Method for reducing laser annealing carbon precipitation amount of SiC material and SiC material

Abstract

The invention provides a method for reducing the laser annealing carbon precipitation amount of a SiC material and the SiC material. The method comprises the steps that (1) a silicon-nickel alloy layer is formed on the back face of a SiC substrate; (2) laser annealing treatment is carried out on the surface of the formed silicon-nickel alloy layer, so that ohmic contact is formed between the silicon-nickel alloy layer and the SiC substrate; by adopting the method disclosed by the invention, not only can the precipitation of carbon be effectively reduced and the particle size of the precipitated carbon be reduced, but also good ohmic contact is formed between the silicon-nickel alloy layer and the SiC substrate, and the specific contact resistivity is relatively low.

Description

Technical Field

[0001] This invention relates to the field of SiC laser annealing technology, and in particular to a method for reducing the amount of carbon deposited during laser annealing of SiC materials and SiC materials. Background Technology

[0002] As a third-generation semiconductor material, SiC possesses many superior properties, such as high temperature resistance, high pressure resistance, and radiation resistance. This makes SiC devices significantly more advantageous than traditional devices, and they are consistently considered among the most promising semiconductor devices. Ohmic contact is one of the most crucial steps in SiC device fabrication, and laser annealing is an emerging process for creating ohmic contacts on the back side of SiC, offering advantages such as high throughput and low thermal budget.

[0003] The most widely used metal for SiC ohmic contacts is Ni. It is generally believed that Ni can catalyze the decomposition of SiC, promote the formation of C vacancies, increase the carrier concentration beneath the contact, thereby enhancing the carrier tunneling effect and reducing the specific contact resistance to form an ohmic contact. The formation of an ohmic contact is, in principle, accompanied by the decomposition of SiC and the formation of free C. The free C portion precipitates onto the outer surface of the alloy layer. This C on the outer surface not only affects the specific contact resistance of the ohmic contact but also the adhesion between the back ohmic contact layer and the thickened metal layer, causing the back metal layer to detach and reducing the reliability of the packaged device. Therefore, the amount of C formed after laser annealing should be as small as possible, and the precipitated C must be completely removed. Currently, the Ni+SiC route exhibits significant C precipitation after laser annealing (obvious before and after wiping with a lint-free cloth), making it crucial to find a method to reduce C precipitation. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention provides a method for reducing carbon precipitation in SiC materials during laser annealing, and a SiC material itself. The method of this invention is simple and efficient, requiring only one additional laser annealing step compared to conventional processes. It can not only effectively reduce the amount of carbon precipitation, but also produce smaller carbon particles, resulting in good ohmic contact after SiC laser annealing and a lower specific contact resistivity.

[0005] The objective of this invention is mainly achieved through the following technical solutions.

[0006] This invention provides a method for reducing carbon deposition during laser annealing of SiC materials, the method comprising:

[0007] Step (1): Form a silicon-nickel alloy layer on the back side of the SiC substrate.

[0008] Step (2): Laser annealing is performed on the surface of the formed silicon-nickel alloy layer to form an ohmic contact between the silicon-nickel alloy layer and the SiC substrate.

[0009] Preferably, in step (1), the method for forming the silicon-nickel alloy layer includes: sequentially depositing a Si layer and a Ni layer on the back side of a SiC substrate or sequentially depositing a Ni layer and a Si layer, and then performing a pre-laser annealing treatment.

[0010] Preferably, the resistivity of the silicon-nickel alloy layer is 10-90 μΩ·cm, and more preferably 20-28 μΩ·cm.

[0011] Preferably, the thickness of the Si layer is 40-60 nm, and more preferably 45-55 nm.

[0012] Preferably, in step (1), the method for depositing the Si layer is selected from low-pressure chemical vapor deposition.

[0013] Preferably, the raw materials for the low-pressure chemical vapor deposition method include SiH4 and PH3.

[0014] Preferably, relative to a SiC substrate with a diameter of 150 mm, the flow rate of SiH4 is 850-1050 sccm, more preferably 900-1000 sccm; and the flow rate of PH3 is 10-30 sccm, more preferably 15-25 sccm.

