Silicon carbide microcell charge modulation terminal structure

Abstract

The invention discloses a silicon carbide micro-region charge modulation terminal structure which comprises a silicon carbide substrate layer, an N-epitaxial layer, a P + region, an anode, a cathode, a SiO2 passivation layer and a P-JTE region, the P-JTE region and the P + region are arranged adjacently, the P-JTE region is arranged in the N-epitaxial layer, the upper surface of the P-JTE region is in contact with the bottom surface of the SiO2 passivation layer, and the lower surface of the P-JTE region is in contact with the bottom surface of the SiO2 passivation layer. The P-JTE region comprises a plurality of JTE subregions, an included angle is formed between the edges of the plurality of JTE subregions and the bottom surface of the SiO2 passivation layer, the overlapping depth between two adjacent JTE subregions is smaller than or equal to the depth of the P + region, and the depth of the P-JTE region is larger than or equal to the depth of the P + region. According to the micro-area charge modulation terminal structure, the JTE edge is subjected to structure correction, an inclined plane geometric doping structure is constructed, the charge gradient of edge local ideal change is formed, JTE edge electric field optimization is realized, and the electric field is homogenized.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor devices and relates to a silicon carbide micro-area charge modulation terminal structure. Background Art

[0002] As energy and environmental issues are becoming more and more concerned by people, society has higher demands on the efficiency of power electronic systems and the performance of power semiconductor devices. To date, silicon-based power devices have been widely used in many fields. However, as silicon power devices are approaching maturity and the material properties of silicon materials themselves are limited, their device performance can no longer meet the growing demand for high-power applications. Compared with traditional silicon-based semiconductor materials, silicon carbide (SiC) materials are particularly suitable for the preparation of high-voltage and high-power power electronic devices due to their excellent properties such as large bandgap, strong critical breakdown electric field, and high thermal conductivity.

[0003] When preparing high-voltage SiC power devices, the junction termination extension (JTE) terminal structure is often used to extend the main junction depletion region to alleviate the electric field concentration at the edge of the main junction, thereby improving and stabilizing the breakdown voltage. Compared with the field limiting ring (FLRs) terminal, the JTE terminal has the advantages of simple preparation process, significant improvement in breakdown efficiency, and high design and process size tolerance. It is widely used in the preparation of high-voltage, especially ultra-high-voltage SiC power devices. The essence of the JTE terminal is to balance the peak electric field at the edge of the inner main junction and the edge of the JTE by completely depleting the internal charge of the junction termination region. Therefore, the electric field balance is extremely sensitive to the amount of doping charge. In order to reduce the sensitivity of the JTE terminal to the amount of charge and widen the doping dose process window, the multi-zone effect concept is generally adopted in the design, that is, by setting multiple doping dose partitions of the JTE and setting an auxiliary ring at the edge of each JTE to construct a lateral gradient charge gradient, so as to achieve a balanced electric field within a wider doping dose range. However, considering the characteristics of SiC shallow junction injection, the multi-zone structure still has a strong single-point peak electric field at the edge of each partition or ring. In addition, the multi-zone auxiliary ring structure also increases the design variables and process complexity. Summary of the invention

[0004] In order to solve the problem of doping charge sensitivity of JTE terminals in the prior art, the present invention provides a silicon carbide micro-area charge modulation terminal structure. The technical solution adopted by the present invention is:

[0005] A silicon carbide micro-area charge modulation terminal structure, comprising:

[0006] Silicon carbide substrate layer;

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

[0008] A P+ region, wherein the P+ region is disposed inside the N-epitaxial layer, and an upper surface of the P+ region is flush with an upper surface of the N-epitaxial layer;

[0009] an anode, the anode being disposed above the P+ region;

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

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

[0012] A P-JTE region, wherein the P-JTE region is disposed adjacent to the P+ region, the P-JTE region is disposed inside the N-epitaxial layer, and an upper surface of the P-JTE region contacts a bottom surface of the SiO2 passivation layer;

[0013] The P-JTE area includes several JTE partitions, which are respectively represented as JTE1 partition, JTE2 partition, JTE3 partition...JTE n Partition, n is the number of JTE partitions, n = 2 to 10;

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

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

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

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

[0018] In one embodiment of the present invention, the doping concentration of the P-JTE region is 1×10 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-epitaxial layer is 5×10 13 cm -3 ~2×10 16 cm -3 , thickness is 5-200μm, and the doping elements are nitrogen or phosphorus.

