A nitride power device with a composite drain structure and a method of fabricating the same

Abstract

The application discloses a nitride power device with a composite drain structure, which comprises a GaN channel layer, an AlGaN barrier layer, source metal, drain metal and gate metal, the channel layer and the barrier layer form a heterojunction, and the source metal, the drain metal and the gate metal are arranged on the barrier layer; a plurality of p-type nitride structures are arranged between the drain metal and the barrier layer and are arranged in a separate and spaced manner, and the drain metal and the p-type nitride structures form an ohmic contact. The application further discloses a manufacturing method of the nitride power device with the composite drain structure. The p-type nitride structure is introduced to the drain, the drain metal and the p-type nitride structure form an ohmic contact, the hole injection is realized when a forward bias is applied, the channel resistance is reduced, and the peak current processing capacity of the device is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a nitride power device with a composite drain structure and a manufacturing method thereof. Background Art

[0002] The spontaneous polarization and piezoelectric polarization effects of wide-bandgap semiconductor gallium nitride-based materials (GaN, AlGaN, InGaN, etc.) generate a high-density and high-mobility 2DEG within the AlGaN / GaN heterojunction channel, making GaN-based HEMT devices a highly efficient, high-power density power device solution, offering higher breakdown voltage and power density. Many applications require GaN devices to remain operational or unaffected during transient high-current conditions (such as startup, power outages, lightning strikes, short-circuit faults, etc.), making the peak current handling capability of GaN devices crucial. Conventional HEMT devices, however, have limited peak current handling capabilities, requiring application limitations. For example, a freewheeling diode built into the half-bridge to limit the switching current, or external protection devices, can prevent device damage. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a nitride power device with a composite drain structure and a method for manufacturing the same.

[0004] In order to achieve the above objectives, the technical solution of the present invention is:

[0005] A nitride power device with a composite drain structure, characterized in that it includes a GaN channel layer, an AlGaN barrier layer, a source metal, a drain metal, and a gate metal, wherein the channel layer and the barrier layer form a heterojunction, and the source metal, the drain metal, and the gate metal are arranged on the barrier layer; and further includes a plurality of p-type nitride structures, wherein the plurality of p-type nitride structures are arranged between the drain metal and the barrier layer and are discretely spaced apart, and the drain metal forms an ohmic contact with the p-type nitride structures.

[0006] Optionally, the plurality of p-type nitride structures are strip-shaped structures, arranged along the gate length direction, and the length of the plurality of p-type nitride structures in the gate width direction is less than or equal to the drain metal structure.

[0007] Optionally, the plurality of p-type nitride structures are strip-shaped structures, arranged along the gate width direction, and have a length in the gate length direction that is less than or equal to that of the drain metal.

[0008] Optionally, the plurality of p-type nitride structures are block structures and are arranged at equal intervals.

[0009] Optionally, the doping concentration of the p-type nitride structure is 1×10 17 -1×1021 cm -3 .

[0010] Optionally, the areas of the plurality of p-type nitride structures account for 0.2-0.8 of the area of ​​the drain metal.

[0011] Optionally, the material of the p-type nitride structure is p-GaN, p-AlGaN, p-InGaN or p-InAlGaN.

[0012] Optionally, the material of the drain metal includes Ni, Pd, Au, and alloys and compounds including at least one of Ni, Pd, and Au.

[0013] Optionally, it further includes a p-type nitride layer disposed between the gate metal and the barrier layer, and the p-type nitride layer is disposed in the same layer as the p-type nitride structure.

[0014] The method for manufacturing the nitride power device with a composite drain structure is characterized by comprising the following steps:

[0015] 1) providing an epitaxial structure including a channel layer and a barrier layer, defining a drain region on the barrier layer, and forming a plurality of discrete and spaced p-type nitride structures in the drain region;

[0016] 2) Depositing a drain metal in the drain region to cover the p-type nitride structure, and preparing a gate metal.

[0017] Optionally, in step 1), a p-type nitride epitaxial layer is formed on the barrier layer, and the p-type nitride epitaxial layer is etched to form the p-type nitride structure; or, the p-type nitride structure is formed in a partial area of ​​the drain region by a selective epitaxial process.

