Low-temperature preparation method of ultrathin silicon nitride film
By using tris(dimethylamino)silane and ammonia as precursors, and hot-vapor phase deposition reactions are carried out under 300°C to 400°C by alternate feeding methods, the problem of high reaction temperature of the existing silicon nitride film preparation method is solved, and the controllable preparation and high-precision film thickness control of ultra-thin silicon nitride films are realized.
Patent Information
- Application Number
- CN202411642863.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2025-03-14
AI Technical Summary
The existing silicon nitride film preparation methods have high reaction temperatures, making it difficult to achieve controllable preparation of ultra-thin films, and there are problems of high cost and complex processes.
A hot-vapor phase deposition reaction was carried out under 300°C to 400°C by using tris(dimethylamino)silane and ammonia as precursors, and an ultra-thin silicon nitride film was prepared by alternate feeding.
It realizes the preparation of ultra-thin nano-scale silicon nitride films under relatively mild conditions, with high film thickness accuracy and controllable growth rate. They are suitable for various substrate surfaces, simplifying process steps and facilitating mass production.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductors, relates to semiconductor functional films, and specifically to a low-temperature preparation method for an ultra-thin silicon nitride film. Background Art
[0002] The high-speed integration of the electronic and electrical industry has prompted semiconductor components to develop in the direction of miniaturization, high voltage, high current, and high power density, which poses a great challenge to the assembly and packaging materials of components. Among them, silicon nitride (Si3N4) plays an important role in semiconductor manufacturing due to its excellent physical, chemical and electrical properties. First, as an insulating layer, it effectively prevents current leakage, especially in integrated circuits and MOS devices, effectively ensuring the stability of electrical performance; secondly, silicon nitride film is used as a passivation layer to protect the semiconductor surface from oxidation, moisture and pollution, significantly improving the reliability and life of the device; in addition, with its excellent chemical corrosion resistance, silicon nitride film is often used as a mask material in the etching process to protect the device from etching damage. As a diffusion barrier, it can prevent impurities from entering the semiconductor material and ensure the long-term electrical performance of the device. Stable; in high-speed and high-frequency devices, the low dielectric constant of silicon nitride helps to reduce capacitance, reduce signal delay, and improve overall performance. It is also used in advanced packaging technology to help improve packaging density and device reliability, significantly extending the service life of the device. These characteristics make silicon nitride film an indispensable and important material in modern semiconductor manufacturing.
[0003] The physical structure of silicon nitride is mainly composed of Si-N tetrahedral units formed by covalent bonds between silicon and nitrogen atoms, which form a three-dimensional network structure by sharing nitrogen atoms. There are two main crystal forms of silicon nitride: α-type and β-type, both of which belong to the hexagonal crystal system. The α-type structure is more complex and has higher hardness, while the β-type structure is more stable and suitable for high-temperature applications. The strong covalent bonds of silicon nitride give it high hardness, strength and chemical stability, and it has low density, low thermal expansion coefficient and excellent thermal stability. In semiconductors and high-temperature environments, amorphous silicon nitride is often used as a thin film material, showing excellent electrical insulation and mechanical properties. These characteristics make silicon nitride an ideal material for high-temperature and high-strength applications. Common preparation methods for silicon nitride include vapor deposition (CVD), physical vapor deposition (PVD), reactive atmosphere method, liquid phase synthesis and solid phase synthesis. CVD and PVD methods are commonly used in thin film preparation, but they face the problems of high cost, complex process and extremely high reaction temperature, and cannot achieve controllable preparation of ultra-thin films; reactive atmosphere method and liquid phase synthesis are suitable for powder or solid materials, but require high temperature and complex control; although solid phase synthesis can produce high-purity silicon nitride, the reaction time is long and the particle size is difficult to control. The above problems have hindered the effective application of silicon nitride in the semiconductor field.
[0004] Atomic layer deposition (ALD) technology can achieve atomic-level precision thin film growth on various complex structure surfaces by periodically alternating pulses of two precursors. Compared with physical / chemical vapor deposition, it has the advantages of precise control of film thickness, large-area three-dimensional uniformity, low deposition temperature, and high degree of automation. It has very broad application prospects in many fields such as microelectronics, display materials, solar photovoltaics, surface engineering, nanomaterials, catalysis, and composite materials. After more than 50 years of development, there are now hundreds of inorganic materials that can be prepared by ALD technology, including metal oxides, sulfides, nitrides, precious metals, etc., as well as some organic polymer films and inorganic-organic composite film materials.
