Method for preparing SiCN film based on double-target reaction magnetron sputtering and application of SiCN film

Abstract

The invention belongs to the technical field of semiconductor material preparation, and particularly relates to a method for preparing a SiCN thin film based on double-target reaction magnetron sputtering and application of the SiCN thin film. According to the invention, through co-sputtering of a Si target (radio frequency) and a C target (direct current) and in combination with N2 reaction gas, precise regulation and control of components and performance of the thin film are realized. The low-temperature, accurate, uniform and adjustable preparation of the SiCN film is realized through double-target reaction magnetron sputtering, and the method has environmental protection property and mass production potential, has remarkable technical advantages in the fields of semiconductors, photoelectrons, MEMS (Micro Electro Mechanical Systems) and the like, and has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material preparation technology, specifically relating to a method for preparing SiCN thin films based on dual-target reactive magnetron sputtering and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] SiCN thin films have broad application prospects in many fields due to their excellent chemical stability, mechanical hardness, thermal stability, and tunable dielectric properties. Currently, the main methods for preparing SiCN thin films include chemical vapor deposition (CVD) and physical vapor deposition (PVD). While CVD (such as PECVD) produces films with good uniformity, it suffers from problems such as high deposition temperatures and the use of toxic reactive gases. Traditional physical vapor deposition methods (such as magnetron sputtering), although able to lower deposition temperatures, lack the flexibility to control element ratios, making it difficult to meet the demands of high-performance thin films.

[0004] In existing magnetron sputtering technologies, a single target material (such as SiC or Si3N4) is typically combined with a reactive gas (such as N2 or CH4). However, this approach suffers from problems such as imprecise control of film composition and poor uniformity. Therefore, there is an urgent need to develop a SiCN thin film preparation method that can precisely control film composition, achieve low-temperature deposition, and is suitable for industrial production. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for preparing SiCN thin films based on dual-target reactive magnetron sputtering and its applications. This invention achieves precise control of the Si, C, and N atomic ratios in the thin film by independently controlling the sputtering power of the Si and C targets and the N2 gas flow rate. Simultaneously, it optimizes the stress, density, and uniformity of the thin film, resulting in a uniformity of better than 5% across the entire 6-inch wafer, and an atomic ratio difference of better than 3 percentage points between the wafer edges and the center, making mass production feasible.

[0006] Specifically, the present invention provides the following technical solution: A first aspect of the present invention provides a method for preparing SiCN thin films based on dual-target reactive magnetron sputtering, comprising the following steps: S1. Place the Si target at the RF target position and the C target at the DC target position; then evacuate the process chamber, introduce Ar gas as the ignition gas, and introduce N2 gas as the reaction gas. S2. First, start DC sputtering on the C target, then start RF sputtering on the Si target. After the dual targets are stably ignited, open the baffle to allow sputtered ions to deposit on the substrate. At the same time, control the atomic ratio of Si to C by adjusting the power ratio of the Si target and the C target, and control the atomic content of N by adjusting the N2 flow rate to form a SiCN thin film with adjustable composition. Then, anneal the film to obtain the final product.

[0007] Preferably, in step S1, the vacuum degree of the vacuum treatment is ≤5×10⁻⁶. -4 Pa.

[0008] Preferably, in step S1, the Ar inlet flow rate is 100 sccm and the N2 inlet flow rate is 2 sccm. Too low a flow rate will lead to inaccurate flow meter control and will also affect the film-forming components.

[0009] Preferably, in step S2, the radio frequency sputtering power of the Si target is 500~800W, and the DC sputtering power of the C target is 300~500W.

[0010] Preferably, in step S2, the N2 flow rate is 1~5 sccm to precisely control the atomic content of N in the film.

[0011] Preferably, in step S2, the atomic ratio of Si:C:N in the SiCN thin film is 50~70%:20~30%:10~20%; more preferably, the atomic ratio of Si:C:N is 60%:25%:15%.

[0012] Preferably, in step S2, the annealing treatment is carried out at 500~1000℃ for 0.5~2 h to adjust the grain size, density and stress state of the film.

[0013] Preferably, in step S2, the annealing process increases the film grain size from 35~45 nm to 80~90 nm, and the film stress gradually changes from compressive stress to tensile stress.

[0014] In a second aspect, the present invention provides a SiCN thin film prepared by dual-target reactive magnetron sputtering, which is prepared by the method described in the first aspect.

[0015] Preferably, the SiCN film thickness is 300 nm to 1 μm, and the thickness is correlated with stress. The initial stress of a 300 nm thick film is -400 MPa, and the initial stress of a 1 μm thick film is close to 0 MPa.

[0016] A third aspect of the present invention provides an application of the SiCN thin film prepared by dual-target reactive magnetron sputtering as described in the second aspect in optoelectronic devices, copper interconnect dielectric barrier layers for integrated circuits, superhard coatings, or microelectromechanical systems.

