A method for low temperature deposition of nitride films on silicon substrates

Abstract

The application discloses a method for depositing nitride film on silicon substrate at low temperature, which comprises the following steps: pre-cleaning and passivating single crystal silicon substrate by chemical method; placing the silicon substrate into a pre-baked vacuum chamber, introducing gas, ionizing the gas to generate plasma by using a radio frequency plasma source in the vacuum chamber, and performing physical and chemical etching on the silicon substrate by the plasma; introducing nitrogen source gas, exciting the nitrogen source gas into nitrogen plasma by the radio frequency plasma source, and pre-bonding the nitrogen plasma and the silicon substrate; starting a metal beam source furnace in the vacuum chamber, directly spraying metal atomic beam onto the silicon substrate, and reacting the metal atomic beam with the nitrogen plasma on the surface of the silicon substrate; and rotating the silicon substrate to periodically pass above the beam source furnace and the radio frequency plasma source, and depositing the low-temperature nitride film layer by layer. By accurately controlling the process parameters, the obtained nitride film is smooth, free of holes or protruding defects, and the low-temperature growth of the atom-level smooth nitride film is realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processes, and more specifically to a method for low-temperature deposition of nitride thin films on a silicon substrate. Background Technology

[0002] Nitride materials are widely used in deep ultraviolet LEDs, MiniLEDs, MicroLEDs, flexible displays, solar cells, power RF devices and other fields due to their excellent parameter properties, and have a huge market and broad application prospects.

[0003] High In and high Al content growth and low-cost flexible displays are two trends in nitride material research. Because nitrides such as InN are easily decomposed and desorbed at high temperatures (around 600°C), and inexpensive and easily fabricated amorphous substrates cannot withstand high temperatures, there is a demand for new technologies for low-temperature epitaxy of nitride materials.

[0004] Currently, the mainstream nitride growth technologies include metal-organic chemical vapor deposition (MOCVD), hydride epitaxy (HVPE), and molecular beam epitaxy (MBE). MOCVD equipment has a complex structure and high cost, and the high-temperature (typically 800–1200℃) growth process results in carbon pollution and component segregation. HVPE is carried out at high temperatures (typically 600–1100℃) and is suitable for bulk material preparation, but it cannot grow complex quantum well structures. MBE has a slow growth rate and is suitable for preparing small-sized nitride materials.

[0005] However, mainstream preparation methods cannot meet the technical requirements for high-quality low-temperature epitaxy of nitride materials. Therefore, designing a new method for low-temperature deposition of nitride thin films is a problem that this invention urgently needs to solve. Summary of the Invention

[0006] The purpose of this invention is to at least solve one of the above-mentioned technical problems. To this end, this invention provides a method for low-temperature deposition of nitride thin films on silicon substrates. The method can prepare atomically flat nitride thin films on silicon substrates at low temperatures, reduce costs, increase production capacity, and solve problems such as easy decomposition and desorption of some nitrides at high temperatures, carbon contamination, and component segregation.

[0007] Specifically, the present invention proposes the following technical solution: A method for low-temperature deposition of a nitride thin film on a silicon substrate, characterized by comprising the following steps: Step S1: Pre-clean and passivate the single-crystal silicon substrate using a chemical method; Step S2: Place the pre-cleaned silicon substrate into a pre-baked vacuum chamber, introduce gas, and use the radio frequency plasma source in the vacuum chamber to ionize the gas to generate plasma. The plasma then performs physical and chemical etching on the silicon substrate. Step S3: Nitrogen source gas is introduced into the vacuum chamber, and the nitrogen source gas is excited into nitrogen plasma by a radio frequency plasma source. The nitrogen plasma is pre-bonded with the silicon substrate. Step S4: Start the metal beam source furnace in the vacuum chamber and spray the metal atomic beam directly onto the silicon substrate obtained after step 3. The metal atomic beam reacts with the nitrogen plasma on the surface of the silicon substrate. The silicon substrate rotates and periodically passes over the beam source furnace and the radio frequency plasma source in sequence to perform layer-by-layer deposition of low-temperature nitride films.

[0008] Further, step S1 specifically involves immersing the single-crystal silicon substrate in the etching solution and letting it stand for 2 to 10 minutes; after cleaning, removing it, rinsing it clean, and shaking it dry for subsequent use; the etching solution is one or more of HF, BOE, SCI, and HF / EG.

