A GaN HEMT device with graded doped fluoride ion termination

Abstract

The present invention belongs to the field of power semiconductor technology and relates to a GaN HEMT device with a gradient-doped stepped fluorine ion terminal. The loading effect of dry etching is utilized to form a stepped groove from the source to the drain, with the window width gradually decreasing and the depth gradually becoming shallower. Furthermore, a fluorine ion region under the gate, achieved through a one-time fluorine ion implantation, and a gradient-doped stepped fluorine ion terminal are introduced, thereby achieving both enhanced mode and high withstand voltage. The gradient-doped stepped fluorine ion terminal can effectively reduce the electric field spike near the gate and introduce a new electric field spike at the terminal end near the drain, thereby optimizing the surface electric field distribution in the drift region and improving the withstand voltage of the device. At the same time, compared to a terminal structure in which fluorine ions are implanted in the barrier layer, implanting fluorine ions in the dielectric passivation layer can reduce the impact on the mobility of the two-dimensional electron gas, thereby improving the forward conduction and dynamic characteristics of the device.

Description

Technical Field

[0001] The present invention belongs to the technical field of power semiconductors, and in particular relates to a GaN HEMT device with a gradually doped stepped fluorine ion terminal. Background Art

[0002] GaN HEMT (High Electron Mobility Transistor) devices hold broad application prospects in high-current, low-power, and medium- and low-voltage switching applications. However, high electric field concentration excites hot electrons, leading to gate failure or a sharp increase in leakage current, and the device's breakdown voltage is far from its theoretical limit. Current methods for improving device breakdown voltage include field plate technology, fluorine ion implantation, termination technology, polarized superjunction technology, and compensatory doping technology. Furthermore, the presence of a high-density two-dimensional electron gas at the heterojunction interface makes it difficult to achieve high-threshold-voltage enhancement-mode high-voltage devices. This not only increases the risk of false-start circuits, but also increases overall circuit power consumption and the complexity of driver circuit design. Typical approaches to achieving enhancement-mode devices include recessed gate technology, P-GaN technology, cascode technology, fluorine ion implantation, and thin-barrier technology. Summary of the Invention

[0003] Based on the application needs of GaN HEMT devices, the present invention proposes a GaN HEMT device with a graded doped stepped fluorine ion termination. The device utilizes the loading effect of dry etching to form a stepped trench with decreasing depth from source to drain as the window width decreases. Furthermore, a fluorine ion region under the gate, created through a single fluorine ion implantation, and a graded doped stepped fluorine ion termination are introduced, achieving both enhancement mode and high withstand voltage.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0005] A GaN HEMT device with a graded doped step fluorine ion terminal comprises a substrate 1, a GaN buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, and a dielectric passivation layer 5, which are stacked in sequence from bottom to top along the vertical direction of the device; along the lateral direction of the device, the device surface comprises a source 6, a fluorine ion trench gate structure, a graded doped step fluorine ion terminal 8, and a drain 9, which are sequentially arranged from one side to the other; the source 6 and the drain 9 both penetrate the dielectric passivation layer 5 along the vertical direction of the device and extend into the AlGaN barrier layer 4, with the lower surface forming an ohmic contact with the AlGaN barrier layer 4; the fluorine ion trench gate structure comprises a fluorine ion region 80 under the gate and a gate 7, which penetrates the dielectric passivation layer 5 into the AlGaN barrier layer 4, and the lower surface forms ... In the barrier layer 4, the gate 7 extends into the dielectric passivation layer 5 along the device vertical direction, and its upper surface extends left and right to cover the dielectric passivation layer 5. Its right side does not contact the left edge of the gradually doped step fluorine ion terminal 8, and its lower surface contacts the fluorine ion region 80 under the gate. The gradually doped step fluorine ion terminal 8 is composed of a plurality of dielectric grooves 101 to 10N with successively shallower depths and narrower widths along the direction from the source to the drain, and a plurality of fluorine ion regions 81 to 8N in contact with the bottom of the grooves. The width of each fluorine ion region is the same as the width of the dielectric groove in contact with it. The fluorine ion region is only within the dielectric passivation layer 5, and the longitudinal distance from the upper surface of the AlGaN barrier layer 4 increases gradually along the direction from the source to the drain.

[0006] As a preferred embodiment, the spacings between the fluorine ion regions 81 to 8N in the graded-doped step fluorine ion terminal 8 in the lateral direction of the device are unequal, and the spacings increase sequentially along the direction from the source to the drain.