[0015] Preferably, the conditions for depositing the Si layer using low-pressure chemical vapor deposition include: a temperature of 500-600℃, preferably 540-550℃; and a pressure of 200-600 mtorr, preferably 300-500 mtorr.

[0016] Preferably, the thickness of the Ni layer is 80-120 nm, and more preferably 90-110 nm.

[0017] Preferably, in step (1), the method for depositing the Ni layer is selected from vacuum evaporation or physical vapor deposition, and is preferably physical vapor deposition.

[0018] Preferably, the conditions for the physical vapor deposition method include: a power of 1000-3000W, preferably 1500-2500W; and an Ar flow rate of 10-30 sccm, preferably 15-25 sccm.

[0019] Preferably, in step (1), the conditions for pre-laser annealing include: energy density of 2J-3J, pulse width of 90-110ns, and oxygen content ≤10ppm. More preferably, the energy density is 2.2J-2.6J, the pulse width is 95-105ns, and the oxygen content is ≤5ppm.

[0020] Preferably, in step (2), the conditions for laser annealing include: an energy density of 4-5 J, a pulse width of 90-110 ns, and an oxygen content of ≤10 ppm; more preferably, the energy density is 4.2-4.8 J, the pulse width is 95-105 ns, and the oxygen content is ≤5 ppm.

[0021] Preferably, the back side of the SiC substrate is cleaned before step (1).

[0022] In a second aspect, the present invention provides a SiC material prepared by the method described in the first aspect.

[0023] Compared with existing technologies, the method for reducing carbon deposition in SiC materials by laser annealing and the SiC materials involved in this invention have the following advantages:

[0024] (1) The method of the present invention is simple and efficient, and effectively reduces the amount of carbon released.

[0025] (2) The carbon particles are smaller.

[0026] (3) The ohmic contact formed after SiC laser annealing is ≤6.2×10⁻⁶. -5 ·Ω·cm 2 . Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the Si layer deposited on the back side of the SiC substrate according to the present invention;

[0028] Figure 2 This is a schematic diagram of a Ni layer deposited on the Si layer surface of the SiC substrate of the present invention;

[0029] Figure 3 This is a schematic diagram of the silicon-nickel alloy layer formed after the first laser annealing according to the present invention;

[0030] Figure 4 The images shown are actual photographs of SiC material. The left image is an actual photograph of SiC material after the second laser annealing in Example 1 of the present invention, after being wiped with a lint-free cloth. The right image is an actual photograph of SiC material after laser annealing in Comparative Example 1, after being wiped with a lint-free cloth.

[0031] Figure 5 This is the EDS elemental analysis diagram of SiC material after laser annealing in Example 1 of the present invention;

[0032] Figure 6 The image shows the EDS elemental analysis of SiC material after laser annealing in Comparative Example 1. Detailed Implementation

[0033] The inventors of this invention discovered that forming a Ni-silicide alloy layer on the back side of a SiC substrate (wafer) followed by laser annealing not only effectively reduces carbon precipitation and the particle size of the precipitated carbon, but also allows the Ni-silicide alloy layer to form a good ohmic contact with the SiC substrate, resulting in a lower specific contact resistivity. Analysis suggests that the presence of Ni-silicide slows down the thermal decomposition of SiC to produce carbon and reduces the diffusion rate of carbon atoms, making it difficult for the precipitated carbon to reach the outer surface of the Ni-silicide layer.

[0034] Based on the above research, this invention provides a method for reducing carbon deposition during laser annealing of SiC materials, such as... Figure 3 As shown, the method includes:

[0035] Step (1): Form a silicon-nickel alloy layer on the back side of the SiC substrate;

[0036] Step (2): Laser annealing is performed on the surface of the formed silicon-nickel alloy layer to form an ohmic contact between the silicon-nickel alloy layer and the SiC substrate.

