grown GaN layer is preferably used as the buffer layer 2. In addition, III-V compound materials such as AlN can also be used.

[0015] Preferably, the thickness of the buffer layer 2 is between 1 and 30 nm, preferably between 1 and 10 nm, and most preferably between 3 nm and 10 nm. The dislocation density of the buffer layer 2 should be as small as possible, otherwise it will affect the subsequent film quality. Preferably, the dislocation density is controlled within 1×10 11 / cm 2 the following.

[0016] Preferably, the ohmic electrode 4 includes a titanium layer, an aluminum layer, a nickel layer and a gold layer from bottom to top, wherein the thickness of the titanium layer is 10-30nm, the thickness of the aluminum layer is 80-150nm, the thickness of the nickel layer is 30-60nm, and the thickness of the gold layer is 50-500nm. + - The GaN epitaxial layer 3a forms an ohmic contact.

[0017] Preferably, the Schottky electrode 5 includes a nickel nitride layer and a gold layer from bottom to top, the nickel nitride layer has a thickness of 10-30 nm, and the gold layer has a thickness of 50-500 nm. - The -GaN epitaxial layer 3b forms a Schottky contact.

[0018] The second aspect of the present invention provides a method for manufacturing the sub-vertical structure gallium nitride Schottky barrier diode according to the first aspect of the present invention, comprising the following steps:

[0019] A. Buffer layer 2, n are grown on substrate 1 in sequence + -GaN epitaxial layer 3a, n - -GaN epitaxial layer 3b;

[0020] B. In n - The local area of ​​the GaN epitaxial layer 3b is etched to - -GaN epitaxial layer 3b is removed, exposing n + The region of the GaN epitaxial layer 3a constitutes the ohmic electrode setting region 13a, and the unetched n - -GaN epitaxial layer 3b region constitutes Schottky electrode setting region 13b;

[0021] C. On the upper surface of the ohmic electrode setting region 13a, the upper surface of the Schottky electrode setting region 13b and n + -GaN epitaxial layer 3a and n - -Depositing a first insulating protective layer 6a on the step sidewall surface formed by the GaN epitaxial layer 3b, wherein the first insulating protective layer 6a has windows formed on the upper surfaces of the ohmic electrode setting region 13a and the Schottky electrode setting region 13b respectively;

[0022] D. depositing a nickel nitride layer on the upper surface window portion of the Schottky electrode setting area 13b by using a method of electron beam evaporation of nickel assisted by nitrogen ion injection, and then evaporating a gold layer on the nickel nitride layer by electron beam evaporation to form a Schottky electrode 5, wherein the edge of the Schottky electrode 5 is covered on the first insulating protection layer 6a to form a field plate structure;

[0023] E. The ohmic electrode 4 is formed in the upper surface window portion of the ohmic electrode setting area 13 a by electron beam evaporation process.

[0024] Preferably, the substrate 1 is sapphire with a thickness of 430 μm, and the surface orientation of the epitaxial growth surface of the substrate is a C-plane and is inclined 0.15 degrees to the m-plane.

[0025] The buffer layer 2 can be formed by a well-known film forming method such as metal organic chemical vapor epitaxy (MOCVD) or molecular beam epitaxy (MBE).

[0026] Preferably, a metal organic chemical vapor epitaxy method (MOCVD method) is used with trimethylgallium (TMGa) and NH 3 The GaN layer is a raw material and deposited under low temperature conditions as a buffer layer 2, and its thickness is 10 to 30 nm.

[0027] Preferably, the n + -GaN epitaxial layers 3a and n - -GaN epitaxial layer 3b is deposited by metal organic chemical vapor phase epitaxy. + -GaN epitaxial layer 3a has a thickness of 3 to 5 μm, n - -GaN epitaxial layer 3b has a thickness of 1 to 3 μm, wherein the n + -GaN epitaxial layers 3a and n - -GaN epitaxial layer 3b is an n-type doped gallium nitride layer, which is formed by doping gallium nitride with a tetravalent element (such as silicon or germanium), and its carriers are electrons; more preferably, the n + -GaN epitaxial layers 3a and n - -GaN epitaxial layer 3b is made of SiH 4 As doping source, the doping concentration is 1×10 18 cm -3 ~1×10 19 cm -3 and 8×10 15 cm -3 ~5×10 17 cm -3 within the range.

