CN108511513B - A kind of AlGaN\GaN power device with vertical structure and its preparation method - Google Patents

Abstract

The present invention relates to an AlGaN/GaN power device with a vertical structure and a preparation method thereof, comprising a drain electrode, an n ⁺ ‑GaN layer and an n‑GaN U-shaped trench arranged sequentially from bottom to top, in which the n‑GaN The GaN U-shaped trench is provided with an AlGaN u-shaped trench whose upper surface is flush with the upper surface of the n-GaN U-shaped trench and whose depth is smaller than the depth of the n-GaN U-shaped trench, and the AlGaN u-shaped trench A layer of SiN _x u-shaped gate is arranged on the surface; a p-GaN whose upper surface is flush with the upper surface of the n-GaN U-shaped trench is filled in the SiN _x u-shaped gate; on the upper surface of the p-GaN The middle part is provided with a dielectric passivation layer covering p-GaN, SiN _x u-shaped gate and part of AlGaN u-shaped groove, and the upper surface of the dielectric passivation layer is also provided with a covering dielectric passivation layer and n-GaN U-shaped groove The source electrode of the groove, and the gate electrode connected with p-GaN is arranged symmetrically on both sides of the source electrode. The advantage of the present invention is that: the present invention greatly improves the performance of the device in high-frequency and high-power occasions, thereby greatly improving the reliability of the device and ensuring the stability of the working voltage of the device.

Description

A kind of AlGaN\GaN power device with vertical structure and its preparation method

technical field

The invention belongs to the technical field of semiconductor device manufacturing, in particular to an AlGaN/GaN power device with a vertical structure and a preparation method thereof.

Background technique

At present, AlGaN/GaN heterojunction HEMT devices are very suitable for high-frequency and high-power workplaces due to their high electron saturation velocity, high breakdown field strength, high cut-off frequency, and high saturation current, but they face two problems: heat dissipation Poor performance with saturation electron rate limited. At present, the most widely used substrate for growing GaN material is sapphire substrate, which has the advantages of low cost, mature technology, good stability and high mechanical strength. However, due to the large thermal adaptation between the sapphire substrate and the GaN-based material and the low thermal conductivity, the application of the device in high-power and high-frequency applications is limited. In the field of GaN-based LEDs grown on sapphire, in order to enhance the heat dissipation capability of high-power LEDs, there has been a mature technology of using laser lift-off technology to transfer LEDs to metal substrates that are conducive to heat dissipation. After the laser separates the sapphire substrate from the epitaxial layer, the epitaxial layer is bonded to a metal substrate with good heat dissipation.

At present, most of the popular AlGaN/GaN heterojunction HEMTs on the market are planar structures, and the source, drain, and gate of the device are all on the top surface of the device. When the working environment temperature rises and the working voltage increases, the reliability of the device In addition, the planar structure AlGaN/GaN heterojunction HEMT is not conducive to the integration with other components.

Therefore, it is very necessary to develop an AlGaN/GaN power device with a vertical structure and a preparation method thereof that can greatly improve device reliability and ensure stable device operating voltage.

Contents of the invention

The technical problem to be solved by the present invention is to provide an AlGaN/GaN power device with a vertical structure and a preparation method thereof, which can greatly improve device reliability and ensure stable device operating voltage.

In order to solve the above technical problems, the technical solution of the present invention is: an AlGaN/GaN power device with a vertical structure, and its innovation point is that it includes drain electrodes, n ⁺ -GaN layers and n- GaN U-shaped trench, an AlGaN u-shaped trench whose upper surface is flush with the upper surface of the n-GaN U-shaped trench and whose depth is smaller than the depth of the n-GaN U-shaped trench is provided in the n-GaN U-shaped trench groove, and the inner surface of the AlGaN u-shaped trench is provided with a layer of SiN _x u-shaped gate; the SiN _x u-shaped gate is filled with a p- GaN; a dielectric passivation layer covering the p-GaN, SiN _x u-shaped gate and part of the AlGaN u-shaped trench is provided in the middle of the upper surface of the p-GaN, and the upper surface of the dielectric passivation layer is also provided with a covering The dielectric passivation layer and the source electrode of the n-GaN U-shaped groove, and the gate electrode connected to the p-GaN is arranged symmetrically on both sides of the source electrode.