[0037] In this invention, the silicon-nickel alloy layer in step (1) can be characterized using methods commonly used in the art, such as by measuring its resistivity. The resistivity of the silicon-nickel alloy layer is 10-90 μΩ·cm, preferably 20-28 μΩ·cm (for example, it can be any value among 20 μΩ·cm, 21 μΩ·cm, 22 μΩ·cm, 23 μΩ·cm, 24 μΩ·cm, 25 μΩ·cm, 26 μΩ·cm, 27 μΩ·cm, and 28 μΩ·cm, or any value between any two points). It is believed that silicon-nickel alloys have various structures, and the resistivity varies accordingly depending on the structure. After laser annealing, the silicon-nickel alloy structure with this preferred resistivity is more conducive to reducing the amount of carbon deposited and the particle size of carbon, so that the silicon-nickel alloy layer and the SiC substrate can form an ohmic contact with a lower specific contact resistance.

[0038] In this invention, the SiC substrate has a front side and a back side. The front side usually refers to the side where the gate and source of the MOSFET device are located, while the opposite side of the front side is the back side (back side), which usually refers to the side where the drain of the MOSFET device is located.

[0039] In a preferred embodiment of the present invention, in step (1), as follows: Figure 1-2 As shown, the method for forming a silicon-nickel alloy layer includes: sequentially depositing a Si layer and a Ni layer or sequentially depositing a Ni layer and a Si layer on the back side of a SiC substrate, followed by pre-laser annealing.

[0040] In a preferred embodiment of the present invention, the thickness of the Si layer is 40-60 nm, preferably 45-55 nm (for example, it can be any value among 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, and 55 nm, or any value between any two points). Using this preferred Si layer thickness is more conducive to forming ohmic contacts with lower specific contact resistivity.

[0041] In a preferred embodiment of the present invention, in step (1), the method for depositing the Si layer is selected from low-pressure chemical vapor deposition.

[0042] In a preferred embodiment of the present invention, the raw materials for the low-pressure chemical vapor deposition method include SiH4 and PH3. Preferably, relative to a SiC substrate with a diameter of 150 mm, the flow rate of SiH4 is 850-1050 sccm (for example, any value among 850 sccm, 870 sccm, 890 sccm, 910 sccm, 930 sccm, 950 sccm, 970 sccm, 990 sccm, 1010 sccm, 1030 sccm, and 1050 sccm, or any value between any two points), preferably 900-1000 sccm; the flow rate of PH3 is 10-30 sccm (for example, any value among 10 sccm, 12 sccm, 14 sccm, 16 sccm, 18 sccm, 20 sccm, 22 sccm, 24 sccm, 26 sccm, 28 sccm, and 30 sccm, or any value between any two points), preferably 15-25 sccm.

[0043] In a preferred embodiment of the present invention, the conditions for depositing a Si layer using low-pressure chemical vapor deposition include: a temperature of 500-600°C, preferably 540-550°C (for example, any value among 540°C, 541°C, 542°C, 543°C, 544°C, 545°C, 546°C, 547°C, 548°C, 549°C, and 550°C, or any value between any two points); and a pressure of 200-600 mtorr, preferably 300-500 mtorr (for example, any value among 300 mtorr, 320 mtorr, 340 mtorr, 360 mtorr, 380 mtorr, 400 mtorr, 420 mtorr, 440 mtorr, 460 mtorr, 480 mtorr, and 500 mtorr, or any value between any two points).

[0044] In this invention, the Si layer is a polycrystalline silicon layer or a monocrystalline silicon layer.

[0045] In a preferred embodiment of the present invention, the thickness of the Ni layer is 80-120 nm, preferably 90-110 nm (for example, it can be any value among 90 nm, 92 nm, 94 nm, 96 nm, 98 nm, 100 nm, 102 nm, 104 nm, 106 nm, 108 nm, and 110 nm, or any value between any two points). Using this preferred Ni layer thickness is more conducive to forming ohmic contacts with lower specific contact resistivity.

[0046] In this invention, the specific contact resistivity can be measured using methods commonly used in the art, such as the TLM (Transmission Line Method).

[0047] In this invention, the particle size of the precipitated carbon can be determined using methods commonly used in this invention, such as Raman analysis.

