Cu / TiN / beta-Ga2O3 Schottky diode and preparation method thereof

Abstract

The embodiment of the invention discloses a Cu / TiN / beta-Ga2O3 Schottky diode and a preparation method thereof. The Schottky diode comprises a cathode metal layer, an anode metal layer and a cathode metal layer, a Ga2O3 substrate layer; a Ga2O3 epitaxial layer; the TiN layer is located at the middle position of the upper surface of the Ga2O3 epitaxial layer; the two dielectric layers are located on the upper surface of the Ga2O3 epitaxial layer and are oppositely arranged on the two sides of the TiN layer; and the anode metal electrode layer adopts Cu as anode metal and is positioned on the upper surfaces of the TiN layer and the dielectric layer. According to the invention, the TiN layer is grown between the gallium oxide and the anode metal layer, so that the expansion of the Schottky metal layer to the gallium oxide layer is reduced, a relatively uniform contact interface is formed, and the uniformity of the height of the Cu / TiN / beta-Ga2O3 Schottky barrier is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power semiconductor devices, and particularly to a Cu / TiN / β-Ga 2 O 3 Schottky diode with high thermal stability and a preparation method thereof. Background Art

[0002] Power semiconductor devices have the advantages of large drive current, high breakdown voltage, fast speed, low power consumption, large output power, etc., and can achieve power control and conversion in different ranges. They are widely used in the power management of satellites, spacecrafts, and electric vehicles, and have great development potential in the fields of space and vehicle applications.

[0003] Gallium oxide (Ga 2 O 3 ) as an ultra-wide bandgap semiconductor is regarded as an ideal material for next-generation high-voltage and high-temperature power devices due to its ultra-high critical breakdown electric field strength and theoretical Baliga figure of merit; among them, β-Ga 2 O 3 Schottky barrier diodes have attracted much attention due to their low conduction loss, fast switching characteristics, and high-voltage resistance capabilities. However, like traditional gallium oxide Schottky diodes, β-Ga 2 O 3 Schottky barrier diodes are also prone to solid-state reactions between the metal and Ga 2 O 3 , resulting in an increase in the non-uniformity of its contact interface, making the metal / β-Ga 2 O 3 interface have insufficient thermal stability. For example, under high-temperature or long-term working conditions, Schottky metal electrodes (such as Ni, Pt, Ti, etc.) and β-Ga 2 O 3 are prone to solid-state diffusion reactions, resulting in the penetration of metal atoms into the β-Ga 2 O 3 surface layer to form a non-stoichiometric interfacial oxide layer; the interfacial reaction products will also significantly change the uniformity of the Schottky barrier height, leading to problems such as barrier localization distortion (manifested as a sharp increase in reverse leakage current, degradation of breakdown voltage, and deterioration of switching characteristics).

[0004] In summary, this non-uniformity not only affects the long-term stability and reliability of the device, but also directly reduces the thermal stability of the β-Ga 2 O 3 Schottky diode, making it difficult to meet the requirements for working in extreme environmental conditions. In addition, the unsatisfactory interfacial characteristics will also cause additional energy losses and reduce the overall system efficiency. That is to say, the problem of its poor high thermal stability has become one of the key factors restricting its wider application. Summary of the Invention

[0005] Based on this, in order to solve the deficiencies of the prior art, a Cu / TiN / β-Ga 2 O 3 Schottky diode with a high thermal stability interface structure is specifically proposed to give full play to the performance advantages of its ultra-wide bandgap semiconductor.

[0006] In order to achieve the above object, the technical solution is as follows:

[0007] A Cu / TiN / β-Ga 2 O 3 Schottky diode, characterized in that it sequentially includes, from bottom to top:

[0008] Cathode metal layer;

[0009] Ga 2 O 3 Substrate layer, the Ga 2 O 3 substrate layer is located on the upper surface of the cathode metal layer;

[0010] Ga 2 O 3 Epitaxial layer, the Ga 2 O 3 epitaxial layer is located on the upper surface of the Ga 2 O 3 substrate layer;

[0011] TiN layer, the TiN layer is located at the middle position on the upper surface of the Ga 2 O 3 epitaxial layer;

[0012] Dielectric layer, two dielectric layers are located on the upper surface of the Ga 2 O 3 epitaxial layer and are oppositely arranged on both sides of the TiN layer;

[0013] Anode metal electrode layer, the anode metal electrode layer uses Cu as the anode metal and is located on the upper surfaces of the TiN layer and the dielectric layer;

[0014] And a protective electrode metal layer, the protective electrode metal layer is located on the upper surface of the anode metal electrode layer.

[0015] Optionally, in one embodiment, the thickness of the TiN layer is between 1-10 nm.