[0028] Preferably, a silicon dioxide insulating film layer is deposited by PECVD as the first insulating protective layer 6a;

[0029] Preferably, the formation process of the ohmic electrode 4 includes depositing a titanium layer, an aluminum layer, a nickel layer and a gold layer on the surface of a local area of ​​the ohmic electrode setting area 13a (i.e., the window portion of the upper surface of the ohmic electrode setting area 13a) in sequence by electron beam evaporation process, and heat treating in a nitrogen atmosphere at 500°C-950°C for 10-300 seconds; wherein the thickness of the titanium layer is 10-30nm, the thickness of the aluminum layer is 80-150nm, the thickness of the nickel layer is 30-60nm, the thickness of the gold layer is 50-500nm, and the titanium layer and the n + - The GaN epitaxial layer 3a forms an ohmic contact.

[0030] Preferably, the formation process of the Schottky electrode 5 includes depositing a nickel nitride layer and a gold layer from bottom to top on the surface of a local area of ​​the Schottky electrode setting area 13b (i.e., the window portion on the upper surface of the Schottky electrode setting area 13b), wherein the nickel nitride layer has a thickness of 10-30nm, and the gold layer has a thickness of 50-500nm. - -GaN epitaxial layer forms a Schottky barrier contact.

[0031] Preferably, the diode further comprises a second insulating protective layer 6b, which is deposited on the first insulating protective layer 6a, a part of the Schottky electrode 5 and a part of the ohmic electrode 4 by using a PECVD method; the second insulating protective layer 6b is deposited by using a PECVD method, wherein SiO 2 The insulating film layer is the second insulating protection layer 6b, and has a thickness of 100 to 500 nm.

[0032] The sub-vertical structure described in the present invention refers to a structure in which the Schottky electrode and the ohmic electrode are neither arranged on the same surface nor on the upper and lower surfaces of the device. For example, the surface provided with the Schottky electrode and the surface provided with the ohmic electrode form a step structure.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention makes full use of the characteristics of GaN epitaxial layer materials, such as wide bandgap, high electric field breakdown strength, high electron mobility and high electron saturation velocity, to deposit a nickel nitride layer and a gold layer on the surface of the gallium nitride material to form a Schottky electrode, and sequentially deposit titanium / aluminum / nickel / gold layers on the surface of the gallium nitride material to form an ohmic electrode, thereby constituting the sub-vertical structure of the GaN Schottky barrier diode of the present invention. The sub-vertical structure of the GaN Schottky barrier diode of the present invention can be used in harsh high-temperature environments, and the reverse recovery speed of the device is high, so it is suitable for use in high-frequency circuits, thereby improving the power conversion efficiency of microwave systems.

[0035] 2. Compared with the conventional planar Schottky barrier diode, the sub-vertical GaN Schottky barrier diode of the present invention has increased forward current and improved reverse breakdown voltage.

[0036] 3. The present invention uses a method of nitrogen ion assisted implantation electron beam evaporation of nickel to manufacture a high-quality nickel nitride thin film layer to replace the metal layer deposited by the traditional method. The nickel nitride layer and the n - -The excellent Schottky barrier contact formed by the GaN epitaxial layer realizes a Schottky barrier diode with low reverse leakage current and stable performance.

[0037] 4. The present invention adopts a field plate structure at the edge of the Schottky electrode, so that the electric field strength in the edge area of ​​the Schottky electrode is relaxed, further improving the reverse withstand voltage characteristics of the Schottky barrier diode.

[0038] 5. The upper surface of the entire Schottky barrier diode of the present invention, except for the ohmic electrode and the Schottky electrode, is covered with an insulating layer to prevent leakage current from the surface and protect the Schottky barrier diode from external influences. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic cross-sectional view of the structure of the gallium nitride Schottky barrier diode of the present invention;

[0040] Figure 2 A top view of an ohmic electrode setting region and a Schottky electrode setting region of a gallium nitride Schottky barrier diode according to one embodiment of the present invention;

[0041] Figure 3 A top view of an ohmic electrode setting region and a Schottky electrode setting region of a gallium nitride Schottky barrier diode according to one embodiment of the present invention;

[0042] Figure 4 A top view of an ohmic electrode setting region and a Schottky electrode setting region of a gallium nitride Schottky barrier diode according to one embodiment of the present invention;

[0043] Description of reference numerals: 1, substrate, 2, buffer layer, 3a, n + -GaN epitaxial layer, 3b, n - -GaN epitaxial layer, 4, ohmic electrode, 5, Schottky electrode, 6a, first insulating layer, 6b, second insulating layer, 13a, ohmic electrode setting area; 13b, Schottky electrode setting area. DETAILED DESCRIPTION

[0044] In order to better understand the purpose, structure and function of the present invention, a sub-vertical gallium nitride Schottky barrier diode of the present invention is further described in detail below with reference to the accompanying drawings.

