SiC MOSFET device for improving single-particle radiation recombination efficiency

Abstract

The invention relates to the technical field of MOS (Metal Oxide Semiconductor), and discloses a SiC MOSFET (Metal Oxide Semiconductor Field Effect Transistor) device for improving single-particle radiation recombination efficiency, which comprises a drain electrode, a semiconductor epitaxial layer, a metal source electrode and a grid electrode, and is characterized in that an isolation medium is deposited on the outer surface of the grid electrode; the semiconductor epitaxial layer comprises a substrate layer, an epitaxial layer, a P well layer and a heavily doped N well layer; the P well layer comprises a lightly doped P well layer and a heavily doped P well layer; p-type doped regions are formed between the adjacent lightly doped P well layers through ion implantation, and N-type impurity ions are injected into the P-type doped regions to form N-type polycrystalline silicon. According to the invention, the P-type doped region is formed by injecting P-type impurities in the SiC MOSFET device, the N-type polycrystalline silicon is formed by ion injection in the P-type doped region, and the N-type polycrystalline silicon is in short circuit with the source metal, so that the trench structure transfers a strong electric field at a gate oxide interface to the bottom of the JFET region, the electric field intensity in the thin gate oxide is greatly reduced, and the single-particle gate penetration resistance of the SiC MOSFET device is improved.

Description

Technical Field

[0001] The present invention relates to the field of MOS semiconductor technology, and more particularly to a SiC MOSFET device for improving single particle radiation recombination efficiency. Background Art

[0002] Silicon carbide high-voltage power devices have better electrothermal properties than traditional silicon devices and can work normally in more demanding environments. Therefore, they have broad application prospects in photovoltaic power generation, electric vehicles, aerospace, etc. For the aerospace field, power devices must not only meet the requirements of high voltage, high power, high frequency and low loss, but also have good radiation resistance.

[0003] For high-voltage SiC power devices, radiation hardening is a major problem. Current SiC power devices often experience single-particle burnout when the blocking voltage is less than 1 / 3 and the LET is no higher than 10MeV.cm2 / mg, which is far lower than theoretical expectations. Single-particle radiation usually involves very complex electrothermal coupling responses inside the device. When heavy ions bombard the power device, a large number of electron-hole pairs are generated along the trajectory of motion. These electron-hole pairs drift under the action of the electric field, forming a large instantaneous current inside the device. Some electrons and holes will also accumulate at both ends of the device, thereby reconstructing the electric field inside the device, resulting in strong electric field breakdown in the device, such as single-particle gate breakdown. In addition, this large amount of electron-hole motion and strong electric field coupling generate a large amount of instantaneous heat inside the device, which may cause single-particle burnout in the device. For conventional planar gate SiC MOSFETs, the JFET region is the most sensitive area to single-particle radiation because it has the strongest electric field strength in the forward blocking state.

[0004] like Figure 2As shown in the common planar gate SiC MOSFET device structure in Figure 1, when heavy ions bombard the power device, a large number of electron-hole pairs will be generated along the trajectory of movement. These electron-hole pairs drift under the electric field formed by the reverse blocking voltage, forming a huge instantaneous current inside the device, especially the JFET region of the SiC MOSFET device, which becomes the weakest position due to the high electric field strength. On the one hand, the movement of a large number of electrons and holes under the action of the electric field will form an instantaneous large current in the local area of ​​the device, resulting in a large amount of power consumption and temperature rise in the local area of ​​the device, and eventually causing serious ablation damage to the local part of the device. In this process, the instantaneous large current and high temperature may also cause the parasitic NPN transistor in the SiC MOSFET device to turn on, exacerbating the single particle burning of the SiC MOSFET device. On the other hand, a large number of electrons and holes drift under the action of the electric field, and the excess carriers that are not extracted or recombined in time are accumulated on the surface and back of the device. In particular, the accumulation of a large number of holes on the surface of the JFET region may cause the gate oxide to break down, causing the SiC MOSFET device to have a single particle gate penetration and damage the device. Summary of the invention

[0005] The main technical problem solved by the present invention is to provide a SiC MOSFET device that improves the single particle radiation recombination efficiency, thereby solving the problems in the above-mentioned background technology.

[0006] To solve the above technical problems, according to one aspect of the present invention, more specifically, a SiC MOSFET device for improving single particle radiation recombination efficiency comprises a drain, a semiconductor epitaxial layer, a metal source, and a gate, wherein an isolation dielectric is deposited on the outer surface of the gate;

[0007] The semiconductor epitaxial layer includes a substrate layer, an epitaxial layer, a P-well layer and a heavily doped N-well layer;

[0008] The P-well layer includes a lightly doped P-well layer and a heavily doped P-well layer;

[0009] A P-type doped region is formed between adjacent lightly doped P-well layers by ion implantation, and N-type impurity ions are implanted inside the P-type doped region to form N-type polysilicon;

[0010] The gate in a single MOS cell is divided into two, and the length of each gate covers the P-type doped region.