[0016] Optionally, in one embodiment, the total thickness of the Ga 2 O 3 epitaxial layer is 12 μm, and the doping concentration is 5×1015 cm -3 ~1.5×10 16 cm -3 vary between

[0017] Optionally, in one embodiment, the doping concentration of the substrate of the Ga 2 O 3 substrate layer varies between 1.0×10 18 cm -3 ~2×10 19 cm -3 vary between

[0018] Optionally, in one embodiment, the cathode metal of the cathode metal layer is metal titanium Ti.

[0019] In addition, the present invention also provides a method for manufacturing a Cu / TiN / β-Ga 2 O 3 Schottky diode, characterized by comprising the following steps:

[0020] S1. Prepare a Ga 2 O 3 substrate layer of the Cu / Ti / β-Ga 2 O 3 Schottky diode device structure;

[0021] S2. Epitaxially grow a drift region on the upper surface of the substrate layer once to form a Ga 2 O 3 epitaxial layer,

[0022] S3. Deposit a cathode metal on the lower surface of the substrate layer and perform a rapid annealing treatment to form a cathode metal layer;

[0023] S4. Deposit a corresponding field plate dielectric on the upper surface of the drift region, and perform photolithography and etching processes to form a field plate at the anode edge by etching technology;

[0024] S5. Perform a pretreatment of the Schottky contact layer structure, that is, first clean the upper surface of the aforementioned Ga 2 O 3 epitaxial layer, secondly perform a post-etching treatment on the field plate, and perform a high-temperature pretreatment on the current semiconductor device structure;

[0025] S6. Use the ALD technology to grow a TiN thin film on the upper surface of the aforementioned Ga 2 O 3 epitaxial layer and etch the TiN thin film located above the field plate to form the TiN layer;

[0026] S7. The anode metal electrode layer and the protective electrode metal layer are sequentially formed by magnetron sputtering deposition technology to form a Schottky diode device;

[0027] S8. The Schottky diode device is placed in a nitrogen atmosphere at 300°C - 500°C for rapid annealing treatment.

[0028] Implementing the embodiments of the present invention will have the following beneficial effects:

[0029] First, by growing a TiN layer between gallium oxide and the anode metal layer, the present invention reduces the expansion of the Schottky metal layer into the gallium oxide layer, forms a relatively uniform contact interface, and effectively improves the uniformity of the Schottky barrier height of Cu / TiN / β-Ga 2 O 3 At the same time, through the corresponding process treatment, the order of magnitude of the reverse leakage current of the Schottky barrier diode remains almost unchanged at different test temperatures. Therefore, the Cu / TiN / β-Ga 2 O 3 SBD Schottky diode structure of the present invention has higher thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0031] Among them:

[0032] Figure 1 is the cell structure schematic diagram of the Cu / TiN / β-Ga 2 O 3 SBD device with high thermal stability;

[0033] Figure 2 is Figure 1 the forward conduction current density-voltage curve of the SBD device with the cell structure shown at different test temperatures. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. It can be understood that the terms "first", "second", etc. used in the present invention may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. Both the first element and the second element are elements, but they are not the same element.

[0036] Traditional β-Ga 2 O 3 Due to core problems such as poor thermal stability at the metal / semiconductor interface and high interface state density in Schottky diodes, their high-temperature electrical performance and reliability are far from reaching the theoretical expectations, severely restricting their further commercial applications. Therefore, there is an urgent need to develop a new type of β-Ga 2 O 3 Schottky diode to fully utilize the performance advantages of its ultra-wide bandgap semiconductor.

[0037] For the above purpose, in this embodiment, a Cu / TiN / β-Ga 2 O 3 Schottky diode is specifically proposed. As Figure 1 shown, this Cu / TiN / β-Ga 2 O 3 Schottky diode successively includes from bottom to top:

[0038] Cathode metal layer;

[0039] Ga 2 O 3 Substrate layer, and the Ga 2 O 3 substrate layer is located on the upper surface of the cathode metal layer;

[0040] Ga 2 O 3 Epitaxial layer, and the Ga 2 O 3 epitaxial layer is located on the upper surface of the Ga 2 O 3 substrate layer;

[0041] TiN layer, and the TiN layer is located at the middle position on the upper surface of the Ga 2 O 3 epitaxial layer;

[0042] The dielectric layer, and two of the dielectric layers are located on the upper surface of the Ga 2 O 3 epitaxial layer and are oppositely arranged on both sides of the TiN layer;

[0043] The anode metal electrode layer, which uses Cu as the anode metal and is located on the upper surfaces of the TiN layer and the dielectric layer;

[0044] And the protective electrode metal layer, which is located on the upper surface of the anode metal electrode layer.

