A hydrogen plasma treated partitioned passivated p-gan bridge hemt device

Abstract

The application belongs to the technical field of power semiconductors, and relates to a hydrogen plasma processing partitioned passivation p-GaN bridge HEMT device. The structure has the advantages of high withstand voltage, low dynamic resistance, high threshold voltage, high gate breakdown voltage, high threshold voltage stability and the like. The structure replaces the etching technology by hydrogen plasma passivation processing, can significantly reduce the AlGaN surface trap concentration, improve the interface quality, inhibit the current collapse effect and dynamic resistance degradation; the thin layer p-GaN extending from the gate to the drift region as an active passivation region, uses the charge balance mechanism to improve the device breakdown voltage; the p-GaN cap layer after the gate surface passivation can improve the device threshold voltage, gate breakdown voltage and gate service life; the p-GaN bridge arranged in the longitudinal direction between the gate and the source realizes the introduction of the "discharge path" of the gate region, relieves the charge storage effect of the gate region, and realizes higher threshold voltage stability.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor technology, specifically referring to a hydrogen plasma-treated, partitioned passivated p-GaN bridge HEMT device. Background Technology

[0002] Benefiting from its advantages such as high breakdown voltage, fast switching speed, low conduction loss, low off-state leakage current, and high-temperature resistance, GaN power devices are widely used in high-frequency, high-voltage, and high-power applications. p-GaN gate HEMT technology is widely adopted in industry due to its stable positive threshold voltage and mature process, and it has enormous application potential in the power semiconductor field. However, p-GaN HEMTs require low gate leakage current to ensure normal device operation and a long lifespan. To suppress gate leakage current, a gate metal that can form a Schottky contact with the p-GaN layer is typically chosen to construct the Schottky p-GaN gate.

[0003] However, p-GaN HEMTs still face some unresolved issues in practical applications: ① The Schottky gate exhibits significant gate leakage current, and under high gate bias, holes injected into p-GaN via tunneling can bombard the metal / p-GaN interface, creating defects. Both of these factors contribute to a lower gate breakdown voltage, which in turn leads to a smaller gate voltage swing and a narrower gate safe operating region. ② Due to the low activation rate of Mg dopants, the hole concentration in p-GaN is low, resulting in a threshold voltage as low as 0–2V for p-GaN gate HEMTs. This lower threshold voltage increases the likelihood of false turn-on. ③ The Schottky junction and p-GaN / AlGaN / GaN... PIN diodes form a back-to-back diode group, leaving the p-GaN layer in a floating state. This floating p-GaN layer in the gate region generates a charge storage effect, leading to threshold voltage drift. ④ Traditional etching processes introduce high concentrations of surface traps and interface states on the AlGaN barrier layer surface, exacerbating current collapse and dynamic resistance degradation. ⑤ Currently, the breakdown voltage and specific on-resistance of GaN power devices are far from their theoretical limits; achieving high breakdown voltage and low on-resistance remains a relentless pursuit. Therefore, improving device structure to enhance breakdown voltage, increase gate breakdown voltage, reduce gate leakage current, achieve higher and more stable threshold voltage, and mitigate current collapse and dynamic resistance degradation is of great significance. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a hydrogen plasma-treated, partitioned passivated p-GaN bridge HEMT device. This structure employs hydrogen plasma treatment instead of etching to achieve an enhancement-mode device; the gate p-GaN surface is also treated with hydrogen plasma; three p-GaN regions exist (gate p-GaN, a thin, spaced-apart p-GaN bridge extending from the gate to the source, and a thin p-GaN layer extending from the gate towards the drift region).

[0005] The technical solution of this invention is as follows:

[0006] A hydrogen plasma-treated, partitioned passivated p-GaN bridge HEMT device includes a substrate layer 1, a nucleation layer 2, a buffer layer 3, a GaN channel layer 4, a barrier layer 5, and a high-resistivity GaN material 6, which are stacked sequentially from bottom to top along the vertical direction of the device; a first conductive material 7, a gate structure, and a third conductive material 12 are arranged sequentially from left to right along the horizontal direction; there is a gap between the gate structure and the first conductive material 7 and the third conductive material 12; the first conductive material 7 and the third conductive material 12 extend vertically downward from their surfaces to the GaN channel layer 4 and form ohmic contacts with the GaN channel layer 4, and their leads are the source electrode and the drain electrode, respectively.