[0045] A sub-vertical gallium nitride Schottky barrier diode, comprising:

[0046] A substrate 1 and a buffer layer 2, n arranged in sequence from bottom to top on the upper surface of the substrate 1 + -GaN epitaxial layers 3a and n - -GaN epitaxial layer 3b, the n - -GaN epitaxial layer 3b has a Schottky electrode setting area 13b on its upper surface. + - The upper surface of the GaN epitaxial layer 3a is partially exposed, and the exposed portion is the ohmic electrode setting area 13a;

[0047] The first insulating protective layer 6a covers the ohmic electrode setting area 13a and the Schottky electrode setting area 13b, and the first insulating protective layer 6a also covers the n + -GaN epitaxial layer 3a and n - - On the step sidewall surface formed by the GaN epitaxial layer 3b, the first insulating protection layer 6a is respectively formed with windows on the upper surfaces of the ohmic electrode setting area 13a and the Schottky electrode setting area 13b;

[0048] A Schottky electrode 5, which is arranged in the window portion of the Schottky electrode arrangement region 13b, and the edge of the Schottky electrode 5 covers the first insulating protection layer 6a to form a field plate structure;

[0049] The ohmic electrode 4 is arranged in the window of the ohmic electrode arrangement area 13a.

[0050] Among them, the n - -GaN epitaxial layer 3b is used as the drift layer of the subvertical structure gallium nitride Schottky barrier diode of the present invention, regulating n - The thickness of the GaN epitaxial layer 3b can conveniently achieve the desired reverse breakdown voltage of the Schottky barrier diode.

[0051] Preferably, the diode further includes a second insulating protection layer 6 b disposed on the first insulating protection layer 6 a , a partial region of the Schottky electrode 5 , and a partial region of the ohmic electrode 4 .

[0052] The ohmic electrode 4 includes a titanium layer, an aluminum layer, a nickel layer and a gold layer from bottom to top, wherein the titanium layer and the n + -GaN epitaxial layer 3a forms an ohmic contact, and the titanium layer and the n +The region in contact with the GaN epitaxial layer 3a is an ohmic contact region.

[0053] The Schottky electrode 5 includes a nickel nitride layer and a gold layer from bottom to top, wherein the nickel nitride layer and the n - -GaN epitaxial layer 3b forms a Schottky contact, and the nickel nitride layer and the n - The region in contact with the GaN epitaxial layer 3 b is a Schottky contact region.

[0054] The present invention is further described in detail below in conjunction with embodiments.

[0055] Example 1

[0056] This embodiment discloses a gallium nitride Schottky barrier diode with sapphire as substrate 1, using a 430 μm thick C-plane sapphire with an inclination of 0.15 degrees to the m-plane as the substrate, and the specific manufacturing method is as follows:

[0057] Z1: The substrate 1 with a clean surface is placed on the tray of the MOCVD reactor, and the surface is re-cleaned at high temperature (1020°C) in a reducing atmosphere, and then cooled to 550°C, and the organic compound of gallium trimethylgallium (TMGa) and ammonia (NH 3 ) as raw material, perform low-temperature growth of GaN material to form GaN buffer layer 2, and then gradually increase the temperature to crystallize the atomic sequence of the low-temperature GaN material. The thickness of GaN buffer layer 2 is controlled to be 10nm.

[0058] Z2: epitaxial growth of n using metal organic chemical vapor phase epitaxy + -GaN epitaxial layers 3a and n - -GaN epitaxial layer 3b, trimethylgallium (TMGa) as a gallium source and ammonia (NH ) as a nitrogen source are introduced into the reactor. 3 ), the epitaxial growth conditions are: furnace pressure 760Torr, temperature 1050℃, molar ratio of group V / III elements is 3600. The doping gas SiH 4 Si doping is used as the source to obtain n + -GaN epitaxial layers 3a and n - -GaN epitaxial layer 3b, adjust the doping gas SiH 4 The flow rate of the gallium organic compound (TMGa) can be adjusted to control its growth rate, and the desired thickness can be obtained by controlling the growth time. In this embodiment, n + -GaN epitaxial layer 3a has a thickness of 5 μm and a doping concentration of 5×10 18 cm -3 .n - -GaN epitaxial layer 3b has a thickness of 1.5 μm and a doping concentration of 8×1016 cm -3 .