[0045] Based on the above design, it can be seen that in the present invention, a TiN layer is grown between the gallium oxide and the anode metal to form a TiN interface layer, reducing the extension of the Schottky metal layer into the gallium oxide layer, forming a relatively uniform contact interface, and improving the uniformity of the Cu / TiN / β-Ga 2 O 3 Schottky barrier height, making the order of magnitude of the reverse leakage current of the Schottky barrier diode almost unchanged at different test temperatures, thereby significantly improving the thermal stability and electrical performance of the Cu / β-Ga 2 O 3 Schottky diode. The TiN interface layer plays a diffusion barrier role on the one hand. That is, due to the crystal structure of TiN, its high melting point and chemical inertness can effectively block the diffusion of Cu atoms into the β-Ga 2 O 3 layer and effectively suppress the corresponding diffusion coefficient. At the same time, the aforementioned rapid annealing process enables the TiN and β-Ga of this device 2 O 3 interface to form a stable Ti-O-N chemical bonding layer through high-temperature annealing, effectively blocking the redox reaction between Cu and Ga 2 O 3 ; on the other hand, the energy band structure of the TiN interface layer and the β-Ga 2 O 3 interface can effectively improve the uniformity of the Schottky barrier height (SBH). The improvement of the SBH uniformity weakens the local "hot spot" effect of the reverse leakage current, and the thermionic emission current distribution is more uniform at high temperatures. As a result, the order of magnitude of the reverse leakage current of the Schottky barrier diode is almost unchanged at different test temperatures. Therefore, it can be said that the TiN interface layer is a dual-functional layer structure (diffusion barrier layer + barrier modulation layer), which can effectively improve the thermal stability of the Cu / β-Ga 2 O 3 interface.

[0046] Among them, in some specific embodiments, the thickness of the TiN layer is controlled between 1 - 10 nm. The reason is that if the thickness of the TiN layer is too large, the free electron concentration at its interface will decrease, and electrons are difficult to pass through the barrier, thereby affecting the forward conduction performance of the device.

[0047] Among them, in some specific embodiments, the Ga 2 O 3 The total thickness of the epitaxial layer is 12 μm, and the doping concentration varies between 5×10 15 cm -3 ~1.5×10 16 cm -3 Preferably, its total thickness is 12 μm and the doping concentration is 1.0×10 16 cm -3 .

[0048] Among them, in some specific embodiments, the Ga 2 O 3 The substrate doping concentration of the substrate layer varies between 1.0×10 18 cm -3 ~2×10 19 cm -3 Preferably, the doping concentration of its substrate is 3.0×10 18 cm -3 .

[0049] Among them, in some specific embodiments, the cathode metal of the cathode metal layer is metal titanium Ti to prevent the internal structure from being eroded by the external environment (such as moisture, oxygen or other harmful substances), extend the service life of the Schottky diode device and maintain its performance stable.

[0050] Based on the same inventive concept, the present invention also proposes a preparation method of a Cu / TiN / β-Ga 2 O 3 Schottky diode, which is characterized by including the following steps:

[0051] S1. Prepare the Ga 2 O 3 substrate layer of the Cu / Ti / β-Ga 2 O 3 Schottky diode device structure;

[0052] S2. Form a drift region by epitaxy on the upper surface of the substrate layer to form a Ga 2 O 3 epitaxial layer,

[0053] S3. Deposit a cathode metal on the lower surface of the substrate layer and perform a rapid annealing treatment to form a cathode metal layer;

[0054] S4. Deposit a corresponding field plate dielectric on the upper surface of the drift region (deposit 300 nm SiO by PECVD 2), and perform photolithography and etching processes to form a field plate at the anode edge through etching technology;

[0055] S5. Perform pretreatment on the Schottky contact layer structure, that is, first clean the upper surface of the aforementioned Ga 2 O 3 epitaxial layer, secondly perform over-etching post-treatment on the field plate, and perform high-temperature pretreatment on the current semiconductor device structure;

[0056] S6. Use ALD technology to grow a TiN thin film on the upper surface of the aforementioned Ga 2 O 3 epitaxial layer and etch the TiN thin film located above the field plate to form the TiN layer;

[0057] S7. Use magnetron sputtering deposition technology to sequentially form the anode metal electrode layer and the protective electrode metal layer to form a Schottky diode device;

[0058] S8. Place the Schottky diode device in a nitrogen atmosphere at 300°C - 500°C for rapid annealing treatment for 5 minutes.

[0059] Through the above process steps, such as optimizing the cleaning process, introducing the TiN layer, etc., accurately control the device interface quality, barrier uniformity and high-temperature stability, and significantly improve the device performance.

[0060] Among them, in some specific embodiments, the cleaning of the upper surface of the aforementioned Ga 2 O 3 epitaxial layer in S5 means sequentially cleaning and drying with acetone, isopropyl alcohol (IPA) and deionized water to remove organic pollutants and particles to ensure that the interface for subsequent metal deposition is pollution-free.

