GaN-based HEMT device structure

Abstract

The utility model discloses a GaN-based HEMT (High Electron Mobility Transistor) device structure. Comprising a substrate, a nitride buffer layer, a nitride channel layer and a nitride barrier layer, a pattern layer is also arranged between the substrate and the nitride buffer layer; the pattern layer comprises a first structure layer, a second structure layer and a third structure layer, the first structure layer comprises a plurality of convex structures, the second structure layer covers the top surfaces and the side surfaces of the plurality of convex structures, and the third structure layer continuously covers the second structure layer and part of the substrate between the adjacent convex structures; the second structural layer is a film layer with passivation doping, and the third structural layer is a film layer with a nanoporous structure. The lateral epitaxial growth capability of nitride materials is improved, dislocation extension is blocked, and the epitaxial quality is improved; according to the GaN-based HEMT device and the manufacturing method thereof, the two-dimensional electron gas in the nitride channel layer is prevented from being influenced by charge aggregation, so that the stability of drain electrode output current in the nitride channel layer is ensured, current collapse is avoided, and the GaN-based HEMT device with excellent performance is obtained.

Description

Technical Field

[0001] The utility model relates to the technical field of third-generation semiconductors, in particular to a GaN-based HEMT device structure. Background Art

[0002] Gallium nitride (GaN), as a third-generation semiconductor material, has the characteristics of high bandgap width, high critical breakdown electric field, high carrier saturation migration velocity, high thermal conductivity and direct band gap. It has great application prospects in the field of high-temperature, high-frequency and high-power microelectronic devices.

[0003] In recent years, almost all industries have undergone electronic transformation, and GaN high electron mobility transistors (HEMTs) are representative of this transformation, which has great potential in high-frequency power applications. Due to heterogeneous epitaxy on heterogeneous substrates such as silicon, sapphire or SiC, the lattice constant and thermal mismatch between different materials will produce dislocations or defects, which will extend upward with the growth of the epitaxial layer, and even the entire epitaxial layer, forming a leakage channel that seriously affects the performance of the device. At present, the leakage performance of the device is usually improved by increasing the thickness of the buffer layer on the substrate, but the yield is low and the cost is high. Electrons entering the buffer layer increase the leakage current of the buffer layer, which is prone to breakdown and causes device damage and failure.

[0004] In summary, further reducing the defect distribution in the epitaxial layer and improving the crystal quality of the epitaxial layer based on the existing process, and improving the leakage performance of semiconductor devices are of great significance for promoting the application and industrialization of GaN HEMT. Utility Model Content

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a GaN-based HEMT device structure.

[0006] In order to achieve the above-mentioned utility model purpose, the technical solution adopted by the utility model includes:

[0007] In a first aspect, the utility model provides a GaN-based HEMT device structure, comprising a substrate, a nitride buffer layer, a nitride channel layer, and a nitride barrier layer stacked in sequence along a first direction;

[0008] A graphic layer is also provided between the substrate and the nitride buffer layer;

[0009] The graphic layer comprises a first structural layer, a second structural layer and a third structural layer sequentially arranged along the first direction, the first structural layer comprises a plurality of convex structures arranged in an array along a second direction intersecting the first direction, the second structural layer is divided into a plurality of independent film layers, respectively covering the top surfaces and side surfaces of the plurality of convex structures, and the third structural layer continuously covers the second structural layer and a portion of the substrate between any adjacent convex structures;

[0010] Wherein, the second structural layer is a film layer with passivation doping, and the third structural layer is a film layer with a nanoporous structure.

[0011] Based on the above technical solution, compared with the prior art, the beneficial effects of the utility model at least include:

[0012] The GaN-based HEMT device structure provided by the utility model forms a graphic layer located between a substrate and a buffer layer by arranging a plurality of protruding structures in a first structure layer, cooperating with a second structure layer with passivation doping covering the top surface and the side surface thereof, and a third structure layer with a nano-scale porous structure that completely covers and isolates, thereby at least improving the lateral epitaxial growth ability of the nitride material when the device structure is formed, blocking dislocation extension, and improving the epitaxial quality; and utilizing the intermediate passivation doped film layer to play a passivation role on charge defects, significantly reducing the charge accumulation capture effect, avoiding the influence of charge accumulation on the two-dimensional electron gas in the nitride channel layer, thereby ensuring the stability of the drain output current in the nitride channel layer, avoiding current collapse, and obtaining a GaN-based HEMT device with excellent performance.