[0048] In a preferred embodiment of the present invention, in step (1), the method for depositing the Ni layer is selected from vacuum evaporation or physical vapor deposition, preferably physical vapor deposition.

[0049] In a preferred embodiment of the present invention, the physical vapor deposition method includes the following conditions: power of 1000-3000W, preferably 1500-2500W, more preferably 1800-2200W; and Ar flow rate of 10-30 sccm, preferably 15-25 sccm, more preferably 18-22 sccm.

[0050] The inventors of this invention further discovered that pre-laser annealing at a lower energy density allows Ni to react with Si to form nickel silicon, and then laser annealing at a higher energy density allows nickel silicon to form an ohmic contact with SiC with low specific contact resistivity, which can effectively reduce carbon precipitation. To further reduce carbon precipitation, in a preferred embodiment of this invention, the pre-laser annealing conditions in step (1) include: an energy density of 2-3 J, a pulse width of 90-110 ns, and an oxygen content ≤10 ppm; preferably, the energy density is 2.2-2.6 J (for example, any value from 2.2 J, 2.24 J, 2.28 J, 2.32 J, 2.36 J, 2.4 J, 2.44 J, 2.48 J, 2.52 J, 2.56 J, 2.6 J). The pulse width is 95-105ns (e.g., any value between two points), and the oxygen content is ≤5ppm (e.g., any value between two points, such as 95ns, 96ns, 97ns, 98ns, 99ns, 100ns, 101ns, 102ns, 103ns, 104ns, 105ns).

[0051] In step (2), the conditions for laser annealing include: an energy density of 4-5 J, a pulse width of 90-110 ns, and an oxygen content ≤10 ppm; preferably, the energy density is 4.2-4.8 J (for example, it can be any value among 4.2 J, 4.24 J, 4.28 J, 4.32 J, 4.36 J, 4.4 J, 4.44 J, 4.48 J, 4.52 J, 4.56 J, 4.6 J, 4.7 J, and 4.8 J, or any value between any two points). The pulse width is 95-105 ns (e.g., any value among 95 ns, 96 ns, 97 ns, 98 ns, 99 ns, 100 ns, 101 ns, 102 ns, 103 ns, 104 ns, and 105 ns, or any value between any two points), and the oxygen content is ≤5 ppm (e.g., any value among 0.1 ppm, 1 ppm, 2 ppm, 3 ppm, 4 ppm, and 5 ppm, or any value between any two points). Using this preferred laser annealing condition also allows for smaller carbon particle sizes, further reducing the specific contact resistivity of the ohmic contact surface.

[0052] In a preferred embodiment of the present invention, the back side of the SiC substrate is cleaned before step (1). The cleaning method can be a commonly used cleaning method in the art, such as the SC-1 cleaning method.

[0053] In a second aspect, the present invention provides a SiC material prepared by the method described in the first aspect.

[0054] The following detailed description of preferred embodiments of the present invention illustrates the principles of the invention and is not intended to limit the scope of the invention.

[0055] Carbon content: Elemental analysis of the laser-annealed SiC material was performed using energy dispersive spectroscopy (EDS) to obtain the mass percentage of carbon precipitated in the detection area. The lower the carbon content, the less carbon is precipitated in the SiC material.

[0056] Precipitated carbon particle size: The particle size of precipitated carbon was determined using Raman spectroscopy.

[0057] Ohmic contact: Characterized by specific contact resistivity. The lower the specific contact resistivity, the better the ohmic contact effect. Specific contact resistivity is determined by the TLM (Transmission Line Method).

[0058] Resistivity: Measured using a four-probe instrument, model CDE ResMap168.

[0059] Preparation Example 1

[0060] a) Prepare SC-1 clear solution with a volume ratio of ammonia water: H2O2: deionized water = 1:2:10, and treat the SiC substrate in SC-1 clear solution at 40℃ for 5 minutes.

[0061] b) Quickly rinse the SiC substrate with cold deionized water to remove residual cleaning solution and contaminants;

[0062] c) Use cold deionized water for overflow quenching to lower the solution temperature and prevent the silicon wafer from drying out quickly, thus obtaining a cleaned SiC substrate.