[0007] The beneficial effect of the present invention is that it utilizes the loading effect of dry etching to form a stepped groove with a depth that gradually decreases as the window width decreases from the source to the drain, and introduces a fluorine ion region under the gate and a gradually doped stepped fluorine ion terminal achieved by a one-time fluorine ion implantation, thereby achieving both enhanced mode and high withstand voltage. Specifically, the fluorine ion region under the gate can deplete the two-dimensional electron gas under the gate to achieve enhanced mode, and the gradually doped stepped fluorine ion terminal can effectively reduce the electric field spike near the gate and introduce a new electric field spike at the terminal end near the drain, thereby optimizing the surface electric field distribution in the drift region and improving the withstand voltage of the device. At the same time, compared with the terminal structure in which fluorine ions are implanted in the barrier layer, implanting fluorine ions in the dielectric passivation layer can reduce the impact on the mobility of the two-dimensional electron gas, thereby improving the forward conduction and dynamic characteristics of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram of the two-dimensional structure of Example 1;

[0009] Figure 2 is a top view of the gradually doped step fluorine ion terminal in Example 2; DETAILED DESCRIPTION

[0010] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments:

[0011] Example 1

[0012] A GaN HEMT device with a graded doped step fluorine ion terminal comprises a substrate 1, a GaN buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, and a dielectric passivation layer 5, which are stacked in sequence from bottom to top along the vertical direction of the device; along the lateral direction of the device, the device surface comprises a source 6, a fluorine ion trench gate structure, a graded doped step fluorine ion terminal 8, and a drain 9, which are sequentially arranged from one side to the other; the source 6 and the drain 9 both penetrate the dielectric passivation layer 5 along the vertical direction of the device and extend into the AlGaN barrier layer 4, with the lower surface forming an ohmic contact with the AlGaN barrier layer 4; the fluorine ion trench gate structure comprises a fluorine ion region 80 under the gate and a gate 7, which penetrates the dielectric passivation layer 5 into the AlGaN barrier layer 4, and the lower surface forms ... In the barrier layer 4, the gate 7 extends into the dielectric passivation layer 5 along the device vertical direction, and its upper surface extends left and right to cover the dielectric passivation layer 5. Its right side does not contact the left edge of the gradually doped step fluorine ion terminal 8, and its lower surface contacts the fluorine ion region 80 under the gate. The gradually doped step fluorine ion terminal 8 is composed of a plurality of dielectric grooves 101 to 10N with successively shallower depths and narrower widths along the direction from the source to the drain, and a plurality of fluorine ion regions 81 to 8N in contact with the bottom of the grooves. The width of each fluorine ion region is the same as the width of the dielectric groove in contact with it. The fluorine ion region is only within the dielectric passivation layer 5, and the longitudinal distance from the upper surface of the AlGaN barrier layer 4 increases gradually along the direction from the source to the drain.

[0013] The aforementioned GaN HEMT device with a graded-doped stepped fluoride termination utilizes the loading effect of dry etching to form a stepped trench with decreasing depth from source to drain as the window width decreases. Furthermore, a fluoride ion region under the gate, created through a single fluorine ion implantation, and a graded-doped stepped fluoride termination are introduced to achieve both enhancement-mode operation and high withstand voltage. The fluoride ion region under the gate depletes the two-dimensional electron gas under the gate, achieving enhancement-mode operation. The graded-doped stepped fluoride termination effectively reduces the electric field spike near the gate and introduces a new electric field spike at the terminal end near the drain, making the surface electric field more uniform and further improving the device's withstand voltage.

[0014] Example 2

[0015] This example differs from Example 1 in that the spacing between the fluoride regions 81-8N in the graded-doped step fluoride termination increases from source to drain. Because the spacing between the fluoride regions near the gate decreases, the fluoride regions near the gate are more densely distributed. Compared to Example 1, this example has the advantage of optimizing the spacing between the fluoride regions, effectively reducing the electric field spike at the gate corner and improving the device's withstand voltage.

Claims

1. A GaN HEMT device with a gradient doped step fluorine ion terminal, comprising, along the vertical direction of the device, a substrate (1), a GaN buffer layer (2), a GaN channel layer (3), an AlGaN barrier layer (4), and a dielectric passivation layer (5) stacked in sequence from bottom to top; along the lateral direction of the device, the device surface comprises, from one side to the other, a source electrode (6), a fluorine ion trench gate structure, a gradient doped step fluorine ion terminal (8), and a drain electrode (9); the source electrode (6) and the drain electrode (9) both penetrate the dielectric passivation layer (5) in the vertical direction of the device and extend into the AlGaN barrier layer (4), with the lower surface forming an ohmic contact with the AlGaN barrier layer (4); the fluorine ion trench gate structure comprises, from bottom to top, a fluorine ion region under the gate (80) and a gate electrode (7), wherein the gate under the gate The fluoride ion region (80) passes through the dielectric passivation layer (5) and enters the AlGaN barrier layer (4); the upper surface of the gate (7) extends leftward and rightward to cover the dielectric passivation layer (5) and does not contact the edge of the gradually doped step fluoride ion terminal (8); the lower surface of the gate (7) contacts the fluoride ion region (80) below the gate; the gradually doped step fluoride ion terminal (8) is composed of a plurality of dielectric grooves with successively shallower depths and successively narrower widths and a plurality of fluoride ion regions in contact with the groove bottoms along the direction from the source to the drain; the width of each fluoride ion region is the same as the width of the dielectric groove in contact; the fluoride ion region is only in the dielectric passivation layer (5), and the longitudinal distance from the upper surface of the AlGaN barrier layer (4) gradually increases along the direction from the source to the drain.

2. The GaN HEMT device with graded doping step fluoride ion termination according to claim 1, characterized in that: The spacing between the fluorine ion regions in the gradually doped step fluorine ion terminal (8) in the lateral direction of the device is unequal, and the spacing increases in sequence along the direction from the source to the drain.

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