[0013] The above description is only an overview of the technical solution of the utility model. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them according to the contents of the specification, the following is a preferred embodiment of the utility model with detailed drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of a partial cross-sectional structure of a GaN-based HEMT device structure provided by a typical implementation case of the utility model;

[0015] Figure 2 It is a complete cross-sectional structural schematic diagram of a GaN-based HEMT device structure provided in a typical implementation case of the utility model.

[0016] Description of reference numerals:

[0017] 1. Substrate; 2. Graphic layer; 21. First structure layer; 22. Second structure layer; 23. Third structure layer; 3. Nitride buffer layer; 4. Nitride channel layer; 5. Nitride barrier layer; 6. Source; 7. Drain; 8. Gate. DETAILED DESCRIPTION

[0018] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the utility model after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0020] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0021] See also Figure 1 The embodiment of the utility model provides a GaN-based HEMT device structure, comprising a substrate 1, a nitride buffer layer 3, a nitride channel layer 4 and a nitride barrier layer 5 which are sequentially stacked along a first direction; a graphic layer 2 is also arranged between the substrate 1 and the nitride buffer layer 3; the graphic layer 2 comprises a first structure layer 21, a second structure layer 22 and a third structure layer 23 which are sequentially arranged along the first direction, the first structure layer 21 comprises a plurality of protruding structures arranged in an array along a second direction intersecting with the first direction, the second structure layer 22 is divided into a plurality of independent film layers, respectively covering the top surfaces and side surfaces of the plurality of protruding structures, the third structure layer 23 continuously covers the second structure layer 22 and a portion of the substrate 1 between any adjacent protruding structures; wherein the second structure layer 22 is a film layer with passivation doping, and the third structure layer 23 is a film layer with a nanoporous structure.

[0022] In some embodiments, the bottom width of the protrusion structure is 1 to 3 μm, and the height is 0.1 to 2 μm.

[0023] In some embodiments, the pitch between the plurality of protruding structures is 0.1-1 μm.

[0024] In some embodiments, the thickness of the second structure layer 22 is 1 to 20 nm, and the thickness of the third structure layer 23 is 2 to 50 nm.

[0025] In some embodiments, the pore size of the third structural layer 23 is 5 to 150 nm.

[0026] In some embodiments, the thickness of the nitride buffer layer 3 is 1-5 μm, the thickness of the nitride channel layer 4 is 100-1000 nm, and the thickness of the nitride barrier layer 5 is 5-30 nm.

[0027] In some embodiments, the protruding structure is a silicon dioxide protruding structure, the second structural layer 22 is a fluorine and / or chlorine doped silicon nitride film, and the third structural layer 23 is a porous silicon nitride film.

[0028] In some embodiments, the substrate 1 includes any one of a silicon substrate 1, a sapphire substrate 1 or a silicon carbide substrate 1; the nitride buffer layer 3 is an iron and / or carbon doped gallium nitride film layer, the nitride channel layer 4 is a gallium nitride film layer, and the nitride barrier layer 5 is an aluminum gallium nitride film layer.

[0029] As some typical application examples of the above technical solution, a HEMT epitaxial device structure at least includes a substrate 1, a nitride buffer layer 3 with a thickness of 1 to 5 μm, a nitride channel layer 4 with a thickness of 100 to 1000 nm, and a nitride barrier layer 5 with a thickness of 5 to 30 nm, wherein a first structure layer 21, a second structure layer 22, and a third structure layer 23 are arranged between the substrate 1 and the nitride buffer layer 3;

[0030] The first structure layer 21 is SiO2, with a bottom width of 1 to 3 μm, a height of 0.1 to 2 μm, and a spacing of 0.1 to 1 μm; the second structure layer 22 is Si-XN, with a thickness of 1 to 20 nm, where X is one of Cl and F; the third structure layer 23 is SiN with a porous structure, with a thickness of 2 to 50 nm and a pore size of 5 to 150 nm; the substrate 1 is one of silicon, sapphire or silicon carbide; the nitride buffer layer 3 is a doped GaN layer, the dopant is one of C or Fe, and the doping concentration is 1×10 1a cm -3 ~5×10 1a cm -3 ; The nitride channel layer 4 is a GaN layer; the nitride barrier layer 5 is an AlGaN layer, and the Al component accounts for 0.2 to 0.5.

