A 4h-sic epitaxial structure and growth method for controlling tsd defects
By growing 6H-SiC heteroepitaxial and 4H-SiC homoepitaxial on 4H-SiC substrates and combining them with a staged growth process, the problem of TSD defect control was solved, and the quality of 4H-SiC epitaxial wafers and device performance were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI YOFC ADVANCED SEMICONDUCTOR CO LTD
- Filing Date
- 2022-12-07
- Publication Date
- 2026-06-05
AI Technical Summary
Existing 4H-SiC epitaxial growth technology is difficult to effectively control TSD defects, leading to a decrease in device performance, yield and reliability. TSD defects penetrating into the active region have a negative impact on the device.
6H-SiC heteroepitaxial growth and 4H-SiC homoepitaxial growth were performed on a 4H-SiC substrate. TSD defects were controlled by a staged growth process, including growing a 6H-SiC buffer layer and a high-temperature, low-pressure, highly doped 4H-SiC buffer layer under Si-rich conditions to disrupt TSD propagation and transform it into Frank stacking faults. A high-quality, low-dislocation-density 4H-SiC buffer layer was grown to shield TSD.
It effectively reduces TSD defect density, lowers device leakage current, increases reverse breakdown voltage, and improves epitaxial wafer quality and performance stability.
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Figure CN115832018B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a 4H-SiC epitaxial structure and growth method for controlling TSD defects. Background Technology
[0002] With the rapid development of the semiconductor industry, the performance of silicon-based devices has approached its theoretical limit. To achieve further progress, the development of new materials is imperative. As one of the third-generation semiconductor materials, SiC has a wider bandgap, thus exhibiting higher avalanche critical electric field, thermal conductivity, operating temperature, chemical stability, and radiation resistance.
[0003] Currently, the fabrication of 4H-SiC power devices still faces numerous challenges in defect control and the growth of large-diameter thick-film epitaxial materials, hindering further performance improvements and applications in power electronics. Most mature 4H-SiC batch growth processes utilize chemical vapor deposition (CVD) in a two-stage process: first, a buffer layer is homogeneously grown on the 4H-SiC substrate, followed by a drift layer. Growing a buffer layer between the substrate and the drift layer helps eliminate stress, prevents cross-contamination of substrate surface defects, and simultaneously controls the doping concentration of the drift layer.
[0004] Several defects that adversely affect devices can occur during 4H-SiC epitaxial growth, including micropipes, block phase defects (BPD), triangular defects, total reverse breakdown voltage (TSD), and tert-terminated defects (TED). Current industrial technologies have achieved zero-micropipe 4H-SiC substrate materials and techniques to control BPD and triangular defects. However, existing 4H-SiC epitaxial growth technologies have the following drawbacks: To reduce costs, low-angle 4H-SiC substrates are used for growth, which suppresses the step-current growth mode and significantly increases TSD defect density. TSD defects increase leakage current and reduce reverse breakdown voltage, negatively impacting device performance. Furthermore, current defect control techniques cannot effectively control TSD density, allowing numerous TSD defects to penetrate the active region, negatively affecting device performance, yield, and reliability.
[0005] TSD (Treading Srew Dislocation) is a difficult defect to solve in current 4H-SiC epitaxial growth technology. TSD defects mainly originate from two sources: over 70% originate from the substrate, and the remainder originate from regrowth during the epitaxial growth process. The primary direct cause of TSD defects is stacking faults caused by inclusions. Controlling TSD defects to optimize the quality of 4H-SiC epitaxial growth is a pressing issue that needs to be addressed.