[0009] Furthermore, step S2 specifically involves setting the temperature inside the vacuum chamber to 200 ℃~320 ℃; the power range of the radio frequency coil of the radio frequency plasma source to 150 W~450 W; and the etching time to 30~180 min.

[0010] More preferably, the gas introduced in step S2 is one or more of nitrogen, argon, hydrogen, and silane, the gas flow rate in the vacuum chamber is in the range of 10 sccm to 50 sccm, and the vacuum degree in the vacuum chamber is maintained at 5E-3 Pa to 2E-1 Pa.

[0011] Furthermore, in step S3, the power range of the radio frequency coil of the radio frequency plasma source is 300 to 500 W, the beam current voltage range is 0 to +400 V, the extraction voltage range is -200 to -400 V, and the neutralization current is 8 to 12 A.

[0012] More preferably, the nitrogen source gas introduced in step S3 is one or both of nitrogen and ammonia, the gas flow rate in the vacuum chamber is in the range of 3 sccm to 20 sccm, and the vacuum degree in the vacuum chamber is maintained at 5E-3 Pa to 5E-1 Pa.

[0013] Furthermore, in step S4, the deposition time is 1 to 120 min; the temperature inside the vacuum chamber is set to 200 ℃ to 350 ℃, and the vacuum degree inside the vacuum chamber is 5E-3 Pa to 5E-1 Pa.

[0014] More preferably, in step S4, the metal source used in the metal beam source furnace is one or more of Al, Ga, and In. After heating the metal source to 600-1000 °C, the furnace lid of the metal beam source furnace is opened, and one or more metal atomic beams are sprayed onto the silicon substrate that has been treated above. The temperature of the silicon substrate is 300 °C-500 °C.

[0015] Furthermore, in step S4, the furnace cover of the metal beam source furnace is opened when the silicon substrate rotates past directly above it, and the furnace cover of the metal beam source furnace is closed when the silicon substrate rotates away from it.

[0016] Furthermore, in step S4, the silicon substrate is held above the radio frequency plasma source for a duration of 30–90 s.

[0017] The beneficial effects achieved by this invention are: First, the present invention provides a method for low-temperature deposition of nitride thin films on silicon substrates to meet the requirements of high-quality low-temperature epitaxial growth of nitride materials. Second, the method provided by the present invention not only effectively removes the natural oxide layer on the surface of the silicon substrate, but also performs plasma treatment on the substrate, effectively suppressing the formation of amorphous compounds of Si on the surface of the silicon substrate when depositing the nitride thin film on the silicon substrate.

[0018] Compared to existing technologies, the method for low-temperature deposition of nitride thin films on silicon substrates provided by this invention significantly reduces costs and effectively increases production capacity. It also features low carbon pollution and no component segregation, achieving low-temperature atomic-level flatness growth of nitride thin films. The resulting nitride thin films have smooth surfaces free of pores or protrusions. Furthermore, because the growth process is carried out at low temperatures, it avoids the decomposition and desorption of some nitrides at high temperatures, as well as the remelting reaction with the substrate at high temperatures. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0020] Figure 1 This is a process flow diagram of low-temperature deposition of nitride thin films on a silicon substrate provided in an embodiment of the present invention.

[0021] Figure 2 This is an atomic force microscope schematic diagram of a single-crystal silicon wafer after plasma etching according to an embodiment of the present invention.

[0022] Figure 3 This is an atomic force microscope diagram of an embodiment of the present invention after AlN thin film deposition at low temperature. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. The present invention provides a method for low-temperature deposition of a nitride thin film on a silicon substrate, comprising the following steps: Step S1: Use chemical methods to pre-clean the commercially purchased single-crystal silicon substrate to remove the oxide layer on the surface of the silicon substrate and passivate it. Step S2: Place the pre-cleaned silicon substrate into a pre-baked vacuum chamber, introduce etching gas into the vacuum chamber, and use the radio frequency plasma source in the vacuum chamber to ionize the gas to generate plasma; use the generated plasma to perform physical and chemical etching on the silicon substrate. Step S3: After the silicon substrate is processed, nitrogen source gas is introduced into the vacuum chamber; the nitrogen source gas is excited into nitrogen plasma by the radio frequency plasma source in the vacuum chamber, so that the nitrogen plasma in the vacuum chamber reaches the set concentration range and pre-bonds with the silicon substrate. Step S4: Start the metal beam source furnace in the vacuum chamber to directly spray one or more metal atomic beams onto the silicon substrate obtained after step 3, where they react with nitrogen plasma on the substrate surface. The silicon substrate rotates and periodically passes over the metal beam source furnace and the radio frequency plasma source in sequence to perform a layer-by-layer deposition process of low-temperature nitride thin films.

