Method for laser-assisted preparation of silicon carbide film

Abstract

A method for preparing a silicon carbide film with assistance of laser comprises the steps that S1, a base material is provided, raw material gas is introduced, the surface of the base material is scanned through an ultraviolet laser beam, and the raw material gas is deposited on a scanning path to form silicon carbide crystal grains of a specific crystal form; and S2, carrying out secondary deposition on the surface of the base material on which the silicon carbide crystal grains with the specific crystal form are deposited by adopting a chemical vapor deposition process to form the silicon carbide film with the same crystal form. The method comprises the following steps: depositing silicon carbide crystal grains in a specific crystal form on a scanning path by using ultraviolet laser, and depositing a silicon carbide film on the surface of a base material on which the silicon carbide crystal grains in the specific crystal form are formed by using a chemical vapor deposition process; the silicon carbide crystal grains can effectively improve the utilization rate of raw materials of the chemical vapor deposition process and reduce the reaction time, and help a silicon carbide film to be formed more easily and be combined with a base material more firmly.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and in particular relates to a method for laser-assisted preparation of a silicon carbide film. Background Art

[0002] In the semiconductor manufacturing process, due to the excellent wear resistance, corrosion resistance and good thermal stability of silicon carbide (SiC), process equipment parts made of silicon carbide have been widely used. Among them, chemical vapor deposition (CVD) is a more commonly used method for preparing silicon carbide.

[0003] The chemical vapor deposition process (CVD) is based on methyltrichlorosilane (MTS / CH3SiCl3) as the main raw material. With the assistance of hydrogen (H2) and argon (Ar), high-quality silicon carbide (SiC) film deposition can be achieved under high temperature conditions (such as around 1500°C). The raw gas (MTS, H2, Ar) is introduced into the CVD reaction chamber and mixed by natural convection or forced flow. Under high temperature, MTS undergoes thermal decomposition to generate active free radicals such as CH3 and SiCl3. These free radicals then undergo chemical reduction reaction with H2 to generate SiC. These SiC finally gather on the surface of the substrate to form a high-purity, high-density silicon carbide (SiC) film.

[0004] However, in the existing silicon carbide (SiC) film preparation process, since SiC grains are difficult to form on the substrate surface in the initial stage of deposition, the raw material utilization rate of the chemical vapor deposition process (CVD) is low (about 10%); and since the crystal form matching of silicon carbide (SiC) and the substrate is difficult to control, the bonding force between the formed silicon carbide (SiC) film and the substrate is also relatively weak. Summary of the invention

[0005] The present application provides a method for laser-assisted preparation of silicon carbide thin film, which first uses ultraviolet laser to deposit silicon carbide grains of a specific crystal form on a scanning path, and then uses a chemical vapor deposition process to deposit a silicon carbide thin film on the surface of a substrate on which the silicon carbide grains of the specific crystal form are formed; the silicon carbide grains can effectively improve the utilization rate of raw materials in the chemical vapor deposition process and reduce the reaction time, helping the silicon carbide thin film to be easier to form and more firmly bonded to the substrate.

[0006] Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

[0007] To achieve one, part or all of the above purposes or other purposes, the present invention provides a method for laser-assisted preparation of silicon carbide thin films.

[0008] A method for laser-assisted preparation of a silicon carbide film, comprising:

[0009] Step S1: providing a substrate, introducing a raw material gas, and scanning the surface of the substrate using an ultraviolet laser beam, so that the raw material gas is deposited on the scanning path to form silicon carbide grains of a specific crystal form;

[0010] Step S2: using a chemical vapor deposition process to perform secondary deposition on the surface of the substrate on which silicon carbide grains of a specific crystal form are deposited, to form a silicon carbide film with the same crystal form.

[0011] The raw material gas includes methyltrichlorosilane and hydrogen. The methyltrichlorosilane is cracked under the irradiation of the ultraviolet laser beam and reacts with the hydrogen to form silicon carbide grains which are deposited on the surface of the substrate.

[0012] The crystal form of the formed silicon nitride grains is controlled by adjusting the scanning direction of the ultraviolet laser beam.

[0013] In the step S1, argon gas needs to be introduced as a protective gas to form a protective film to protect the ultraviolet laser beam.

[0014] The process temperature of step S1 is 20-50°C.

[0015] The substrate is a graphite substrate or a silicon substrate.

[0016] The power of the ultraviolet laser beam is not less than 1000W.

