Lateral gallium nitride based power device and method of making the same

Abstract

The application provides a transverse gallium nitride-based power device and a preparation method thereof. The power device comprises: an aluminum nitride nucleation layer, a gallium nitride buffer layer and a carbon-doped gallium nitride insulation layer which are sequentially stacked on a substrate, wherein the carbon-doped gallium nitride insulation layer has a plurality of grooves, a longitudinal structure is used to increase the gate-drain distance and improve the withstand voltage; an aluminum gallium nitride / gallium nitride heterojunction formed on the surface of the carbon-doped gallium nitride insulation layer; a source electrode, a drain electrode and a gate electrode formed on the surface of the aluminum gallium nitride / gallium nitride heterojunction, the plurality of grooves are located in the withstand voltage area between the gate electrode and the drain electrode, and an auxiliary depletion layer covers the surface of the aluminum gallium nitride / gallium nitride heterojunction in the withstand voltage area between the gate electrode and the drain electrode; and a heavily doped P-type gallium nitride layer formed on the surface of the auxiliary depletion layer above the protruding part between any two adjacent grooves, the heavily doped P-type gallium nitride layer is connected to the source electrode through the gate electrode by a connecting structure.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a lateral gallium nitride-based power device and its fabrication method. Background Technology

[0002] Gallium nitride (GaN), representing third-generation wide-bandgap semiconductor materials, possesses superior physical and chemical properties, such as a large bandgap, high breakdown electric field strength, high saturated electron drift velocity, strong radiation resistance, and good chemical stability. These properties make it particularly suitable for fabricating high-voltage, high-temperature, high-frequency, and high-power power electronic devices. Another prominent feature of GaN materials is their ability to achieve an electron surface density of 10⁻⁶ in undoped AlGaN / GaN by utilizing their inherent polarization effect. 13 cm -2 High-concentration two-dimensional electron gas (2DEG) on the order of magnitude. 2DEG has a high areal density and high mobility in the two-dimensional plane of the channel. GaN field-effect transistors with lateral conduction made up of this characteristic are currently the most common and most promising epitaxial structure.

[0003] In traditional AlGaN / GaN field-effect transistors, a relatively long, lightly doped N-drift region is required to ensure sufficient breakdown voltage. The larger the size of the lightly doped N-drift region, the higher the breakdown voltage rating, but the on-resistance also increases dramatically. On-resistance increases with voltage to the power of 2.4-2.6, thus reducing the current rating. To obtain a certain on-resistance value, the silicon wafer area must be increased, leading to increased cost. Therefore, it is essential to resolve the contradiction between low on-resistance, high breakdown voltage, and small size with high integration in GaN-based power devices. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a lateral gallium nitride-based power device and its fabrication method, which features high breakdown voltage, low on-resistance, and does not increase device size.

[0005] On one hand, the present invention provides a lateral gallium nitride-based power device, comprising:

[0006] An aluminum nitride nucleation layer, a gallium nitride buffer layer, and a carbon-doped gallium nitride insulating layer are sequentially stacked on a substrate, wherein the carbon-doped gallium nitride insulating layer has multiple trenches.

[0007] An aluminum gallium nitride / gallium nitride heterojunction is formed on the surface of the carbon-doped gallium nitride insulating layer;

[0008] The source, drain, and gate are formed on the surface of the aluminum gallium nitride / gallium nitride heterojunction, the plurality of trenches are located in the breakdown region between the gate and the drain, and an auxiliary depletion layer is covered on the surface of the aluminum gallium nitride / gallium nitride heterojunction portion between the gate and the drain;

[0009] And a heavily doped p-type gallium nitride layer formed on the surface of the auxiliary depletion layer above the protrusion between any two adjacent trenches, the heavily doped p-type gallium nitride layer being connected to the source across the gate via a connection structure.

[0010] Optionally, the auxiliary depletion layer is a lightly doped p-type gallium nitride layer with a thickness between 3 and 500 nm.

[0011] Optionally, the depth of the trench is 0.1 to 5 μm.

[0012] Optionally, the etching angle of the trench is 90° to 135°.

[0013] Optionally, the thickness of the aluminum gallium nitride / gallium nitride heterojunction's aluminum gallium nitride barrier layer is between 3 and 50 nm.

