CN108198758B - A vertical structure gallium nitride power diode device and its manufacturing method - Google Patents

Abstract

The invention provides a method for manufacturing a gallium nitride power diode device with a vertical structure, which comprises the following steps: step one, providing a substrate and an epitaxial layer on the substrate; step two, providing the surface of the epitaxial layer for patterning and etching the groove; depositing first anode metal on the surface of the epitaxial layer between the grooves; step four, covering a second anode metal in the groove and on the surface of the first layer of anode metal; and fifthly, manufacturing a cathode on the back of the device. The invention can improve the forward output current and the reverse blocking voltage of the device and improve the device performance of the gallium nitride power diode.

Description

A vertical structure gallium nitride power diode device and its manufacturing method

technical field

The invention relates to the technical field of semiconductors, in particular to a vertical structure gallium nitride power diode device and a manufacturing method thereof.

Background technique

Modern technology constantly puts forward higher requirements on the volume, reliability, withstand voltage, power consumption and other aspects of semiconductor power devices. As the feature size of transistors shrinks, due to physical laws such as short channel effects and limitations of manufacturing costs, mainstream silicon-based materials and CMOS technologies are developing to the 10nm process node and it is difficult to continue to improve. Gallium nitride has a wide band gap, high thermal conductivity, strong atomic bonds, good chemical stability, high operating temperature, high breakdown voltage, strong radiation resistance and other properties, suitable for optoelectronics, high-temperature high-power devices and High frequency microwave devices and other applications. Therefore, gallium nitride is considered to be a new generation of integrated circuit semiconductor materials and has broad application prospects.

The geometries of semiconductor power diodes fall into two categories: lateral and vertical. The high-power GaN-based diode with lateral structure using sapphire as the growth substrate has the advantages of large size, low cost and good CMOS process compatibility, but it is difficult to obtain high output current, low heat dissipation efficiency, and current congestion. The current density is low, the production cost is high, and it is inevitably plagued by problems such as high-voltage current collapse caused by surface states.

In the prior art, in order to solve the problem of heat dissipation of a high-power GaN-based semiconductor diode with a lateral structure, a flip-chip technology is proposed. However, the flip-chip technology is complicated in process and high in production cost. In addition, the substrate cost of the traditional vertical structure GaN-based diode is extremely high, and the substrate peeling technology is extremely demanding, which is not easy to achieve.

Therefore, there is an urgent need to design a new vertical structure GaN-based power diode and its fabrication method, so as to solve the problems of small output current and current collapse of the lateral structure high-power GaN-based semiconductor diode, and effectively apply to high-voltage and high-power electronics field of application.

SUMMARY OF THE INVENTION

The vertical structure gallium nitride power diode device and the manufacturing method thereof provided by the present invention can effectively improve the output current of the gallium nitride-based semiconductor diode device, solve the problem of current collapse, and improve the performance of the gallium nitride-based semiconductor device. performance of diode devices.

In a first aspect, the present invention provides a method for fabricating a gallium nitride power diode device with a vertical structure, including:

Step 1, providing a substrate and an epitaxial layer on the substrate;

Step 2, providing the surface of the epitaxial layer for patterning and etching grooves;

Step 3, depositing a first anode metal on the surface of the epitaxial layer between the grooves;

Step 4, covering the second anode metal in the groove and on the surface of the first layer of anode metal;

Step 5, making a cathode on the back of the device.

Optionally, the substrate in the first step is a heavily doped N ⁺ -GaN substrate, and the epitaxial layer is a lightly doped N ^- -GaN epitaxial layer.

Optionally, in the second step, the groove is obtained by etching a gate groove etching process.

Optionally, the third step further includes the step of patterning the first anode metal, so as to realize the surface contact of the epitaxial layer with the groove.

Optionally, the first anode metal is an alloy or a non-alloy.

Optionally, the first anode metal is a superalloy for achieving good contact with the surface of the epitaxial layer.

Optionally, the fourth step further includes the step of patterning the second anode metal, so as to cover the inside of the groove and the surface of the first anode metal.

