A low threshold voltage SiC round gate VDMOSFET power device

Abstract

The invention provides a low threshold voltage SiC circular gate VDMOSFET power device, comprising a drain electrode, an N-type heavily doped substrate layer, an N-type lightly doped epitaxial layer, a P-type well region, a source electrode and a gate electrode from bottom to top in a vertical direction; the gate electrode is circular; the entire gate electrode is cylindrical, and except for the top portion, the gate electrode is surrounded by a high-k dielectric; a dielectric groove is provided on the P-type well region, and the longitudinal depth of the dielectric groove is less than the depth of the P-type well region; the source electrode and the drain electrode are both arranged in the dielectric groove; the contact portion between the gate electrode and the source electrode presents a natural transition, and there is no sharp angle, so the breakdown problem caused by charge accumulation is not likely to occur, thereby improving the reliability of the VDMOSFET.

Description

[Technical field]

[0001] The invention relates to a low threshold voltage SiC circular gate VDMOSFET power device. [Background technology]

[0002] SiC DevicesSiC materials have attracted extensive attention and research due to their superior physical properties. Their high-temperature, high-power electronic devices have the advantages of high input impedance, fast switching speed, high operating frequency, high temperature and high pressure resistance, and have been widely used in switching power supplies, high-frequency heating, automotive electronics, and power amplifiers.

[0003] However, it still has technical and economic problems such as high threshold voltage, high driving voltage at saturation current, many material defects, low channel mobility, and high cost, which seriously restrict the development of SiC power devices. [Summary of the invention]

[0004] The technical problem to be solved by the present invention is to provide a low threshold voltage SiC circular gate VDMOSFET power device, thereby improving the reliability of the VDMOSFET.

[0005] The present invention is implemented as follows: a low threshold voltage SiC circular gate VDMOSFET power device includes a drain electrode, an N-type heavily doped substrate layer, an N-type lightly doped epitaxial layer, a P-type well region, a source electrode and a gate electrode vertically from bottom to top;

[0006] The gate is circular; the entire gate is cylindrical, and except for the top, it is surrounded by high-k dielectric;

[0007] A dielectric groove is provided on the P-type well region, and the longitudinal depth of the dielectric groove is less than the depth of the P-type well region;

[0008] The source electrode and the drain electrode are both arranged in the dielectric groove.

[0009] Furthermore, the source is a ring structure, and the gate is arranged inside the source.

[0010] Furthermore, a protrusion is provided in the dielectric groove, and the bottom of the gate is connected to the protrusion.

[0011] Furthermore, the source is an annular structure, and its inner bottom protrudes horizontally inward to form a convex portion; the convex portion is connected to the outer side of the protrusion, and the upper surface of the convex portion is connected to the bottom of the gate.

[0012] Furthermore, the dielectric volumes of the gates are equal.

[0013] The advantages of the present invention are: a low threshold voltage SiC circular gate VDMOSFET power device of the present invention;

[0014] 1. It has a circular gate structure, where the gate structure is located at the center of the power device and the shape of the gate is circular;

[0015] Second, the source is a ring surrounding the circular gate. Because the electric field controlled by the circular gate can diffuse in all directions, the circular source area controlled by the circular gate is larger under the same area conditions, so its on-resistance is smaller under the same area;

[0016] 3. The gate structure is circular, so the contact part with the source presents a natural transition, there is no sharp angle, and it is not easy to cause breakdown problems caused by charge accumulation, which improves the reliability of VDMOSFET.

Brief Description of the Drawings

[0017] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0018] Figure 1 A top view of a circular gate SiC VDMOSFET power device provided by an embodiment of the present invention;

[0019] Figure 2 A cross-sectional view of the center position of a circular gate SiC VDMOSFET power device provided by an embodiment of the present invention;

[0020] Figure 3 A non-central cross-sectional view of a circular gate SiC VDMOSFET power device provided in an embodiment of the present invention. [Specific implementation method]

[0021] The embodiment of the present invention solves the technical problems in the prior art such as high threshold voltage, high driving voltage at saturation current, more material defects, low channel mobility and high cost by providing a low threshold voltage SiC circular gate VDMOSFET power device, thereby achieving the technical effects of low on-resistance, low threshold voltage and high reliability.

[0022] See also Figures 1 to 3 As shown, a low threshold voltage SiC circular gate VDMOSFET power device of the present invention includes a drain electrode, an N-type heavily doped substrate layer, an N-type lightly doped epitaxial layer, a P-type well region, a source electrode and a gate electrode vertically from bottom to top;

[0023] The gate is circular; the entire gate is cylindrical, and except for the top, it is surrounded by high-k dielectric;

[0024] A dielectric groove is provided on the P-type well region, and the longitudinal depth of the dielectric groove is less than the depth of the P-type well region;

[0025] The source electrode and the drain electrode are both arranged in the dielectric groove.

[0026] In another embodiment of the present invention, the source is a ring structure, and the gate is disposed inside the source.

[0027] In another embodiment of the present invention, a protrusion is provided in the dielectric groove, and the bottom of the gate is connected to the protrusion.

[0028] In another embodiment of the present invention, the source is an annular structure, and its inner bottom protrudes horizontally inward to form a protrusion; the protrusion is connected to the outer side of the protrusion, and the upper surface of the protrusion is connected to the bottom of the gate.

[0029] In another embodiment of the present invention, the dielectric thickness, length and width of the gate are equal, that is, the volume sizes are consistent; the dielectric of the gate may be silicon dioxide or other high-K dielectrics.

[0030] The source of the circular gate SiC VDMOSFET power device is a ring structure surrounding the circular gate. Because the electric field controlled by the circular gate can diffuse in all directions, the source area controlled by the circular gate is larger under the same area and voltage conditions, so its on-resistance is smaller under the same area.

[0031] The source of the circular gate SiC VDMOSFET power device is a ring structure surrounding the circular gate. Because the electric field controlled by the circular gate can diffuse in all directions, the source controlled by the circular gate can be turned on under lower voltage conditions. When the threshold voltage is measured using the constant current method, its threshold voltage is lower.

[0032] The dielectric thickness and width of the entire circular gate are equal, ensuring that the electric field generated by the gate in all directions is equal, enhancing consistency, and reducing uneven electric field distribution caused by different dielectric thickness and width.

[0033] The gate structure is circular, so there is a natural transition with the source contact part, and there will be no electric field concentration effect caused by sharp angles, which will lead to charge accumulation and breakdown, thereby improving the reliability of VDMOSFET.

[0034] Since a circular gate structure is adopted, it can cut off the P-well region and generate current under a lower gate voltage, so its threshold voltage is lower.

[0035] The power device can be used for SiC power devices and SiC power integrated circuits.

[0036] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A low threshold voltage SiC round gate VDMOSFET power device, characterized in that: It includes a drain electrode, an N-type heavily doped substrate layer, an N-type lightly doped epitaxial layer, a P-type well region, a source electrode and a gate electrode from bottom to top; The gate is circular; the entire gate is cylindrical, and except for the top, it is surrounded by high-k dielectric; A dielectric groove is provided on the P-type well region, and the longitudinal depth of the dielectric groove is less than the depth of the P-type well region; The source electrode is arranged in the dielectric groove, and the drain electrode is arranged at the bottom side; A protrusion is provided in the dielectric groove, and the bottom of the gate is connected to the protrusion; The source electrode is a ring structure, and the gate electrode is arranged inside the source electrode; The inner bottom of the source electrode protrudes inward horizontally to form a protruding portion; the protruding portion is connected to the outer side of the protruding portion, and the upper surface of the protruding portion is connected to the bottom of the gate.

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