[0006] Patent CN 103820768 A discloses a method for homogeneous rapid epitaxial growth of 4H-SiC epitaxial layers on 4H-SiC substrates. The method involves first cleaning the 4H-SiC substrate and placing it in the growth chamber of a vertical hot-wall low-pressure CVD (CVD) system; evacuating the reaction chamber; setting the reaction chamber pressure and introducing a hydrogen gas flow; heating the reaction chamber to the etching temperature for in-situ etching of the substrate; adjusting the hydrogen flow and increasing the reaction chamber temperature; when the reaction chamber temperature reaches the pre-growth temperature, introducing a growth source gas for pre-growth; after reaching the growth temperature, adjusting the growth source gas flow rate for epitaxial growth; after growth, turning off the growth source gas and stopping heating, and cooling in a hydrogen flow; evacuating the reaction chamber and continuing to cool it to room temperature in an argon flow; and then filling the growth chamber with argon to atmospheric pressure. However, this method cannot effectively control TSD (Transient Defects), allowing a large number of TSD defects to penetrate into the active region, negatively impacting device performance, yield, and reliability. Summary of the Invention
[0007] To address the aforementioned technical problems, this invention provides a 4H-SiC epitaxial structure and growth method for controlling TSD defects. This method can hinder the propagation of TSD defects from the substrate to the epitaxial layer, effectively reduce the TSD defect density and TSD-derived defect density, increase the reverse breakdown voltage of the device, and improve the quality of the epitaxial wafer.
[0008] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is: the 4H-SiC epitaxial structure for controlling TSD defects includes a 4H-SiC substrate and an epitaxial buffer layer I, a 4H-SiC buffer layer II and a 4H-SiC drift layer grown thereon in sequence, wherein the epitaxial buffer layer I is set as a 6H-SiC buffer layer or a 4H-SiC buffer layer II.
[0009] The thickness of the 4H-SiC buffer layer II is set to 1-2 μm, and the thickness of the 4H-SiC drift layer is set to 3-5 μm.
[0010] The thickness of the 6H-SiC buffer layer is set to 1–2 μm.
[0011] The thickness of the 4H-SiC buffer layer I is set to 10–20 μm.
[0012] A method for growing a 4H-SiC epitaxial structure with controlled TSD defects, grown in the reaction chamber of a CVD device, includes the following steps:
[0013] 1) In-situ etching of the 4H-SiC substrate;
[0014] 2) An epitaxial buffer layer I is grown on a 4H-SiC substrate;
[0015] 3) A 4H-SiC buffer layer is grown on epitaxial buffer layer I;
[0016] 4) Grow a 4H-SiC drift layer on the 4H-SiC buffer layer.
[0017] The operation method of step 1) is as follows: After cleaning the 4H-SiC substrate, place it in the reaction chamber, evacuate the reaction chamber, adjust the temperature of the reaction chamber to 1450-1500℃ and the pressure to 50-200mbar; after introducing a hydrogen gas flow of 160-240slm and an HCl gas flow of 30-100sccm into the reaction chamber, perform in-situ etching for 10-30min.
[0018] In step 2), the method for growing a 6H-SiC buffer layer on a 4H-SiC substrate is as follows: stop the flow of HCl gas into the reaction chamber, adjust the temperature of the reaction chamber to 2000-2400℃ and the pressure to 40-100mbar, and introduce carrier gas H2, chlorine-containing silicon source gas, carbon source gas and aluminum source gas into the reaction chamber at flow rates of 160-240slm, 80-500sccm, 80-500sccm and 40-100sccm respectively, with a C / Si ratio of 0.5-0.8, and a growth time of 2-4h.
[0019] In step 2), the method for growing the 4H-SiC buffer layer I on the 4H-SiC substrate is as follows: The flow of HCl gas into the reaction chamber is stopped; the temperature of the reaction chamber is adjusted to 1800–2000℃, and the pressure to 40–100 mbar; H2, a chlorine-containing silicon source gas, and a carbon source gas are introduced into the reaction chamber at flow rates of 80–120 slm, 40–250 sccm, and 40–250 sccm, respectively; the C / Si ratio of the introduced gas is 0.5–0.9; and the N doping concentration is 5 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 The growth time is 1-3 hours; the temperature of the reaction chamber is adjusted to 1580-1700℃ and maintained for 5-20 minutes for annealing.