[0007] The high-resistivity GaN material 6 is characterized in that it is a high-resistivity GaN material formed by hydrogen plasma passivation of P-type GaN material; the gate structure is composed of P-type GaN material 9, high-resistivity GaN material 6 and second conductive material 11 stacked on the upper surface of the barrier layer 5, and the lead-out end of the second conductive material 11 is the gate electrode; there is a P-type GaN material 8 between the upper surface of the barrier layer 5, the first conductive material 7 and the gate structure, and the left and right ends of the P-type GaN material 8 are in contact with the first conductive material 7 and the P-type GaN material 9, respectively; there is a P-type GaN material 10 extending horizontally to the right from the gate structure on the upper surface of the barrier layer 5, the left end of the P-type GaN material 10 is in contact with the P-type GaN material 9, and there is a gap between the right end and the third conductive material 12, and the gap is filled with high-resistivity GaN material 6; the thickness of the P-type GaN material 8 and the P-type GaN material 10 is lower than that of the P-type GaN layer 9.

[0008] Furthermore, the P-type GaN materials 8 are arranged at intervals in the longitudinal direction, and the gaps in the P-type GaN materials 8 in the longitudinal direction are filled with high-resistivity GaN materials 6.

[0009] Furthermore, the P-type GaN materials 10 are arranged at intervals in the longitudinal direction, and the gaps in the P-type GaN materials 10 in the longitudinal direction are filled with high-resistivity GaN material 6.

[0010] Furthermore, the barrier layer 5 is composed of one or more of AlN, AlGaN, InGaN, and InAlN.

[0011] The beneficial effects of this invention are as follows:

[0012] 1. Achieving low dynamic resistance: By replacing etching with hydrogen plasma passivation, the surface trap concentration of AlGaN can be significantly reduced and the interface quality improved, thereby suppressing the current collapse effect and dynamic resistance degradation of the device.

[0013] 2. Achieving high breakdown voltage: The thin layer of p-GaN extending from the gate to the drift region serves as an active passivation region, utilizing a charge balance mechanism to achieve a mechanism similar to that of a superjunction, thereby improving the device breakdown voltage;

[0014] 3. Achieving high threshold voltage and high gate breakdown voltage: p-GaN with a gate surface treated by hydrogen plasma can be used as a gate cap layer to improve the device threshold voltage, gate breakdown voltage and gate lifetime;

[0015] 4. Achieving threshold voltage stability: The thin p-GaN bridges that extend from the gate to the source and are spaced apart in the longitudinal direction introduce a "discharge path" in the gate region, which alleviates the charge storage effect in the gate region and thus achieves higher threshold voltage stability. Attached Figure Description

[0016] Figure 1 This is a structural schematic diagram of Example 1;

[0017] Figure 2 This is a structural schematic diagram of Example 2;

[0018] Figure 3 This is a schematic diagram of the structure of Example 3;

[0019] Figure 4 This is a schematic diagram of the process flow for layered and partitioned hydrogen plasma passivation in Example 3;

[0020] Figure 5 This is a comparison of the simulation results of the electric field distribution near the drain end of the gate in Example 1 and the conventional p-GaN gate HEMT device in the blocking state;

[0021] Figure 6 These are the transfer characteristic curves of Example 1 and the conventional p-GaN gate HEMT device before and after different drain stresses. Detailed Implementation

[0022] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0023] Example 1

[0024] like Figure 1 As shown, a hydrogen plasma-treated partitioned passivated p-GaN bridge HEMT device includes a substrate layer 1, a nucleation layer 2, a buffer layer 3, a GaN channel layer 4, a barrier layer 5, and a high-resistivity GaN material 6 stacked sequentially from bottom to top along the vertical direction of the device; a first conductive material 7, a gate structure, and a third conductive material 12 are arranged sequentially from left to right along the horizontal direction; there is a gap between the gate structure and the first conductive material 7 and the third conductive material 12; the first conductive material 7 and the third conductive material 12 extend vertically downward from the surface to the GaN channel layer 4 and form an ohmic contact with the GaN channel layer 4, and their leads are the source electrode and the drain electrode, respectively;