[0059] Z3: In n - -GaN epitaxial layer 3b is evenly coated with photoresist, and after pre-baking, exposure, development and other processes, the n - The surface of the GaN epitaxial layer 3b has a photoresist in some areas, and the photoresist is used as a mask to remove the n-GaN epitaxial layer 3b without the photoresist by plasma etching. - -GaN epitaxial layer 3b is removed to expose n + -GaN epitaxial layer 3a, exposed n + -GaN epitaxial layer 3a upper surface is ohmic electrode setting area 13a, and then remove the unetched n - - Photoresist on the GaN epitaxial layer 3b region (ie, the Schottky electrode setting region 13b).

[0060] Z4: PECVD is used to deposit the ohmic electrode on the entire surface of the chip, i.e., the ohmic electrode setting area 13a, the Schottky electrode setting area 13b, and the n - -GaN epitaxial layers 3b and n + - On the sidewall of the step formed by the GaN epitaxial layer 3a, SiO 2 Insulating film layer, thickness is 500nm.

[0061] Z5: In SiO 2 The surface of the insulating film layer is uniformly coated with photoresist. After pre-baking, exposure, development and other processes, the photoresist on the ohmic electrode setting area 13a where the ohmic contact is to be formed is removed, and the photoresist on the non-ohmic contact area is retained. The photoresist is used as a mask, and a wet etching method is adopted, that is, BHF etching is used to remove the SiO2 on the ohmic contact area. 2 The insulating film layer exposes the n-type area where the ohmic contact is to be formed. + -GaN epitaxial layer 3a, then use electron beam evaporation to evaporate titanium layer, aluminum layer, nickel layer and gold layer in sequence, the thickness of each layer is 10nm, 100nm, 30nm, 150nm respectively. Then use gold peeling method to peel off the metal layer in the non-ohmic contact area, remove the residual photoresist on the chip surface, and then perform heat treatment in nitrogen atmosphere, the heat treatment temperature is 820℃, the heat treatment time is 30 seconds, and the ohmic electrode 4 is formed.

[0062] Z6: Evenly apply photoresist on the surface of the semi-finished chip forming the ohmic electrode 4, and after pre-baking, exposure, development and other processes, remove the photoresist on the Schottky electrode setting area 13b where the Schottky contact is to be formed, and retain the photoresist on the non-Schottky contact area on the chip surface. Use this photoresist as a mask and adopt a wet etching method, that is, use BHF to remove the SiO2 The insulating film layer is removed to expose the n-type Schottky contact area. - -GaN epitaxial layer, remove the photoresist on the surface of the chip in the non-Schottky contact area.

[0063] After that, photoresist is applied to the chip surface, and the area where the Schottky electrode is to be formed is exposed by photolithography. Then, a nickel nitride film with a thickness of 15 nm is deposited by using a method of electron beam evaporation of nickel assisted by nitrogen ion implantation. When depositing the nickel nitride film, the area where the nickel nitride film is to be deposited is n - -The nitrogen ion current density at the GaN epilayer is 0.02 μA cm -2 , the ions reach n - -GaN epitaxial layer surface is controlled between 20eV and 30eV. Under this condition, a good and dense nickel nitride film layer can be obtained. Then, a gold film is evaporated by electron beam, and its thickness is 500nm. Then, the metal layer in the non-Schottky electrode area is peeled off by gold peeling method, so that the edge of Schottky electrode 5 covers the first insulating layer 6a to form a field plate structure, and the manufacture of Schottky electrode 5 is completed. And remove the residual photoresist on the chip surface.

[0064] Preferably, a second insulating protection layer 6b may be provided on the surface of the diode according to the following steps:

[0065] SiO is deposited on the entire surface of the chip using PECVD. 2 The insulating film layer has a thickness of 300nm. The photoresist is evenly coated on the chip surface, and after pre-baking, exposure, development and other processes, the photoresist is not retained above the area corresponding to the part of the ohmic electrode 4 and the part of the Schottky electrode 5 on the chip surface. Then, the wet etching method is adopted, that is, BHF is used to remove the part of the SiO2 on the area of ​​the ohmic electrode 4 and the area of ​​the Schottky electrode 5. 2 The insulating film layer is removed to expose the pad area of ​​the ohmic electrode 4 and the Schottky electrode 5. At the same time, the second insulating protective layer 6b covers the first insulating protective layer 6a, and a portion of the edge of the second insulating protective layer 6b covers the edge of the ohmic electrode 4, and a portion of the edge covers the edge of the Schottky electrode 5. Then the photoresist on the surface of the chip is removed to complete the manufacture of the Schottky diode.

