Diamond-based vertical schottky diode with mesa termination composite structure

Abstract

The present application belongs to the technical field of semiconductor, and relates to a diamond-based vertical Schottky diode with a mesa terminal composite structure. The structure comprises, from bottom to top, an anode metal, a p+ heavily doped substrate, an intrinsic drift layer, a dielectric layer, a cathode metal and a diamond regrown layer. The present application adopts a composite terminal structure, and a metal field plate structure is used to adjust and optimize the electric field at the main junction. A groove structure is introduced near the dielectric layer at the end of the metal field plate to adjust and optimize the electric field at the end of the dielectric layer and the surface of the semiconductor, and to shift the breakdown point to the corner of the diamond. Meanwhile, the high resistance of the intrinsic diamond is used to share the electric field, thereby reducing the electric field peak in the dielectric layer and effectively relieving the problems of edge electric field concentration and dielectric breakdown.

Description

Technical Field

[0001] This invention relates to the field of semiconductor devices, and more specifically to a diamond-based vertical Schottky diode with a mesa terminal structure. Background Technology

[0002] Diamond, as a candidate material for next-generation ultra-wide bandgap semiconductors, possesses characteristics such as ultra-wide bandgap, high mobility, high thermal conductivity, high intrinsic breakdown electric field, corrosion resistance, and radiation resistance, making it suitable for high-frequency, high-temperature, high-voltage, and high-power applications. In particular, the oxygen-terminated surface can achieve suitable Schottky contacts and passivate surface defects, which is beneficial for realizing high-quality gold-semiconductor contact interfaces. The heavily doped p-type layer of diamond exhibits a metallic conduction mechanism, which can reduce the resistance of heavily doped substrates and achieve ohmic contacts with low contact resistance. These properties make diamond a so-called "ultimate semiconductor," with promising applications in next-generation power electronic devices.

[0003] Schottky diodes (MIPDs) with a metal-intrinsic-heavily doped substrate structure can effectively avoid the problem of diamond's poor ionization at room temperature and can utilize the high mobility of the intrinsic layer. However, Schottky diodes are affected by the electric field concentration at the electrode edges, leading to premature breakdown. Diamond, lacking suitable n-type doping, ion implantation, and anisotropic etching processes, typically uses metal field plates to optimize the surface electric field. This presents a new problem: the intrinsic breakdown electric field of diamond is 10–20 MV / cm, which is close to or even exceeds that of most dielectric materials. This leads to the risk of premature breakdown of the dielectric layer in metal field plate termination structures. Consequently, the breakdown voltage improvement under metal field plate termination structures is not significant, and may even be lower than that under structures without field plates. Furthermore, dielectric breakdown is a hard breakdown, so the transfer of the breakdown point is also a problem that needs to be addressed. Summary of the Invention

[0004] The breakdown voltage mechanism of a metal field plate involves introducing an additional charge, generating an additional electric field. This electric field weakens the electric field spikes at the edges of the main junction electrodes, but simultaneously introduces new electric field spikes within the dielectric layer at the end of the field plate. Because of the hypercritical breakdown electric field of diamond, the breakdown point occurs within the dielectric layer at the end of the field plate. Figure 4 As shown.

[0005] The present invention provides a diamond Schottky diode with a mesa-terminal composite structure to solve the above problems: including an anode metal O1 and a p-terminal metal P-terminal. + Substrate 02, intrinsic drift layer 03, dielectric layer 04, cathode metal 05, diamond regeneration layer 06, wherein, anode metal 01, p + The substrate 02 and the intrinsic drift layer 03 are stacked sequentially from bottom to top;

[0006] The diamond regrowth layer 06 is located on the both ends of the upper surface of the intrinsic drift layer 03, and the diamond regrowth layer 06 is formed by etching a groove in the dielectric layer 04 and filling the groove with non-doped intrinsic diamond, so as to share the electric field of the dielectric layer 04 at the end of the field plate by virtue of the low k and high resistance characteristics of the diamond; the diamond regrowth layer 06 is in contact with the dielectric layer 04 on both sides, and the bottom of the diamond regrowth layer 06 is in contact with the intrinsic drift layer 03;

[0007] The cathode metal 05 is located on the middle of the upper surface of the intrinsic drift layer 03, and extends to both ends, and the cathode metal 05 is formed by etching a groove through the dielectric layer 04 in the middle of the dielectric layer 04, and etching grooves without penetrating the dielectric layer 04 on both sides of the through groove, so as to form a stepped dielectric layer 04, and the cathode metal 05 completely covers the through groove and the bottom of the groove without penetrating, and also extends to the upper surface of the dielectric layer 04 on both sides; the cathode metal 05 and the intrinsic drift layer 03, the p + type substrate 02 constitute a Metal-Intrinsic-p + structure, and the cathode metal 05 covers the part on the top of the stepped dielectric layer 04, constituting a metal field plate structure.