[0014] On the other hand, the present invention provides a method for fabricating a lateral gallium nitride-based power device, the method comprising:

[0015] An aluminum nitride nucleation layer, a gallium nitride buffer layer, and a carbon-doped gallium nitride insulating layer are sequentially formed on the substrate.

[0016] Multiple trenches were etched into the carbon-doped gallium nitride insulating layer;

[0017] An aluminum gallium nitride / gallium nitride heterojunction is formed on the surface of the carbon-doped gallium nitride insulating layer with trenches;

[0018] An auxiliary depletion layer is formed on the surface of the aluminum gallium nitride / gallium nitride heterojunction;

[0019] A heavily doped p-type gallium nitride layer is formed on the surface of the auxiliary depletion layer above the protrusion between any two adjacent trenches, wherein the width of the heavily doped p-type gallium nitride layer is smaller than the distance between the two trenches;

[0020] The auxiliary depletion layer is etched to expose a portion of the surface of the aluminum gallium nitride / gallium nitride heterojunction;

[0021] A source, drain, and gate are formed on the surface of the exposed aluminum gallium nitride / gallium nitride heterojunction portion;

[0022] A connection structure is formed between the source electrode and the heavily doped p-type gallium nitride layer.

[0023] Optionally, the auxiliary depletion layer is a lightly doped p-type gallium nitride layer with a thickness between 3 and 500 nm.

[0024] Optionally, the depth of the trench is 0.1 to 5 μm.

[0025] Optionally, the etching angle of the trench is 90° to 135°.

[0026] Optionally, the thickness of the aluminum gallium nitride / gallium nitride heterojunction's aluminum gallium nitride barrier layer is between 3 and 50 nm.

[0027] This invention provides a lateral gallium nitride-based power device and its fabrication method. By utilizing trenches in a carbon-doped gallium nitride insulating layer, an aluminum gallium nitride / gallium nitride heterojunction is longitudinally folded, increasing the spacing between the gate and drain. This structure reduces the device size while ensuring high breakdown voltage, which is beneficial for cost reduction and device integration improvement, providing a feasible solution for the industrialization of gallium nitride-based power devices. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a lateral gallium nitride-based power device according to an embodiment of the present invention;

[0029] Figures 2 to 9 This is a schematic diagram of the process flow for a method of fabricating a lateral gallium nitride-based power device according to an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of this disclosure.

[0031] The accompanying drawings illustrate various structural schematics according to embodiments of the present disclosure. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0032] In the context of this disclosure, when a layer / element is referred to as being "above" another layer / element, the layer / element may be directly above the other layer / element, or there may be an intermediate layer / element between them. Additionally, if a layer / element is "above" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0033] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0034] One embodiment of the present invention provides a lateral gallium nitride-based power device, such as... Figure 1 As shown, the device includes:

[0035] An aluminum nitride (AlN) nucleation layer 101, a gallium nitride (GaN) buffer layer 102, and a carbon-doped gallium nitride insulating layer 103 are sequentially stacked on a substrate 100, wherein the carbon-doped gallium nitride insulating layer has multiple trenches.

[0036] An aluminum gallium nitride / gallium nitride (AlGaN / GaN) heterojunction 104 is formed on the surface of a carbon-doped gallium nitride insulating layer 103;

[0037] The source 107, drain 108 and gate 109 are formed on the surface of the aluminum gallium nitride / gallium nitride heterojunction 104. Multiple trenches on the carbon-doped gallium nitride insulating layer 103 are located in the breakdown region between the gate 109 and the drain 108. An auxiliary depletion layer 105 is covered on the surface of the aluminum gallium nitride / gallium nitride heterojunction portion in the breakdown region between the gate 109 and the drain 108.

[0038] And, heavily doped p-type gallium nitride (P-type gallium nitride) on the surface of the auxiliary depletion layer 105 formed above the protrusion between any two adjacent trenches. + The heavily doped p-type gallium nitride layer 106 is connected to the source 107 across the gate 109 via a connection structure 110.

[0039] In one implementation, the substrate 100 is a sapphire substrate, which eliminates the risk of longitudinal breakdown when the device drain is subjected to high voltage.