In another aspect, the present invention provides a diode device fabricated according to the above-mentioned method, comprising:

a substrate and an epitaxial layer on the substrate;

a first anode metal deposited between the grooves etched on the surface of the epitaxial layer;

a second anode metal filled in the groove etched on the surface of the epitaxial layer and covering the surface of the first anode metal;

The cathode on the back of the device.

The vertical structure gallium nitride power diode device and the manufacturing method thereof provided by the embodiments of the present invention can avoid the damage of the semiconductor material caused by the high temperature injection activation of the traditional vertical structure gallium nitride power diode, and improve the forward output current and reverse direction of the device. Blocking voltage, reducing process difficulty, and improving device performance of gallium nitride power diodes.

Description of drawings

FIG. 1 is a schematic diagram of the overall structure of a vertical structure gallium nitride power diode device according to an embodiment of the present invention;

2A-2E are schematic structural diagrams of a fabrication process of a vertical structure gallium nitride power diode device according to an embodiment of the present invention.

FIG. 3 is a process flow diagram of a manufacturing method of a vertical structure GaN power diode device according to an embodiment of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In a first aspect, the present invention provides a vertical structure gallium nitride (GaN) power diode device structure. FIG. 1 shows a schematic diagram of the overall structure of a vertical structure gallium nitride power diode device according to an embodiment of the present invention. As shown in the figure, 100 is a heavily doped N ⁺ -GaN substrate. Specifically, a large amount of group V impurities such as phosphorus, arsenic or antimony are added to the gallium nitride semiconductor material to form an N ⁺ substrate. A heavily doped N ⁺ -GaN substrate is formed by thermal diffusion or ion implantation; 101 is a lightly doped N ^- -GaN epitaxial layer/drift region. Specifically, a small amount of phosphorus, arsenic is added to the gallium nitride semiconductor material. Or antimony and other V group impurities to form the N ^-- GaN epitaxial layer/drift region, in particular, the N ^{--GaN epitaxial layer/drift region can be formed by thermal diffusion or ion implantation; 102 is the N-- GaN} epitaxial layer/drift region. The first layer of anode metal deposited on 101, specifically, can be deposited by processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, sputtering, atomic layer deposition (ALD), etc. In particular, The material of the first layer of anode metal can include but is not limited to Ti or Al, preferably, the first layer ^of anode metal is fabricated by patterning; The second layer of anode metal in the etched groove and covering the surface of the first layer of anode metal 102, specifically, the second layer of anode metal 103 can be formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), Electroplating, sputtering, atomic layer deposition (ALD) and other processes are realized. In particular, the material of the second layer of anode metal may include but not limited to Ni or Au. Preferably, the second layer of anode metal is fabricated by patterning; 108 is a diode the cathode of the device.

2A-2E are schematic diagrams illustrating a manufacturing process structure of a vertical structure gallium nitride power diode device according to an embodiment of the present invention.

As shown in FIG. 2A, a heavily doped N ⁺ -GaN substrate 100 and a lightly doped N ^-- GaN epitaxial layer/drift region 101 are provided. Specifically, a large or small amount of group V impurities such as phosphorus, arsenic or antimony are respectively added to the GaN semiconductor material to form a heavily doped N ⁺ -GaN substrate 100 or a lightly doped N ^- -GaN epitaxial layer/ Drift region 101 . In particular, a heavily doped N ⁺ -GaN substrate 100 or a lightly doped N ^- -GaN epitaxial layer/drift region 101 can be formed by thermal diffusion or ion implantation.

As shown in FIG. 2B , patterned grooves are etched in the lightly doped N ⁻ -GaN epitaxial layer/drift region 101 by a gate trench etching technique. Specifically, the gate trench etching may include forming a barrier layer using oxides such as SiO ₂ , and patterning the surface of the barrier layer by spin-coating photoresist and performing dry etching/wet etching to obtain an etching window . Then, the N ^- -GaN epitaxial layer/drift zone 101 material in the above patterned etching window is etched by dry etching technology to form grooves corresponding to the surface of the N ^- -GaN epitaxial layer/drift zone, and then the remaining barriers are removed Floor. A device with grooves is obtained as shown in Figure 2B.