[0020] The operation method of step 3) is as follows: Adjust the temperature of the reaction chamber to 1400–1600℃ and the pressure to 60–150 mbar. Introduce carrier gas H2, chlorine-containing silicon source gas, carbon source gas, and N2 into the reaction chamber at flow rates of 160–240 slm, 80–500 sccm, 80–500 sccm, and 40–100 sccm, respectively. Then, adjust the temperature of the reaction chamber again to 1580–1700℃ and the pressure to 50–200 mbar. Change the flow rates of the chlorine-containing silicon source gas, carbon source gas, and N2 to 80–300 sccm, 80–300 sccm, and 80–500 sccm, respectively. The C / Si ratio of the introduced gas is 1.0–1.2, and the N doping concentration is 5 × 10⁻⁶. 17 cm -3 ~2×10 18 cm -3 The growth period is 1 to 3 hours.
[0021] The operation method for step 4) is as follows: the temperature of the reaction chamber is adjusted to 1400-1600℃, the pressure is 40-200 mbar, and chlorine-containing silicon source gas, carbon source gas, and N2 are introduced into the reaction chamber at flow rates of 80-300 sccm, 80-300 sccm, and 40-300 sccm, respectively. The C / Si ratio of the introduced gas is 1.0-1.2, and the N doping concentration is 8 × 10⁻⁶. 15 cm -3 ~2×10 16 cm -3 The growth time is 0.5 to 2 hours; the temperature of the reaction chamber is adjusted to 20 to 30°C and maintained for 5 to 20 minutes for annealing.
[0022] The beneficial effects of this invention are:
[0023] 1. This invention controls TSD defects by employing two methods. One method involves growing 6H-SiC heteroepitaxial growth on a 4H-SiC substrate, which disrupts the propagation of TSD during substrate growth. Furthermore, the Si-rich growth environment is more conducive to the transformation of TSD defects into Frank stacking faults on the basal plane, thus annihilating the TSD defects. The other method involves growing 4H-SiC homoepitaxial growth on a 4H-SiC substrate using a staged lateral and longitudinal growth process. In the lateral growth stage, the lateral vector of the step flow growth can be increased, which can transform TSD defects into lateral Frank stacking faults.
[0024] Before growing the 4H-SiC drift layer, a high-quality, low-dislocation-density 4H-SiC buffer layer II is grown to shield TSD defects as well as BPD and TED defects, which can improve the quality of the subsequently grown 4H-SiC drift layer.
[0025] 2. In this invention, when growing a 6H-SiC buffer layer on a 4H-SiC substrate, 6H-SiC can be grown on the (0001)Si surface of 4H-SiC; moreover, under Si-rich conditions, 6H-SiC has a lower hexagonal degree, making it easier to grow; under Al-doped conditions, 6H-SiC is more likely to nucleate; and under high temperature and high pressure conditions, SiC is more likely to transform into the 6H-SiC crystal form, making the nucleation and growth of the 6H-SiC buffer layer more stable.
[0026] 3. In this invention, when growing the 4H-SiC buffer layer I on a 4H-SiC substrate, 4H-SiC homoepitaxial growth is performed on the 4H-SiC(0001)Si surface. The growth environment is as follows: the C / Si ratio of the introduced gas is 0.5–0.9, the growth temperature is 1800–2000℃, the pressure is 40–100 mbar, and the N doping concentration is 5 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 The high-temperature, low-pressure, low-speed, and high-doping growth mode can increase the lateral vector of step flow growth and effectively control TSD defects. Attached Figure Description
[0027] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:
[0028] Figure 1 This is a schematic diagram of the structure of the 4H-SiC epitaxial structure of the present invention, according to Embodiment 1.
[0029] Figure 2 This is a schematic diagram of the structure of the 4H-SiC epitaxial structure in Embodiment 2 of the present invention;
[0030] The labels in the above figures are: 1. 4H-SiC substrate, 2. 6H-SiC buffer layer, 3. 4H-SiC buffer layer I, 4. 4H-SiC buffer layer II, and 5. 4H-SiC drift layer. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.
[0032] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.