[0005] Research shows that existing silicon nitride film processes all use chlorine-containing silicon sources such as silicon chloride (SiCl4), dichlorosilane (SiH2Cl2), and hexachlorodisilane (Si2Cl6), and the deposition temperature is higher than 450°C or plasma-enhanced deposition is used. The use of plasma generation equipment increases equipment costs, has strict requirements on the experimental environment, and is not suitable for coating the surface of powder substrates with thin films; the reaction activity of halogen compounds is lower than that of metal organic sources, and the residual halogen atoms in the film will seriously affect the performance of the device. By increasing the reaction temperature, the generation of hydrogen halides (HCl, HI) and the desorption of NH3 in the surface reaction can be promoted, thereby reducing the halogen atom content. At the same time, the byproduct hydrogen chloride (HCl) generates hydrochloric acid when it meets water vapor, which will directly corrode the deposition equipment, reduce the service life of the equipment, increase the preparation cost of silicon nitride films, and is not conducive to the promotion of its industrial application. Summary of the invention
[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a low-temperature preparation method for an ultra-thin silicon nitride film, so as to solve the technical problem that the reaction temperature of the prior art preparation method for silicon nitride film needs to be further reduced.
[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:
[0008] A low-temperature preparation method for an ultra-thin silicon nitride film, wherein tri(dimethylamino)silane and ammonia are used as precursors, tri(dimethylamino)silane and ammonia are fed alternately, and a thermal vapor deposition reaction is performed under the condition that the temperature of the reaction chamber is 300°C to 400°C to obtain an ultra-thin silicon nitride film.
[0009] The present invention also has the following technical features:
[0010] The alternating feeding method is as follows: in the first step, tri(dimethylamino)silane is introduced onto the substrate surface, and then nitrogen is used to purge the sample surface; in the second step, ammonia is introduced, and after the thermal vapor deposition reaction is completed, nitrogen is used to purge the sample surface to complete a deposition cycle; the first and second steps are repeated to complete multiple deposition cycles.
[0011] In the first step, the injection time of tri(dimethylamino)silane is 1 to 5 seconds, and the nitrogen purge time is 10 to 30 seconds.
[0012] In the second step, the ammonia injection time is 10 to 100 seconds, and the nitrogen purge time is 10 to 30 seconds.
[0013] The thickness of the ultra-thin silicon nitride film is precisely controlled by the number of cycles of the deposition cycle of the thermal vapor deposition reaction. The growth rate of the ultra-thin silicon nitride film is / Number of cycles.
[0014] The surface roughness of the ultra-thin silicon nitride film is less than 2nm.
[0015] The ammonia concentration is greater than or equal to 10 vol.%.
[0016] Compared with the prior art, the present invention has the following technical effects:
[0017] (I) The method of the present invention realizes the controllable preparation of ultra-thin nano-scale silicon nitride films at 450°C under relatively mild conditions and without relying on plasma generation equipment. The method of the present invention realizes the preparation of ultra-thin silicon nitride films with angstrom-level film thickness accuracy and adjustable stoichiometric ratio by changing the number of cycles and the injection time of nitrogen-containing precursors.
[0018] (II) The present invention can prepare silicon nitride thin films with a film thickness accuracy of 0.1 nanometers on the surfaces of various substrates. The preparation method is relatively convenient, does not require pre-treatment and post-treatment steps, and is easy to achieve mass production. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a surface scanning electron microscope image of the original substrate in Example 1.
[0020] Figure 2 This is a scanning electron microscope image of the sample obtained after completing 1000 cycles of silicon nitride deposition in Example 1.
[0021] Figure 3 This is the X-ray photoelectron spectrum of the sample obtained after completing 1000 cycles of silicon nitride deposition in Example 1.
[0022] Figure 4 This is a transmission electron microscope photograph of the sample obtained after completing 100 cycles of silicon nitride deposition in Example 2.
[0023] Figure 5 This is a transmission electron microscopy element distribution map of the sample obtained after completing 100 cycles of silicon nitride deposition in Example 2.
[0024] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION
[0025] It should be noted that, unless otherwise specified, all raw materials, reagents and equipment in the present invention are raw materials, reagents and equipment known in the prior art and can be obtained from commercial channels.
[0026] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.
[0027] Embodiment 1:
[0028] This embodiment provides a low-temperature preparation method for an ultra-thin silicon nitride film. Specifically, a 40 nm thick silicon nitride film is prepared by thermal atomic layer deposition. The method is performed according to the following steps:
[0029] Step 1, preparation process:
[0030] A silicon wafer Si (100) substrate was placed in the reactor of the atomic layer deposition device, the temperature was controlled at 400°C, the purge gas nitrogen flow rate was 100 ml / min, the pressure in the reactor was 1 Torr, and the ammonia flow rate was 120 ml / min.