[0011] Furthermore, the heavily doped P-well layer is in ohmic contact with the metal source.

[0012] Furthermore, the heavily doped N-well layer is in ohmic contact with the metal source.

[0013] Furthermore, the N-type polysilicon is in ohmic contact with the metal source.

[0014] Furthermore, the epitaxial layer includes a carrier storage layer located on the upper layer.

[0015] Furthermore, surfaces of two gates in a single MOS cell are covered by an isolation medium.

[0016] Furthermore, the epitaxial layer includes a lightly doped N layer, a carrier storage layer and an N body region;

[0017] The N body region specifically includes a heavily doped N body region 1, a lightly doped N body region 1, a heavily doped N body region 2 and a lightly doped N body region 2.

[0018] Furthermore, the cross-sectional profiles of the heavily doped N body region 1, the lightly doped N body region 1, the heavily doped N body region 2, and the lightly doped N body region 2 have the same thickness and are arranged in sequence from top to bottom.

[0019] Furthermore, in a single MOS cell, the lightly doped N layer is located on the left and right sides of the N body region.

[0020] The beneficial effects of the SiC MOSFET device for improving the single particle radiation recombination efficiency of the present invention are as follows:

[0021] 1. In the present invention, a P-type doped region is formed by injecting P-type impurities in a SiC MOSFET device, and ions are implanted in the P-type doped region to form N-type polysilicon, and the N-type polysilicon and the source metal are short-circuited. In this way, the trench structure transfers the strong electric field at the gate oxide interface to the bottom of the JFET region, greatly reducing the electric field strength in the thin gate oxide, thereby improving the single particle gate penetration resistance of the SiC MOSFET device.

[0022] 2. The P-type doped regions at the bottom and sidewalls of the trench enhance the hole extraction efficiency near the JFET region at the moment of heavy ion bombardment, which can quickly and efficiently remove the electron-hole pairs generated by heavy ion bombardment, reduce the current and radiation response time generated by single particle radiation, and effectively improve the single particle radiation resistance of SiC MOSFET.

[0023] 3. Since the P-type doped region forms a trench structure, the pinch-off effect of JFET at high blocking voltage is enhanced. The doping concentration of the carrier storage layer can be increased without affecting the voltage blocking capability of the device. The higher doping concentration of the carrier storage layer and the N-type polysilicon short-circuited to the source in the trench can greatly improve the recombination efficiency of holes and electrons at the moment of single-particle radiation, thereby improving the radiation resistance of SiC MOSFET devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0025] Figure 1 Schematic diagram of a SiC MOSFET device for improving single particle radiation recombination efficiency in the present invention;

[0026] Figure 2 Schematic diagram of the MOS cell structure of a common planar gate device.

[0027] In the figure: 1. drain; 2. substrate layer; 3. lightly doped N layer; 4. carrier storage layer; 5. lightly doped P well layer; 6. metal source; 7. heavily doped N well layer; 8. gate; 9. isolation dielectric; 10. N-type polysilicon; 11. P-type doped region; 12. heavily doped P well layer; 13. heavily doped N body region 1; 14. lightly doped N body region 1; 15. heavily doped N body region 2; 16. lightly doped N body region 2. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0029] like Figure 1 As shown, in order to solve the shortcomings of the prior art, the present invention proposes a SiC MOSFET device for improving the single particle radiation recombination efficiency, comprising a drain 1, a semiconductor epitaxial layer, a metal source 6, and a gate 8, wherein an isolation dielectric 9 is deposited on the outer surface of the gate 8;

[0030] The semiconductor epitaxial layer includes a substrate layer 2, an epitaxial layer, a P-well layer and a heavily doped N-well layer 7; the epitaxial layer 3 includes a carrier storage layer 4 located on the upper layer, and the P-well layer includes a lightly doped P-well layer 5 and a heavily doped P-well layer 12; a P-type doped region 11 is formed between adjacent lightly doped P-well layers 5 by ion implantation, and N-type impurity ions are implanted inside the P-type doped region 11 to form N-type polysilicon 10. In the SiC MOSFET device, the P-type doped region 11 is formed by implanting P-type impurities, and the N-type polysilicon 10 is formed by ion implantation in the P-type doped region 11, and the N-type polysilicon 10 is short-circuited with the source metal 6, so that the trench structure (such as Figure 1 As shown, the boundary between the P-type doped region and the carrier storage layer 4 is equivalent to a trench) to transfer the strong electric field at the gate oxide interface to the bottom of the JFET region, greatly reducing the electric field strength in the thin gate oxide, thereby improving the single particle gate penetration resistance of the SiC MOSFET device.