[0066] In this embodiment, the top view of the ohmic electrode setting region 13a and the Schottky electrode setting region 13b of the sub-vertical structure Schottky barrier diode is as shown in FIG. Figure 2As shown. On the surface of the square chip, there are two rectangular areas, namely, the right side is the ohmic electrode setting area 13a, and the left side is the Schottky electrode setting area 13b. The ohmic electrode 4 and the Schottky electrode 5 are respectively set on the ohmic electrode setting area 13a and the Schottky electrode setting area 13b. The area ratio of the ohmic electrode setting area 13a to the Schottky electrode setting area 13b is between 1: (1 to 1.5).

[0067] The shapes and positions of the ohmic electrode setting area and the Schottky electrode setting area are not limited to the above description, and there are many other options, such as: Figure 3 As shown, the circular area in the center of the chip is the Schottky electrode setting area 13b, and the area outside the Schottky electrode setting area 13b is the ohmic electrode setting area 13a. The area ratio of the ohmic electrode setting area 13a to the Schottky electrode setting area 13b is between 1: (1 to 1.5).

[0068] For example Figure 4 As shown, the Schottky electrode setting area 13b is set at the center of the chip and is an irregular graphic area. The ohmic electrode setting area 13a is set around the Schottky electrode setting area 13b. The Schottky electrode 5 is set at the center of the chip, and the ohmic electrode 4 is set at a corner of the chip.

[0069] The distance between the ohmic electrode 4 and the Schottky electrode 5 is 2-20 microns, preferably 10 microns. For the field plate structure of the Schottky electrode, the first insulating layer 6a is embedded under the Schottky electrode 5 by 1-10 microns, preferably 5 microns.

[0070] In the present invention, the nickel nitride film of the Schottky electrode 5 is - The GaN epitaxial layer 3b forms a Schottky contact, becoming the most important component of the GaN Schottky barrier diode, and completing the nonlinear rectification function of the Schottky barrier diode.

[0071] The nickel nitride film of the Schottky electrode is deposited by the method of nitrogen ion assisted injection electron beam evaporation nickel. By adjusting the ratio of the number of nitrogen ions generated by the nitrogen ion gun and the electron beam nickel evaporation rate and the energy of the nitrogen ions reaching the Schottky electrode deposition surface, NiN and Ni can be obtained. 2 N or Ni 3 N thin film or mixed thin film layer.

[0072] The present invention adopts a nickel nitride film layer formed by a method of nitrogen ion-assisted injection electron beam evaporation of nickel to replace the traditional metal to form Schottky contact, thereby reducing reverse leakage current and improving the stability of the Schottky barrier diode.

[0073] In the present invention, relatively cheap sapphire is used as the substrate, which reduces the manufacturing cost of the product. The present invention changes the method of using the traditional planar structure of the Schottky diode using sapphire as the substrate, and proposes a sub-vertical structure Schottky diode, thereby improving the reverse withstand voltage characteristics of the Schottky diode and improving the forward current density of the Schottky diode. A relatively high-performance device is obtained with a cheap substrate.

[0074] In addition, in the structure of the Schottky electrode of the present invention, a field plate structure is explicitly adopted to ease the electric field strength at the edge of the Schottky electrode, further improving the reverse breakdown voltage of the device. In summary, the present invention comprehensively improves the forward and reverse characteristics of the Schottky barrier diode from two aspects: the structure of the device and the manufacturing process of the device.

