A silicon carbide micro-area charge modulation terminal structure

Abstract

This invention discloses a silicon carbide micro-region charge modulation termination structure, which includes: a silicon carbide substrate, an N-epitaxial layer, a P+ region, an anode, a cathode, a SiO2 passivation layer, and a P-JTE region. The P-JTE region is adjacent to the P+ region and is located inside the N-epitaxial layer. The upper surface of the P-JTE region is in contact with the bottom surface of the SiO2 passivation layer. The P-JTE region includes several JTE partitions, and the edges of the JTE partitions form an angle with the bottom surface of the SiO2 passivation layer. The overlap depth between two adjacent JTE partitions is less than or equal to the depth of the P+ region, and the depth of the P-JTE region is greater than or equal to the depth of the P+ region. The micro-region charge modulation termination structure of this invention modifies the JTE edges by constructing a sloped geometric doped structure, forming an ideally varying charge gradient at the edges, thus optimizing the electric field at the JTE edges and homogenizing the electric field.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology and relates to a silicon carbide micro-region charge modulation terminal structure. Background Technology

[0002] With energy and environmental issues receiving increasing attention, society demands higher efficiency from power electronic systems and places higher requirements on the performance of power semiconductor devices. Today, silicon-based power devices are widely used in many fields. However, as silicon power device development nears maturity and the inherent material properties of silicon limit their performance to meet the growing demands of high-power applications, their performance is no longer sufficient. Compared to traditional silicon-based semiconductor materials, silicon carbide (SiC) materials, with their large bandgap, strong critical breakdown electric field, and high thermal conductivity, are particularly suitable for fabricating high-voltage, high-power power electronic devices.

[0003] In the fabrication of high-voltage SiC power devices, junction extension technology (JTE) structures are often used to extend the depletion region of the main junction, thereby alleviating the electric field concentration at the main junction edge and improving and stabilizing the breakdown voltage. Compared to field limiting rings (FLRs), JTE terminations have advantages such as simple fabrication process, significantly improved breakdown efficiency, and high design and process size tolerance, and are widely used in the fabrication of high-voltage, especially ultra-high-voltage, SiC power devices. The essence of JTE termination is to balance the peak electric field at the inner main junction edge and the JTE edge by completely depleting the charge inside the junction termination region. Therefore, the electric field balance is extremely sensitive to the amount of doping charge. To reduce the sensitivity of JTE terminations to charge and broaden the doping dose process window, a multi-region effect concept is generally adopted in the design. This involves setting multiple doping dose zones for the JTE and setting auxiliary rings at the edges of each JTE to construct a laterally gradually changing charge gradient, thereby achieving an electric field equilibrium over a wider doping dose range. However, considering the characteristics of shallow junction implantation in SiC, a strong single-point peak electric field still exists at the edge of each zone or ring in the multi-region structure. In addition, the multi-zone auxiliary ring structure also increases design variables and process complexity. Summary of the Invention

[0004] To address the issue of charge sensitivity in JTE terminals in existing technologies, this invention provides a silicon carbide micro-region charge modulation terminal structure. The technical solution adopted in this invention is as follows:

[0005] A silicon carbide micro-region charge modulation terminal structure includes:

[0006] Silicon carbide substrate;

[0007] An N-epitaxial layer is disposed above the silicon carbide substrate layer;

[0008] The P+ region is disposed inside the N-epitaxial layer, and the upper surface of the P+ region is flush with the upper surface of the N-epitaxial layer.

[0009] Anode, wherein the anode is disposed above the P+ region;

[0010] A cathode is disposed on the back side of the silicon carbide substrate layer;

[0011] A SiO2 passivation layer is disposed on the N- epitaxial layer, and the bottom surface of the SiO2 passivation layer is in contact with the upper surface of the P+ region.

[0012] The P-JTE region is adjacent to the P+ region and is located inside the N-epitaxial layer. The upper surface of the P-JTE region is in contact with the bottom surface of the SiO2 passivation layer.