[0017] One or more embodiments of the present invention have at least the following beneficial effects: (1) The method of preparing SiCN thin films based on dual-target reactive magnetron sputtering of the present invention can achieve precise control of the element ratio of the thin film and adjust the performance of the thin film. The content of Si, C and N can be independently controlled: by adjusting the sputtering power of the Si target (RF) and the C target (DC) and the N2 reaction gas flow rate, the atomic ratio of Si, C and N in the thin film (e.g. 60%:25%:15%) can be precisely controlled.

[0018] (2) Compared with PECVD (which requires high temperature reaction), the method of preparing SiCN thin film based on dual-target reactive magnetron sputtering of the present invention can be formed at room temperature, avoiding the damage of high temperature to heat-sensitive substrates (such as flexible devices and pre-processed wafers).

[0019] (3) The method for preparing SiCN thin films based on dual-target reactive magnetron sputtering of the present invention only requires Ar and N2, without the need for toxic gases such as silane and ammonia, making it more environmentally friendly and easier to maintain.

[0020] (4) The 6-inch wafer prepared by the method of dual-target reactive magnetron sputtering of the present invention has a uniformity of <5%: the difference in the ratio of atoms at the edge and the center is <3%, which is significantly better than that of traditional magnetron sputtering (usually >10%), and meets the stringent requirements of the semiconductor industry for uniformity.

[0021] (5) High stability of dual-target co-sputtering: By step-by-step initiation (C target first, then Si target) and impedance matching optimization, the sputtering process is ensured to be stable and suitable for mass production. In addition, by discovering the correlation between thickness and stress (the initial stress of a 300nm film is -400 MPa (compressive stress), and the stress of a 1 μm film is close to 0 MPa, and the stress state can be directly controlled by adjusting the thickness) and optimizing the performance through annealing (annealing (500-1000℃) can increase the grain size from 40 nm to 90 nm, improving compactness; the stress changes from compressive stress to tensile stress), the method proposed in this invention has significant technical advantages in the fields of semiconductors, optoelectronics, and MEMS. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a graph showing the stress variation with film thickness in the preparation of SiCN thin films according to an embodiment of the present invention. Figure 2 The stress variation of the SiCN thin film prepared for the embodiment of the present invention at a thickness of 300 nm with different annealing temperatures is shown in the figure. Detailed Implementation

[0024] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] Given the current limitations of SiCN thin film preparation processes, such as imprecise control of film composition and poor uniformity, this invention proposes a method for preparing SiCN thin films based on dual-target reactive magnetron sputtering. This method enables precise control of film composition, low-temperature deposition, and is suitable for industrial production.

[0026] A first typical embodiment of the present invention provides a method for preparing SiCN thin films based on dual-target reactive magnetron sputtering, comprising the following steps: S1. Place the Si target at the RF target position and the C target at the DC target position; then evacuate the process chamber, introduce Ar gas as the ignition gas, and introduce N2 gas as the reaction gas. S2. First, start DC sputtering on the C target, then start RF sputtering on the Si target. After the dual targets are stably ignited, open the baffle to allow sputtered ions to deposit on the substrate. At the same time, control the atomic ratio of Si to C by adjusting the power ratio of the Si target and the C target, and control the atomic content of N by adjusting the N2 flow rate to form a SiCN thin film with adjustable composition. Then, anneal the film to obtain the final product.

[0027] In one or more embodiments of this implementation, in step S1, the vacuum degree of the vacuum treatment is ≤5×10 - 4 Pa.

[0028] In one or more embodiments of this implementation, in step S1, the flow rate of Ar is 100 sccm and the flow rate of N2 is 2 sccm.

[0029] In one or more embodiments of this implementation, in step S2, the radio frequency sputtering power of the Si target is 500~800W, and the DC sputtering power of the C target is 300~500W.

[0030] In one or more embodiments of this implementation, in step S2, the N2 flow rate is 1~5 sccm to precisely control the atomic content of N in the film.

[0031] In one or more embodiments of this implementation, in step S2, the atomic ratio of Si:C:N in the SiCN thin film is 50~70%:20~30%:10~20%.

[0032] In one or more embodiments of this implementation, the atomic ratio of Si:C:N is 60%:25%:15%.

[0033] In one or more embodiments of this implementation, in step S2, the annealing treatment is carried out at 500~1000°C for 0.5~2 hours to adjust the grain size, density and stress state of the film.

[0034] In one or more embodiments of this implementation, in step S2, the annealing process increases the thin film grain size from 35~45 nm to 80~90 nm, and the thin film stress gradually changes from compressive stress to tensile stress.

[0035] A second typical embodiment of the present invention provides a SiCN thin film prepared by dual-target reactive magnetron sputtering, which is obtained by the above method.

[0036] In one or more embodiments of this implementation, the SiCN film thickness is 300 nm to 1 μm, and the thickness is correlated with stress. The initial stress of a 300 nm thick film is -400 MPa, and the initial stress of a 1 μm thick film is close to 0 MPa.

[0037] A third typical embodiment of the present invention provides an application of the SiCN thin film prepared by dual-target reactive magnetron sputtering in optoelectronic devices, copper interconnect dielectric barrier layers of integrated circuits, superhard coatings, or microelectromechanical systems.

