Composite substrate table for polycrystalline diamond deposition and preparation method
By synergistically designing a composite substrate stage and a multi-component atmosphere process, the problem of synergistically optimizing the growth rate, crystal quality, and residual stress of polycrystalline diamond was solved, enabling the controllable preparation of high-performance polycrystalline diamond.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-28
- Publication Date
- 2026-04-14
AI Technical Summary
In existing MPCVD technology, it is difficult to optimize the growth rate, crystal quality and surface morphology of polycrystalline diamond in a coordinated manner. Traditional substrate stage structures lead to uneven plasma density and mismatched thermal expansion coefficients, resulting in residual stress accumulation and crystallization defects.
A composite substrate stage design is adopted, including a molybdenum substrate, a tungsten ring, and a copper sheet. Combined with a multi-component atmosphere process, a uniform plasma environment and temperature field are achieved by optimizing the substrate stage structure and gas ratio, thereby reducing residual stress.
It significantly improves the deposition uniformity and crystal quality of polycrystalline diamond, reduces residual stress, and optimizes performance to meet the needs of different applications.
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Figure CN121853166A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microwave plasma chemical vapor deposition technology, and in particular to a composite substrate stage for polycrystalline diamond deposition and its preparation method. Background Technology
[0002] Polycrystalline diamond (PCD), an advanced material composed of micron- or nano-scale diamond grains, possesses ultra-high hardness, excellent wear resistance, exceptional thermal conductivity, and stable chemical properties, playing an irreplaceable role in industrial fields such as high-end cutting tools, oil and gas drilling, and high-power electronic heat dissipation. Among numerous preparation techniques, microwave plasma chemical vapor deposition (MPCVD) has become the preferred technology for preparing high-quality, large-area PCD polycrystalline diamond due to its high-density plasma, absence of electrode contamination, and precise process control. Currently, the industry generally uses the H2-CH4 system as the process basis and attempts to introduce various auxiliary gases to optimize the performance of polycrystalline diamond, but existing technical routes still have significant limitations.
[0003] Current research and practice are generally limited to introducing single or dual auxiliary gases, such as nitrogen (N2), argon (Ar), carbon dioxide (CO2), or oxygen (O2), making it difficult to achieve synergistic optimization of polycrystalline diamond performance and resulting in a "one-for-one" dilemma. Specifically: while the introduction of nitrogen can effectively improve the deposition rate, it is often accompanied by a deterioration in crystal quality and a surge in surface roughness; oxygen can improve the purity of polycrystalline diamond through strong etching, but its inhibitory effect on growth rate and the uncontrollability of etching intensity limit its application; argon helps to increase plasma density and improve surface morphology, but its ability to remove non-diamond phases is limited, making it difficult to independently support breakthroughs in comprehensive performance. This "single-point optimization" model cannot achieve a systematic balance between key indicators such as high-speed growth, high crystal quality, and excellent surface morphology, becoming the primary bottleneck restricting the comprehensive upgrading of PCD performance.
[0004] On the other hand, the optimization of the deposition process is inseparable from the support of the substrate stage structure. A good substrate stage design is the key physical basis for maintaining a stable plasma environment, achieving a uniform temperature field distribution, and reducing the residual stress of polycrystalline diamond. However, traditional substrate stages generally suffer from the defect of simple structural design: the external geometry is simple (often using a flat plate or cone shape), which makes it difficult to effectively confine the plasma, resulting in severe attenuation of plasma density at the edge of the deposition area and uneven distribution of active species, which directly affects the uniformity of polycrystalline diamond growth. The substrate stage material is often a single component such as pure molybdenum, and its thermal conductivity and coefficient of thermal expansion are difficult to match the requirements of diamond growth, which can easily cause excessive temperature gradients during the deposition process (the temperature difference between the center and the edge can reach more than 50°C), causing the accumulation of residual stress in polycrystalline diamond (the edge tensile stress is usually ≥0.5GPa), which becomes the cause of cracking and crystallization defects in polycrystalline diamond. At the same time, most substrate stages lack targeted heat dissipation design, making it difficult to balance the contradiction between high-speed deposition and temperature control, which further leads to a narrow process optimization window.
[0005] Therefore, developing a gas process capable of systematically and synergistically controlling growth rate and overall quality, coupled with an optimized composite substrate stage structure design, has become an urgent need to promote the development of MPCVD technology and achieve a dual leap in PCD material performance and deposition efficiency. Thus, there is a pressing need to propose a composite substrate stage design and a controllable preparation method for polycrystalline diamond. Summary of the Invention
[0006] The purpose of this invention is to provide a composite substrate stage for polycrystalline diamond deposition and its preparation method, so as to solve the problems existing in the prior art.