[0008] Further, the substrate is a boron-doped heavily doped layer with a thickness of 200-300 μm and a doping concentration of 10 19 cm -3 Above, the doping impurity is boron (B), and has a metal conduction mechanism.

[0009] Further, the intrinsic drift layer 03 has a thickness of 10-18 μm, is a non-doped intrinsic diamond layer, and the surface is treated with oxygen to form an oxygen terminal surface structure.

[0010] Further, the anode metal is Au; and the cathode metal 05 is one or several multi-layer metals of Pt / Mo / Al.

[0011] Further, the dielectric layer is made of high-k insulating material HfO2, and the stepped thickness is 1 μm, and the maximum thickness is 2 μm.

[0012] Further, the horizontal length of the metal field plate is 15 μm, the horizontal distance between the end of the metal field plate and the diamond regrowth layer 06 is 1-3 μm, and the distance between the end of the metal field plate and the dielectric mesa structure is 1-3 μm.

[0013] The gain effect of the present application: by designing the junction terminal structure, the trench structure is used to share the electric field peak in the field plate end dielectric layer, so as to realize the adjustment of the main junction electric field by the metal field plate, reduce the electric field peak in the field plate end dielectric layer, thereby reducing the risk of dielectric breakdown, thereby improving the breakdown voltage; the stepped field plate is designed, the length of the second stage field plate is 1-3 μm, so as to introduce the corner, which also plays a role in sharing the electric field peak at the end of the field plate; at the same time, by adjusting the mesa structure parameters at the top of the dielectric layer, the movement of the breakdown point can be realized, such as Figure 5 As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor.

[0015] Figure 2 As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor.

[0016] Figure 3 As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor

[0017] Figure 4 As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor.

[0018] Figure 5 As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor. DETAILED DESCRIPTION

[0019] The present application will be described in detail below with reference to the accompanying drawings

[0020] As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor. Figure 1 As shown in the figure, the breakdown point can be transferred from the dielectric layer to the semiconductor.

[0021] From bottom to top, it includes anode metal 01, p+ type substrate 02, intrinsic drift layer 03, dielectric layer 04, cathode metal 05, diamond regrowth layer 06;

[0022] The anode metal 01, p+ type substrate 02, and intrinsic drift layer 03 are stacked sequentially. Utilizing the surface properties of oxygen-terminated diamond, a suitable Schottky contact is formed between the cathode metal 05 and the intrinsic drift layer 03. The system also includes a trench structure located within the dielectric layer 04, with sidewalls covered by the dielectric layer 04, bottom contacting the intrinsic drift layer 03, and filled with diamond 06. The bottom of the dielectric layer 04 contacts the intrinsic drift layer 03, and the top is stepped. The cathode metal 05 is located on top of the intrinsic drift layer 03 and the trench structure, forming a Metal-Intrinsic-P+ structure with the intrinsic drift layer 03 and the p+ type substrate 02. One end of the cathode metal 05, near the dielectric layer 04, extends to cover the top of the stepped dielectric layer 04, forming a stepped metal field plate structure.

[0023] The substrate is a heavily boron-doped layer with a thickness of 200–300 μm and a doping concentration of 10. 19 cm -3 The dopant is boron (B), and it has a metallic conduction mechanism; the intrinsic drift layer 03 has a thickness of 10-18 μm, is an unintentionally doped diamond intrinsic layer, and its surface is treated with oxygen to form an oxygen-terminated surface structure; the anode metal is Au; the cathode metal 05 is one or more multilayer metals of Pt / Mo / Al; the dielectric layer is a high-k insulating material, HfO2, and its stepped thickness is 1 μm, with a maximum thickness of 2 μm; the horizontal length of the metal field plate is 15 μm, and the horizontal distance from the end of the metal field plate to the intrinsic drift layer 03 is 1-3 μm, and the distance from the end of the metal field plate to the dielectric layer mesa structure is 1-3 μm.

[0024] like Figure 4 As shown, the breakdown point under a single-stage metal field plate is located within the dielectric layer at the end of the field plate.

[0025] like Figure 2 The diagram shows the IV curves of the diamond Schottky diode, the Schottky diode with a stepped field plate, and the diamond-based Schottky diode with a mesa-terminated composite structure provided by this invention, on a semi-logarithmic coordinate system. Compared to the first two devices, the diamond-based Schottky diode with a mesa-terminated composite structure of this invention has a high rectification ratio, low leakage current, and does not affect the on-resistance of the device.

