High voltage gan-based diode with stepped floating metal ring and method of fabrication

Abstract

The application discloses a high-voltage GaN-based diode with a stepped floating metal ring, which comprises an N+ GaN layer, an N-GaN layer, a stepped floating metal ring, a cathode and an anode; the N-GaN layer is arranged above the N+ GaN layer, the stepped floating metal ring is arranged in the N-GaN layer, the cathode is arranged on the bottom surface of the N+ GaN layer, and the anode is arranged on the top surface of the N-GaN layer; the stepped floating metal ring structure in the application does not introduce additional parasitic capacitance and has little influence on the N-GaN layer of the middle current conduction part; the forward current density is not obviously reduced; and the vertical stepped floating metal ring structure disperses the electric field in the vertical direction and can greatly improve the breakdown voltage compared with the horizontal floating metal ring.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microelectronic device technology and process technology, in particular to a high-voltage GaN-based diode with a stepped floating metal ring and a manufacturing method thereof. BACKGROUND

[0002] With the gradual maturity of semiconductor technology, the third generation of semiconductor materials represented by GaN, SiC and semiconductor diamond has emerged and gradually become a research hotspot in the semiconductor industry. Compared with traditional semiconductor materials, GaN has good chemical stability, high working temperature, high breakdown voltage and low on-resistance, which makes up for the shortcomings of the previous two generations of semiconductor materials.

[0003] At present, in the conventional lateral structure, current collapse and self-heating effect are important problems restricting the development of devices, and the vertical structure of GaN devices has the advantages of high power density, high reliability, uniform heat distribution, etc., and has many advantages over planar GaN devices. Diode as a basic two-terminal device has important applications in rectification, detection, limiting, etc. due to its low opening voltage, high switching frequency and other advantages, and it is developing in the direction of high breakdown voltage, high switching ratio and low on-resistance. However, there are problems of junction edge electric field concentration and non-uniform electric field distribution in GaN-based power diodes, which seriously restrict the voltage improvement of GaN-based power diodes.

[0004] Therefore, a high-voltage GaN-based diode with a stepped floating metal ring and a manufacturing method thereof have become a problem to be solved. SUMMARY

[0005] The technical problem to be solved by the present application is the problem of junction edge electric field concentration and non-uniform electric field distribution in GaN-based power diodes, which seriously restricts the voltage improvement of GaN-based power diodes.

[0006] To solve the above technical problems, the technical scheme provided by the present application is as follows: a high-voltage GaN-based diode with a stepped floating metal ring, the high-voltage GaN-based diode comprising an N+ GaN layer, an N-GaN layer, a stepped floating metal ring, a cathode and an anode.

[0007] The N-GaN layer is arranged above the N+ GaN layer, the stepped floating metal ring is arranged inside the N-GaN layer, the cathode is arranged on the bottom surface of the N+ GaN layer, and the anode is arranged on the top surface of the N-GaN layer.

[0008] Further, the thickness of the N+ GaN layer is 1-4 um, and the thickness of the N-GaN layer is 3-9 um.

[0009] A high-voltage GaN-based diode with a stepped floating metal ring and a manufacturing method thereof, comprising a high-voltage GaN-based diode with a stepped floating metal ring, and a manufacturing method thereof is shown as follows:

[0010] Step 1, epitaxial material growth:

[0011] A 3-9 um N-GaN layer is grown on a 1-4 um N+ GaN layer by using an MOCVD process;

[0012] Step 2, manufacturing of a groove:

[0013] An ICP etching technology is used to set a groove on the N-GaN layer structure, the groove has a depth of 0.2-1.5 um, a width of 1-3 um, a hole number of 2 or more, and the depth of the groove on the left and right sides of the anode is symmetrical and decreases in a stepped manner from the edge to the anode;

[0014] Step 3, manufacturing of a cathode:

[0015] A cathode is manufactured on the bottom surface of the N+ GaN layer;

[0016] Step 4, manufacturing of an anode and a stepped floating metal ring:

[0017] A top surface anode and a floating metal ring Schottky metal are deposited.