[0017] The ultraviolet laser light source is processed by scanning the optical path to form the ultraviolet laser beam, which is a strip-shaped beam.

[0018] The UV laser light source is provided by a gas excimer laser or a solid-state laser.

[0019] The temperature of the chemical vapor deposition process is 1300-1500°C.

[0020] Compared with the prior art, the beneficial effects of the present invention mainly include:

[0021] The silicon carbide grains deposited on the scanning path by ultraviolet laser in the present application can effectively improve the utilization rate of raw materials in the chemical vapor deposition process and reduce the reaction time, helping the silicon carbide film to be formed more easily and more firmly bonded to the substrate;

[0022] The present application controls the crystal form of the formed silicon nitride grains by adjusting the scanning direction of the ultraviolet laser beam, thereby controlling the crystal form of the silicon carbide film, making it easier to form a silicon carbide film with an ideal crystal form.

[0023] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic flow chart of a method for laser-assisted preparation of silicon carbide film provided in an embodiment of the present application.

[0026] Figure 2 This is a diagram of the structure of the laser device provided in an embodiment of the present application.

[0027] Figure 3 A cross-sectional view of a laser device provided in an embodiment of the present application.

[0028] Figure 4 Schematic diagram of the ultraviolet laser light source provided in an embodiment of the present application.

[0029] Figure 5 Schematic diagram of the ultraviolet laser beam provided in an embodiment of the present application.

[0030] Figure 6 A schematic diagram of the scanning light path provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

[0032] The present application provides a method for laser-assisted preparation of silicon carbide thin film, which first uses ultraviolet laser to deposit silicon carbide grains of a specific crystal form on a scanning path, and then uses a chemical vapor deposition process to deposit a silicon carbide thin film on the surface of a substrate on which the silicon carbide grains of the specific crystal form are formed; the silicon carbide grains can effectively improve the utilization rate of raw materials in the chemical vapor deposition process and reduce the reaction time, helping the silicon carbide thin film to be easier to form and more firmly bonded to the substrate.

[0033] The following will describe the various embodiments of the present application in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are provided in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in the present application can be implemented.

[0034] Example:

[0035] like Figure 1 As shown, a method for laser-assisted preparation of silicon carbide film comprises:

[0036] Step S1: providing a substrate 1, introducing a raw material gas, and scanning the surface of the substrate using an ultraviolet laser beam, so that the raw material gas is deposited on the scanning path to form silicon carbide grains of a specific crystal form;

[0037] Step S2: using a chemical vapor deposition process to perform secondary deposition on the surface of the substrate on which silicon carbide grains of a specific crystal form are deposited, to form a silicon carbide film with the same crystal form.

[0038] Specifically, first place the substrate 1 into Figure 2 In the chamber of the laser device shown, raw material gas is introduced, and the scanning direction of the ultraviolet laser beam 2 on the substrate 1 is adjusted by moving the substrate 1, so that the raw material gas is deposited on the scanning path to form silicon carbide grains of a specific crystal form;

[0039] As a preferred embodiment of the present invention, the substrate 1 in this embodiment is a graphite substrate or a silicon substrate.

[0040] like Figure 3 As shown, the raw material gas includes methyltrichlorosilane and hydrogen. Methyltrichlorosilane (CH3SiCl3) and hydrogen (H2) are introduced as raw material gases. Under the action of an ultraviolet laser beam 2 of a specific wavelength, the methyltrichlorosilane molecules absorb light energy and undergo photolysis to generate active free radicals such as CH3* and SiCl3*. This process is usually more efficient and controllable than simply relying on high-temperature thermal energy decomposition.

[0041] Methyltrichlorosilane (CH3SiCl3) is cracked under the irradiation of an ultraviolet laser beam 2 of a specific wavelength to generate active free radicals such as CH3 and SiCl3. These active free radicals undergo a reduction reaction with hydrogen. Specifically, the silicon atoms in SiCl3 are reduced by hydrogen and hydrogen chloride (HCl) is released, while CH3 participates in the formation of a carbon structure. At the same time, carbon and silicon atoms combine to form silicon carbide (SiC) grains, which are deposited on the surface of the substrate 1. The laser not only promotes the decomposition of the precursor, but also directly heats the surface of the substrate to accelerate the growth and arrangement of SiC grains.

