A gallium oxide longitudinal field effect transistor with integrated freewheeling diode

Abstract

The application belongs to the technical field of power semiconductor, and relates to a gallium oxide vertical field effect transistor with an integrated freewheeling diode. When the gate / source voltage is zero, the difference in work function between the gate / source electrode metal and the gallium oxide semiconductor depletes a conductive channel; as the gate / source voltage increases, the depletion region gradually narrows until a high-concentration electron accumulation layer is formed on the channel sidewall. Therefore, when forward conduction occurs, the application can reduce the on-resistance and enhance the forward current capacity; when forward blocking occurs, the leakage current of the field effect transistor is effectively reduced, the breakdown voltage of the device is improved, and the threshold voltage is improved; when forward blocking or forward conduction occurs, the integrated diode is in an off state, which does not affect the on and withstand voltage characteristics of the field effect transistor. When reverse current is continued, the integrated diode is turned on, has a low on-voltage and a low on-voltage drop. The field effect transistor and the integrated diode of the application are compatible in process, are integrated by single-chip process, and are beneficial to reducing parasitic inductance and the size of a module.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor technology and relates to a gallium oxide longitudinal field-effect transistor with an integrated freewheeling diode. Background Technology

[0002] Power MOSFETs offer superior switching performance compared to bipolar devices, making them widely used in high-frequency power switching. Gallium oxide (GaO) possesses an ultra-wide bandgap and a high breakdown electric field; its Baliga figure of merit is 4 times that of GaN, 10 times that of SiC, and 3444 times that of Si. Theoretically, it offers higher operating temperatures, greater power output, lower losses, smaller size, and stronger radiation resistance. Therefore, GaO is expected to become a preferred material for high-voltage, high-power, low-loss power devices, meeting the demands of high power density, high conversion efficiency, and compact, lightweight power systems, and has broad application prospects.

[0003] Currently, effective P-type doping of gallium oxide (GaO) has not yet been achieved, making it difficult for GaO-based power MOSFETs to achieve enhancement-mode devices with positive threshold voltages. Furthermore, the absence of parasitic reverse conduction current in the PN junction body diode necessitates packaging with a separate freewheeling diode into a module to achieve reverse freewheeling functionality. Therefore, challenges exist in circuit design, parasitic inductance, packaging cost, module area, and chip heat dissipation. Schottky diodes are commonly used as integrated freewheeling diodes in GaN and SiC power MOSFETs; however, Schottky contacts occupy additional chip area and have significant leakage current, while temperature has a substantial impact on Schottky performance. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a gallium oxide longitudinal field-effect transistor with an integrated freewheeling diode.

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

[0006] A gallium oxide longitudinal field-effect transistor with an integrated freewheeling diode includes a drain electrode 1, an N-type gallium oxide drain region 2 located on the upper surface of the drain electrode 1, and an N-type gallium oxide drift region 3 located on the upper surface of the N-type gallium oxide drain region 2.

[0007] The device is characterized in that the upper surface of the N-type gallium oxide drift region 3 has a first fin-shaped gallium oxide drift region 4-1 and a second fin-shaped gallium oxide drift region 4-2 spaced apart along the transverse direction of the device; the upper surface of the first fin-shaped gallium oxide drift region 4-1 has a first N+ highly doped gallium oxide region 5-1, and the upper surface of the second fin-shaped gallium oxide drift region 4-2 has a second N+ highly doped gallium oxide region 5-2; the upper surface of the N-type gallium oxide drift region 3 and the sidewalls of the first fin-shaped gallium oxide drift region 4-1 and the second fin-shaped gallium oxide drift region 4-2 are covered with a first insulating medium 6; the device element is divided by the extension line of the centerline of the first insulating medium 6 between the first fin-shaped gallium oxide drift region 4-1 and the second fin-shaped gallium oxide drift region 4-2. The cell is defined as a transistor region and a diode region, and the first finned gallium oxide drift region 4-1 is located in the transistor region, and the second finned gallium oxide drift region 4-2 is located in the diode region. The upper surface of the first insulating medium 6 in the transistor region is covered with a gate electrode 7; the surface of the gate electrode 7 is covered with a second insulating medium 8, and the second insulating medium 8 extends to contact the sidewall of the first N+ highly doped gallium oxide region 5-1; the upper surfaces of the second insulating medium 8 and the first N+ highly doped gallium oxide region 5-1 are covered with a source electrode 9; the upper surface of the first insulating medium 6 in the diode region is covered with a source electrode 9, and the source electrode 9 of the diode region completely covers the second N+ highly doped gallium oxide region 5-2, and the source electrode 9 of the transistor region is in contact with the source electrode 9 of the diode region.