[0040] There is no auxiliary depletion layer below the source 107, drain 108, and gate 109. The auxiliary depletion layer 105 can be lightly doped p-type gallium nitride (P-type gallium nitride). - A GaN layer with a thickness between 3 and 500 nm is used. This is achieved through a heavily doped p-type gallium nitride layer 106, and a lightly doped p-type gallium nitride (P-GaN) layer. -A good ohmic contact can be formed between the AlGaN auxiliary depletion layer 105 and the source 107. The auxiliary depletion layer 105 and the source 107 maintain the same potential, which plays an auxiliary depletion role in the AlGaN / GaN heterojunction channel. This effectively reduces the doping concentration of the breakdown voltage region between the gate and the drain, optimizes the electric field distribution, and improves the breakdown voltage of the device.

[0041] For multiple trenches on the carbon-doped gallium nitride insulating layer 103, the number of trenches is set according to the actual process, and the width of each trench can be the same or different. The trench depth can be designed to be 0.1–5 μm, refer to [reference]. Figure 1 The etching angle θ of the trench is taken as 90° to 135°.

[0042] The lateral gallium nitride-based power device of this invention incorporates a trench design in the carbon-doped gallium nitride insulating layer, which longitudinally folds the aluminum gallium nitride / gallium nitride heterojunction, increasing the spacing between the gate and drain. This structure reduces the device size while ensuring high breakdown voltage, which is beneficial for cost reduction and device integration, providing a feasible solution for the industrialization of gallium nitride-based power devices.

[0043] In addition, in the embodiments of the present invention, the AlGaN / GaN heterojunction has an AlGaN barrier layer of 3-50 nm, and the use of a thin barrier layer facilitates the realization of enhancement-mode devices.

[0044] On the other hand, another embodiment of the present invention provides a method for fabricating a lateral gallium nitride-based power device. Figures 2 to 9 The process flow of this preparation method is shown.

[0045] refer to Figure 2 First, an aluminum nitride nucleation layer 201, a gallium nitride buffer layer 202, and a carbon-doped gallium nitride insulating layer 203 are sequentially formed on a substrate 200.

[0046] Next, as Figure 3 As shown, multiple trenches are etched on the carbon-doped gallium nitride insulating layer 203. In this step, the number of trenches is set according to the actual process, and the width of each trench can be the same or different. The trench depth can be designed to be 0.1–5 μm, and the trench etching angle θ is taken as 90°–135°.

[0047] Then, as Figure 4 As shown, an aluminum gallium nitride / gallium nitride heterojunction 204 is formed on the surface of a trenched carbon-doped gallium nitride insulating layer 203. To obtain an enhancement-mode device, the AlGaN barrier layer in the AlGaN / GaN heterojunction is a thin barrier layer of 3–50 nm.

[0048] Subsequently, such as Figure 5As shown, an auxiliary depletion layer 205 is formed on the surface of the aluminum gallium nitride / gallium nitride heterojunction 204. The auxiliary depletion layer 205 can be formed by deposition; optionally, the auxiliary depletion layer 205 can be lightly doped p-type gallium nitride (P... - -GaN) layer, with a thickness between 3 and 500 nm.

[0049] Then, as Figure 6 As shown, heavily doped p-type gallium nitride (P-type gallium nitride) is formed on the surface of the auxiliary depletion layer 205 located between any two adjacent trenches. + The width of the heavily doped p-type gallium nitride layer 206 is smaller than the distance between the two trenches. Specifically, the pattern of the heavily doped p-type gallium nitride layer 206 can be fabricated first, and then the p-type layer can be deposited. + -GaN. Alternatively, a layer of P can be deposited. + -GaN, then etched, to finally obtain the desired pattern.

[0050] Next, as Figure 7 As shown, the auxiliary depletion layer 205 is etched to expose a portion of the surface of the aluminum gallium nitride / gallium nitride heterojunction. The exposed surface portion is subsequently used to fabricate the source, drain, and gate of the device.

[0051] Next, as Figure 8 As shown, a source 207, a drain 208, and a gate 209 are formed on the surface of the exposed aluminum gallium nitride / gallium nitride heterojunction portion.

[0052] In this embodiment, the ohmic contact metals of the source electrode 207 and the drain electrode 208 are Ti / Al / Ni / Au stacked structures, and a lift-off process is used, followed by rapid thermal annealing at 850°C and in a N2 atmosphere for 30 seconds.