[0042] The incompletely decomposed MTS and the intermediate products diffuse to the surface of the heated graphite substrate. After reaching the surface of the substrate, the intermediate products begin to adsorb and participate in further surface chemical reactions, forming SiC crystal structures while releasing by-products. The gaseous by-products formed are separated from the surface of the substrate. Finally, any original gas and by-products that have not participated in the reaction will be discharged and may be properly purified to reduce environmental pollution.

[0043] In addition, if Figure 3 As shown, argon gas needs to be introduced into the chamber of the laser equipment as a protective gas to form a protective film to protect the ultraviolet laser beam 2 from reacting with methyltrichlorosilane (CH3SiCl3) and hydrogen (H2), and finally being discharged through the exhaust pipe.

[0044] As an inert gas, argon can form a protective film to prevent reaction products (such as corrosive gases such as HCl) from contaminating or damaging the ultraviolet laser beam 2, which helps to maintain the stability and efficiency of the ultraviolet laser beam. Argon has good thermal conductivity and can help to evenly distribute heat, especially in the laser heating area, which can promote the uniformity of the temperature field, which is very important for the formation of silicon carbide (SiC) grains. And because argon is inert, it will not participate in the chemical reaction of methyltrichlorosilane (CH3SiCl3) and hydrogen (H2), and will be directly discharged through the exhaust pipe, which can reduce unnecessary side reactions.

[0045] The ultraviolet laser beam 3 is a strip-shaped beam. The light spot of the ultraviolet laser light source is shaped into a rectangular ultraviolet laser beam 3 through a scanning optical path. Specifically, Figure 6 As shown, the output of the energy of the ultraviolet laser light source is firstly precisely controlled by an attenuator, the light spot in the X direction is then expanded by a beam expander, the expanded light spot is adjusted to parallel light by a telephoto lens group, the laser energy is then homogenized by a homogenizer lens group, the homogenized laser is further collimated by a collimator lens group, and finally the laser strip beam is focused on the surface of the base material by a focusing lens group.

[0046] Considering the cracking energy of MTS, it is key to select a UV laser light source with a suitable wavelength, such as lasers in the deep ultraviolet (DUV) range, such as 248nm, 355nm, etc.; in order to continuously and stably output high-power UV lasers, high-power UV lasers, such as Excimer lasers or solid-state lasers, can be selected to provide UV laser light sources, help provide the required high energy density, generate continuous and stable high-power output, and ensure that the power of the UV laser light source is not less than 1000W.

[0047] Moreover, in order to ensure that MTS only deposits and produces SiC on the scanning path, it is necessary to ensure that MTS is cracked and participates in the reaction at the laser focus. Microfluidics technology or precision gas control systems can be used to accurately control the delivery of MTS gas. Mass flow controllers (MFCs) can be used to adjust the gas flow rate, and the gas can be evenly delivered to the laser focus area by designing suitable nozzles or diffusers.

[0048] As a preferred embodiment of the present invention, the process temperature of step S1 of this embodiment is 20-50°C, which is a relatively low temperature range. Within this temperature range, the gas flow rate and mixing ratio can be more conveniently controlled to ensure that gases such as MTS, hydrogen and argon can be evenly transported to the reaction area; lower temperatures are usually used to ensure that reaction gases (such as MTS and hydrogen) can be smoothly transported to the reaction chamber and remain in a stable state before laser irradiation, which helps to avoid unnecessary chemical changes or decomposition of the reactants before entering the reaction zone, thereby ensuring that the reaction mainly occurs in the local high temperature area irradiated by the laser; and low temperature conditions help to improve the overall safety of the system, especially for flammable and explosive gases such as hydrogen, low temperatures can reduce their explosion risks.

[0049] The present application adjusts the scanning direction of the ultraviolet laser beam 2 on the substrate 1 by moving the substrate 1, and controls the crystal form of the formed silicon nitride grains by controlling the scanning direction, thereby controlling the crystal form of the silicon carbide film, making it easier to form a silicon carbide film with an ideal crystal form; and the crystal form of the silicon nitride grains formed in the early stage has an auxiliary effect on the crystal form of the silicon nitride prepared by CVD in the later stage. In addition, the crystal form of the silicon nitride prepared by CVD is affected by specific process conditions.

[0050] The scanning direction of the ultraviolet laser beam will affect the growth direction of SiC grains. Under certain conditions, scanning along a certain direction may promote the preferential growth of a specific crystal plane, while scanning in different directions may lead to different thermal stress distributions, affecting the nucleation and growth mode of the grains. At the same time, the degree of overlap in the scanning path (i.e., the distance between adjacent scanning lines) will also affect the growth of SiC grains. Using different scanning strategies (such as spiral scanning, cross scanning, etc.) can change the arrangement of the grains.