[0063] Example 1

[0064] Step (1): A 50 nm thick polycrystalline silicon layer was deposited on the back side of the SiC substrate cleaned in Preparation Example 1 (low-pressure chemical vapor deposition: temperature 545℃, pressure 400 mtorr, SiH4 flow rate 950 sccm, PH3 flow rate 20 sccm); and a 100 nm thick Ni layer was deposited on the surface of the polycrystalline silicon layer (physical vapor deposition: power 2000 W, Ar flow rate 20 sccm); then a pre-laser annealing treatment was performed on the surface of the Ni layer (energy density 2.4 J, pulse width 100 ns, oxygen content 3 ppm) to form a thin layer. The resistivity of the thin layer was measured to be 25 μΩ·cm, which is a silicon-nickel alloy layer.

[0065] Step (2): Laser annealing treatment (energy density of 4.5J, pulse width of 100ns, oxygen content of 3ppm) is performed on the surface of the formed silicon-nickel alloy layer to form an ohmic contact between silicon-nickel and SiC.

[0066] The SiC material forming the ohmic contact was analyzed, and the carbon content of the precipitated material was measured (EDS elemental analysis chart shown in the figure). Figure 5 The particle size of the precipitated carbon and the detection data of the ohmic contact are shown in Table 1.

[0067] Example 2

[0068] Step (1): A 45 nm thick polycrystalline silicon layer was deposited on the back side of the SiC substrate cleaned in Preparation Example 1 (low-pressure chemical vapor deposition: temperature 540 °C, pressure 300 mtorr, SiH4 flow rate 900 sccm, PH3 flow rate 15 sccm); then a 90 nm thick Ni layer was deposited on the surface of the polycrystalline silicon layer (physical vapor deposition: power 1500 W, Ar flow rate 15 sccm); then pre-laser annealing was performed on the surface of the Ni layer (energy density 2.2 J, pulse width 95 ns, oxygen content 3 ppm) to form a thin layer. The resistivity of the thin layer was measured to be 24 μΩ·cm, which is a silicon-nickel alloy layer.

[0069] Step (2): Laser annealing (energy density of 4.8J, pulse width of 105ns, oxygen content of 3ppm) is performed on the surface of the formed silicon-nickel alloy layer to form an ohmic contact between silicon-nickel and SiC.

[0070] The SiC material forming the ohmic contact was tested, and the data on the carbon content, carbon particle size, and ohmic contact are shown in Table 1.

[0071] Example 3

[0072] Step (1): A 55 nm thick polycrystalline silicon layer was deposited on the back side of the SiC substrate cleaned in Preparation Example 1 (low-pressure chemical vapor deposition: temperature 550 °C, pressure 500 mtorr, SiH4 flow rate 1000 sccm, PH3 flow rate 25 sccm); then a 110 nm thick Ni layer was deposited on the surface of the polycrystalline silicon layer (physical vapor deposition: power 2500 W, Ar flow rate 25 sccm); then pre-laser annealing was performed on the surface of the Ni layer (energy density 2.6 J, pulse width 105 ns, oxygen content 3 ppm) to form a thin layer. The resistivity of the thin layer was measured to be 27 μΩ·cm, which is a silicon-nickel alloy layer.

[0073] Step (2): Laser annealing (energy density of 4.2J, pulse width of 95ns, oxygen content of 3ppm) is performed on the surface of the formed silicon-nickel alloy layer to form an ohmic contact between silicon-nickel and SiC.

[0074] The SiC material forming the ohmic contact was tested, and the data on the carbon content, carbon particle size, and ohmic contact are shown in Table 1.

[0075] Example 4

[0076] The method was carried out according to Example 1, except that in step (1), the thickness of the deposited polycrystalline silicon layer was 30 nm. In step (1), a thin layer was formed after pre-laser annealing, and the resistivity of the thin layer was measured to be 55 μΩ·cm, which is a silicon-nickel alloy layer.

[0077] The SiC material forming the ohmic contact was tested, and the data on the carbon content, carbon particle size, and ohmic contact are shown in Table 1.