[0061] Among them, in some specific embodiments, due to over-etching, the over-etching post-treatment of the field plate and the high-temperature pretreatment of the current semiconductor device structure in S5 mean: using a 25wt% tetramethylammonium hydroxide (TMAH) solution to perform wet chemical treatment on the sample etched in S4 (the wet chemical treatment is carried out at 90°C for 5 minutes), and then washing and drying the chemically treated sample with deionized water to remove dry etching residues and repair the surface roughness caused by dry etching, and reduce the interface state density.

[0062] Among them, in some specific embodiments, the high-temperature pretreatment of the current semiconductor device structure in S5, that is, perform O 2 treatment at a high temperature of 400°C for 5 minutes to remove residual hydrocarbons and other surface substances and enhance the interface adhesion force.

[0063] Among them, in some specific embodiments, the thickness of the TiN layer is preferably 5 nm.

[0064] Among them, in some specific embodiments, the preferred protective electrode metal layer deposits Ti(5 nm) by magnetron sputtering, and after deposition, it is annealed at 400 °C for 5 minutes under N 2 atmosphere.

[0065] Based on the above preferred values, a Cu / TiN / β-Ga 2 O 3 Schottky diode device is prepared and corresponding tests are carried out, such as Figure 2 the Cu / TiN / β-Ga 2 O 3 Schottky diode device. At different test temperatures, the current density curve of the device. When the device is placed under forward bias, the turn-on voltage of the device is about 2 V, and the on-resistance of the device is 24.9 mΩ·cm -2 . It can be seen from the figure that when the device is placed under small-voltage reverse bias, the reverse leakage current density of the device can reach 10 -8 A / cm -2 . When the test temperature of the device is changed (100 °C - 200 °C), the order of magnitude of the reverse leakage current of the device hardly changes. That is, the Cu / TiN / β-Ga 2 O 3 SBD Schottky diode structure described in this case has higher thermal stability.

[0066] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A Cu / TiN / β-Ga2O3 Schottky diode, characterized in that: From bottom to top, they include: cathode metal layer; A Ga2O3 substrate layer, wherein the Ga2O3 substrate layer is located on the upper surface of the cathode metal layer; A Ga2O3 epitaxial layer, wherein the Ga2O3 epitaxial layer is located on an upper surface of the Ga2O3 substrate layer; A TiN layer, wherein the TiN layer is located at a middle position of an upper surface of the Ga2O3 epitaxial layer; A dielectric layer, wherein two dielectric layers are located on the upper surface of the Ga2O3 epitaxial layer and are arranged on both sides of the TiN layer relatively; an anode metal electrode layer, wherein the anode metal electrode layer uses Cu as an anode metal and is located on the upper surfaces of the TiN layer and the dielectric layer; and a protective electrode metal layer, wherein the protective electrode metal layer is located on the upper surface of the anode metal electrode layer.

2. The Cu / TiN / β-Ga2O3 Schottky diode according to claim 1, characterized in that: The thickness of the TiN layer is between 1-10 nm.

3. The Cu / TiN / β-Ga2O3 Schottky diode according to claim 1, characterized in that: The total thickness of the Ga2O3 epitaxial layer is 12 μm, and the doping concentration is 5×10 15 cm -3 ~1.5×10 16 cm -3 Changes between.

4. The Cu / TiN / β-Ga2O3 Schottky diode according to claim 1, characterized in that: The substrate doping concentration of the Ga2O3 substrate layer is in the range of 1.0×10 18 cm -3 ~2×10 19 cm -3 between.

5. The Cu / TiN / β-Ga2O3 Schottky diode according to claim 1, characterized in that: The cathode metal of the cathode metal layer is metal titanium Ti.

6. A method for preparing a Cu / TiN / β-Ga2O3 Schottky diode as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1. preparing the Ga2O3 substrate layer of the Cu / Ti / β-Ga2O3 Schottky diode device structure; S2, forming a drift region on the upper surface of the substrate layer by epitaxy once to form a Ga2O3 epitaxial layer, S3, depositing cathode metal on the lower surface of the substrate layer and performing rapid annealing to form a cathode metal layer; S4, depositing a corresponding field plate medium on the upper surface of the drift region, and performing photolithography and etching to form a field plate at the edge of the anode by etching technology; S5, pre-treating the Schottky contact layer structure, that is, first cleaning the upper surface of the Ga2O3 epitaxial layer, then post-etching the field plate, and performing high-temperature pre-treatment on the current semiconductor device structure; S6, growing a TiN film on the upper surface of the Ga2O3 epitaxial layer using ALD technology and etching the TiN film located above the field plate to form the TiN layer; S7, using magnetron sputtering deposition technology to sequentially form the anode metal electrode layer and the protective electrode metal layer to form a Schottky diode device; S8, placing the Schottky diode device in a nitrogen atmosphere at 300° C.-500° C. for rapid annealing treatment.

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