[0024] As described above, the method for low-temperature deposition of nitride thin films on silicon substrates provided by the present invention employs a molecular beam epitaxy process, which achieves epitaxial growth of nitride thin films through alternating deposition of metal atoms and nitrogen plasma.

[0025] In step S1, the commercially purchased silicon substrate is pre-cleaned by chemical methods to remove the oxide layer and impurities on the surface of the silicon substrate to be treated, and to passivate its surface.

[0026] Specifically, commercially purchased monocrystalline silicon wafers are immersed in an etching solution and left to stand for 2–10 minutes, the exact time depending on the thickness of the oxide layer. This process aims to allow the surface silicon oxide layer to fully react and be removed within the appropriate time. Simultaneously, the cleaning solution effectively prevents further oxidation or other surface reactions on the silicon substrate by reacting with the substrate surface. After cleaning, the wafer is removed, rinsed thoroughly with deionized water, and then spun dry at high speed for subsequent use.

[0027] Furthermore, in the above embodiments, the etching solution is one or more of HF, BOE, SCI, and HF / EG. The centrifugal speed of the spin dryer is 800–2600 rpm, the spin drying time is 5–15 min, and the spin drying temperature is 40–80 min.

[0028] It should be noted that in the above etching solutions, HF is hydrofluoric acid; BOE is a mixture of HF and NH4F, the solution has a stable pH value and is not affected by the addition of a small amount of acid, and the etching rate is stable; SC1 is a mixture of ammonium hydroxide, hydrogen peroxide and water, and the higher the concentration and the higher the temperature, the faster the etching; HF / EG is a mixture of hydrofluoric acid and ethylene glycol, and its main characteristic is that it does not react with the substrate silicon or the silicon damaged by dry etching.

[0029] In step S2, the pre-cleaned silicon substrate is placed in a pre-baked vacuum chamber, and gas is introduced. The gas is ionized using a radio frequency plasma source within the vacuum chamber to generate plasma. The generated plasma is then used to perform physical and chemical etching on the silicon substrate.

[0030] Specifically, the silicon substrate, pre-cleaned in step 1, is placed in a pre-baked vacuum chamber, and the chamber temperature is set to 200 °C–320 °C. Gas is introduced into the vacuum chamber, and the gas is ionized using a radio frequency plasma source within the vacuum chamber. The power applied to the radio frequency coil of the radio frequency plasma source ranges from 150 W to 450 W. The generated plasma is used to perform physical and chemical etching on the silicon substrate, with an etching time of 30–180 min.

[0031] It is easy to understand that by setting the temperature inside the vacuum chamber to 200℃~320℃, the silicon substrate can be etched. The etching rate is stable and will not be too fast or too slow. When the temperature is too low, the etching rate is too fast, and it is difficult to control the surface morphology of the silicon substrate. When the temperature is too high, the etching rate is too slow, and it is difficult to achieve the expected etching effect.

[0032] It should be noted that, by controlling the aforementioned process parameters and testing with an atomic force microscope (AFM), such as... Figure 1 As shown, the surface roughness of the etched silicon substrate is less than 0.2 nm (10 μm × 10 μm range).

[0033] In a preferred embodiment, the gas introduced in step S2 is one or more of nitrogen, argon, hydrogen, and silane, the gas flow rate in the vacuum chamber is in the range of 10 sccm to 50 sccm, and the vacuum degree in the vacuum chamber is maintained at 5E-3 Pa to 2E-1 Pa.

[0034] As mentioned above, ionization using an SVT radio frequency plasma source is mainly used for the dissociation of nitrogen, hydrogen, and argon gases. The dissociation process does not generate high-energy ions, which helps in the growth of high-quality thin films and allows for substrate cleaning without damaging the substrate surface. The SVT radio frequency plasma source requires two bias voltages to operate. The applied beam current voltage is a positive bias for plasma focusing. The applied extraction voltage is a negative bias for plasma acceleration and extraction of positively charged ions from the plasma.