[0031] It should be noted that, in the above exemplary device structure, the selection of the substrate 1, the nitride buffer layer 3, the nitride channel layer 4 and the nitride barrier layer 5 are all common choices in HEMT devices, and are not limited to the scope of the above examples. Those skilled in the art may make appropriate adjustments and selections based on the existing technical solutions, which also fall within the protection scope of the present utility model; and the technical effect of the present utility model is mainly brought about by the specific structure of the above three-layer structure layer. Although there is a doped layer, such as the second structure layer 22, the preparation of the doped layer belongs to a completely existing process method and has been widely used in this field. The technical effect of the present utility model utilizes the characteristics of the doped layer, rather than relying on the specific preparation process of the doped layer. Similarly, the preparation of multiple protruding structures and the preparation of the third structure layer 23 with nanopores also belong to the existing process. Those skilled in the art can select the process without relying on the innovation of the preparation method to achieve the technical effect of the present utility model.

[0032] For other structural features, see Figure 2 In some embodiments, the GaN-based HEMT device structure further includes a source 6, a drain 7 and a gate 8, the source 6 and the drain 7 are electrically connected to the nitride channel layer 4 respectively, and the gate 8 establishes a Schottky connection with the nitride barrier layer 5.

[0033] In some embodiments, the source 6 and the drain 7 are disposed on the nitride channel layer 4 and are respectively located on both sides of the nitride barrier layer 5 and form ohmic contacts with the nitride barrier layer 5 respectively. The gate 8 is disposed on the barrier layer and is located between the source 6 and the drain 7.

[0034] As some typical application examples of the above technical solution, the HEMT device at least further includes a source 6, a drain 7, and a gate 8; wherein the source 6 and the drain 7 are located on the nitride channel layer 4 and on both sides of the nitride barrier layer 5, respectively forming ohmic contacts with the nitride barrier layer 5, and the gate 8 is located on the barrier layer and between the source 6 and the drain 7, forming a Schottky contact with the nitride barrier layer 5.

[0035] Of course, even if a person skilled in the art sets the structure of the source 6, the drain 7 and the gate 8 to a method different from that illustrated here, as long as the basic functions of the device are achieved, it still falls within the scope of the implementation of the present invention.

[0036] Based on the above technical solution, the utility model improves the crystal quality of the epitaxial wafer, reduces the defect density in the nitride material epitaxial layer, and improves the leakage performance of the epitaxial wafer by setting the first structure layer 21SiO2, the third structure layer 23 and the second structure layer 22, specifically;

[0037] The first structure layer 21SiO2 improves the lateral epitaxy of the nitride material, blocks the dislocations below the SiO2 structure pattern from extending upward, and improves the crystal quality of the nitride material. The third structure layer 23SIN utilizes its own nanoporous film structure to strengthen the lateral epitaxy between adjacent first structure layer 21SiO2 patterns, blocks the dislocations below the area between the SiO2 patterns from extending upward, and further improves the crystal quality of the nitride material.

[0038] The second structure layer 22Si-XN utilizes the doped atoms X to effectively passivate the multiple dangling bonds Si· between the first structure layer 21 and the second structure layer 22, which can significantly reduce the charge accumulation capture effect and avoid the influence of charge accumulation on the two-dimensional electron gas in the nitride channel layer 4, thereby ensuring the output current stability of the drain 7 in the nitride channel layer 4 and avoiding current collapse.

[0039] The technical solution of the utility model is further described in detail below through several embodiments and in combination with the accompanying drawings. However, the selected embodiments are only used to illustrate the utility model, and do not limit the scope of the utility model.