Further, the source electrode covers an area slightly smaller than that of the dielectric passivation layer in a direction parallel to the SiN _x u-shaped gate.

Further, the thickness of the drain electrode is 20nm-500nm, the thickness of the n ⁺ -GaN layer is 500nm-3μm, the depth of the n-GaN U-shaped groove is 2μm-5μm, and the n-GaN U-shaped The width between the notches of the trench is 2 μm to 3 μm, the depth of the AlGaN u-shaped groove is 1.5 μm to 4 μm, the width between the notches of the AlGaN u-shaped groove is 1 μm to 2 μm, and the SiN _x The thickness of the u-shaped gate is 10nm to 50nm, the thickness of the dielectric passivation layer is 50nm to 500nm, the length of the source electrode is 100nm to 500nm, and the thickness is 20nm to 500nm, and the side length of the gate electrode is 500nm ~ 2μm.

A method for manufacturing the aforementioned AlGaN/GaN power device with a vertical structure, the innovation of which is that the method includes the following steps:

(1) On the sapphire substrate, using Si as the dopant, the doping concentration is 1×10 ¹⁸ cm ^-3 to 5×10 ¹⁹ cm ^-3 , and growing an n ⁺ -GaN layer;

(2) On the n ⁺ -GaN layer, use Si as the dopant with a doping concentration of 1×10 ¹⁷ cm ^-3 to 5×10 ¹⁸ cm ^-3 to grow an n-GaN layer;

(3) Etching vertically on the n-GaN layer to the interface between the n ⁺ -GaN layer and the n-GaN layer, and finally forming an n-GaN U-shaped trench;

(4) AlGaN is grown in the etched n-GaN U-shaped trench until the n-GaN U-shaped trench is filled;

(5) Etching vertically again on AlGaN, the etching depth and width are slightly smaller than the GaN trench, forming an AlGaN u-shaped trench;

(6) A high-quality SiN _x thin layer is grown in the AlGaN u-shaped trench as a gate dielectric to form a SiN _x u-shaped gate;

(7) growing p-GaN in the SiN _x u-shaped gate until the u-shaped trench is filled, the dopant is Mg, and the doping concentration is 5×10 ¹⁶ cm ^-3 to 5×10 ¹⁸ cm ^-3 ;

(8) Uniformly grow a layer of dielectric passivation layer on the surface of the device;

(9) Perform selective etching on the dielectric passivation layer, etch horizontally until the interface between the Al-GaN layer and the n-GaN layer is exposed, and vertically etch until a sufficient length is left in the middle to make the source electrode;

(10) A layer of metal is deposited on the surface of the device by evaporation or other methods, and the deposited first layer of metal is etched vertically until the middle part exposes a part of the dielectric passivation layer, exposing the strips that form a U-shaped trench across the AlGaN A source electrode, and a bulk metal is exposed at both ends of the AlGaN u-shaped trench as a gate electrode;

(11) The sapphire at the bottom is removed by laser lift-off, and a layer of metal is deposited as a drain electrode on the lower surface of the exposed n ⁺ -GaN layer by means of evaporation or the like.

Further, the metal in the step (10) and step (11) is selected from Ti/Al/Ni/Au one or more metal alloys or metal multilayer composite structures.

The advantage of the present invention is that: the AlGaN/GaN power device with a vertical structure and its preparation method, the present invention enables the two-dimensional electron gas to move along the vertical direction and form a channel through the interface between n-GaN and AlGaN arranged in the vertical direction , to enhance the moving rate of the two-dimensional electron gas; at the same time, the control ability of the two-dimensional electron gas is improved through the gate of the u-shaped trench structure; and the p-GaN filled in the u-shaped trench gate can make the HEMT work without a gate In the case of bias voltage, the enhanced HEMT can be formed to form a wider range of applications; in addition, through the spatial separation of the gate electrode drawn from both ends and the coating of passivation layers in other areas, gate pollution caused by other processes can be avoided Causes the problem of unstable turn-on voltage.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

FIG. 1 is a side view of an AlGaN/GaN power device with a vertical structure according to the present invention.

FIG. 2 is a top view of an AlGaN/GaN power device with a vertical structure according to the present invention.