[0035] Additionally, it should be noted that the SVT radio frequency plasma source has certain requirements for vacuum level. Excessively low vacuum levels, especially during prolonged use, will adversely affect the SVT radio frequency plasma source. Therefore, the gas flow rate range is 10 sccm to 50 sccm, and the chamber vacuum level is maintained at 5E-3 Pa to 2E-1 Pa. Pa.

[0036] In step S3, after the silicon substrate is processed, nitrogen source gas is introduced into the vacuum chamber. The nitrogen source gas is excited into nitrogen plasma by a radio frequency plasma source in the vacuum chamber, so that the nitrogen plasma in the chamber reaches a set concentration range and pre-bonds with the Si substrate.

[0037] In the above embodiments, the power range of the radio frequency coil loaded onto the radio frequency plasma source is 300 to 500 W, the beam current voltage range of the radio frequency plasma source is 0 to +400 V, the extraction voltage range of the radio frequency plasma source is -200 to -400 V, and the neutralization current of the radio frequency plasma source is 8 to 12 A.

[0038] As an optional implementation, the nitrogen source gas introduced is one or both of nitrogen and ammonia. The gas flow rate in the vacuum chamber ranges from 3 sccm to 20 sccm, and the vacuum level in the vacuum chamber is maintained between 5E-3 Pa and 5E-1 Pa. After the nitrogen source gas is excited into plasma by a radio frequency plasma source, it is sprayed onto the surface of the above-treated Si substrate. The temperature in the vacuum chamber is between 300 °C and 500 °C.

[0039] In step S4, the metal beam source furnace within the vacuum chamber is activated, directly spraying one or more metal atomic beams onto the silicon substrate obtained after step 3, where they react with nitrogen plasma on the substrate surface. The silicon substrate rotates and periodically passes sequentially over the metal beam source furnace and the radio frequency plasma source, undergoing a layer-by-layer deposition process of low-temperature nitride thin films. By precisely controlling each process parameter, low-temperature growth of nitride thin films with atomically flatness is achieved.

[0040] It should be noted that, as Figure 2As shown, the nitride film obtained in step 4 was tested by atomic force microscopy (AFM). The results showed that the nitride film grown at low temperature on the silicon substrate after step 2 was smooth, without holes or protrusions, and inherited the surface morphology of the silicon substrate very well. The surface roughness was less than 0.2 nm (10 μm × 10 μm range).

[0041] In the above embodiments, the metal source used in the metal beam furnace is one or more of Al, Ga, and In. After heating the metal source to 600–1000 °C, the furnace lid is opened, and one or more metal atomic beams are sprayed onto the pre-treated silicon substrate. The silicon substrate rotates and periodically passes over the metal beam furnace and the radio frequency plasma source sequentially, performing a layer-by-layer deposition process of low-temperature nitride thin films. The silicon substrate temperature is 300 °C–500 °C, and the deposition time is 1–120 min.

[0042] As described above, in an optional implementation, in step S4, by controlling the rotation mode and dwell time of the silicon substrate, the substrate sequentially passes over a metal beam source furnace and a radio frequency plasma source, satisfying different III / V ratios, to perform a layer-by-layer deposition process of low-temperature nitride thin films, thereby achieving low-temperature growth of nitride thin films with atomically flat surfaces. The vacuum chamber temperature is set to 200 ℃~350 ℃, and the vacuum degree inside the vacuum chamber is 5E-3 Pa~5E-1 Pa.

[0043] It should be noted that in the above-described silicon substrate rotation control method, the rotation of the silicon substrate is linked to the opening and closing of the metal beam source furnace lid, and the residence time of the substrate above the RF plasma source in each rotation cycle can be specifically set. The timing of the opening and closing of the metal beam source furnace lid can be set according to the time it takes for the silicon substrate to pass directly above the metal beam source furnace. When the silicon substrate passes near the direct overhead of the metal beam source furnace, the furnace lid is opened; when the silicon substrate leaves the metal beam source furnace, the furnace lid is closed. This avoids the excessive amount of Group III reactants caused by the metal atom beam drifting and filling the entire reaction chamber under low vacuum. The residence time of the substrate above the plasma source can compensate for the insufficient effective concentration of Group V plasma. The silicon substrate rotation residence time is set to 30–90 s.