[0013] The P-JTE area includes several JTE partitions, referred to as JTE1 partition, JTE2 partition, JTE3 partition, ... JTE partition. n Partitions, where n is the number of JTE partitions, n = 2 to 10;

[0014] The edges of several JTE partitions form angles θ1, θ2, θ3...θ with the bottom surface of the SiO2 passivation layer. n , the θ1, θ2, θ3...θ n The angle is 5–30°, and θ is satisfied. n ≤θ n-1 ≤......≤θ2≤θ1;

[0015] The overlap depth d0 between two adjacent JTE partitions is less than or equal to the depth d of the P+ region. p ;

[0016] The overlap length between two adjacent JTE partitions is L = d0 / tanθ n-1 +d0 / tanθ n ;

[0017] The depth d of the P-JTE region n The depth d of the P+ region is greater than or equal to the depth of the P+ region. p .

[0018] In one embodiment of the present invention, the doping concentration of the P-JTE region is 1×10⁻⁶. 16 cm -3 ~1×10 18 cm -3 And the doping concentration of the JTE1 partition is N1, the JTEn The doping concentration of the partition is N n Satisfying: N1 = 2 n-1 N n The doping element is aluminum.

[0019] In one embodiment of the present invention, the doping concentration of the N-epipolar layer is 5 × 10⁻⁶. 13 cm -3 ~2×10 16 cm -3 The thickness is 5-200μm, and the doping element is nitrogen or phosphorus.

[0020] In one embodiment of the present invention, the doping concentration of the P+ region is 5 × 10⁻⁶. 18 ~1×10 19 cm -3 Depth d p =0.5-1.2μm, the doping element is aluminum.

[0021] In one embodiment of the present invention, both the anode and the cathode are ohmic contact electrodes.

[0022] In one embodiment of the present invention, the silicon carbide substrate layer is N-type doped.

[0023] The beneficial effects of this invention are:

[0024] The silicon carbide micro-region charge modulation terminal structure of the present invention modifies the edge of the JTE by constructing a sloped geometric doping structure to form a locally ideal charge gradient at the edge. Based on this micro-region structure, a micro-region charge modulation model is constructed between two adjacent JTE regions. By optimizing the micro-region structure parameters, the electric field at the edge of the JTE is optimized, eliminating single-point electric field concentration, thereby homogenizing the electric field, achieving macroscopic electric field balance, and further expanding the doping dose figure of merit window. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a silicon carbide micro-region charge modulation terminal structure provided in an embodiment of the present invention;

[0026] Figure 2 The peak electric field variation diagram of the charge modulation terminal structure of silicon carbide micro-region provided in the embodiment of the present invention;

[0027] Figure 3 A comparison chart of "breakdown voltage-JTE dose" curves for different terminal structures provided in embodiments of the present invention.

[0028] In the attached figure: 1. Silicon carbide substrate, 2. N-epitaxial layer, 3. P+ region, 4. P-JTE region, 5. Anode, 6. Cathode, 7. SiO2 passivation layer. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] In traditional multi-region JTE structures, the peak electric field rapidly shifts from the outer edge of the first JTE region to the outermost multi-region JTE region, causing a sharp deterioration in the device breakdown voltage. This embodiment provides a silicon carbide micro-region charge modulation termination structure, as shown in the attached diagram. Figure 1 The silicon carbide micro-region charge modulation terminal structure includes: a silicon carbide substrate 1; an N-epitaxial layer 2 disposed above the silicon carbide substrate 1; a P+ region 3 disposed inside the N-epitaxial layer 2, with the upper surface of the P+ region 3 flush with the upper surface of the N-epitaxial layer 2; an anode 5 disposed above the P+ region 3; a cathode 6 disposed on the back side of the silicon carbide substrate 1; a SiO2 passivation layer 7 disposed on the N-epitaxial layer 2, with the bottom surface of the SiO2 passivation layer 7 partially contacting the upper surface of the P+ region 3; and a P-JTE region 4 disposed adjacent to the P+ region, with the P-JTE region 4 disposed inside the N-epitaxial layer 2 and the upper surface of the P-JTE region 4 contacting the bottom surface of the SiO2 passivation layer 7.