[0078] Example 5

[0079] The method of Example 1 was followed, except that in step (2), the thickness of the deposited polycrystalline silicon layer was 70 nm. In step (1), a thin layer was formed after pre-laser annealing, and the resistivity of the thin layer was measured to be 18 μΩ·cm, which is a silicon-nickel alloy layer.

[0080] The SiC material forming the ohmic contact was tested, and the data on the carbon content, carbon particle size, and ohmic contact are shown in Table 1.

[0081] Example 6

[0082] The method was carried out according to Example 1, except that in step (1), the pre-laser annealing conditions were an energy density of 3.2 J, a pulse width of 90 ns, and an oxygen content of 3 ppm. In step (1), a thin layer was formed after pre-laser annealing, and the resistivity of the thin layer was measured to be 17 μΩ·cm, which is a silicon-nickel alloy layer.

[0083] The SiC material forming the ohmic contact was tested, and the data on the carbon content, carbon particle size, and ohmic contact are shown in Table 1.

[0084] Example 7

[0085] The procedure was carried out according to Example 1, except that in step (2), the laser annealing conditions were an energy density of 3 J, a pulse width of 90 ns, and an oxygen content of 3 ppm. In step (1), a thin layer was formed after pre-laser annealing, and the resistivity of the thin layer was measured to be 30 μΩ·cm, indicating that it was a silicon-nickel alloy layer.

[0086] The SiC material forming the ohmic contact was tested, and the data on the carbon content, carbon particle size, and ohmic contact are shown in Table 1.

[0087] Comparative Example 1

[0088] Step (1): A 150 nm thick Ni layer was deposited on the back side of the SiC substrate cleaned in Preparation Example 1 (physical vapor deposition: power 2000 W, Ar flow rate 20 sccm); then a pre-laser annealing treatment was performed on the surface of the Ni layer (energy density 2.4 J, pulse width 100 ns, oxygen content 3 ppm) to form a thin layer, and the resistivity of the thin layer was measured to be 6.84 μΩ·cm;

[0089] Step (2): Perform laser annealing on the surface of the formed thin layer (energy density of 4.5J, pulse width of 100ns, oxygen content of 3ppm).

[0090] The SiC material after laser annealing was analyzed, and the content of precipitated carbon was determined (EDS elemental analysis chart shown in the figure). Figure 6 The particle size of the precipitated carbon and the detection data of the ohmic contact are shown in Table 1.

[0091] Comparative Example 2

[0092] Step (1): A 50 nm thick polycrystalline silicon layer was deposited on the back side of the SiC substrate cleaned in Preparation Example 1 (low-pressure chemical vapor deposition: temperature 545 °C, pressure 400 mtorr, SiH4 flow rate 950 sccm, PH3 flow rate 20 sccm); then a 100 nm thick Ni layer was deposited on the surface of the polycrystalline silicon layer (physical vapor deposition: power 2000 W, Ar flow rate 20 sccm);

[0093] Step (2): Laser annealing treatment (energy density of 4.5J, pulse width of 90ns, oxygen content of 3ppm) is performed on the surface of the Ni layer to form a thin layer. The resistivity of the thin layer is measured to be 10μΩ·cm, which is a silicon-nickel alloy layer.

[0094] The laser-annealed SiC material was tested, and the data on the content of precipitated carbon, the particle size of precipitated carbon, and the ohmic contact are shown in Table 1.

[0095] Test Example 1

[0096] The SiC substrates of Example 1 after their second laser annealing and Comparative Example 1 after laser annealing were wiped with white lint-free cloths, and the wiping results are as follows: Figure 4 As shown.

[0097] Table 1

[0098]

[0099] As shown in Table 1, using the technical solution of this invention for laser annealing significantly reduces the amount of carbon precipitation in the SiC material (the carbon content can be as low as 7.8%), and the particle size of the precipitated carbon is smaller (reaching 95.65 nm). Furthermore, the specific contact resistivity of the ohmic contact is lower (reaching 8.2 × 10⁻⁶). -6 Ω·cm 2 ).