[0040] Example 1

[0041] This embodiment illustrates a GaN-based HEMT device, which is specifically as follows:

[0042] like Figure 1 and 2 As shown, the GaN-based HEMT device includes a substrate 1, a nitride buffer layer 3 with a thickness of 3 μm, a nitride channel layer 4 with a thickness of 600 nm, and a nitride barrier layer 5 with a thickness of 15 nm, and a first structure layer 21, a second structure layer 22, and a third structure layer 23 are arranged between the substrate 1 and the nitride buffer layer 3;

[0043] The first structure layer 21 is SiO2, with a bottom width of 2 μm, a height of 1.2 μm, and a spacing of 0.5 μm; the second structure layer 22 is Si-XN, with a thickness of 10 nm, where X is Cl; the third structure layer 23 is SiN with a porous structure, with a thickness of 25 nm and a pore size distribution range of 5 to 150 nm; the substrate 1 is one of silicon, sapphire or silicon carbide; the nitride buffer layer 3 is a doped GaN layer, the dopant is one of C or Fe, and the doping concentration is 2.5×10 18 cm -3 ; The nitride channel layer 4 is a GaN layer; the nitride barrier layer 5 is an AlGaN layer, and the Al component accounts for 0.3.

[0044] The source 6 and the drain 7 are located on the nitride channel layer 4 and on both sides of the nitride barrier layer 5, respectively forming ohmic contacts with the nitride barrier layer 5; the gate 8 is located on the barrier layer and between the source 6 and the drain 7, forming a Schottky contact with the nitride barrier layer 5.

[0045] Comparative Example 1

[0046] This comparative example is substantially the same as Example 1, except that:

[0047] a. removing the first structural layer 21, the second structural layer 22 and the third structural layer 23;

[0048] b. Only the first structural layer 21 is retained, and the second structural layer 22 and the third structural layer 23 are removed;

[0049] c. Only the first structural layer 21 and the third structural layer 23 are retained, and the second structural layer 22 is removed;

[0050] d. Only the first structural layer 21 and the second structural layer 22 are retained, and the third structural layer 23 is removed;

[0051] e. During the preparation process, only the top surface of the protruding structure is covered with the second structural layer 22 , but the side wall of the protruding structure is not covered.

[0052] Off-state leakage is an important factor restricting the performance improvement of HEMT devices. The off-state leakage performance of the HEMT devices of Example 1 and Comparative Example 1 was tested by scanning the reverse gate voltage from 0V to -10V. The data are shown in the following table:

[0053] Off-state gate leakage current mA / mm Example 1 <![CDATA[1.6×10 -3 ]]> Comparative Example a <![CDATA[1.9×10 -1 ]]> Comparative Example b <![CDATA[8.8×10 -2 ]]> Comparative Example c <![CDATA[3.2×10 -2 ]]> Control Example d <![CDATA[3.8×10 -2 ]]> Comparative Example e <![CDATA[8.2×10 -3 ]]>

[0054] The leakage current of control example a is two orders of magnitude higher than that of embodiment 1. The reason is that control example a does not have the first structure layer 21, the second structure layer 22 and the third structure layer 23, and there is no lateral epitaxial effect in the HEMT device structure. The dislocation is not fully turned and is interrupted and extended, and a leakage channel is presented in the HEMT device structure layer.

[0055] The leakage current of the control example b is lower than that of the control example a, but is still one order of magnitude higher than that of the embodiment 1. The reason is that the first structure layer 21 of the control example b can promote the lateral epitaxy effect of the structure layer of the HEMT device to a certain extent.

[0056] The leakage current of control examples c and d is significantly reduced compared with control example a. The reason is that the third structural layer of control example b improves the lateral epitaxial growth ability of the nitride material when the device structure is formed, blocks the dislocation extension, and improves the epitaxial quality, thereby reducing the formation of the leakage channel. In control example c, the intermediate passivation doped film layer is used to passivate the charge defects, significantly reduce the charge accumulation and capture effect, and avoid the risk of charge accumulation forming charge diffusion to form a leakage channel. From the fact that the leakage current of control examples c and d is not much different, it can be determined that the second structural layer and the third structural layer in the present invention are both beneficial to improving the leakage performance of the HEMT device.