[0025] The high-resistivity GaN material 6 is characterized in that it is a high-resistivity GaN material formed by hydrogen plasma passivation of P-type GaN material; the gate structure is composed of P-type GaN material 9, high-resistivity GaN material 6 and second conductive material 11 stacked on the upper surface of the barrier layer 5, and the lead-out end of the second conductive material 11 is the gate electrode; there is a P-type GaN material 8 between the upper surface of the barrier layer 5, the first conductive material 7 and the gate structure, and the left and right ends of the P-type GaN material 8 are in contact with the first conductive material 7 and the P-type GaN material 9, respectively; there is a P-type GaN material 10 extending horizontally to the right from the gate structure on the upper surface of the barrier layer 5, the left end of the P-type GaN material 10 is in contact with the P-type GaN material 9, and there is a gap between the right end and the third conductive material 12, and the gap is filled with high-resistivity GaN material 6; the thickness of the P-type GaN material 8 and the P-type GaN material 10 is lower than that of the P-type GaN layer 9.

[0026] The working principle of this invention is as follows: This invention proposes a hydrogen plasma-treated, partitioned passivated p-GaN bridge HEMT device. This structure uses hydrogen plasma passivation instead of etching, which significantly reduces the trap concentration on the AlGaN surface and improves interface quality, thereby suppressing the current collapse effect and dynamic resistance degradation of the device. A thin layer of p-GaN extending from the gate to the drift region serves as an active passivation region, utilizing a charge balance mechanism to achieve a superjunction-like effect, thus improving the device breakdown voltage. The p-GaN on the gate surface, after hydrogen plasma treatment, can serve as a gate cap layer, improving the device threshold voltage, gate breakdown voltage, and gate lifetime. Thin p-GaN bridges, spaced apart in the longitudinal direction and extending from the gate to the source, introduce a "discharge path" to the gate region, mitigating the charge storage effect in the gate region and achieving higher threshold voltage stability. In summary, this structure simultaneously possesses advantages such as high withstand voltage, low dynamic resistance, high threshold voltage, high gate breakdown voltage, and high threshold voltage stability.

[0027] Figure 5This image compares the simulation results of the electric field distribution near the drain end of the gate in the blocking state between the hydrogen plasma-treated partitioned passivated p-GaN bridge HEMT device proposed in this invention and a conventional p-GaN gate HEMT device. Simulations were performed using Sentaurus TCAD software. The simulation results show that the active passivation region of the proposed structure effectively suppresses the electric field spikes near the drain edge of the gate, thus improving the device's breakdown voltage.

[0028] Figure 6 The present invention presents transfer characteristic curves of a hydrogen plasma-treated, partitioned passivated p-GaN bridge HEMT device and a conventional p-GaN gate HEMT device before and after different drain stresses. Figure 6 It can be seen that the threshold voltage V of the structure proposed in this invention TH The threshold voltage reached 2.23V, significantly higher than the 1.88V of conventional devices, demonstrating that the p-GaN bridge between the gate and source and the p-GaN cap layer passivating the gate can improve the threshold voltage. Furthermore, the transfer characteristic curve of the proposed structure did not show significant shift after being subjected to different drain stresses, exhibiting extremely strong threshold voltage stability. This is attributed to the p-GaN bridge between the gate and source introducing a "discharge path" for free carriers in the gate region, mitigating the charge storage effect. In contrast, the transfer characteristic curve of conventional devices showed a significant shift, with a substantial increase in threshold voltage.

[0029] Example 2

[0030] The difference between this example and Example 1 is that in this example, a hydrogen plasma-processed partitioned passivated p-GaN bridge HEMT device is described, wherein the p-type GaN materials 8 are arranged at intervals in the longitudinal direction, and the gaps in the p-type GaN materials 8 in the longitudinal direction are filled with high-resistivity GaN materials 6.