[0020] In one embodiment of the present invention, the doping concentration of the P+ region is 5×10 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 doping type of the silicon carbide substrate layer is N-type.

[0023] Beneficial effects of the present invention:

[0024] The silicon carbide micro-area charge modulation terminal structure of the present invention performs structural correction on the JTE edge, constructs a slope geometric doping structure, and forms a charge gradient with an ideal local change at the edge. Based on the micro-area structure, a micro-area charge modulation model is constructed between two adjacent JTEs. By optimizing the micro-area structural parameters, the electric field at the JTE edge is optimized, single-point electric field concentration is eliminated, and the electric field is homogenized, so that the macroscopic electric field balance and the doping dose figure of merit window are further expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a silicon carbide micro-area charge modulation terminal structure provided by an embodiment of the present invention;

[0026] Figure 2 A graph showing the peak value of the electric field of a silicon carbide micro-area charge modulation terminal structure provided by an embodiment of the present invention;

[0027] Figure 3 A comparison chart of “breakdown voltage-JTE dose” curves of different terminal structures provided in an embodiment of the present invention.

[0028] In the accompanying drawings: 1. Silicon carbide substrate layer, 2. N-epitaxial layer, 3. P+ region, 4. P-JTE region, 5. anode, 6. cathode, 7. SiO2 passivation layer. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The electric field peak of the conventional multi-region JTE structure quickly transfers from the outer edge of the first region JTE to the outer edge of the outermost multi-region JTE, and the device breakdown voltage deteriorates sharply. This embodiment provides a silicon carbide micro-region charge modulation terminal structure, referring to the attached Figure 1 The silicon carbide micro-area charge modulation terminal structure includes: a silicon carbide substrate layer 1; an N-epitaxial layer 2, the N-epitaxial layer is arranged above the silicon carbide substrate layer 1; a P+ region 3, the P+ region 3 is arranged inside the N-epitaxial layer 2, and the upper surface of the P+ region 3 is flush with the upper surface of the N-epitaxial layer 2; an anode 5, the anode 5 is arranged above the P+ region 3; a cathode 6, the cathode 6 is arranged on the back of the silicon carbide substrate layer 1; a SiO2 passivation layer 7, the SiO2 passivation layer 7 is arranged on the N-epitaxial layer 2, and the bottom surface of the SiO2 passivation layer 7 is in partial contact with the upper surface of the P+ region 3; a P-JTE region 4, the P-JTE region is arranged adjacent to the P+ region, the P-JTE region 4 is arranged inside the N-epitaxial layer 2, and the upper surface of the P-JTE region 4 is in contact with the bottom surface of the SiO2 passivation layer 7.

[0031] In the embodiment of the present invention, the P-JTE area includes several JTE partitions, namely, JTE1 partition, JTE2 partition, JTE3 partition, JTE4 partition, JTE5 partition, JTE6 partition, JTE7 partition, JTE8 partition, JTE9 partition ... n Partition, n is the number of JTE partitions, n = 2 to 10; the edges of several JTE partitions and the bottom surface of the SiO2 passivation layer form angles θ1, θ2, θ3...θ n ,θ1,θ2,θ3...θ n is 5 to 30° and satisfies θ n ≤θ n-1 ≤......≤θ2≤θ1; the overlapping 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 P-JTE region n Greater than or equal to the depth d of the P+ region p When the P-JTE region satisfies the above parameters, the electric field distribution can be optimized more effectively, the electric field concentration at the junction edge can be improved, and the electric field distribution at the device edge can be made more uniform, thereby increasing the breakdown voltage and expanding the device's figure of merit dose window, thereby improving the device's reliability.