[0031] In embodiments of the present invention, the P-JTE area includes several JTE partitions, namely JTE1 partition, JTE2 partition, JTE3 partition, ... JTE n The number of JTE partitions is n, where n = 2 to 10; the edges of several JTE partitions form angles θ1, θ2, θ3...θ with the bottom surface of the SiO2 passivation layer. n θ1, θ2, θ3......θ n The angle is 5–30°, and θ is satisfied. n ≤θ n-1 ≤......≤θ2≤θ1; The overlap depth d0 between two adjacent JTE partitions is less than or equal to the depth d of the P+ region. p The overlap length between two adjacent JTE partitions is L = d0 / tanθ n-1 +d0 / tanθ n ; Depth d of the P-JTE region n The depth d of the region greater than or equal to P+ p The P-JTE region, by satisfying the above parameters, can more effectively optimize the electric field distribution, improve the electric field concentration at the junction edge, and make the electric field distribution at the device edge more uniform, thereby increasing the breakdown voltage, expanding the figure of merit window of the device, and thus improving the reliability of the device.

[0032] Due to the modulation effect of the micro-region charge modulation terminal structure, the transfer process of the electric field peak in the silicon carbide micro-region charge modulation terminal structure of this invention is relatively slow. The electric field intensity on the inner side of the micro-region at the JTE overlap gradually decreases, while the maximum peak electric field moves towards the outer side of the micro-region at the overlap. The coupling effect established between the inner and outer sides delays the transfer of the maximum peak electric field position. The entire JTE region exhibits a very uniform electric field distribution, eliminating single-point electric field concentration, thereby homogenizing the electric field, balancing the macroscopic electric field, further expanding the doping dose figure of merit window, and improving the process tolerance. At the same time, this structure simplifies the design and process complexity of two-region JTEs, i.e., it avoids the setting and process implementation of additional auxiliary rings.

[0033] In an embodiment of the present invention, the doping concentration of P-JTE region 4 is 1×10⁻⁶. 16 cm -3 ~1×10 18 cm -3 And the doping concentration of JTE1 partition is N1, JTE n The doping concentration of the partition is N n Satisfying: N1 = 2 n-1 N n The doping concentration of the JTE partition satisfies N1 = 2. n-1 N n A charge gradient is necessary to effectively broaden the figure of merit dose window. A charge gradient that is too large or too small is not conducive to broadening the figure of merit dose window and will relatively deteriorate the breakdown characteristics.

[0034] The dopant element in P-JTE region 4 is aluminum. Aluminum has a lower ionization energy than boron (B), and boron will undergo abnormal diffusion during subsequent high-temperature processes. Therefore, aluminum is more stable and controllable in P-type doping compared to boron. Meanwhile, considering the higher ionization energy of other trivalent elements such as gallium (Ga), they are generally not used as P-type dopant elements.

[0035] In one embodiment of the present invention, the doping concentration of the N-epipolar layer is 5 × 10⁻⁶. 13 cm -3 ~2×10 16 cm -3 The thickness ranges from 5 to 200 μm. The doping concentration ranges from 5 × 10⁻⁶ μm. 13 cm -3 ~2×10 16 cm -3 The wide range of doping concentrations and thicknesses (5-200 μm) allows SiC PiN diodes to flexibly adjust their electrical performance according to specific application requirements. Lower doping concentrations and thicker epitaxial layers can improve the breakdown voltage of the device, because the breakdown voltage is related to the width of the depletion layer, and a thicker epitaxial layer allows the depletion layer to have sufficient space to expand, thereby improving the device's breakdown voltage capability.