[0007] To achieve the above objectives, the present invention provides a composite substrate stage for polycrystalline diamond deposition, comprising a molybdenum substrate, a tungsten ring, and a copper sheet. The external geometry of the molybdenum substrate is a frustum-shaped arc-sided cone. The interior of the molybdenum substrate is provided with mounting grooves and heat dissipation grooves. The tungsten ring is mounted in the mounting groove at the top of the molybdenum substrate. The copper sheet is embedded in the heat dissipation groove at the bottom of the molybdenum substrate. The tungsten ring, the molybdenum substrate, and the copper sheet are tightly fitted together, and the height difference between each mating surface of the tungsten ring, the molybdenum substrate, and the copper sheet is controlled within 0.1 mm.
[0008] Preferably, the side surface of the frustum-shaped arc is a smoothly transitioning arc surface.
[0009] Preferably, the copper sheet is made of high thermal conductivity pure copper material, and the thermal conductivity of the copper sheet is higher than that of the molybdenum base; the coefficient of thermal expansion of the tungsten ring is between that of the molybdenum base and that of diamond.
[0010] Preferably, the tungsten ring has a ring-shaped structure, with an outer diameter of not more than 50.4 mm and a thickness of not less than 1 mm.
[0011] Preferably, the copper sheet has a boss structure, the top diameter of the copper sheet matches the inner diameter of the heat dissipation groove structure, and the overall thickness of the copper sheet is no more than 5mm.
[0012] This invention provides a controllable preparation method for polycrystalline diamond, comprising the following steps: S1, mounting the tungsten ring and the copper sheet on the molybdenum substrate respectively, and pre-treating the composite substrate stage and the silicon substrate by cleaning, polishing and diamond micron powder inoculation; S2, placing the pre-treated silicon substrate in the support position of the composite substrate stage and loading it into the deposition chamber of the diamond preparation device; S3, introducing a base atmosphere and an auxiliary gas into the deposition chamber, and generating plasma under high-power microwave excitation for deposition; S4, after deposition, removing the sample by programmed cooling.
[0013] Preferably, the base atmosphere includes hydrogen and methane; the auxiliary gas includes nitrogen, argon and carbon dioxide; the performance of polycrystalline diamond is directionally controlled by adjusting the volume fraction ratio of argon and carbon dioxide in the total gas flow rate.
[0014] Preferably, in step S3, the volume fraction of nitrogen in the total gas flow rate is fixed at 1%.
[0015] Preferably, in step S3, the volume fraction of argon is adjusted within the range of 0.1% to 0.8%, and the volume fraction of carbon dioxide is adjusted within the range of 0.1% to 0.8%.
[0016] Preferably, when aiming for a high growth rate, the argon gas fraction is controlled to be no more than 0.3% and the carbon dioxide volume fraction is no more than 0.3%; when aiming for high crystal quality, the argon gas fraction is controlled to be between 0.5% and 0.8% and the carbon dioxide volume fraction is no more than 0.2% to 0.5%; when aiming for a comprehensive performance that balances growth rate, grain size, and crystal quality, the argon gas fraction is controlled to be between 0.3% and 0.5% and the carbon dioxide volume fraction is between 0.3% and 0.5%, and the absolute value of the difference between the volume fractions of argon and carbon dioxide does not exceed 0.1%.
[0017] Compared with the prior art, the present invention has the following advantages and technical effects:
[0018] This invention achieves significant progress through the synergistic design of optimized substrate stage structure and multi-component atmosphere process. Specifically, the frustum-shaped composite substrate stage provided by this invention, combined with a molybdenum, copper, and tungsten composite material and a heat dissipation trench structure, creates a uniform and stable thermal field and plasma environment for the deposition process, thereby effectively improving the uniformity of deposition temperature and significantly reducing the residual stress in polycrystalline diamond.
[0019] Based on this, by introducing nitrogen, argon and carbon dioxide into a base atmosphere of hydrogen and methane to form a multi-component synergistic atmosphere, and by precisely controlling their ratio, it is possible to selectively guide the growth of polycrystalline diamond towards different performance directions such as high speed, high quality or large grains, to meet the diverse application needs of heat sinks, optical windows or electronic devices.