[0008] Furthermore, the upper surface of the first insulating medium 6 of the diode region also has a second insulating medium 8, and the second insulating medium 8 of the diode region is connected to the second insulating medium 8 of the transistor region. At the same time, it extends along the surface of the first insulating medium 6 outside the sidewall of the second fin gallium oxide drift region 4-2 towards the direction close to the second N+ highly doped gallium oxide region 5-2, and does not contact the second N+ highly doped gallium oxide region 5-2.

[0009] The beneficial effects of this invention are that the field-effect transistor has a high threshold voltage and a high breakdown voltage, and the freewheeling diode has a low turn-on voltage and a low on-state voltage drop, thus realizing monolithic integration of the field-effect transistor and the freewheeling diode. Attached Figure Description

[0010] Figure 1 This is a cross-sectional structural diagram of Embodiment 1 of the present invention;

[0011] Figure 2 This is a cross-sectional structural diagram of Embodiment 2 of the present invention; Detailed Implementation

[0012] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0013] Example 1:

[0014] like Figure 1 As shown, this example includes a drain electrode 1, an N-type gallium oxide drain region 2 located on the upper surface of the drain electrode 1, and an N-type gallium oxide drift region 3 located on the upper surface of the N-type gallium oxide drain region 2; characterized in that the upper surface of the N-type gallium oxide drift region 3 has first fin-shaped gallium oxide drift regions 4-1 and second fin-shaped gallium oxide drift regions 4-2 spaced apart along the transverse direction of the device; the upper surface of the first fin-shaped gallium oxide drift region 4-1 has a first N+ highly doped gallium oxide region 5-1, and the upper surface of the second fin-shaped gallium oxide drift region 4-2 has a second N+ highly doped gallium oxide region 5-2; the upper surface of the N-type gallium oxide drift region 3 and the sidewalls of the first fin-shaped gallium oxide drift region 4-1 and the second fin-shaped gallium oxide drift region 4-2 are covered with a first insulating medium 6; the first fin-shaped gallium oxide drift region 4-1 and the second fin-shaped gallium oxide drift region 4-2 are covered with a first insulating medium 6; the first fin-shaped gallium oxide drift region 4-1 and the second fin-shaped gallium oxide drift region 4-2 are covered with a first insulating medium 6. The extension line of the first insulating medium 6 between regions 4-2 serves as a boundary line, defining the device cell as a transistor region and a diode region. The first finned gallium oxide drift region 4-1 is located in the transistor region, and the second finned gallium oxide drift region 4-2 is located in the diode region. The upper surface of the first insulating medium 6 in the transistor region is covered with a gate electrode 7. The surface of the gate electrode 7 is covered with a second insulating medium 8, which extends to contact the sidewall of the first N+ highly doped gallium oxide region 5-1. The upper surfaces of the second insulating medium 8 and the first N+ highly doped gallium oxide region 5-1 are covered with a source electrode 9. The upper surface of the first insulating medium 6 in the diode region is covered with a source electrode 9, and the source electrode 9 of the diode region completely covers the second N+ highly doped gallium oxide region 5-2. The source electrode 9 of the transistor region is in contact with the source electrode 9 of the diode region.

[0015] The working principle of this example is as follows:

[0016] This invention proposes a gallium oxide longitudinal field-effect transistor (GaOLFET) with an integrated freewheeling diode. When the applied voltage to the gate electrode 7 is zero, the work function difference between the gate electrode metal and the gallium oxide semiconductor of the first finned gallium oxide drift region 4-1 depletes the conductive channel, and the field-effect transistor is turned off. As the gate voltage increases, the depletion region narrows and the device enters a forward conduction state, achieving a positive threshold voltage. When the gate voltage further increases, a high-concentration electron accumulation layer forms on the sidewall of the first finned gallium oxide drift region 4-1, enhancing the forward current capability and reducing the on-resistance. In the forward blocking state, the leakage current is effectively suppressed and the breakdown voltage is increased because the conductive channel is pinched off. Furthermore, the source electrode 9 also functions as the anode of the integrated diode. During the operation of the field-effect transistor, when the applied voltage to the source electrode 9 is zero, the work function difference between the source electrode metal and the gallium oxide semiconductor of the second finned gallium oxide drift region 4-2 depletes the conductive channel, and the integrated diode is in a turned-off state, without affecting the conduction and breakdown voltage characteristics of the field-effect transistor. During reverse freewheeling, the source electrode 9 is at a positive voltage relative to the drain electrode 1, which shrinks the depletion region of the second finned gallium oxide drift region 4-2, creating a current path between the source electrode 9 and the drain electrode 1. This allows the integrated freewheeling diode to conduct, exhibiting a low turn-on voltage and a low forward voltage drop. Therefore, the field-effect transistor of this invention has a high threshold voltage and a high breakdown voltage, while the freewheeling diode has a low turn-on voltage and a low forward voltage drop, enabling monolithic integration of the field-effect transistor and the freewheeling diode.

[0017] Example 2:

[0018] like Figure 2 As shown, the difference between this embodiment and Embodiment 1 is that the upper surface of the first insulating medium 6 in the diode region also has a second insulating medium 8, and the second insulating medium 8 in the diode region is connected to the second insulating medium 8 in the transistor region. Simultaneously, it extends along the surface of the first insulating medium 6 outside the sidewall of the second finned gallium oxide drift region 4-2 towards the second N+ highly doped gallium oxide region 5-2, and does not contact the second N+ highly doped gallium oxide region 5-2. Compared to Embodiment 1, the second insulating medium 8 on the second side forms a stepped field plate with the first insulating medium 6, further modulating the electric field distribution and increasing the breakdown voltage.

Claims

1. A gallium oxide longitudinal field effect transistor with integrated freewheeling diode, comprising a drain electrode (1), an N-type gallium oxide drain region (2) on the upper surface of the drain electrode (1), an N-type gallium oxide drift region (3) on the upper surface of the N-type gallium oxide drain region (2); characterized in that the upper surface of the N-type gallium oxide drift region (3) has a first fin-shaped gallium oxide drift region (4-1) and a second fin-shaped gallium oxide drift region (4-2) distributed at intervals along the lateral direction of the device; the upper surface of the first fin-shaped gallium oxide drift region (4-1) has a first N+ highly doped gallium oxide region (5-1), and the upper surface of the second fin-shaped gallium oxide drift region (4-2) has a second N+ highly doped gallium oxide region (5-2); the upper surface of the N-type gallium oxide drift region (3) and the sidewalls of the first fin-shaped gallium oxide drift region (4-1) and the second fin-shaped gallium oxide drift region (4-2) are covered with a first insulating medium (6); the first insulating medium (6) is used as a boundary line to define a transistor region and a diode region, and the first fin-shaped gallium oxide drift region (4-1) is located in the transistor region and the second fin-shaped gallium oxide drift region (4-2) is located in the diode region; the upper surface of the first insulating medium (6) in the transistor region is covered with a gate electrode (7); the surface of the gate electrode (7) is covered with a second insulating medium (8) which extends to contact the sidewall of the first N+ highly doped gallium oxide region (5-1); the upper surface of the second insulating medium (8) and the first N+ highly doped gallium oxide region (5-1) are covered with a source electrode (9); the upper surface of the first insulating medium (6) in the diode region is covered with a source electrode (9), and the source electrode (9) in the diode region completely covers the second N+ highly doped gallium oxide region (5-2), and the source electrode (9) in the transistor region is in contact with the source electrode (9) in the diode region.

2. A gallium oxide longitudinal field effect transistor with integrated freewheeling diode according to claim 1, characterized in that The upper surface of the first insulating medium (6) in the diode region also has a second insulating medium (8), and the second insulating medium (8) in the diode region is connected to the second insulating medium (8) in the transistor region, and also extends along the surface of the first insulating medium (6) outside the sidewall of the second fin-shaped gallium oxide drift region (4-2) in the direction close to the second N+ highly doped gallium oxide region (5-2) without contacting the second N+ highly doped gallium oxide region (5-2).

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