3-15 are the flow charts of the fabrication of the AlGaN/GaN power device with vertical structure according to the present invention.

Detailed ways

The following examples can enable those skilled in the art to understand the present invention more comprehensively, but the present invention is not limited to the scope of the described examples.

Example

The AlGaN/GaN power device with a vertical structure in this embodiment, as shown in Figures 1 and 2, includes a drain electrode 1, an n ⁺ -GaN layer 2 and an n-GaN U-shaped trench 3 arranged in sequence from bottom to top, An AlGaN u-shaped trench 4 whose upper surface is flush with the upper surface of the n-GaN U-shaped trench 3 and whose depth is smaller than the depth of the n-GaN U-shaped trench 3 is provided in the n-GaN U-shaped trench 3, and the AlGaN A layer of SiN _x u-shaped gate 5 is provided on the inner surface of the u-shaped trench 4; a p-GaN 6 whose upper surface is flush with the upper surface of the n-GaN U-shaped trench 3 is filled in the SiN _x u-shaped gate 5; The middle part of the upper surface of p-GaN 6 is provided with a dielectric passivation layer 8 covering p-GaN 6, _SiNx u-shaped gate 5 and part of the AlGaN u-shaped trench 4, and the upper surface of the dielectric passivation layer 8 is also provided with a covering dielectric The passivation layer 8 and the source electrode 9 of the n-GaNU-shaped trench 3, and the gate electrode 7 connected to the p-GaN 6 are arranged symmetrically on both sides of the source electrode 9.

In this embodiment, the source electrode 9 covers an area slightly smaller than the dielectric passivation layer 8 in the direction parallel to the SiN _x u-shaped gate 5; the thickness of the drain electrode 1 is 20nm-500nm, and the thickness of the n ⁺ -GaN layer 2 is 500nm to 3μm, the depth of the n-GaN U-shaped groove 3 is 2μm to 5μm, the width between the notches of the n-GaN U-shaped groove 3 is 2μm to 3μm, and the depth of the AlGaN u-shaped groove 4 is 1.5 μm to 4 μm, the width between the openings of the AlGaN u-shaped trench 4 is 1 μm to 2 μm, the thickness of the SiN _x u-shaped gate 5 is 10nm to 50nm, the thickness of the dielectric passivation layer 8 is 50nm to 500nm, and the source electrode The length of 9 is 100nm-500nm, the thickness is 20nm-500nm, and the side length of gate electrode 7 is 500nm-2μm.

The AlGaN/GaN power device with a vertical structure in this embodiment is prepared through the following steps:

(1) As shown in FIG. 3 , on the sapphire substrate 10 , a layer with a thickness of 500 nm is grown on the sapphire substrate 10 with Si as the dopant at a doping concentration of 1×10 ¹⁸ cm ^-3 to 5×10 ¹⁹ cm ^-3 . ~3 μm n ⁺ -GaN layer 2;

(2) As shown in Fig. 4, on the n ⁺ -GaN layer 2, Si is used as the dopant, and the doping concentration is 1×10 ¹⁷ cm ^-3 ~ 5×10 ¹⁸ cm ^-3 to grow a layer thickness An n-GaN layer of 2 μm to 5 μm;

(3) As shown in Figure 5, etch vertically on the n-GaN layer to the interface between the n ⁺ -GaN layer and the n-GaN layer, and finally form a groove with a depth of 2 μm to 5 μm and a width between the notches an n-GaN U-shaped trench 3 of 2 μm to 3 μmu;

(4) As shown in FIG. 6 , grow AlGaN in the etched n-GaN U-shaped trench 3 until the n-GaN U-shaped trench 3 is filled;

(5) As shown in FIG. 7 , vertically etch the AlGaN again to etch an AlGaN u-shaped groove 4 with a depth of 1.5 μm to 4 μm and a width between the notches of 1 μm to 2 μm;

(6) As shown in FIG. 8 , grow a high-quality SiN _x thin layer in the AlGaN u-shaped trench 4 as a gate dielectric to form a SiN _x u-shaped gate 5 with a thickness of 10 nm to 50 nm;

