Substrate voltage regulation GaN HEMT power device

Abstract

The invention belongs to the technical field of power semiconductors, and discloses a substrate voltage regulation GaN HEMT power device which comprises a P substrate, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, a passivation layer and a floating field plate structure which are sequentially stacked from bottom to top in the vertical direction of the device. A source electrode, a gate structure and a drain electrode which are not in contact with one another are sequentially arranged on the surface of the AlGaN barrier layer in the transverse direction of the device; the floating field plate structure comprises a plurality of floating field plates which are not in contact with one another, the P substrate is connected with any one field plate in the floating field plate structure through metal, so that the potential of the P substrate is the same, the voltage of the floating field plate can regulate and control the voltage of the substrate, high voltage resistance is realized, and dynamic resistance degradation is inhibited. The method has the advantages that under the condition that on resistance is not increased, high voltage resistance is achieved, collapse of a dynamic resistor is restrained, additional process steps are not increased, the area of a chip is not increased additionally, and cost is saved.

Description

Technical Field

[0001] The present invention belongs to the field of power semiconductors, and in particular relates to a substrate voltage-regulated GaN HEMT power device. Background Art

[0002] As a third-generation semiconductor material, GaN has the advantages of wide bandgap, high critical breakdown electric field, and low dielectric constant. GaN HEMT (High Electron Mobility Transistor) devices can produce high-concentration and high-mobility two-dimensional electron gas (2DEG) through polarization effect at the heterojunction interface. Compared with silicon-based devices, they can obtain higher breakdown voltage and lower on-resistance. Compared with silicon carbide devices, they can have higher operating frequency, which is suitable for application in high-frequency, small-volume and relatively low-power electronic chips. However, there are still problems such as high electric field spikes at the electrodes and large leakage current caused by material defects in GaN HEMT devices. These factors restrict the further improvement of the performance of GaN power devices. At present, common technologies for improving the withstand voltage of HEMT devices include field plate technology, fluorine ion implantation technology, back barrier technology, etc. For example, patent application CN101414622A discloses a composite field plate heterojunction field effect transistor based on a source field plate and a drain field plate, which includes a heterojunction field effect transistor structure of several non-contacting floating field plates on the passivation layer between the source and drain field plates, which increases the area of ​​the device depletion region and improves the breakdown voltage, but the structure fails to solve the problems of excessive leakage current and current collapse caused by buffer layer defects. B. Li et al. proposed a substrate bias modulated field effect transistor structure in the document 900V Normally-OFF GaN-on-Si Transistors Achieved by Substrate Potential Modulation (SPM), which integrates an additional MOS tube to control the substrate voltage potential to obtain high withstand voltage and suppress dynamic resistance degradation, but the MOS tube integrated in the structure adds additional process steps and chip area, increasing the manufacturing cost of the device. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a substrate voltage-regulated GaN HEMT power device, which achieves high withstand voltage and suppresses dynamic resistance degradation without adding additional process steps and does not increase chip area, thus saving costs.

[0004] A substrate voltage-regulated GaN HEMT power device according to the present invention comprises a P substrate, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, a passivation layer and a floating field plate structure which are sequentially stacked from bottom to top along the vertical direction of the device; along the lateral direction of the device, a source electrode, a gate structure and a drain electrode which are not in contact with each other are sequentially arranged on the surface of the AlGaN barrier layer;

[0005] The floating field plate structure includes a plurality of floating field plates that are not in contact with each other, and the P substrate is connected to any field plate in the floating field plate structure through metal.

[0006] Furthermore, the gate structure includes a gate electrode and a P-type GaN layer stacked from top to bottom.

[0007] Furthermore, the gate structure comprises a gate trench, which extends downward from the surface into the AlGaN barrier layer in a vertical direction, and the inner wall is covered with a gate dielectric layer. The gate is arranged in the gate trench and contacts the bottom wall and side wall of the gate trench.

[0008] Furthermore, the lower ends of the source electrode and the drain electrode extend into the GaN channel layer to form an ohmic contact with the GaN channel layer.

[0009] Furthermore, the floating field plate structure includes a plurality of floating field plates that are not in contact with each other and are distributed at equal intervals along the lateral direction of the device.

[0010] The beneficial effects described in the present invention are as follows: the present invention adopts the floating field plate technology, connects the floating field plate potential to the substrate, and when blocked, when the depletion region extends to below the floating field plate connected to the substrate, the floating field plate is at a high potential, and the high substrate voltage connected thereto can assist in depleting the drift region and improve the withstand voltage; when turned on, the floating field plate potential and the substrate are both at a low potential, so the on-resistance hardly increases; during the switching process, when the device is in the on state, the net negative charge stored in the buffer layer flows to the substrate and then recombine in the floating field plate, thereby suppressing the dynamic resistance degradation. The present invention is realized in the process through layout design, does not require the addition of additional process steps, and does not increase the chip area, thus saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0012] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0013] Figure 3 is a blocking characteristic curve diagram of Example 2 of the present invention and a conventional HEMT;

[0014] Figure 4The two-dimensional electric field distribution of Example 2 of the present invention and a conventional HEMT in the blocking state, wherein (a) is the two-dimensional electric field distribution of the conventional structure HEMT in the blocking state, and (b) is the two-dimensional electric field distribution of Example 2 in the blocking state;

[0015] Figure 5 is a schematic diagram of the three-dimensional structure of Example 2;