As shown in FIG. 2C, a first layer of anode metal is deposited on the surface of the N ^-- GaN epitaxial layer/drift region between the grooves. Specifically, the first layer of anode metal 102 may be deposited by processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, sputtering, atomic layer deposition (ALD). In particular, the material of the first layer of anode metal can include but not limited to Ti or Al, the first layer of anode metal 102 can exist in alloy or non-alloy, and can be combined with N ^- -GaN epitaxial layer/drift after superalloying The area surface forms a good contact. Preferably, the first layer of anode metal is patterned.

As shown in FIG. 2D , the second layer of anode metal 103 is filled in the grooves etched by the N ⁻ -GaN epitaxial layer/drift region 101 through the gate trench etching technique, and covers the surface of the first layer of anode metal 102 . Specifically, the second layer of anode metal 103 can be realized by processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, sputtering, atomic layer deposition (ALD), etc. In particular, the material of the second layer of anode metal Can include, but is not limited to, Ni or Au. Preferably, the second layer of anode metal is patterned.

As shown in FIG. 2E , 108 is the cathode of the diode device, and the diode cathode 108 is disposed on the backside of the diode device, that is, disposed on the backside of the heavily doped N ⁺ -GaN substrate 100 .

In another aspect, the present invention provides a method for fabricating a vertical structure GaN power diode device. FIG. 3 shows a process flow diagram of a method for fabricating a vertical structure GaN power diode device according to an embodiment of the present invention. As shown, S31 represents providing a heavily doped N ⁺ -GaN substrate and a lightly doped N ^-- GaN epitaxial layer/drift region; S32 represents in a lightly doped N ^-- GaN epitaxial layer/drift region The patterned grooves are etched by gate groove etching technology; S33 represents the deposition of a first layer of anode metal on the surface of the N ^- -GaN epitaxial layer/drift region between the above grooves; S34 represents the first layer of anode metal in the above grooves and the first A second layer of anode metal is formed on the surface of the layer of anode metal; S35 represents making the cathode of the diode device on the back of the device.

The vertical structure of the gallium nitride power diode device and the manufacturing method thereof provided by the embodiments of the present invention can form a pattern area in the gallium nitride drift region through the groove etching technology, and deposit two layers of anode metal on the surface, so as to avoid the traditional vertical structure. The semiconductor material damage caused by the high-temperature injection activation of GaN power diodes increases the forward output current and reverse blocking voltage of the device, reduces the process difficulty, improves the device performance of GaN power diodes, and promotes the development of GaN-based power diodes. Applications of power diodes in high current and high power conversion.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical scope disclosed by the present invention can easily think of changes or substitutions. All should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (8)

1. A method for manufacturing a gallium nitride power diode device with a vertical structure is characterized by comprising the following steps:

step one, providing a substrate and an epitaxial layer on the substrate;

step two, providing the surface of the epitaxial layer for patterning and etching a groove;

depositing first anode metal on the surface of the epitaxial layer between the grooves, wherein the first anode metal is paved on the epitaxial layer between the grooves;

step four, covering a second anode metal in the groove and on the surface of the first layer of anode metal;

and fifthly, manufacturing a cathode on the back of the device.

2. The method for manufacturing a diode device according to claim 1, wherein the substrate in the first step is heavily doped N⁺-a GaN substrate, said epitaxial layer being lightly doped N^--a GaN epitaxial layer.

3. The method for manufacturing a diode device according to claim 1, wherein in the second step, the groove is obtained by etching through a gate trench etching process.

4. The method for manufacturing a diode device according to claim 1, wherein the third step further comprises a step of patterning the first anode metal for surface contact with the epitaxial layer between the grooves.

5. The method of claim 1, wherein the first anode metal is an alloy or an unalloyed metal.

6. The method of claim 5, wherein the first anode metal is a high temperature alloy for good contact with the surface of the epitaxial layer.

7. The method of claim 1, wherein the fourth step further comprises a step of patterning the second anode metal to cover the inside of the recess and the surface of the first anode metal.

8. A diode device made according to the method of claim 1, comprising:

a substrate and an epitaxial layer on the substrate;

first anode metal deposited between grooves etched on the surface of the epitaxial layer, wherein the first anode metal is paved on the epitaxial layer between the grooves;

the second anode metal is filled in the groove etched on the surface of the epitaxial layer and covers the surface of the first anode metal;

a cathode on the back side of the device.

Images