[0031] Compared to Example 1, the advantage of this example is that the p-type GaN materials 8 arranged at intervals in the longitudinal direction result in a smaller cross-sectional area for the p-GaN bridge between the gate and source, which can effectively reduce the gate leakage current of the device.

[0032] Example 3

[0033] The difference between this example and Example 1 is that in this example, a hydrogen plasma-processed partitioned passivated p-GaN bridge HEMT device is described, wherein the p-type GaN materials 10 are arranged at intervals in the longitudinal direction, and the gaps in the p-type GaN materials 10 in the longitudinal direction are filled with high-resistivity GaN materials 6.

[0034] Compared to Example 1, the advantage of this example is that the P-type GaN materials 10 arranged at intervals in the longitudinal direction realize a superjunction-like mechanism in the longitudinal direction, which enhances the electric field modulation effect of the active passivation region in the longitudinal direction and further enhances the voltage withstand capability of the device.

[0035] Figure 4 This is a schematic diagram of the process flow for the partitioned hydrogen plasma passivation of p-GaN bridge HEMT devices proposed in this invention. Figure (a) shows the initial epitaxial wafer structure; Figure (b) shows the hydrogen plasma surface layer injection process; Figure (c) shows the hydrogen plasma intermediate layer injection process; and Figure (d) shows the hydrogen plasma deep layer injection process.

Claims

1. A hydrogen plasma-treated partitioned passivated p-GaN bridge HEMT device, comprising a substrate layer (1), a nucleation layer (2), a buffer layer (3), a GaN channel layer (4), a barrier layer (5), and a high-resistivity GaN material (6) stacked sequentially from bottom to top along the vertical direction of the device; a first conductive material (7), a gate structure, and a third conductive material (12) are sequentially arranged from left to right along the lateral direction of the device surface; there is a gap between the gate structure and the first conductive material (7) and the third conductive material (12); the first conductive material (7) and the third conductive material (12) extend from the device surface downward along the vertical direction into the GaN channel layer (4) and form an ohmic contact with the GaN channel layer (4), and their leads are the source electrode and the drain electrode, respectively; Its features are, The high-resistivity GaN material (6) is a high-resistivity GaN material formed by hydrogen plasma passivation of P-type GaN material; the gate structure is composed of a first P-type GaN material (9), a high-resistivity GaN material (6), and a second conductive material (11) stacked on the upper surface of the barrier layer (5), and the lead-out end of the second conductive material (11) is the gate electrode; a second P-type GaN material (8) is provided between the barrier layer (5), the first conductive material (7), the high-resistivity GaN material (6), and the gate structure, and the left and right ends of the second P-type GaN material (8) are respectively connected to the first conductive material (7) and the first P-type GaN material (9). The second P-type GaN material (8) is in contact with the barrier layer (5) and the high-resistivity GaN material (6) at its upper and lower ends respectively; the upper surface of the barrier layer (5) has a third P-type GaN material (10) extending horizontally to the right from the gate structure. The left end of the third P-type GaN material (10) is in contact with the first P-type GaN material (9), and there is a gap between the right end and the third conductive material (12). The gap is filled with high-resistivity GaN material (6); the thickness of the second P-type GaN material (8) and the third P-type GaN material (10) is lower than that of the first P-type GaN material (9).

2. The hydrogen plasma-treated partitioned passivated p-GaN bridge HEMT device according to claim 1, characterized in that, The second P-type GaN material (8) is arranged at intervals in the longitudinal direction, and the gaps in the second P-type GaN material (8) in the longitudinal direction are filled with high-resistivity GaN material (6).

3. The hydrogen plasma-treated, partitioned passivated p-GaN bridge HEMT device according to claim 1, characterized in that, The third P-type GaN material (10) is arranged at intervals in the longitudinal direction, and the gaps in the third P-type GaN material (10) in the longitudinal direction are filled with high-resistivity GaN material (6).

4. The hydrogen plasma-treated, partitioned passivated p-GaN bridge HEMT device according to claim 1, characterized in that, The barrier layer (5) is composed of one or more of AlN, AlGaN, InGaN, and InAlN.

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