[0033] Example 1
[0034] like Figure 1 As shown, a 4H-SiC epitaxial structure for controlling TSD defects is characterized by comprising a 4H-SiC substrate and an epitaxial buffer layer I, a 4H-SiC buffer layer II, and a 4H-SiC drift layer grown sequentially thereon. The epitaxial buffer layer I is configured as a 6H-SiC buffer layer. The thickness of the 4H-SiC buffer layer II is set to 1–2 μm, the thickness of the 4H-SiC drift layer is set to 3–5 μm, and the thickness of the 6H-SiC buffer layer is set to 1–2 μm. Epitaxial growth of the 6H-SiC buffer layer on the 4H-SiC substrate disrupts the propagation of TSD during substrate growth, causing TSD defects to annihilate. After the 6H-SiC buffer layer is grown, the process parameters are adjusted, and homogeneous 4H-SiC epitaxial growth is performed again. The growth of the 4H-SiC buffer layer II on the 6H-SiC buffer layer can shield the influence of 6H-SiC isomers on the subsequent growth of the 4H-SiC epitaxial layer, improving the quality of the subsequently grown 4H-SiC drift layer.
[0035] The above-mentioned method for growing 4H-SiC epitaxial structures is carried out in the reaction chamber of a CVD equipment, specifically using the HTCVD process, and includes the following steps:
[0036] 1) In-situ etching of 4H-SiC substrate: Select a positive-axis N-type SiC carbon substrate, clean the 4H-SiC substrate and place it in the reaction chamber, evacuate the reaction chamber, adjust the reaction chamber to 50-200 mbar, continuously introduce hydrogen gas at a flow rate of 160-240 slm and HCl gas at a flow rate of 30-100 sccm into the reaction chamber, adjust the temperature of the reaction chamber to 1450-1500℃ and maintain the temperature constant for 10-30 min, and perform in-situ etching of 4H-SiC substrate.
[0037] 2) Growth of a 6H-SiC buffer layer on a 4H-SiC substrate: Stop the flow of HCl gas into the reaction chamber, adjust the temperature of the reaction chamber to 2000–2400℃ and the pressure to 40–100 mbar; introduce carrier gas H2, chlorine-containing silicon source gas, carbon source gas and aluminum source gas into the reaction chamber at flow rates of 160–240 slm, 80–500 sccm, 80–500 sccm and 40–100 sccm respectively, where the chlorine-containing silicon source gas is trichlorosilane gas, the carbon source gas is C3H8 gas and the aluminum source gas is trimethylaluminum gas, the C / Si ratio of the introduced gas is 0.5–0.8, and the growth time is 2–4 h.
[0038] 3) Growth of a 4H-SiC buffer layer on a 6H-SiC buffer layer: The temperature of the reaction chamber was adjusted to 1400–1600℃, and the pressure to 60–150 mbar. Carrier gas H2, chlorine-containing silicon source gas, carbon source gas, and N2 were introduced into the reaction chamber at flow rates of 160–240 slm, 80–500 sccm, 80–500 sccm, and 40–100 sccm, respectively. The chlorine-containing silicon source gas was trichlorosilane. The carbon source gas used is C3H8 gas for the pre-growth of 6H-SiC. The temperature of the reaction chamber is then adjusted to 1580–1700℃, the pressure to 50–200 mbar, and the flow rates of the chlorine-containing silicon source gas, carbon source gas, and N2 are changed to 80–300 sccm, 80–300 sccm, and 80–500 sccm, respectively. The C / Si ratio of the introduced gas is 1.0–1.2, and the N doping concentration is 5 × 10⁻⁶. 17 cm -3 ~2×10 18 cm -3 The growth time was 1 to 3 hours, and the growth of 4H-SiC buffer layers with a thickness of 1 to 2 μm was achieved.