[0038] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0039] Example This embodiment provides a method for preparing SiCN thin films based on dual-target reactive magnetron sputtering. The specific preparation process is as follows: (1) Placement of target materials: As required, place the Si target on the RF target position and the C target on the DC target position, and check the insulation to ensure that there are no problems with the placement of the target materials; (2) Vacuuming of the chamber: Evacuate the process chamber to a vacuum level ≤ 5 × 10 -4 Pa; (3) Adjust impedance matching: The impedance matching value of the RF sputtering target needs to be adjusted so that the target material can be sputtered normally and the reflected power is reduced; (4) Introducing reaction gas: Introducing Ar gas to initiate ignition, and simultaneously introducing N2 to carry out the reaction. The introducing flow rate of Ar is 100 sccm, and the introducing flow rate of N2 is 2 sccm. (5) Ignition co-sputtering: In the process program, first apply the power of the C target to enable the C target to ignite and sputter normally. After 10 s, apply the radio frequency power of the Si target to enable the Si target to ignite and sputter normally. When both targets can be ignited and sputtered normally, open the baffle under the target material at the same time. The sputtered ions can then be deposited on the substrate to form a SiCN composite film.

[0040] In this embodiment, the sputtering power is set to 600 W for Si target and 400 W for C target, and the Si:C:N atomic ratio at the deposition site is 60:25:15. If you want to increase or decrease the Si or C atomic ratio, you only need to increase or decrease the corresponding target power. If you want to increase or decrease the N atomic content in the film, you can increase or decrease the N2 flow rate.

[0041] (6) Thin film post-treatment: Thin film post-treatment (annealing) can adjust the compactness, stress, and high-temperature stability of the SiCN composite film. The sputtered SiCN thin film grains are very small, about 40 nm. The film thickness and post-treatment temperature can be set according to process requirements.

[0042] Specific test details are as follows: Figures 1-2 As shown: 1) Thin film stress is directly related to thickness. The thicker the thin film, the more the stress will gradually change from compressive stress to tensile stress. 2) As the post-processing temperature increases, the grains gradually grow (the grain size is about 90nm when annealed at 900℃ for 1 h), the film thickness will decrease slightly, the film density will be better, and the stress will gradually increase towards tensile stress.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing SiCN thin films based on dual-target reactive magnetron sputtering, characterized in that, Includes the following steps: S1. Place the Si target at the RF target position and the C target at the DC target position; then evacuate the process chamber, introduce Ar gas as the ignition gas, and introduce N2 gas as the reaction gas. S2. First, start DC sputtering on the C target, then start RF sputtering on the Si target. After the dual targets are stably ignited, open the baffle to allow sputtered ions to deposit on the substrate. At the same time, control the atomic ratio of Si to C by adjusting the power ratio of the Si target and the C target, and control the atomic content of N by adjusting the N2 flow rate to form a SiCN thin film with adjustable composition. Then, anneal the film to obtain the final product.

2. The method for preparing SiCN thin films based on dual-target reactive magnetron sputtering as described in claim 1, characterized in that, In step S1, the vacuum degree of the vacuum treatment is ≤5×10⁻⁶. -4 Pa; Preferably, the flow rate of Ar is 100 sccm and the flow rate of N2 is 2 sccm.

3. The method for preparing SiCN thin films based on dual-target reactive magnetron sputtering as described in claim 1, characterized in that, In step S2, the radio frequency sputtering power of the Si target is 500~800W, and the DC sputtering power of the C target is 300~500W.

4. The method for preparing SiCN thin films based on dual-target reactive magnetron sputtering as described in claim 1, characterized in that, In step S2, the N2 flow rate is 1~5 sccm.

5. The method for preparing SiCN thin films based on dual-target reactive magnetron sputtering as described in claim 1, characterized in that, In step S2, the atomic ratio of Si:C:N in the SiCN thin film is 50~70%:20~30%:10~20%; preferably, the atomic ratio of Si:C:N is 60%:25%:15%.

6. The method for preparing SiCN thin films based on dual-target reactive magnetron sputtering as described in claim 1, characterized in that, In step S2, the annealing treatment is carried out at 500~1000℃ for 0.5~2 hours.

7. The method for preparing SiCN thin films based on dual-target reactive magnetron sputtering as described in claim 1, characterized in that, In step S2, the annealing process increases the film grain size from 35~45 nm to 80~90 nm, and the film stress gradually changes from compressive stress to tensile stress.

8. A SiCN thin film prepared by dual-target reactive magnetron sputtering, which is prepared by the method described in any one of claims 1 to 7.

9. The SiCN thin film prepared by dual-target reactive magnetron sputtering as described in claim 8, characterized in that, The SiCN film has a thickness of 300 nm to 1 μm, and the thickness is correlated with stress.

10. The application of the SiCN thin film prepared by dual-target reactive magnetron sputtering as described in claim 8 or 9 in optoelectronic devices, copper interconnect dielectric barrier layers for integrated circuits, superhard coatings, or microelectromechanical systems.

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