[0051] The crystal orientation of the silicon carbide grains in this application is <111> , scanning with an ultraviolet laser beam can make the silicon carbide film <111> The ratio of crystal orientation increases.

[0052] As a preferred embodiment of the present invention, the silicon carbide film generated in this embodiment is a 3C-SiC film.

[0053] In step S2 of the present application, a chemical vapor deposition process is used to perform secondary deposition on the surface of a substrate on which silicon carbide grains of a specific crystal form are deposited, to form a silicon carbide film having the same crystal form, at a temperature of 1300-1500°C.

[0054] 1300-1500℃ is a typical high-temperature CVD process condition, which is suitable for preparing high-quality silicon carbide (SiC) films. Under such high temperature conditions, the reaction gases (such as methyltrichlorosilane MTS and hydrogen H2) will undergo pyrolysis and chemical reactions to generate SiC films deposited on the substrate surface. Among them, methyltrichlorosilane (MTS / CH3SiCl3) is the main precursor, providing carbon and silicon elements; hydrogen (H2) is a reducing agent, participating in the reaction and helping to control the deposition rate; and argon (Ar) is generally used as a protective gas; the ratio of MTS, H2 and Ar needs to be carefully adjusted to ensure the best reaction conditions and crystal control.

[0055] The present application provides a method for laser-assisted preparation of silicon carbide thin film, which first uses ultraviolet laser to deposit silicon carbide grains of a specific crystal form on a scanning path, and then uses a chemical vapor deposition process to deposit a silicon carbide thin film on the surface of a substrate on which the silicon carbide grains of the specific crystal form are formed; the silicon carbide grains can effectively improve the utilization rate of raw materials in the chemical vapor deposition process and reduce the reaction time, helping the silicon carbide thin film to be easier to form and more firmly bonded to the substrate.

[0056] In order to facilitate the description, some common English nouns or letters used in the present invention are only used for exemplary reference rather than restrictive interpretation or specific usage, and the protection scope of the present invention should not be limited by their possible Chinese translations or specific letters.

[0057] It should also be noted that, in this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

Claims

1. A method for laser-assisted preparation of silicon carbide thin film, characterized in that: include: Step S1: providing a substrate, introducing a raw material gas, and scanning the surface of the substrate using an ultraviolet laser beam, so that the raw material gas is deposited on the scanning path to form silicon carbide grains of a specific crystal form; Step S2: using a chemical vapor deposition process to perform secondary deposition on the surface of the substrate on which silicon carbide grains of a specific crystal form are deposited, to form a silicon carbide film with the same crystal form.

2. The method for laser-assisted preparation of silicon carbide thin film according to claim 1, characterized in that: The raw material gas includes methyltrichlorosilane and hydrogen. The methyltrichlorosilane is cracked under the irradiation of the ultraviolet laser beam and reacts with the hydrogen to form silicon carbide grains which are deposited on the surface of the substrate.

3. The method for laser-assisted preparation of silicon carbide thin film according to claim 2, characterized in that: Controlling the crystal form of the formed silicon carbide grains by adjusting the scanning direction of the ultraviolet laser beam; The crystal orientation of the silicon carbide grains is <111> .

4. The method for laser-assisted preparation of silicon carbide thin film according to claim 1, characterized in that: In the step S1, argon gas needs to be introduced as a protective gas to form a protective film to protect the ultraviolet laser beam.

5. The method for laser-assisted preparation of silicon carbide thin film according to claim 1, characterized in that: The process temperature of step S1 is 20-50°C.

6. The method for laser-assisted preparation of silicon carbide thin film according to claim 1, characterized in that: The substrate is a graphite substrate or a silicon substrate.

7. The method for laser-assisted preparation of silicon carbide thin film according to claim 1, characterized in that: The power of the ultraviolet laser beam is not less than 1000W.

8. The method for laser-assisted preparation of silicon carbide thin film according to claim 1, characterized in that: The ultraviolet laser light source is processed by scanning the optical path to form the ultraviolet laser beam, which is a strip-shaped beam.

9. The method for laser-assisted preparation of silicon carbide thin film according to claim 8, characterized in that: The UV laser light source is provided by a gas excimer laser or a solid-state laser.

10. The method for laser-assisted preparation of silicon carbide thin film according to claim 1, characterized in that: The temperature of the chemical vapor deposition process is 1300-1500°C.

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