[0031] Step 2, silicon nitride film growth process:
[0032] In the first step, tri(dimethylamino)silane is continuously injected for 3 seconds under the carrier of nitrogen to chemically adsorb with the functional groups on the Si surface. After stopping the injection, nitrogen is purged for 10 seconds to remove excess tri(dimethylamino)silane and products in the reactor. In the second step, ammonia with a concentration of 10 vol.% is continuously injected for 20 seconds to chemically react with the silicon-containing functional groups adsorbed on the surface of the substrate to generate silicon nitride. After stopping the injection, nitrogen is purged for 10 seconds to remove excess ammonia and reaction products in the reactor.
[0033] Step 3, cyclic growth process:
[0034] Repeat the first and second steps of the above step 2 to complete 1000 cycles of deposition to obtain a silicon nitride film.
[0035] In this embodiment, the film thickness is tested by ellipsometer (HORIBA JOBIN YVON), the surface morphology of the sample is observed by scanning electron microscope (Zeiss Gemini 300), and the elemental composition, chemical state and molecular structure of the sample surface are obtained by X-ray photoelectron spectroscopy (Thermo K-Alpha).
[0036] By executing 1000 deposition cycles, the thickness of the obtained film can be precisely controlled. The ellipsometer tested and fitted the film thickness to be 43.1nm, and the average growth rate reached 0.04nm / cycle, achieving angstrom-level control accuracy.
[0037] Figure 1 and Figure 2 They are respectively the Si wafer substrate and the scanning electron microscopy results of the surface morphology of the Si wafer substrate after 1000 silicon nitride cycles. The image shows that after 1000 cycles, dense nanoscale particles with uniform particle size grow on the surface of the sample.
[0038] Figure 3 The X-ray photoelectron energy spectrum of the original sample and the sample surface after growing 1000 cycles of silicon nitride. Comparison of the results before and after deposition shows that N signal can be observed at a binding energy of 399.3 eV. The N element exists in a combined state to form Si-N bonds.
[0039] Embodiment 2:
[0040] This embodiment provides a low-temperature preparation method for an ultra-thin silicon nitride film. Specifically, a 5 nm thick silicon nitride film is prepared on the surface of powder particles by thermal atomic layer deposition. The method is performed in the following steps:
[0041] Step 1, preparation process:
[0042] Barium titanate particles were placed as substrates in an atomic layer deposition device reactor, the temperature was controlled at 350°C, the nitrogen purge flow rate was 100 ml / min, the pressure in the reactor was 1 Torr, and the ammonia flow rate was 50 ml / min.
[0043] Step 2, silicon nitride film growth process:
[0044] In the first step, tri(dimethylamino)silane is continuously injected for 5 seconds under the carrier of nitrogen, and chemical adsorption occurs on the surface functional groups of the barium titanate particle substrate. After the injection is stopped, nitrogen is purged for 15 seconds to remove excess tri(dimethylamino)silane and products in the reactor. In the second step, ammonia with a concentration of 10 vol.% is continuously injected for 30 seconds to chemically react with the silicon-containing functional groups adsorbed on the surface of the substrate to generate silicon nitride. After the injection is stopped, nitrogen is purged for 15 seconds to remove excess ammonia and reaction products in the reactor.
[0045] Step 3, cyclic growth process:
[0046] Repeat the first and second steps of the above step 2 to complete 100 cycles of deposition to obtain a silicon nitride film.
[0047] In this embodiment, the surface morphology of the sample was observed by transmission electron microscopy. Figure 4 The morphology of barium titanate particles coated with 100 cycles of silicon nitride. A uniform coating layer is formed on the surface of the particles. Figure 5 These are the distribution diagrams of Si and N elements, respectively. Si and N elements are evenly distributed on the surface of the particles.
[0048] Comparative Example 1: This comparative example provides a method for preparing a silicon nitride film, which uses the low pressure chemical vapor deposition (LPCVD) technology known in the prior art to prepare the silicon nitride film. This comparative example is one of the best methods for preparing silicon nitride films known so far. The specific steps are as follows: The substrate is placed in a reaction chamber, the temperature is set at 800°C, and chlorosilane (SiCl2H2) and ammonia (NH3) are introduced as precursor gases to react and generate a silicon nitride film.
[0051] The obtained silicon nitride film is of high quality, with a dense and uniform structure and strong film adhesion. However, due to the high temperature conditions of the LPCVD process, its application on materials with low heat resistance is limited, and the high temperature process brings high energy consumption.