[0053] The gate formation process includes gate trench etching and gate metal deposition. Enhancement-mode devices can be achieved through gate trench etching. Gate metals can be Ni / Au, Pt / Ti / Au, Al / Ni / Au, or TiN, etc.

[0054] Then, as Figure 9 As shown, a connection structure 210 is formed between the source 207 and the heavily doped p-type gallium nitride layer 206. This connection structure achieves equipotentiality between the auxiliary depletion layer 205 and the source 207, plays an auxiliary depletion role in the AlGaN / GaN heterojunction channel, effectively reduces the doping concentration of the breakdown voltage region between the gate and drain, optimizes the electric field distribution, and improves the breakdown voltage of the device.

[0055] It should be noted that no specific process conditions are limited in the various steps of the above preparation process, and any selection can be made during the actual implementation.

[0056] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lateral gallium nitride-based power device, characterized in that, include: An aluminum nitride nucleation layer, a gallium nitride buffer layer, and a carbon-doped gallium nitride insulating layer are sequentially stacked on a substrate, wherein the carbon-doped gallium nitride insulating layer has multiple trenches. An aluminum gallium nitride / gallium nitride heterojunction is formed on the surface of the carbon-doped gallium nitride insulating layer; The source, drain, and gate are formed on the surface of the aluminum gallium nitride / gallium nitride heterojunction. The plurality of trenches are located in the breakdown region between the gate and the drain. An auxiliary depletion layer is covered on the surface of the aluminum gallium nitride / gallium nitride heterojunction portion in the breakdown region between the gate and the drain. The auxiliary depletion layer is a lightly doped p-type gallium nitride layer. And a heavily doped p-type gallium nitride layer formed on the surface of the auxiliary depletion layer above the protrusion between any two adjacent trenches, the heavily doped p-type gallium nitride layer being connected to the source across the gate via a connection structure.

2. The lateral gallium nitride-based power device according to claim 1, characterized in that, The thickness of the auxiliary depletion layer is between 3 and 500 nm.

3. The lateral gallium nitride-based power device according to claim 1, characterized in that, The depth of the trench is 0.1~5μm.

4. The lateral gallium nitride-based power device according to claim 1, characterized in that, The etching angle of the trench is 90°~135°.

5. The lateral gallium nitride-based power device according to claim 1, characterized in that, The aluminum gallium nitride / gallium nitride heterojunction has an aluminum gallium nitride barrier layer thickness between 3 and 50 nm.

6. A method for fabricating a lateral gallium nitride-based power device as described in claim 1, characterized in that, The method includes: An aluminum nitride nucleation layer, a gallium nitride buffer layer, and a carbon-doped gallium nitride insulating layer are sequentially formed on the substrate. Multiple trenches were etched into the carbon-doped gallium nitride insulating layer; An aluminum gallium nitride / gallium nitride heterojunction is formed on the surface of the carbon-doped gallium nitride insulating layer with trenches; An auxiliary depletion layer is formed on the surface of the aluminum gallium nitride / gallium nitride heterojunction, wherein the auxiliary depletion layer is a lightly doped p-type gallium nitride layer; A heavily doped p-type gallium nitride layer is formed on the surface of the auxiliary depletion layer above the protrusion between any two adjacent trenches, wherein the width of the heavily doped p-type gallium nitride layer is smaller than the distance between the two trenches; The auxiliary depletion layer is etched to expose a portion of the surface of the aluminum gallium nitride / gallium nitride heterojunction; A source, drain, and gate are formed on the surface of the exposed aluminum gallium nitride / gallium nitride heterojunction portion; A connection structure is formed between the source electrode and the heavily doped p-type gallium nitride layer.

7. The method according to claim 6, characterized in that, The thickness of the auxiliary depletion layer is between 3 and 500 nm.

8. The method according to claim 6, characterized in that, The depth of the trench is 0.1~5μm.

9. The method according to claim 6, characterized in that, The etching angle of the trench is 90°~135°.

10. The method according to claim 6, characterized in that, The aluminum gallium nitride / gallium nitride heterojunction has an aluminum gallium nitride barrier layer thickness between 3 and 50 nm.

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