[0036] The doping element for the N-epitaxial layer is nitrogen or phosphorus. Using nitrogen or phosphorus as the doping element allows for effective control of the electron concentration in the N-epitaxial layer. Nitrogen and phosphorus act as donor impurities in the SiC lattice, providing additional electrons and enabling the N-epitaxial layer to become an N-type semiconductor. During diode operation, these electrons participate in the conduction process as majority carriers. By adjusting the doping concentration, the carrier concentration can be precisely controlled, thereby optimizing the diode's conductivity.

[0037] The doping concentration in the P+ region is 5 × 10⁻⁶. 18 ~1×10 19 cm -3 Depth d p =0.5-1.2μm. This range of doping concentration and thickness allows the diode to flexibly adjust its electrical performance according to specific application requirements, and the depth of the P+ region can control the depletion layer width and electric field distribution of the PN junction.

[0038] The dopant element in the P+ region is aluminum. Aluminum has a lower ionization energy than boron (B), and boron undergoes abnormal diffusion during subsequent high-temperature processes. Therefore, aluminum is more stable and controllable in P-type doping compared to boron. Meanwhile, considering the higher ionization energy of other trivalent elements such as gallium (Ga), they are generally not used as P-type dopant elements.

[0039] In one embodiment of the present invention, the silicon carbide substrate layer 1 is doped with N-type electrons, in which electrons are majority carriers. Electron mobility is generally higher than hole mobility in P-type semiconductors. Higher electron mobility enables faster switching speeds. Furthermore, in the manufacturing process of SiC devices, N-type substrates have good compatibility with some existing process technologies.

[0040] In one embodiment of the present invention, both the anode and cathode are ohmic contact electrodes. Ohmic contact electrodes are characterized by their very low contact resistance. For SiC PiN diodes, when both the anode and cathode are ohmic contact electrodes, a large voltage drop is not generated at the contact interface when current flows through the diode. Low contact resistance means that the power dissipation at the contact interface is also low when a large current flows. Due to the nature of the ohmic contact, a stable electrical connection is formed between the anode and cathode and the SiC material. This connection can maintain stable electrical performance under different operating temperatures, operating currents, and operating voltages. Compared with non-ohmic contacts (such as Schottky contacts), ohmic contacts do not easily exhibit abrupt changes in electrical performance due to temperature variations or current overloads.

[0041] Appendix Figure 1In this example, taking a P-JTE region with two JTE partitions as an example, the P-JTE region includes JTE1 and JTE2 partitions. The edge of JTE1 partition forms an angle θ1 with the bottom surface of the SiO2 passivation layer, and the edge of JTE2 partition forms an angle θ2 with the bottom surface of the SiO2 passivation layer. θ1 and θ2 are both 5–30°, and θ2 ≤ θ1. The overlap depth between JTE1 and JTE2 partitions is d0, which is less than or equal to the depth d of the P+ region. p The overlap length between JTE1 and JTE2 partitions is L = d0 / tanθ1 + d0 / tanθ2; the doping concentration of the P-JTE region is 1 × 10⁻⁶. 16 cm -3 ~1×10 18 cm -3 Furthermore, the doping concentration of partition JTE1 is N1, and the doping concentration of partition JTE2 is N2, satisfying: N1 = 2N2; the depth d of the P-JTE region. n The depth of the region greater than or equal to P+.