[0032] The silicon carbide micro-area charge modulation terminal structure of the present invention has a relatively slow transfer process of the electric field peak due to the modulation effect of the micro-area charge, and the electric field strength inside the micro-area at the JTE overlap gradually decreases, and the maximum peak electric field moves toward the outside of the micro-area at the overlap. The coupling effect established between the inside and the outside delays the transfer of the maximum peak electric field position, and the entire JTE area presents 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, the structural construction simplifies the design and process complexity of the two-area JTE, that is, avoiding the setting and process implementation of additional auxiliary rings.

[0033] In the embodiment of the present invention, the doping concentration of the P-JTE region 4 is 1×10 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 The charge gradient must be large enough to effectively broaden the figure of merit dose window. Too large or too small a charge gradient is not conducive to broadening the figure of merit dose window, and the breakdown characteristics are relatively deteriorated.

[0034] The doping element of P-JTE region 4 is aluminum, which has a lower ionization energy than boron (B), and boron will diffuse abnormally in the subsequent high-temperature process. Therefore, compared with boron, aluminum is more stable and controllable in P-type doping. At the same time, considering that other trivalent elements such as gallium (Ga) have higher ionization energies, they are generally not used as P-type doping elements.

[0035] In one embodiment of the present invention, the doping concentration of the N-epitaxial layer is 5×10 13 cm -3 ~2×10 16 cm -3 , thickness is 5-200μm. Doping concentration range (5×10 13 cm -3 ~2×10 16 cm -3 ) and thickness range (5-200μm) enable SiC PiN diodes to flexibly adjust their electrical properties according to specific application requirements. Lower doping concentrations and thicker epitaxial layer thicknesses can increase the breakdown voltage of the device, because the breakdown voltage is related to the width of the depletion layer. A thicker epitaxial layer allows the depletion layer to have enough space to expand, thereby improving the device's withstand voltage capability.

[0036] The doping elements of the N-epitaxial layer are nitrogen or phosphorus. Using nitrogen or phosphorus as the doping element can effectively control the electron concentration in the N-epitaxial layer. Nitrogen and phosphorus act as donor impurities in the SiC lattice, which can provide additional electrons to make the N-epitaxial layer an N-type semiconductor. During the operation of the diode, 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 conductivity of the diode.

[0037] The doping concentration of the P+ region is 5×10 18 ~1×10 19 cm -3 , depth d p = 0.5-1.2μm. This doping concentration range and thickness range enable 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 doping element in the P+ region is aluminum. The ionization energy of aluminum is smaller than that of boron (B), and boron will diffuse abnormally in the subsequent high-temperature process. Therefore, compared with boron, aluminum is more stable and controllable in P-type doping. At the same time, considering that other trivalent elements such as gallium (Ga) have higher ionization energies, they are generally not used as P-type doping elements.

[0039] In one embodiment of the present invention, the doping type of the silicon carbide substrate layer 1 is N-type. In N-type semiconductors, electrons are majority carriers. The mobility of electrons is generally higher than the mobility of holes in P-type semiconductors. Higher electron mobility can achieve faster switching speeds. At the same time, in the manufacturing process of SiC devices, N-type substrates are more compatible with some existing process technologies.

[0040] In one embodiment of the present invention, both the anode and the cathode are ohmic contact electrodes. The characteristic of the ohmic contact electrode is that its contact resistance is very low. For SiC PiN diodes, when both the anode and the cathode use ohmic contact electrodes, when current passes through the diode, no large voltage drop will be generated due to the contact interface. Low contact resistance means that when a large current passes through, the power consumption of the contact interface is also small. Due to the nature of the ohmic contact, a stable electrical connection is formed between the anode and the cathode and the SiC material. Under different operating temperatures, operating currents, and operating voltages, this connection can maintain stable electrical properties. Compared with non-ohmic contacts (such as Schottky contacts), ohmic contacts will not easily experience sudden changes in electrical properties due to temperature changes or current overloads.