[0016] Among them, 1-P substrate, 2-GaN buffer layer, 3-GaN channel layer, 4-AlGaN barrier layer, 5-passivation layer, 61-source electrode, 63-drain electrode, 7-P-type GaN layer, 8-floating field plate structure, 9-metal, and 10-gate dielectric layer. DETAILED DESCRIPTION

[0017] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0018] Example 1

[0019] like Figure 1 As shown, the present invention provides a substrate voltage-regulated GaN HEMT power device, comprising a P substrate 1, a GaN buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, a passivation layer 5 and a floating field plate structure 8 which are stacked in sequence from bottom to top along the vertical direction of the device; along the lateral direction of the device, on the surface of the AlGaN barrier layer 4 from one side to the other side are a source electrode 61, a gate structure and a drain electrode 63 which are not in contact with each other; the lower ends of the source electrode 61 and the drain electrode 63 extend into the GaN channel layer 3 to form an ohmic contact with the GaN channel layer 3; the floating field plate structure 8 comprises a plurality of floating field plates which are not in contact with each other and are distributed at equal intervals in the lateral direction, and the P substrate 1 is connected to any and only one field plate in the floating field plate structure 8 through a metal 9. The gate structure includes a gate trench, which extends downward from the surface in a vertical direction into the AlGaN barrier layer, and the inner wall of the gate trench is covered with a gate dielectric layer 10, and the gate is arranged in the gate trench and contacts the bottom wall and side wall of the gate trench. As the thickness of the barrier layer under the gate is reduced, the concentration of 2DEG generated by polarization is reduced, the threshold voltage is increased, and in the blocking state, the existence of the gate dielectric layer can reduce the leakage current to achieve the effect of increasing the withstand voltage.

[0020] The GaN HMET power device with substrate-regulated voltage connects the potential of the floating field plate to the substrate so that the floating field plate and the substrate potential are the same. The floating field plate voltage can regulate the substrate voltage to achieve high withstand voltage and suppress dynamic resistance degradation. When blocked, when the depletion region extends to the bottom of the floating field plate connected to the substrate, the floating field plate is at a high potential, and the high substrate voltage connected to it can assist in depleting the drift region and improve the withstand voltage; when turned on, the floating field plate potential and the substrate are both at a low potential, so the on-resistance hardly increases; during the switching process, when the device is in the on state, the net negative charge stored in the buffer layer flows to the substrate and then recombine in the floating field plate, so the dynamic resistance degradation can be suppressed.

[0021] Example 2

[0022] like Figure 2 and Figure 5 As shown, the difference between this example and Example 1 is that the gate structure of a substrate voltage-controlled GaN HEMT power device described in this example includes a gate electrode 62 and a P-type GaN layer 7 stacked from top to bottom. The P-type GaN layer 7 can increase the energy band of the barrier layer under the gate to increase the threshold voltage of the device and realize the device enhancement mode.

[0023] The comparison of the blocking characteristics of Example 2 and conventional HEMT obtained by simulation is shown in the figure below: Figure 3 As shown in FIG. 1 , the forward breakdown voltage of Example 2 is increased by 130% compared with the conventional HEMT. The two-dimensional electric field distribution of the conventional HEMT and Example 2 in the blocking state is shown in FIG. Figure 4 As shown, Figure 4 (a) is the two-dimensional electric field distribution of conventional HEMT in the blocking state. Figure 4 (b) is the two-dimensional electric field distribution in the blocking state of Example 2. Figure 4 In the figure, S represents the source electrode, D represents the drain electrode, G represents the gate electrode, and FP1 and FP2 represent floating field plates. Figure 4 It can be seen that, compared with conventional HEMT, the electric field peak value at the edge of the gate near the drain side of Example 2 is reduced, and the electric field distribution in the drift region is more uniform.

[0024] The above description is only a preferred embodiment of the present invention and is not intended to be a further limitation of the present invention. All equivalent changes made using the contents of the present specification and drawings are within the protection scope of the present invention.

Claims

1. A substrate voltage-regulated GaN HEMT power device, comprising a P substrate (1), a GaN buffer layer (2), a GaN channel layer (3), an AlGaN barrier layer (4), a passivation layer (5) and a floating field plate structure (8) which are stacked in sequence from bottom to top along the vertical direction of the device; along the lateral direction of the device, on the surface of the AlGaN barrier layer (4) are sequentially a source electrode (61), a gate structure and a drain electrode (63) which are not in contact with each other; It is characterized in that The floating field plate structure (8) comprises a plurality of floating field plates that are not in contact with each other, and the P substrate (1) is connected to any one of the field plates in the floating field plate structure (8) via metal (9).

2. The substrate voltage-controlled GaN HEMT power device according to claim 1, characterized in that: The gate structure comprises a gate electrode (62) and a P-type GaN layer (7) stacked from top to bottom.

3. The substrate voltage-controlled GaN HEMT power device according to claim 1, characterized in that: The gate structure comprises a gate trench, which extends downward from the surface of the passivation layer (5) into the AlGaN barrier layer in a vertical direction, the inner wall of the gate trench is covered with a gate dielectric layer (10), and the gate is arranged in the gate trench and contacts the bottom wall and side wall of the gate trench.

4. The substrate voltage-controlled GaN HEMT power device according to claim 1, characterized in that: The lower ends of the source electrode (61) and the drain electrode (63) extend into the GaN channel layer (3) to form an ohmic contact with the GaN channel layer (3).

5. The substrate voltage-controlled GaN HEMT power device according to claim 1, characterized in that: The floating field plate structure (8) comprises a plurality of floating field plates that are not in contact with each other and are distributed at equal intervals along the lateral direction of the device.

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