[0042] As the JTE dose (i.e., effective JTE charge) increases, the peak electric field of a conventional two-region JTE structure rapidly shifts from the outer edge of the first region JTE1 to the outer edge of the second region JTE2. However, in the micro-region charge-modulated JTE structure of this invention, as shown in the attached diagram... Figure 2 The peak electric field undergoes a process of shifting from point b (the apex of the trapezoidal JTE1 in the first region) to point b' (the corresponding point at the intersection of JTE1 in the first region and JTE2 in the second region). The electric field intensity at point b gradually decreases, while the maximum peak electric field moves towards point b'. The coupling effect between points b and b' is significantly reduced, and the speed at which the maximum peak electric field moves from the outer edge of JTE1 in the first region to the outer edge of JTE2 in the second region is accelerated. This optimizes the edge electric field, thereby improving the device's breakdown voltage sensitivity to the JTE dose and widening the figure-of-favor dose window. Simultaneously, the presence of the intersecting geometry of the JTE edge slopes weakens the single-point electric field concentration phenomenon, improving the reverse breakdown voltage reliability of the device.

[0043] The comparison chart of "breakdown voltage-JTE dose" curves for different terminal structures provided in the embodiments of the present invention is attached. Figure 3 , by appendix Figure 3 As can be seen, compared with the traditional structure, the structure proposed in this invention can significantly improve the figure-value dose window of the device as the dose increases, achieving high breakdown efficiency over a wide dose window, and is a highly efficient and reliable terminal structure.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. All content that does not depart from the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A silicon carbide micro-region charge modulation terminal structure, characterized in that, include: Silicon carbide substrate; An N-epitaxial layer is disposed above the silicon carbide substrate layer; The P+ region is disposed inside the N-epitaxial layer, and the upper surface of the P+ region is flush with the upper surface of the N-epitaxial layer. Anode, wherein the anode is disposed above the P+ region; A cathode is disposed on the back side of the silicon carbide substrate layer; A SiO2 passivation layer is disposed on the N- epitaxial layer, and the bottom surface of the SiO2 passivation layer is in contact with the upper surface of the P+ region. The P-JTE region is adjacent to the P+ region and is located inside the N-epitaxial layer. The upper surface of the P-JTE region is in contact with the bottom surface of the SiO2 passivation layer. The P-JTE area includes several JTE partitions, referred to as JTE1 partition, JTE2 partition, JTE3 partition, ... JTE n Partitions, where n is the number of JTE partitions, n = 2 to 10; The edges of several JTE partitions form angles θ1, θ2, θ3...θ with the bottom surface of the SiO2 passivation layer. n , the θ1, θ2, θ3...θ n The angle is 5–30°, and θ is satisfied. n ≤θ n-1 ≤......≤θ2≤θ1; The overlap depth d0 between two adjacent JTE partitions is less than or equal to the depth d of the P+ region. p ; The overlap length between two adjacent JTE partitions is L = d0 / tanθ n-1 +d0 / tanθ n ; The depth d of the P-JTE region n The depth d of the P+ region is greater than or equal to the depth of the P+ region. p .

2. The silicon carbide micro-region charge modulation terminal structure according to claim 1, characterized in that, The doping concentration of the P-JTE region is 1×10⁻⁶. 16 cm -3 ~1×10 18 cm -3 And the doping concentration of the JTE1 partition is N1, the JTE n The doping concentration of the partition is N n Satisfying: N1 = 2 n-1 N n The doping element is aluminum.

3. The silicon carbide micro-region charge modulation terminal structure according to claim 1, characterized in that, The doping concentration of the N-epitaxial layer is 5 × 10⁻⁶. 13 cm -3 ~2×10 16 cm -3 The thickness is 5-200μm, and the doping element is nitrogen or phosphorus.

4. The silicon carbide micro-region charge modulation terminal structure according to claim 1, characterized in that, The doping concentration of the P+ region is 5 × 10⁻⁶. 18 ~1×10 19 cm -3 Depth d p =0.5-1.2μm, the doping element is aluminum.

5. The silicon carbide micro-region charge modulation terminal structure according to claim 1, characterized in that, Both the anode and the cathode are ohmic contact electrodes.

6. The silicon carbide micro-region charge modulation terminal structure according to claim 1, characterized in that, The silicon carbide substrate is N-type doped.

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