(7) As shown in Figure 9, grow p-GaN 6 in the SiN _x u-shaped gate 5 until the u-shaped trench is filled, the dopant is Mg, and the doping concentration is 5×10 ¹⁶ cm ^-3 ~5 ×10 ¹⁸ cm ^-3 ;

(8) As shown in Figure 10, a layer of passivation layer with a thickness of between 50nm and 500nm is uniformly grown on the surface of the device;

(9) As shown in Figure 11, perform selective etching on the dielectric passivation layer, etch horizontally until the interface between the Al-GaN layer and the n-GaN layer is exposed, and vertically etch until a sufficient length is left in the middle to make the source electrode;

(10) As shown in Figure 12, a layer of metal with a thickness of 20nm to 500nm is deposited on the surface of the device by evaporation or other methods, as shown in Figure 13, the deposited first layer of metal is etched vertically until the middle part is exposed Part of the dielectric passivation layer is exposed to form a strip-shaped source electrode with a length of 100nm-500nm across the AlGaN u-shaped trench 4, and a block-shaped source electrode with a side length of 500nm-2μm is exposed at both ends of the AlGaN u-shaped trench 4 metal as gate electrode 7;

(11) As shown in Figure 14, the sapphire at the bottom is removed by laser lift-off, as shown in Figure 15, and a layer with a thickness of 20nm to 500nm is deposited on the lower surface of the exposed n ⁺ -GaN layer 2 by evaporation or other methods metal as the drain electrode 1.

In this embodiment, the metal in step (10) and step (11) is selected from Ti/Al/Ni/Au one or more metal alloys or metal multilayer composite structures.

In this embodiment, there is an AlGaN/GaN power device with a vertical structure and its preparation method. Through the interface between n-GaN and AlGaN arranged in the vertical direction, the two-dimensional electron gas can move in the vertical direction and form a channel, thereby enhancing the two-dimensional electron gas. The movement rate; at the same time, the control ability of the two-dimensional electron gas is improved through the gate of the u-shaped trench structure; the p-GaN filled in the u-shaped trench gate can make the HEMT cut off without a positive gate bias, Form an enhanced HEMT with a wider range of applications; in addition, through the spatially separated gate electrodes drawn from both ends and the coating of passivation layers in other areas, the problem of unstable turn-on voltage caused by gate pollution caused by other process flows can be avoided .

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (2)

1. an AlGaN/GaN power device with a vertical structure is characterized by comprising a drain electrode, an n ⁺ -GaN layer and an n-GaN U-shaped groove which are sequentially arranged from bottom to top, wherein an AlGaN U-shaped groove with an upper surface flush with the upper surface of the n-GaN U-shaped groove and a depth smaller than the depth of the n-GaN U-shaped groove is arranged in the n-GaN U-shaped groove, a SiNx U-shaped gate dielectric layer is arranged on the inner surface of the AlGaN U-shaped groove, a p-GaN with an upper surface flush with the upper surface of the n-GaN U-shaped groove is filled in the SiNx U-shaped gate dielectric layer, a dielectric passivation layer covering the p-GaN, the SiNx U-shaped gate dielectric layer and a part of the U-shaped groove is arranged in the middle of the upper surface of the p-GaN, the SiNx-shaped gate dielectric layer and a part of the U-shaped groove, a dielectric passivation layer covering the dielectric passivation layer and a source electrode of the n-GaN U-shaped groove are further arranged on the upper surface of the dielectric passivation layer, grid electrodes connected with the GaN are symmetrically arranged on two sides of the GaN electrode, the AlGaN/GaN power device with the vertical structure, the AlGaN power device is characterized by comprising a drain electrode, an AlGaN/GaN power device, an AlGaN power device with a drain electrode, an AlGaN/GaN power device, an AlGaN U-GaN power device with a vertical structure, an AlGaN power device, an upper surface, an AlGaN U-GaN power device with a vertical structure, an AlGaN U-GaN power device, an upper surface flush with a vertical structure, an AlGaN U-GaN power device is arranged from bottom, an AlGaN U-GaN power device, an AlGaN.

2. The AlGaN/GaN power device with vertical structure of claim 1, wherein: and the coverage area of the source electrode in the connecting line direction of the symmetrically arranged gates is smaller than that of the dielectric passivation layer.