[0018] Compared with the prior art, the present application has the advantages that the present application adopts the cooperation structure of the N+ GaN layer, the N-GaN layer, the stepped floating metal ring, the cathode and the anode, the stepped floating metal ring structure does not introduce additional parasitic capacitance, and has little influence on the N-GaN layer of the middle current conduction part; the forward current density is not obviously reduced; the vertical stepped floating metal ring structure disperses the electric field in the vertical direction, and can greatly improve the breakdown voltage compared with the horizontal floating metal ring; the present application is reasonable in design, and is worth promoting. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a cross-sectional schematic view of a high-voltage GaN-based diode with a stepped floating metal ring.

[0020] Figure 2 is a flow chart of a manufacturing method of a high-voltage GaN-based diode with a stepped floating metal ring.

[0021] Figure 3 is a reverse semi-logarithmic characteristic curve of a stepped floating metal ring device, a conventional floating metal ring device and a metal ring-free device.

[0022] Figure 4is the electric field distribution curve of the stepped floating metal ring device and the traditional floating metal ring device, the metal ring device without voltage of 200V.

[0023] As shown in the figure: 1, N+GaN layer, 2, N-GaN layer, 3, stepped floating metal ring, 4, cathode, 5, anode. DETAILED DESCRIPTION

[0024] The application is further described in detail below with reference to the accompanying drawings of a high-voltage GaN-based diode with a stepped floating metal ring and a manufacturing method thereof.

[0025] In combination with the Figures 1-4 The application is described in detail.

[0026] A high-voltage GaN-based diode with a stepped floating metal ring, the high-voltage GaN-based diode comprising an N+GaN layer 1, an N-GaN layer 2, a stepped floating metal ring 3, a cathode 4 and an anode 5;

[0027] The N-GaN layer 2 is arranged above the N+GaN layer 1, the stepped floating metal ring 3 is arranged inside the N-GaN layer 2, the cathode 4 is arranged on the bottom surface of the N+GaN layer 1, and the anode 5 is arranged on the top surface of the N-GaN layer 2.

[0028] The thickness of the N+GaN layer 1 is 1-4um, and the thickness of the N-GaN layer 2 is 3-9um.

[0029] A high-voltage GaN-based diode with a stepped floating metal ring and a manufacturing method thereof, comprising a high-voltage GaN-based diode with a stepped floating metal ring, and the manufacturing method of the high-voltage GaN-based diode is as follows:

[0030] Step 1, epitaxial material growth:

[0031] Using MOCVD process, 3-9um N-GaN layer 2 is grown on 1-4um N+GaN layer 1;

[0032] Step 2, manufacturing of grooves:

[0033] Using ICP etching technology, grooves are arranged on the N-GaN layer 2 structure, the groove depth is 0.2-1.5um, the width is 1-3um, the number of holes is 2 or more, and the depth of the grooves on the left and right sides of the anode is symmetrical and decreases in a stepped manner from the edge to the anode;

[0034] Step 3, cathode manufacturing:

[0035] The cathode 4 is manufactured on the bottom surface of the N+GaN layer 1;

[0036] Step 4, manufacturing of anode 5 and stepped floating metal ring 3:

[0037] Depositing a top surface anode and a floating metal ring Schottky metal.

[0038] The embodiment of the present application of high-voltage GaN-based diode with stepped floating metal ring and its manufacturing method is as follows:

[0039] Step 1, epitaxial material growth:

[0040] On the 3um N+GaN layer 1, 4um N-GaN layer 2 is grown by MOCVD process;

[0041] Step 2, manufacturing of grooves:

[0042] First, the glue is spun by a glue spinner at a speed of 3000R / min, and the photoresist model used is AZ6130, and then the NSR1755I7A photoetching machine is used for exposure to form a groove area mask pattern;

[0043] Then, the substrate with the mask is etched by ICP98c type inductive coupled plasma etching machine in Cl2 plasma at an etching rate of 1nm / s, and the depth of the grooves on the left and right sides of the anode is symmetrical and decreases in steps from the edge to the anode, and the etching depth is 1.3um, 1.0um, 0.7um, 0.4um, 0.4um, 0.7um, 1.0um, 1.3um respectively;