[0018] The beneficial effects of the present invention are:

[0019] 1) A p-type nitride structure is introduced into the drain, and the drain metal forms an ohmic contact with the p-type nitride structure. Through hole injection during forward bias, the channel resistance is reduced, the peak current handling capability of the device is improved, and the device reliability is improved.

[0020] 2) By providing a plurality of discrete and spaced p-type nitride structures, when the device is turned on, especially at the moment of excessive current, there will be no local current concentration or even excessive current that may cause device failure, thereby further improving device reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the front view of the nitride power device with a composite drain structure according to Example 1;

[0022] Figure 2 for Figure 1 A top view of the source metal, drain metal, and gate metal, showing the positional relationship between the drain metal and the p-type nitride structure;

[0023] Figure 3 This is a process flow chart of Example 1;

[0024] Figure 4 Schematic diagram of the front view of the nitride power device with a composite drain structure according to Example 2;

[0025] Figure 5 for Figure 4 A top view of the source metal, drain metal, and gate metal, showing the positional relationship between the drain metal and the p-type nitride structure;

[0026] Figure 6 for Figure 5 Cross-sectional view at position d-d';

[0027] Figure 7 This is a process flow chart of Example 2;

[0028] Figure 8 Schematic diagram of the front view of the nitride power device with a composite drain structure according to Example 3;

[0029] Figure 9 Schematic diagram of the positional relationship between the drain metal and the p-type nitride structure of Example 4. DETAILED DESCRIPTION

[0030] The present invention is further explained below with reference to the accompanying drawings and specific embodiments. The drawings are provided for illustrative purposes only to facilitate understanding of the present invention, and their specific proportions may be adjusted according to design requirements. Those skilled in the art will understand that the vertical relationships between components and the definitions of front and back in the figures described herein refer to the relative positions of components. Therefore, they can be flipped to present the same components, and all such representations are within the scope of this specification.

[0031] Example 1

[0032] refer to Figure 1 and Figure 2A nitride power device 100 with a composite drain structure includes a substrate 1, a buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, a plurality of p-type nitride structures 5a, a source metal 6, a drain metal 7, and a gate metal 8. The GaN channel layer 3 and the AlGaN barrier layer 4 form a heterojunction, with a two-dimensional electron gas existing between them. The source metal 6, the drain metal 7, and the gate metal 8 are disposed on the barrier layer 4, with the gate metal 8 located between the source metal 6 and the drain metal 7. A plurality of p-type nitride structures 5a are disposed between the drain metal 7 and the barrier layer 4 and are discretely spaced apart. Ohmic contacts are formed between the drain metal 7 and the p-type nitride structures 5a.

[0033] In this embodiment, several p-type nitride structures 5a are strip-shaped structures arranged along the gate length. Their length in the gate width direction is the same as the length of the drain metal 7 in this direction, both being 500 to 2000 μm. Alternatively, the length of the p-type nitride structures 5a in the gate width direction can be smaller than the length of the drain metal 7 in this direction. The gate length direction here refers to the span of the gate between the source and drain (i.e., the horizontal direction, as indicated by arrow A in the figure). The gate width direction is perpendicular to the gate length direction (i.e., the vertical direction, as indicated by arrow B in the figure). The term "several" here refers to ≥2. The total area of ​​these strip-shaped p-type nitride structures 5a accounts for 0.2-0.8%, for example, 50%, of the area (cross-sectional area) of the drain metal 7. Depending on specific performance requirements and manufacturing process design, they can be arranged in parallel with equal spacing. More specifically, the width of the p-type nitride structures 5a can be set to be the same as the width of the spacing, so that they are evenly distributed in the gate length direction and extend through the drain region in the gate width direction.

[0034] The material of the p-type nitride structure 5a is p-GaN, p-AlGaN, p-InGaN or p-InAlGaN, with a thickness of 50-100 nm and a doping concentration of 1×10 17 -1×10 21 cm -3 , more preferably 1×10 18 -1×10 20 cm -3 The drain metal 7 has a thickness of 200-300nm and covers and encapsulates the p-type nitride structure 5a. Consequently, the drain metal 7 partially forms an ohmic contact with the p-type nitride structure 5a and partially contacts the barrier layer 4. When a forward voltage is applied to the drain, the PN junction formed by the p-type nitride structure and the underlying n-type nitride conducts forward, injecting holes into the channel. Due to the conductivity modulation effect, the channel exhibits very low resistance, allowing the device to handle large currents.