[0039] 4) Growth of a 4H-SiC drift layer on a 4H-SiC buffer layer: The temperature of the reaction chamber was adjusted to 1400–1600℃, and the pressure to 40–200 mbar. Chlorine-containing silicon source gas, carbon source gas, and N2 were introduced into the reaction chamber at flow rates of 80–300 sccm, 80–300 sccm, and 40–300 sccm, respectively. The chlorine-containing silicon source gas was trichlorosilane gas, and the carbon source gas was C3H8 gas. The C / Si ratio of the introduced gas was 1.0–1.2, and the N doping concentration was 8 × 10⁻⁶. 15 cm -3 ~2×10 16 cm -3The growth time was 0.5–2 h, achieving the growth of 4H-SiC drift layers with a thickness of 3–5 μm. The temperature of the reaction chamber was then adjusted to room temperature (20–30 °C) and maintained for 5–20 min for annealing treatment. Annealing treatment reduced residual stress and eliminated lattice damage.
[0040] This invention disrupts the propagation of TSDs during substrate growth by growing 6H-SiC heteroepitaxially on a 4H-SiC substrate. Furthermore, the Si-rich growth environment facilitates the transformation of TSD defects into Frank stacking faults on the basal plane, leading to TSD defect annihilation. Moreover, before growing the 4H-SiC drift layer, a second 4H-SiC homoepitaxial growth is performed by adjusting process parameters to grow a high-quality, low-dislocation-density 4H-SiC buffer layer II. This buffer layer shields the 6H-SiC isomer from the subsequent growth of the 4H-SiC drift layer, improving the quality of the subsequently grown 4H-SiC drift layer and ultimately enhancing the quality of the epitaxial wafer.
[0041] Example 2
[0042] The difference from Example 1 is that the epitaxial buffer layer I is set as 4H-SiC buffer layer I, and the thickness of 4H-SiC buffer layer I is 10-20 μm.
[0043] The difference between the growth method of this 4H-SiC epitaxial structure and the growth method of Example 1 is that the epitaxial growth is performed using MOCVD and the process conditions for growing the 4H-SiC buffer layer I on the 4H-SiC substrate are as follows.
[0044] The specific method for growing 4H-SiC buffer layer I on a 4H-SiC substrate is as follows: The flow of HCl gas into the reaction chamber is stopped, the temperature of the reaction chamber is adjusted to 1800–2000℃, and the pressure is 40–100 mbar. Carrier gas H2, chlorine-containing silicon source gas, and carbon source gas are introduced into the reaction chamber at flow rates of 80–120 slm, 40–250 sccm, and 40–250 sccm, respectively. The chlorine-containing silicon source gas is trichlorosilane gas, and the carbon source gas is C3H8 gas. The C / Si ratio of the introduced gas is 0.5–0.9, and the N doping concentration is 5 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 The growth time is 1-3 hours, allowing 4H-SiC to grow laterally to obtain a 4H-SiC buffer layer I with a thickness of 10-20 μm. The growth temperature in the reaction chamber is then lowered again, and the temperature of the reaction chamber is adjusted to 1580-1700℃ and maintained for 5-20 minutes for annealing. The purpose of annealing is to reduce residual stress and eliminate lattice damage while rapidly cooling down.
[0045] This invention utilizes a staged lateral and longitudinal growth process to grow 4H-SiC homoepitaxial layer on a 4H-SiC substrate. During the lateral growth stage, a high-temperature, low-pressure, and highly doped growth mode is employed. This increases the lateral vector of the step flow growth during the growth of the 4H-SiC buffer layer I, transforming TSD defects into lateral Frank stacking faults. Prior to the growth of the 4H-SiC drift layer, a high-quality, low-dislocation-density 4H-SiC buffer layer II is grown to shield against TSD defects, BPD, and TED defects, thereby improving the quality of the subsequently grown 4H-SiC drift layer.
[0046] In summary, this invention can effectively reduce the density of TSD defects and TSD-derived defects, reduce device leakage current, increase device reverse breakdown voltage, and improve the quality of epitaxial wafers.
[0047] The above description is merely an illustration of some principles of the present invention. This specification is not intended to limit the present invention to the specific structures and applicable scope shown. Therefore, all possible modifications and equivalents that may be used fall within the scope of the patent application of this invention.