[0057] The leakage current of control example e is at the same order of magnitude as that of embodiment 1, but higher than that of embodiment 1. The reason is that control example e does not cover the sidewalls of the protruding structure, and has higher charge accumulation on the sidewalls than the embodiment, which increases the leakage current.

[0058] Therefore, it can be found that in the present invention, the combination and matching of the three structural layers with different functions is crucial to achieving the corresponding technical effects.

[0059] Based on the above embodiments and comparative examples, it can be clearly seen that the present invention provides the following by providing the first structural layer 21, the second structural layer 22 and the third structural layer 23:

[0060] 1) The first structure layer 21 improves the lateral epitaxy of the nitride material, blocks the dislocations below the structure pattern from extending upward, and improves the crystal quality of the nitride material; 2) The third structure layer 23 utilizes its own nanoporous film structure to strengthen the lateral epitaxy between adjacent first structure layer 21 patterns, blocks the dislocations below the area between the patterns from extending upward, and further improves the crystal quality of the nitride material; 3) The second structure layer 22Si-XN utilizes the doping atom X to effectively passivate the multiple dangling bonds Si· between the first structure layer 21 and the second structure layer 22, which can significantly reduce the charge accumulation capture effect, avoid the influence of charge accumulation on the two-dimensional electron gas in the nitride channel layer 4, thereby ensuring the output current stability of the drain 7 in the nitride channel layer 4 and avoiding current collapse.

[0061] In addition, based on the above-mentioned device structure, the second structure layer 22 and the third structure layer 23 can be set to periodically cover each other, which can further enhance the lateral external effect of the second structure layer 22, and the second structure layer 22 can provide more atomic passivation in the thickness direction, so that the cyclic structure will form a charge capture center, and the upper third structure layer 23 can shield the doped atoms in the adjacent second structure layer 22, further preventing the doped atoms from diffusing into the nitride buffer layer 3 and the channel layer.

[0062] It should be understood that the above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A GaN-based HEMT device structure, comprising a substrate, a nitride buffer layer, a nitride channel layer and a nitride barrier layer stacked in sequence along a first direction; It is characterized in that A graphic layer is also provided between the substrate and the nitride buffer layer; The graphic layer comprises a first structural layer, a second structural layer and a third structural layer sequentially arranged along the first direction, the first structural layer comprises a plurality of convex structures arranged in an array along a second direction intersecting the first direction, the second structural layer is divided into a plurality of independent film layers, respectively covering the top surfaces and side surfaces of the plurality of convex structures, and the third structural layer continuously covers the second structural layer and a portion of the substrate between any adjacent convex structures; Wherein, the second structural layer is a film layer with passivation doping, and the third structural layer is a film layer with a nanoporous structure.

2. The GaN-based HEMT device structure according to claim 1, characterized in that: The bottom width of the protrusion structure is 1-3 μm, and the height is 0.1-2 μm.

3. The GaN-based HEMT device structure according to claim 2, characterized in that: The spacing between the plurality of protrusion structures is 0.1-1 μm.

4. The GaN-based HEMT device structure according to claim 1, characterized in that: The thickness of the second structural layer is 1-20 nm, and the thickness of the third structural layer is 2-50 nm.

5. The GaN-based HEMT device structure according to claim 4, characterized in that: The pore size of the third structural layer is 5-150 nm.

6. The GaN-based HEMT device structure according to claim 1, characterized in that: The thickness of the nitride buffer layer is 1-5 μm, the thickness of the nitride channel layer is 100-1000 nm, and the thickness of the nitride barrier layer is 5-30 nm.

7. The GaN-based HEMT device structure according to claim 1, characterized in that: It also includes a source, a drain and a gate. The source and the drain are electrically connected to the nitride channel layer respectively, and the gate establishes a Schottky connection with the nitride barrier layer.

8. The GaN-based HEMT device structure according to claim 7, characterized in that: The source and drain are arranged on the nitride channel layer and are respectively located on both sides of the nitride barrier layer and respectively form ohmic contacts with the nitride barrier layer. The gate is arranged on the barrier layer and is located between the source and the drain.

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