[0035] The metal systems that can be used for the source metal 6 include Ti, Al, Ni, Au, Ta, etc., and alloys and compounds including the above metal systems; the metal systems that can be used for the drain metal 7 include Ni, Pd, Au, etc., and alloys and compounds including the above metal systems; the metal systems that can be used for the gate metal 8 include Ni, Pd, Au, Ti, Al, W, etc., and alloys and compounds including the above metal systems.

[0036] refer to Figure 3 The manufacturing method of the nitride power device 100 is as follows: first, an epitaxial structure including a substrate 1, a buffer layer 2, a GaN channel layer 3, and an AlGaN barrier layer 4 is provided; and a p-type nitride epitaxial layer 5 ( Figure 3-1 ); then, a portion of the drain region is defined as a p-type nitride structure region by photolithography, and then the p-type nitride epitaxial layer 5 outside the p-type nitride structure region is removed by etching methods such as ICP and RIE, thereby forming a plurality of discretely spaced p-type nitride structures 5a ( Figure 3-2 ); Then, the source region, drain region and gate region of the device are defined by photolithography, and the source metal 6, drain metal 7 and gate metal 8 are prepared by evaporation, sputtering and the like. Figure 3-3 ). In addition, during or after the above steps, conventional steps such as defining the active area of ​​the device by photolithography, forming a high-resistance area outside the active area by ion implantation or etching, and depositing a passivation layer are also included.

[0037] In this embodiment, by arranging the p-type nitride in regular strips, the device is turned on, especially at the moment of excessive current, and the current is evenly distributed, without causing local current concentration or even excessive current that causes device failure, thereby further improving the reliability of the device.

[0038] Example 2

[0039] refer to Figure 4-Figure 6 The difference between the nitride power device 200 of Example 2 and Example 1 is that the plurality of p-type nitride structures 5b are strip-shaped structures arranged along the gate width direction, and their length in the gate length direction is the same as the length of the drain metal 7 in that direction, both being 1 to 20 μm; and their length in the gate width direction is 0.5 to 100 μm. Furthermore, the length of the p-type nitride structure 5b in the gate length direction can also be made shorter than the length of the drain metal 7 in that direction. Similarly, the plurality of p-type nitride structures 5b are uniformly arranged in the gate width direction and penetrate the drain in the gate length direction. The term "several" herein refers to ≥2, for example, 4 to 10.

[0040] refer to Figure 7The manufacturing method of the nitride power device 200 is to first provide an epitaxial structure including a substrate 1, a buffer layer 2, a GaN channel layer 3, and an AlGaN barrier layer 4 ( Figure 7-1 ); then, photolithography is used to define a portion of the drain region as a p-type nitride structure region, and a secondary epitaxial growth technique is used to selectively grow the region to form a plurality of discretely spaced p-type nitride structures 5b ( Figure 7-2 ); Then, the source region, drain region and gate region of the device are defined by photolithography, and the source metal 6, drain metal 7 and gate metal 8 are prepared by evaporation, sputtering and the like. Figure 7-3 ).

[0041] The manufacturing method of this embodiment and the manufacturing method of Example 1 are interchangeable and are not limited thereto.

[0042] Example 3

[0043] refer to Figure 8 The nitride power device 300 of Example 3 differs from Example 1 in that it further includes a p-type nitride layer 9 disposed between the gate metal 8 and the barrier layer 4. The p-type nitride layer 9 is co-located with the p-type nitride structure 5a and can be formed simultaneously using the same process. For example, using the method of Example 1, a portion of the drain region is simultaneously defined as a p-type nitride structure region and a gate region (or can be defined separately) by photolithography. Subsequently, an etching method such as ICP or RIE is used to remove the p-type nitride epitaxial layer 5 outside the p-type nitride structure region and the gate region, thereby forming a plurality of discretely spaced p-type nitride structures 5a and a p-type nitride layer 9. Alternatively, for example, the method of Example 2 is used, and photolithography is used to define a portion of the drain region as a p-type nitride structure region and a gate region. Through secondary epitaxial technology, selective epitaxy is performed to form a plurality of discrete and spaced p-type nitride structures 5b in a portion of the drain region, and a p-type nitride layer 9 is formed in the gate region.