Claims
1. A method for growing 4H-SiC epitaxial structures with controlled TSD defects, characterized in that, The 4H-SiC epitaxial structure for controlling TSD defects includes a 4H-SiC substrate and an epitaxial buffer layer I, a 4H-SiC buffer layer II, and a 4H-SiC drift layer grown sequentially thereon, wherein the epitaxial buffer layer I is set as a 6H-SiC buffer layer. 4H-SiC epitaxial structures with controlled TSD defects are grown in the reaction chamber of a CVD equipment. The growth method includes the following steps: 1) In-situ etching of the 4H-SiC substrate; 2) An epitaxial buffer layer I is grown on a 4H-SiC substrate; 3) A 4H-SiC buffer layer is grown on epitaxial buffer layer I; 4) Growth of a 4H-SiC drift layer on a 4H-SiC buffer layer; The operation method for growing a 6H-SiC buffer layer on a 4H-SiC substrate is as follows: stop the flow of HCl gas into the reaction chamber, adjust the temperature of the reaction chamber to 2000~2400℃, the pressure to 40~100mbar, and introduce carrier gas H2, chlorine-containing silicon source gas, carbon source gas and aluminum source gas into the reaction chamber at flow rates of 160~240slm, 80~500sccm, 80~500sccm and 40~100sccm, respectively. The C / Si ratio of the introduced gas is 0.5~0.8, and the growth time is 2~4h.
2. The method for growing 4H-SiC epitaxial structures with controlled TSD defects according to claim 1, characterized in that: The thickness of the 4H-SiC buffer layer II is set to 1~2μm, and the thickness of the 4H-SiC drift layer is set to 3~5μm.
3. The method for growing 4H-SiC epitaxial structures with controlled TSD defects according to claim 1, characterized in that: The thickness of the 6H-SiC buffer layer is set to 1~2μm.
4. The method for growing 4H-SiC epitaxial structures with controlled TSD defects according to claim 1, characterized in that: The operation method of step 1) is as follows: After cleaning the 4H-SiC substrate, place it in the reaction chamber, evacuate the reaction chamber, adjust the temperature of the reaction chamber to 1450~1500℃ and the pressure to 50~200mbar; after introducing a hydrogen gas flow of 160~240slm and an HCl gas flow of 30~100sccm into the reaction chamber, perform in-situ etching for 10~30min.
5. The method for growing 4H-SiC epitaxial structures with controlled TSD defects according to claim 1, characterized in that: The operation method of step 3) is as follows: Adjust the temperature of the reaction chamber to 1400~1600℃ and the pressure to 60~150mbar. Introduce carrier gas H2, chlorine-containing silicon source gas, carbon source gas, and N2 into the reaction chamber at flow rates of 160~240 slm, 80~500 sccm, 80~500 sccm, and 40~100 sccm, respectively. Then, adjust the temperature of the reaction chamber again to 1580~1700℃ and the pressure to 50~200mbar. Change the flow rates of the chlorine-containing silicon source gas, carbon source gas, and N2 to 80~300 sccm, 80~300 sccm, and 80~500 sccm, respectively. The C / Si ratio of the introduced gas is 1.0~1.2, and the N doping concentration is 5×10⁻⁶. 17 cm -3 ~2×10 18 cm -3 The growth period is 1-3 hours.
6. The method for growing 4H-SiC epitaxial structures with controlled TSD defects according to claim 1, characterized in that: The operation method for step 4) is as follows: the temperature of the reaction chamber is adjusted to 1400~1600℃, the pressure is 40~200mbar, and chlorine-containing silicon source gas, carbon source gas, and N2 are introduced into the reaction chamber at flow rates of 80~300sccm, 80~300sccm, and 40~300sccm, respectively. The C / Si ratio of the introduced gas is 1.0~1.2, and the N doping concentration is 8×10⁻⁶. 15 cm -3 ~2×10 16 cm -3 The growth time is 0.5~2h; the temperature of the reaction chamber is adjusted to 20~30℃ and maintained for 5~20min for annealing treatment.