[0100] Compared to Comparative Example 1, which deposited a 150nm thick Ni layer only on the back side of a SiC substrate, the SiC material prepared by Example 1, which sequentially deposited Si and Ni layers on the back side of a SiC substrate, exhibited lower carbon deposition and smaller carbon particle size, as well as a lower specific contact resistivity in the ohmic contact. Analysis suggests that in Comparative Example 1, the pre-laser annealing treatment immediately after depositing the Ni layer on the back side of the SiC substrate prevented the formation of a silicon-nickel alloy layer, leaving it as a Ni layer, thus resulting in a lower measured resistivity. The subsequent laser annealing, forming a thin-layer structure, led to higher carbon deposition and a higher specific contact resistivity in the SiC material, along with a larger carbon particle size.

[0101] from Figure 4 As can be seen, the surface of the SiC material after laser annealing in Example 1 using the technical solution of the present invention is clean, and no black carbon traces appear after wiping with a white lint-free cloth; in contrast, carbon precipitates on the surface of the SiC material after laser annealing in Comparative Example 1, and black carbon traces appear on the surface of the lint-free cloth after wiping. This demonstrates that the method of the present invention can effectively reduce the amount of carbon precipitation.

[0102] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for reducing carbon deposition during laser annealing of SiC materials, characterized in that, The method includes: Step (1): Form a silicon-nickel alloy layer on the back side of the SiC substrate; Step (2): Perform laser annealing on the surface of the formed silicon-nickel alloy layer to make the silicon-nickel alloy layer form an ohmic contact with the SiC substrate.

2. The method according to claim 1, characterized in that, In step (1), the method for forming the silicon-nickel alloy layer includes: sequentially depositing a Si layer and a Ni layer on the back side of a SiC substrate or sequentially depositing a Ni layer and a Si layer, and then performing a pre-laser annealing treatment; And / or, the resistivity of the silicon-nickel alloy layer is 10-90 μΩ·cm, preferably 20-28 μΩ·cm.

3. The method according to claim 2, characterized in that, The thickness of the Si layer is 40-60 nm, preferably 45-55 nm.

4. The method according to claim 2 or 3, characterized in that, In step (1), the method for depositing the Si layer is selected from low-pressure chemical vapor deposition; Preferably, the raw materials for the low-pressure chemical vapor deposition method include SiH4 and PH3; Preferably, relative to a SiC substrate with a diameter of 150 mm, the flow rate of SiH4 is 850-1050 sccm, more preferably 900-1000 sccm; and the flow rate of PH3 is 10-30 sccm, more preferably 15-25 sccm. Preferably, the conditions for depositing the Si layer using low-pressure chemical vapor deposition include: a temperature of 500-600℃, preferably 540-550℃; and a pressure of 200-600 mtorr, preferably 300-500 mtorr.

5. The method according to any one of claims 2-4, characterized in that, The thickness of the Ni layer is 80-120 nm, preferably 90-110 nm.

6. The method according to any one of claims 2-5, characterized in that, In step (1), the method for depositing the Ni layer is selected from vacuum evaporation or physical vapor deposition, preferably physical vapor deposition; Preferably, the conditions for the physical vapor deposition method include: a power of 1000-3000W, preferably 1500-2500W; and an Ar flow rate of 10-30 sccm, preferably 15-25 sccm.

7. The method according to any one of claims 2-6, characterized in that, In step (1), the conditions for pre-laser annealing include: energy density of 2J-3J, pulse width of 90-110ns, and oxygen content ≤10ppm; preferably, energy density of 2.2J-2.6J, pulse width of 95-105ns, and oxygen content ≤5ppm.

8. The method according to any one of claims 1-7, characterized in that, In step (2), the conditions for laser annealing include: energy density of 4-5 J, pulse width of 90-110 ns, and oxygen content ≤10 ppm; preferably, energy density of 4.2-4.8 J, pulse width of 95-105 ns, and oxygen content ≤5 ppm.

9. The method according to any one of claims 1-8, characterized in that, Before performing step (1), the back side of the SiC substrate is cleaned.

10. The SiC material prepared by the method of any one of claims 1-9.

Images