[0044] Example 4

[0045] The difference between Example 4 and Example 1 lies in the structure and arrangement of the p-type nitride structure. In this embodiment, the p-type nitride structure 5c is a block structure and is arranged at equal intervals; more specifically, the cross-section of the p-type nitride structure 5c is circular with a radius of 0.5 to 10 μm, preferably 1 to 5 μm, and is arranged in a honeycomb shape. For example, within the coverage area of ​​the drain metal 7, 5 to 20 p-type nitride structures 5c can be set, and the area and spacing of the p-type nitride structure 5c are designed so that the total area of ​​the p-type nitride structure 5c accounts for 0.2-0.8 of the area of ​​the drain metal 7. In this embodiment, the p-type nitrides are distributed at equal intervals, and the device is turned on, especially at the moment of excessive current, the current is evenly distributed, and there will be no local current concentration, or even excessive current causing device failure, thereby further improving the reliability of the device.

[0046] In addition, in other embodiments, the gate structure may also be a known structure such as a Schottky gate, a recessed gate, or a MIS-HEMT gate, and the specific structure of the gate is not limited.

[0047] The above embodiments are only used to further illustrate a nitride power device with a composite drain structure and a manufacturing method thereof of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the scope of protection of the technical solution of the present invention.

Claims

1. A nitride power device with a composite drain structure, characterized in that: The device comprises a GaN channel layer, an AlGaN barrier layer, a source metal, a drain metal and a gate metal, wherein the channel layer and the barrier layer form a heterojunction, and the source metal, the drain metal and the gate metal are arranged on the barrier layer; the device also comprises a plurality of p-type nitride structures, wherein the plurality of p-type nitride structures are arranged between the drain metal and the barrier layer and are discretely spaced apart, and the drain metal forms an ohmic contact with the p-type nitride structures; the plurality of p-type nitride structures are strip structures or block structures and are spaced apart at equal distances.

2. The nitride power device with a composite drain structure according to claim 1, wherein: The plurality of p-type nitride structures are strip-shaped structures, arranged along the gate length direction, and the length in the gate width direction is less than or equal to the drain metal.

3. The nitride power device with a composite drain structure according to claim 1, wherein: The plurality of p-type nitride structures are strip-shaped structures, arranged along the gate width direction, and have a length in the gate length direction that is less than or equal to the drain metal.

4. The nitride power device with a composite drain structure according to claim 1, wherein: The doping concentration of the p-type nitride structure is 1×10 17 -1×10 21 cm -3 .

5. The nitride power device with a composite drain structure according to claim 1, wherein: The areas of the plurality of p-type nitride structures account for 0.2-0.8 of the area of ​​the drain metal.

6. The nitride power device with a composite drain structure according to claim 1, wherein: The material of the p-type nitride structure is p-GaN, p-AlGaN, p-InGaN or p-InAlGaN.

7. The nitride power device with a composite drain structure according to claim 1, wherein: The material of the drain metal includes Ni, Pd, Au, and alloys and compounds including at least one of Ni, Pd, and Au.

8. The nitride power device with a composite drain structure according to claim 1, wherein: It also includes a p-type nitride layer disposed between the gate metal and the barrier layer, wherein the p-type nitride layer is disposed in the same layer as the p-type nitride structure.

9. A method for manufacturing a nitride power device with a composite drain structure according to any one of claims 1 to 8, characterized in that The following steps are involved: 1) providing an epitaxial structure including a channel layer and a barrier layer, defining a drain region on the barrier layer, and forming a plurality of discrete and spaced p-type nitride structures in the drain region; 2) Depositing a drain metal in the drain region to cover the p-type nitride structure, and preparing a gate metal.

10. The production method according to claim 9, characterized in that: In step 1), a p-type nitride epitaxial layer is formed on the barrier layer, and the p-type nitride epitaxial layer is etched to form the p-type nitride structure; or, the p-type nitride structure is formed in a portion of the drain region by a selective epitaxial process.

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