[0031] In this embodiment, the heavily doped P-well layer 12 is in ohmic contact with the metal source 6, the heavily doped N-well layer 7 is in ohmic contact with the metal source 6, the N-type polysilicon 10 is in ohmic contact with the metal source 6, the gate 8 in a single MOS cell is divided into two, and the length of each gate 8 covers the P-type doped region 11 (the gate 8 above the JFET region covers the P-type doped region 11, and the P-doped region 11 provides shielding protection for the edge of the gate 8), and the surfaces of the two gates 8 in a single MOS cell are covered by the isolation medium 9.

[0032] The epitaxial layer includes a lightly doped N layer 3, a carrier storage layer 4 and an N body region; wherein the N body region specifically includes a heavily doped N body region 13, a lightly doped N body region 14, a heavily doped N body region 2 15 and a lightly doped N body region 2 16, and the thickness of the cross-sectional profiles of the heavily doped N body region 13, the lightly doped N body region 14, the heavily doped N body region 2 15 and the lightly doped N body region 2 16 are the same, and are arranged sequentially from top to bottom; in a single MOS cell, the lightly doped N layer 3 is located on the left and right sides of the N body region.

[0033] like Figure 1 As shown, the high-voltage SiC MOSFET radiation-hardened device structure is achieved by introducing a trench into the device JFET and injecting P-type impurities into the sidewalls and bottom of the trench to form a P-type doped region 11, and the trench is filled with high-concentration N-type polysilicon 10, and the N-type polysilicon and the source metal 6 are short-circuited.

[0034] The trench structure transfers the strong electric field at the gate oxide interface to the bottom of the JFET region, significantly reducing the electric field strength in the thin gate oxide, thereby improving the SiC MOSFET device's ability to resist single particle gate penetration;

[0035] At the same time, the P-type doping region 11 at the bottom and sidewall of the trench increases the hole extraction path area in the active region, which can enhance the hole extraction efficiency in the body at the moment of heavy ion bombardment;

[0036] In addition, due to the introduction of the trench structure, the pinch-off effect of the JFET at high blocking voltage is enhanced, and the doping concentration of the carrier storage layer is increased without affecting the voltage blocking capability of the device. The higher doping concentration of the carrier storage layer 4 and the N-type polysilicon 10 short-circuited with the metal source 6 in the trench can greatly improve the recombination efficiency of holes and electrons at the moment of single particle radiation.

[0037] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention also fall within the protection scope of the present invention.

Claims

1. A SiC MOSFET device for improving single particle radiation recombination efficiency, characterized in that: It comprises a drain electrode (1), a semiconductor epitaxial layer, a metal source electrode (6), and a gate electrode (8), wherein an isolation medium (9) is deposited on the outer surface of the gate electrode (8); The semiconductor epitaxial layer comprises a substrate layer (2), an epitaxial layer, a P-well layer and a heavily doped N-well layer (7); The P-well layer comprises a lightly doped P-well layer (5) and a heavily doped P-well layer (12); A P-type doping region (11) is formed between adjacent lightly doped P-well layers (5) by ion implantation, and N-type impurity ions are implanted inside the P-type doping region (11) to form N-type polysilicon (10); The gate (8) in a single MOS cell is divided into two, and the length of each gate (8) covers the upper P-type doping region (11).

2. The SiC MOSFET device for improving single particle radiation recombination efficiency according to claim 1, characterized in that: The heavily doped P-well layer (12) is in ohmic contact with the metal source electrode (6).

3. The SiC MOSFET device for improving single particle radiation recombination efficiency according to claim 1, characterized in that: The heavily doped N-well layer (7) is in ohmic contact with the metal source electrode (6).

4. The SiC MOSFET device for improving single particle radiation recombination efficiency according to claim 1, characterized in that: The N-type polysilicon (10) is in ohmic contact with the metal source (6).

5. The SiC MOSFET device for improving single particle radiation recombination efficiency according to claim 1, characterized in that: The surfaces of the two gates (8) in a single MOS cell are both covered by an isolation medium (9).

6. A SiC MOSFET device for improving single particle radiation recombination efficiency according to any one of claims 1 to 5, characterized in that: The epitaxial layer comprises a lightly doped N layer (3), a carrier storage layer (4) and an N body region; The N body region specifically includes a heavily doped N body region 1 (13), a lightly doped N body region 1 (14), a heavily doped N body region 2 (15) and a lightly doped N body region 2 (16).

7. The SiC MOSFET device for improving single particle radiation recombination efficiency according to claim 6, characterized in that: The cross-sectional profiles of the heavily doped N body region 1 (13), the lightly doped N body region 1 (14), the heavily doped N body region 2 (15) and the lightly doped N body region 2 (16) have the same thickness and are arranged in sequence from top to bottom.

8. The SiC MOSFET device for improving single particle radiation recombination efficiency according to claim 7, characterized in that: In a single MOS cell, the lightly doped N layer (3) is located on the left and right sides of the N body region.

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