[0075] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A sub-vertical structure gallium nitride Schottky barrier diode, characterized in that: include: A substrate (1), and a buffer layer (2), n + -GaN epitaxial layer (3a) and n - -GaN epitaxial layer (3b); the n - -GaN epitaxial layer (3b) has an upper surface as a Schottky electrode setting area (13b), the n + - the upper surface of the GaN epitaxial layer (3a) is partially exposed, and the exposed portion is an ohmic electrode setting area (13a); A first insulating protective layer (6a), the first insulating protective layer (6a) covers the ohmic electrode setting area (13a) and the Schottky electrode setting area (13b), and the first insulating protective layer (6a) also covers the n + -GaN epitaxial layer (3a) and n - - On the step side wall surface formed by the GaN epitaxial layer (3b), the first insulating protection layer (6a) is provided with windows on the upper surfaces of the ohmic electrode setting region (13a) and the Schottky electrode setting region (13b); A Schottky electrode (5) arranged in a window portion of the Schottky electrode arrangement region (13b), wherein the edge of the Schottky electrode (5) covers the first insulating protection layer (6a) to form a field plate structure; An ohmic electrode (4), the ohmic electrode (4) being arranged in a window of the ohmic electrode arrangement area (13a); The method for manufacturing the sub-vertical structure gallium nitride Schottky barrier diode comprises the following steps: A. Growing buffer layer (2), n + -GaN epitaxial layer (3a), n - -GaN epitaxial layer (3b); B. In n - The local area of ​​the GaN epitaxial layer (3b) is etched to - -GaN epitaxial layer (3b) is removed, exposing n + The region of the GaN epitaxial layer (3a) constitutes the ohmic electrode setting region (13a), and the unetched n - - The GaN epitaxial layer (3b) region constitutes a Schottky electrode setting region (13b); C. On the upper surface of the ohmic electrode setting area (13a), the upper surface of the Schottky electrode setting area (13b) and n + -GaN epitaxial layer (3a) and n - A first insulating protective layer (6a) is deposited on the step side wall surface formed by the GaN epitaxial layer (3b), wherein the first insulating protective layer (6a) is provided with windows on the upper surfaces of the ohmic electrode setting region (13a) and the Schottky electrode setting region (13b); D. depositing a nickel nitride layer on the upper surface window portion of the Schottky electrode setting area (13b) by using a method of electron beam evaporation of nickel assisted by nitrogen ion injection, and then evaporating a gold layer on the nickel nitride layer by electron beam evaporation to form a Schottky electrode (5), wherein the edge of the Schottky electrode (5) covers the first insulating protective layer (6a) to form a field plate structure; E. An ohmic electrode (4) is formed in the upper surface window portion of the ohmic electrode setting area (13a) by using an electron beam evaporation process.

2. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: It also includes a second insulating protective layer (6b) arranged on the first insulating protective layer (6a), a partial area of ​​the Schottky electrode (5), and a partial area of ​​the ohmic electrode (4).

3. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: The substrate (1) is one of sapphire, silicon carbide, silicon, germanium, zinc oxide, lithium aluminum oxide, magnesium oxide, LiGaO2, GaN, GaAs, AlN, AlGaN, AlInN or ZrB2.

4. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: The ohmic electrode (4) comprises a titanium layer, an aluminum layer, a nickel layer and a gold layer from bottom to top, wherein the thickness of the titanium layer is 10-30 nm, the thickness of the aluminum layer is 80-150 nm, the thickness of the nickel layer is 30-60 nm, and the thickness of the gold layer is 50-500 nm. + -GaN epitaxial layer (3a) forms an ohmic contact.

5. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: The Schottky electrode (5) comprises a nickel nitride layer and a gold layer from bottom to top, the nickel nitride layer has a thickness of 10-30 nm, the gold layer has a thickness of 50-500 nm, and the nickel nitride layer and the gold layer have a thickness of 10-30 nm. - -GaN epitaxial layer (3b) forms a Schottky contact.

6. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: The thickness of the buffer layer (2) is between 1 and 30 nm, and the dislocation density is controlled at 1×10 11 / cm 2 the following.

7. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: The + -GaN epitaxial layer (3a) and n - -GaN epitaxial layer (3b) is deposited by metal organic chemical vapor phase epitaxy, n + -GaN epitaxial layer (3a) has a thickness of 3~5μm, n - -The thickness of the GaN epitaxial layer (3b) is 1~3μm.

8. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: The formation process of the ohmic electrode (4) comprises sequentially depositing a titanium layer, an aluminum layer, a nickel layer and a gold layer on the surface of a local area of ​​the ohmic electrode setting area (13a) by electron beam evaporation process, and heat treating in a nitrogen atmosphere at 500°C-950°C for 10-300 seconds.

9. The sub-vertical structure gallium nitride Schottky barrier diode according to claim 1, characterized in that: The diode further comprises a second insulating protective layer (6b), wherein the second insulating protective layer (6b) is deposited on the first insulating protective layer (6a), a partial area of ​​the Schottky electrode (5) and a partial area of ​​the ohmic electrode (4) by using a PECVD method.

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