[0044] The method provided by this invention, which involves plasma treatment and low-temperature deposition of nitride films on silicon substrates, effectively removes the native oxide layer on the silicon substrate surface. The plasma treatment also effectively suppresses the formation of amorphous Si compounds on the silicon substrate surface, thereby improving the quality of the deposited nitride films. The substrate swirl time setting and the linkage control with the metal beam furnace lid allow for precise adjustment of the III / V ratio to grow nitride films with different component contents. The low-temperature growth mode avoids the decomposition and desorption of nitrides at high temperatures and the remelting reaction with the substrate at high temperatures. Compared to the high energy consumption, high cost, carbon pollution, and component segregation of existing MOCVD methods, the limitations of HVPE methods in fabricating complex quantum well structures, and the low growth rate of MBE methods, the low-temperature deposition method of nitride films on silicon substrates provided by this invention significantly reduces costs, effectively increases production capacity, and achieves low carbon pollution and no component segregation. It realizes the low-temperature growth of nitride films with atomically flat surfaces, perfectly meeting the requirements for high-quality low-temperature epitaxial growth of nitride materials.

[0045] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for low-temperature deposition of nitride thin films on a silicon substrate, characterized in that, Includes the following steps: Step S1: Pre-clean and passivate the single-crystal silicon substrate using a chemical method; Step S2: Place the pre-cleaned silicon substrate into a pre-baked vacuum chamber, introduce gas, and use the radio frequency plasma source in the vacuum chamber to ionize the gas to generate plasma. The plasma performs physical and chemical etching on the silicon substrate. The temperature in the vacuum chamber is set to 200 ℃~320 ℃. The power range of the radio frequency coil of the radio frequency plasma source is 150 W~450 W. The etching time is 30~180 min. Step S3: Nitrogen source gas is introduced into the vacuum chamber and excited into nitrogen plasma by a radio frequency plasma source. The nitrogen plasma is pre-bonded with the silicon substrate. The power range of the radio frequency coil of the radio frequency plasma source is 300-500 W, the beam current voltage range is 0-+400 V, the extraction voltage range is -200--400 V, and the neutralization current is 8-12 A. Step S4: Start the metal beam source furnace in the vacuum chamber and directly spray the metal atomic beam onto the silicon substrate obtained after step S3. The metal atomic beam reacts with nitrogen plasma on the surface of the silicon substrate. The silicon substrate rotates and periodically passes over the beam source furnace and the radio frequency plasma source in sequence to perform layer-by-layer deposition of low-temperature nitride films. The deposition time is 1 to 120 minutes. The temperature in the vacuum chamber is set to 200 ℃ to 350 ℃, and the vacuum degree in the vacuum chamber is 5E-3 Pa to 5E-1 Pa. The metal source used in the metal beam source furnace is one or more of Al, Ga, and In. After heating the metal source to 600 to 1000 ℃, open the furnace lid of the metal beam source furnace and spray one or more metal atomic beams onto the silicon substrate that has been treated above. The temperature of the silicon substrate is 300 ℃ to 500 ℃. The silicon substrate stays above the radio frequency plasma source for 30 to 90 seconds.

2. The method for low-temperature deposition of nitride thin films on a silicon substrate according to claim 1, characterized in that, Step S1 specifically involves immersing the single-crystal silicon substrate in the etching solution and letting it stand for 2 to 10 minutes; after cleaning, removing it, rinsing it clean, and drying it for subsequent use; the etching solution is one or more of HF, BOE, SCI, and HF / EG.

3. The method for low-temperature deposition of nitride thin films on a silicon substrate according to claim 1, characterized in that, The gas introduced in step S2 is one or more of nitrogen, argon, hydrogen, and silane. The gas flow rate in the vacuum chamber is in the range of 10 sccm to 50 sccm, and the vacuum degree in the vacuum chamber is maintained at 5E-3 Pa to 2E-1 Pa.

4. The method for low-temperature deposition of nitride thin films on a silicon substrate according to claim 1, characterized in that, The nitrogen source gas introduced in step S3 is one or both of nitrogen and ammonia. The gas flow rate in the vacuum chamber is in the range of 3 sccm to 20 sccm, and the vacuum degree in the vacuum chamber is maintained at 5E-3 Pa to 5E-1 Pa.

5. The method for low-temperature deposition of a nitride thin film on a silicon substrate according to claim 1, characterized in that, In step S4, the furnace lid of the metal beam source furnace is opened when the silicon substrate rotates past directly above it, and the furnace lid of the metal beam source furnace is closed when the silicon substrate rotates away from it.

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