[0044] Step 3, manufacturing of cathode 4:

[0045] First, the photoresist is spun by a glue spinner at a speed of 5000R / min to obtain a photoresist mask thickness of 0.8um;

[0046] Next, the photoresist is baked in a high-temperature oven at a temperature of 80℃ for 10min, and the NSR1755I7A photoetching machine is used for exposure to form a cathode area mask pattern;

[0047] Then, the Ohmiker-50 electron beam evaporation table is used to manufacture the cathode at an evaporation rate of 0.1nm / s, and the ohmic metal is selected as Ti / Al / Ni / Au, wherein the thickness of Ti is 20nm, the thickness of Al is 160nm, the thickness of Ni is 55nm, and the thickness of Au is 45nm. After the evaporation of the ohmic contact metal of the cathode is completed, the metal is stripped to obtain a complete cathode;

[0048] Finally, the RTP500 rapid thermal annealing furnace is used to perform rapid thermal annealing at 750℃ in N2 atmosphere for 30s to alloy the ohmic contact metal and complete the manufacturing of the cathode;

[0049] Step 4, manufacturing of anode 5 and stepped floating metal ring 3:

[0050] First, the glue is spun at a speed of 5000R / min by a glue spinner to obtain a photoresist mask thickness of 0.8um;

[0051] Next, the temperature is 80℃ in the high-temperature oven for 10min, and NSR1755I7A photoetching machine is used for exposure to form an anode and a Schottky metal area mask pattern;

[0052] Finally, Ohmiker-50 electron beam evaporation table is used to evaporate the anode metal at an evaporation rate of 0.1nm / s, and the anode and Schottky metal are selected in turn as Ni / Au, wherein the thickness of Ni is 45nm, and the thickness of Au is 200nm; after evaporation, metal stripping is carried out to obtain a complete device.

[0053] The application adopts the cooperation structure of N+GaN layer 1, N-GaN layer 2, stepped floating metal ring 3, cathode 4 and anode 5, the stepped floating metal ring 3 structure does not introduce additional parasitic capacitance, and has little influence on the N-GaN layer 2 of the middle current conduction part; the forward current density is not obviously reduced; the vertical stepped floating metal ring structure disperses the electric field in the vertical direction, and can greatly improve the breakdown voltage compared with the horizontal floating metal ring; the application has reasonable design, and is worth promoting.

[0054] The above describes the application and its embodiments, which is not limited, and the drawings only show one of the embodiments of the application, and the actual structure is not limited thereto. In summary, if the ordinary skilled in the art is inspired, without departing from the purpose of the application, without creative design, similar structure and embodiments of the technical scheme, which should belong to the protection scope of the application.

Claims

1. A method of fabricating a high voltage GaN-based diode with a stepped floating metal ring, comprising: The high-voltage GaN-based diode comprises an N+ GaN layer (1), an N-GaN layer (2), a stepped floating metal ring (3), a cathode (4) and an anode (5); ​ The N-GaN layer (2) is arranged above the N+ GaN layer (1), the stepped floating metal ring (3) is arranged inside the N-GaN layer (2), the cathode (4) is arranged on the bottom surface of the N+ GaN layer (1), and the anode (5) is arranged on the top surface of the N-GaN layer (2); The thickness of the N+ GaN layer (1) is 1-4 um, and the thickness of the N-GaN layer (2) is 3-9 um; The manufacturing method of the high-voltage GaN-based diode is as follows: Step 1, epitaxial material growth: Using MOCVD process, 3-9 um N-GaN layer (2) is grown on 1-4 um N+ GaN layer (1); Step 2, manufacturing of grooves: Using ICP etching technology, grooves are arranged on the N-GaN layer (2) structure, the groove depth is 0.2-1.5 um, the width is 1-3 um, the hole number is 2 or more, and the depth of the grooves on the left and right sides of the anode is symmetrical and decreases in a stepped manner from the edge to the anode; Step 3, manufacturing of cathode: The cathode (4) is manufactured on the bottom surface of the N+ GaN layer (1); Step 4, manufacturing of anode (5) and stepped floating metal ring (3): Depositing top anode and floating metal ring Schottky metal.

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