[0052] Comparative Example 2:
[0053] This comparative example provides a method for preparing a silicon nitride film, which is basically the same as the method in comparative example 1, except that the temperature in comparative example 1 is set at 400° C., which is the same as the temperature in embodiment 1.
[0054] In this comparative example, at a low temperature of 400°C, the decomposition and reaction rate of the precursor are greatly reduced, resulting in an extremely low film formation rate of the silicon nitride film, poor film quality, and defects such as insufficient density and uneven structure, and poor film adhesion. This shows that it is difficult to obtain a silicon nitride film that meets the requirements at this temperature.
[0055] Comparative Example 3:
[0056] This comparative example provides a method for preparing a silicon nitride film, which is basically the same as the method in Example 1, except that in this comparative example, the temperature is controlled to be 600° C. This comparative example is a method for preparing a silicon nitride film using a high-temperature ALD method.
[0057] In this comparative example, at a high temperature of 600°C, the reaction rate of the precursor molecules increased significantly, resulting in a large amount of silicon nitride deposited in each cycle, making it difficult to accurately control the film thickness. The high reaction rate also led to the occurrence of some side reactions, affecting the uniformity and density of the film, and causing uneven film thickness. This shows that under high temperature conditions, the ALD method is difficult to achieve precise thickness control of ultra-thin silicon nitride films.
[0058] Comparative Example 4:
[0059] This comparative example provides a method for preparing a silicon nitride film, which is basically the same as the method in Example 1, except that in this comparative example, the temperature is controlled to be 500° C. This comparative example is a method for preparing a silicon nitride film by a medium-temperature ALD method.
[0060] In this comparative example, at a medium temperature of 500°C, although the temperature is not too high, the adsorption and desorption balance of the precursor molecules is still affected to a certain extent. Some precursor molecules desorb quickly on the substrate surface, resulting in insufficient deposition of the film in some areas, and the phenomenon of "gap" or "island-like" growth. The thickness of the film is difficult to control, and the local uniformity is poor. The film exhibits a discontinuous structure, especially at the nanometer level, where this discontinuity is more obvious.
[0061] Comparative Example 5:
[0062] This comparative example provides a method for preparing a silicon nitride film. In this comparative example, the silicon nitride film is prepared by a conventional thermal vapor chemical deposition method. In this comparative example, the temperature is controlled at 400°C. In this comparative example, tri(dimethylamino)silane and ammonia are introduced at one time, and the alternating addition method in Example 1 is not adopted.
[0063] In this comparative example, a silicon nitride film was prepared by conventional thermal vapor chemical deposition at 400°C. Due to the low reaction temperature and insufficient reaction kinetics, the film had poor density, high porosity, and uneven thickness distribution. This comparative example illustrates that the alternating introduction of low temperature and reaction precursors produces a synergistic technical effect.
Claims
1. A low-temperature preparation method for an ultra-thin silicon nitride film, characterized in that: The method uses tri(dimethylamino)silane and ammonia as precursors, tri(dimethylamino)silane and ammonia are added alternately, and a thermal vapor deposition reaction is performed at a reaction chamber temperature of 300°C to 400°C to obtain an ultra-thin silicon nitride film.
2. The low-temperature preparation method of an ultra-thin silicon nitride film according to claim 1, characterized in that: The alternating feeding method is as follows: in the first step, tri(dimethylamino)silane is introduced onto the substrate surface, and then nitrogen is used to purge the sample surface; in the second step, ammonia is introduced, and after the thermal vapor deposition reaction is completed, nitrogen is used to purge the sample surface to complete a deposition cycle; the first and second steps are repeated to complete multiple deposition cycles.
3. The low-temperature preparation method of an ultra-thin silicon nitride film according to claim 2, characterized in that: In the first step, the injection time of tri(dimethylamino)silane is 1 to 5 seconds, and the nitrogen purge time is 10 to 30 seconds.
4. The low-temperature preparation method of an ultra-thin silicon nitride film according to claim 2, characterized in that: In the second step, the ammonia injection time is 10 to 100 seconds, and the nitrogen purge time is 10 to 30 seconds.
5. The low-temperature preparation method of an ultra-thin silicon nitride film according to claim 1, characterized in that: The thickness of the ultra-thin silicon nitride film is precisely controlled by the number of cycles of the deposition cycle of the thermal vapor deposition reaction. The growth rate of the ultra-thin silicon nitride film is / Number of cycles.
6. The low-temperature preparation method of an ultra-thin silicon nitride film according to claim 1, characterized in that: The surface roughness of the ultra-thin silicon nitride film is less than 2nm.
7. The low-temperature preparation method of an ultra-thin silicon nitride film according to claim 1, characterized in that: The ammonia concentration is greater than or equal to 10 vol.%.