[0026] like Figure 3 The diagram shows the reverse breakdown curves of a diamond Schottky diode, a Schottky diode with a stepped field plate, and a diamond-based Schottky diode with a mesa-terminated composite structure provided by this invention. Traditional MIP diodes experience a decrease in breakdown voltage due to the electric field concentration effect at the electrode edges, while diodes with field plate terminations may experience premature breakdown of the dielectric layer. The device structure provided by this invention effectively utilizes the field plate while preventing premature breakdown of the dielectric layer, thereby improving the breakdown voltage.

[0027] To solve the above problems, the principle of the present application for reducing the peak electric field in the dielectric layer and improving the device voltage resistance is: through two-stage field plates, increasing the thickness of the field oxide under the edge of the field plate, thereby reducing the induced charge concentration at the end of the field plate, reducing the peak electric field in the dielectric layer; by introducing a stepped field plate structure, thereby introducing a new electric field peak at the corner of the field plate, sharing the electric field at the end of the field plate; through high-k dielectric material, reducing the peak electric field generated in the dielectric layer by the applied voltage; forming a trench structure near the end of the field plate, using the high resistance and low k characteristics of intrinsic diamond to share part of the electric field in the dielectric layer; the mesa structure formed by the intrinsic drift region makes the electric field distribution of the semiconductor region under the end of the field plate more uniform, and a new electric field peak appears at the corner, thereby realizing the transfer of the breakdown point, as shown by the arrows in the figure. Figure 5 ​

Claims

1. A diamond-based vertical Schottky diode with a mesa-terminated composite structure, comprising an anode metal (01), a p-terminated metal (01), and a p-terminated metal (01). + Substrate (02), intrinsic drift layer (03), dielectric layer (04), cathode metal (05), diamond regenerated layer (06), wherein, Anode metal (01), p + The substrate (02) and the intrinsic drift layer (03) are stacked sequentially from bottom to top; The diamond regenerated layer (06) is located at both ends of the upper surface of the intrinsic drift layer (03) near the end face. The diamond regenerated layer (06) is formed by etching grooves in the dielectric layer (04) and filling the grooves with unintentionally doped intrinsic diamond. The low k and high resistance characteristics of diamond are used to share the electric field of the dielectric layer (04) at the end of the field plate. Both sides of the diamond regenerated layer (06) are in contact with the dielectric layer (04), and the bottom of the diamond regenerated layer (06) is in contact with the intrinsic drift layer (03). The cathode metal (05) is located on the upper surface of the intrinsic drift layer (03) in the middle, and extends to both ends on both sides. The cathode metal (05) is formed by etching a groove penetrating the dielectric layer (04) in the middle, and etching grooves that do not penetrate the dielectric layer (04) on both sides of the penetrating groove, thereby forming a stepped dielectric layer (04). The cathode metal (05) completely covers the bottom of the penetrating groove and the non-penetrating groove, and extends to both sides to the upper surface of the dielectric layer (04); the cathode metal (05) and the intrinsic drift layer (03), p + The substrate (02) constitutes a Metal-Intrinsic-p + The structure, and the portion of the cathode metal (05) covering the top of the stepped dielectric layer (04) constitutes a metal field plate structure.

2. The diamond-based vertical Schottky diode with a mesa-terminal composite structure according to claim 1, characterized in that, The p+ type substrate (02) has a thickness of 200–300 μm and a doping concentration of 10%. 19 cm -3 The above describes the doping impurity as boron (B), and due to the properties of diamond, its conduction mechanism is a metallic conduction mechanism.

3. A diamond-based vertical Schottky diode with a mesa-terminal composite structure according to claim 1, characterized in that, The intrinsic drift layer (03) has a thickness of 10–18 μm and is an intrinsic diamond layer that is not intentionally doped.

4. A diamond-based vertical Schottky diode with a mesa-terminated composite structure according to claim 1, characterized in that, The surface of the intrinsic drift layer (03) is treated with oxygen to form an oxygen terminal surface with an affinity of ~1.3 eV.

5. A diamond-based vertical Schottky diode with a mesa-terminated composite structure according to claim 1, characterized in that, The dielectric layer (04) is made of high-k insulating material or dielectric material with a high critical breakdown electric field.

6. A diamond-based vertical Schottky diode with a mesa-terminated composite structure according to claim 1, characterized in that, The thickness of the stepped portion of the stepped dielectric layer (04) is 1 μm, and the maximum thickness is 2 μm.

7. A diamond-based vertical Schottky diode with a mesa-terminated composite structure according to claim 1, characterized in that, The horizontal length of the metal field plate structure is 15μm. The distance from the end of the metal field plate to the diamond regeneration layer (06) is 1-3μm, and the distance from the end of the metal field plate to the mesa structure of the dielectric layer (04) is 1-3μm.

8. A diamond-based vertical Schottky diode with a mesa-terminated composite structure according to claim 1, characterized in that, The anode metal (01) is Au, and the cathode metal (05) is a multilayer metal composed of one or more of Pt / Mo / Al.

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