[0041] Attached Figure 1In the example, the number of JTE partitions is 2, that is, the P-JTE area includes JTE1 partition and JTE2 partition. The edge of JTE1 partition forms an angle θ1 with the bottom surface of SiO2 passivation layer, and the edge of JTE2 partition forms an angle θ2 with the bottom surface of SiO2 passivation layer, θ1 is 5-30°, θ2 is 5-30°, and θ2≤θ1; the overlapping depth between JTE1 partition and JTE2 partition is d0 less than or equal to the depth d of P+ region. p ; The overlap length between JTE1 and JTE2 is L = d0 / tanθ1+d0 / tanθ2; The doping concentration of the P-JTE region is 1×10 16 cm -3 ~1×10 18 cm -3 , and the doping concentration of the JTE1 partition is N1, and the doping concentration of the JTE2 partition is N2, satisfying: N1=2N2; the depth of the P-JTE region d n Greater than or equal to the depth of the P+ region.

[0042] As the JTE dose (i.e., effective JTE charge) increases, the electric field peak of the 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 modulation JTE structure of the present invention, as shown in the attached figure, Figure 2 , the electric field peak undergoes a process of transfer from point b (the vertex of the trapezoid of the first zone JTE1) to point b' (the corresponding point where the first zone JTE1 and the second zone JTE2 overlap), the electric field intensity at point b gradually decreases, the maximum peak electric field moves toward point b', the coupling effect established between point b and point b' is significantly reduced, and the maximum peak electric field moves from the outer edge of the first zone JTE1 to the outer edge of the second zone JTE2, thereby achieving edge electric field optimization, thereby improving the sensitivity of the device breakdown voltage to the JTE dose and widening the figure of merit dose window. At the same time, the existence of the JTE edge bevel cross geometry weakens the single-point electric field concentration phenomenon and improves the reverse withstand voltage reliability of the device.

[0043] The comparison diagram of the “breakdown voltage-JTE dose” curves of different terminal structures provided in the embodiment of the present invention is shown in the attached figure. Figure 3 , by the attached Figure 3 It can be seen that compared with the traditional structure, as the dose increases, the structure proposed by the present invention can well improve the figure of merit dose window of the device, achieve high breakdown efficiency under a wide dose window, and is an 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 contents that do not deviate from the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A silicon carbide micro-area charge modulation terminal structure, characterized in that: include: Silicon carbide substrate layer; An N-epitaxial layer, wherein the N-epitaxial layer is disposed above the silicon carbide substrate layer; A P+ region, wherein the P+ region is disposed inside the N-epitaxial layer, and an upper surface of the P+ region is flush with an upper surface of the N-epitaxial layer; an anode, the anode being disposed above the P+ region; A cathode, the cathode being disposed on the back side of the silicon carbide substrate layer; A SiO2 passivation layer, wherein the SiO2 passivation layer is disposed on the N-epitaxial layer, and a bottom surface of the SiO2 passivation layer is in contact with a portion of an upper surface of the P+ region; A P-JTE region, wherein the P-JTE region is disposed adjacent to the P+ region, the P-JTE region is disposed inside the N-epitaxial layer, and an upper surface of the P-JTE region contacts a bottom surface of the SiO2 passivation layer; The P-JTE area includes several JTE partitions, which are respectively represented as JTE1 partition, JTE2 partition, JTE3 partition...JTE n Partition, n is the number of JTE partitions, n = 2 to 10; The edges of the JTE partitions and the bottom surface of the SiO2 passivation layer form angles θ1, θ2, θ3, ... θ n , the θ1, θ2, θ3...θ n is 5 to 30° and satisfies θ n ≤θ n-1 ≤......≤θ2≤θ1; The overlapping depth d0 between two adjacent JTE partitions is less than or equal to the depth d of the P+ region. p ; The overlapping length L between two adjacent JTE partitions is d0 / tanθ n-1 +d0 / tanθ n ; The depth d of the P-JTE region n Greater than or equal to the depth d of the P+ region p .

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

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

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

6. The silicon carbide micro-area charge modulation terminal structure according to claim 1, characterized in that: The doping type of the silicon carbide substrate layer is N-type.

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