[0020] This deep integration of hardware and process systematically solves the key contradiction in traditional MPCVD technology that makes it difficult to coordinate and control the uniformity of polycrystalline diamond deposition, growth rate, crystal quality and residual stress, providing a reliable technical approach for the controllable preparation of high-performance polycrystalline diamond. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a schematic diagram of the overall structure of the MPCVD diamond preparation apparatus of the present invention.
[0023] Figure 2 This is a schematic diagram of the internal structure of the deposition cavity and a flowchart of the multi-component gas synergistic control process of the present invention.
[0024] Figure 3 This is a three-dimensional structural schematic diagram of the composite substrate stage of the present invention.
[0025] Figure 4 For the present invention Figure 3 A schematic diagram of the two-dimensional cross-sectional structure of the composite substrate stage.
[0026] Figure 5 This is a simulation cloud map of the electric field intensity distribution of the comparative example (flat substrate stage) of the present invention.
[0027] Figure 6 This is a simulation cloud map of the electric field intensity distribution of the comparative example (frustum-shaped substrate stage) of the present invention.
[0028] Figure 7 This is a simulation cloud map of the electric field intensity distribution of an embodiment of the present invention (a frustum-shaped arc-side composite substrate stage).
[0029] Figure 8 This is a simulation cloud map of the electron density distribution of the comparative example (flat substrate stage) of the present invention.
[0030] Figure 9 This is a simulation cloud map of the electron density distribution of the comparative example (frustum-shaped substrate stage) of the present invention.
[0031] Figure 10 This is a simulation cloud map of the electron density distribution of an embodiment of the present invention (a frustum-shaped arc-side composite substrate stage).
[0032] Figure 11 This is a two-dimensional cross-sectional comparison diagram of the different substrate stage structures involved in the comparative examples and embodiments of the present invention.
[0033] Figure 12 for Figure 11 A comparison of surface temperature distribution curves of different substrate stage structures under simulated deposition conditions.
[0034] Figure 13 for Figure 11 Comparison of residual stress distribution curves of diamond films supported by different substrate stage structures after simulated cooling.
[0035] Figure 14 This is a SEM image of the surface morphology of the diamond prepared in Example 1 of the present invention (corresponding to a low Ar / CO2 ratio).
[0036] Figure 15 The image shows the Raman spectrum of the diamond prepared in Example 2 of this invention (corresponding to a high Ar / moderate CO2 ratio).
[0037] Figure 16 The X-ray diffraction (XRD) pattern of the diamond prepared in Example 2 of the present invention (corresponding to a high Ar / moderate CO2 ratio).
[0038] Figure 17 This is a SEM image of the surface morphology of the diamond prepared in Example 3 of the present invention (corresponding to the balanced Ar / CO2 ratio).
[0039] Figure 18 The image shows the Raman spectrum of the diamond prepared in Example 3 of this invention (corresponding to the balanced Ar / CO2 ratio).
[0040] In the figure: 1. Deposition chamber; 2. Silicon substrate; 3. Tungsten ring; 4. Molybdenum base; 5. Copper sheet; 6. Sample stage. Detailed Implementation
[0041] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0042] like Figures 1 to 4As shown, the present invention provides a composite substrate stage for polycrystalline diamond deposition, comprising a molybdenum base 4, a tungsten ring 3, and a copper sheet 5. The external geometry of the molybdenum base 4 is a frustum arc-shaped structure. The interior of the molybdenum base 4 is provided with a mounting groove and a heat dissipation groove structure. The tungsten ring 3 is installed in the mounting groove at the top of the molybdenum base 4. The copper sheet 5 is embedded in the heat dissipation groove structure at the bottom of the molybdenum base 4. The tungsten ring 3, the molybdenum base 4, and the copper sheet 5 are tightly fitted together, and the height difference between each mating surface of the tungsten ring 3, the molybdenum base 4, and the copper sheet 5 is controlled within 0.1 mm.
[0043] The use of a frustum-shaped arc-shaped structure on the exterior of the molybdenum base 4 optimizes the electric field distribution of the sheath formed by microwave plasma above the deposition area. Compared to traditional flat or simple conical structures, this arc-shaped side can guide the electric field lines more smoothly, reducing electric field distortion and concentration in the edge region. This creates favorable conditions for generating uniform and stable high-density plasma, ensuring the uniformity of deposition from a physical perspective.
[0044] By installing the tungsten ring 3 within the mounting groove on top of the molybdenum substrate 4, the interfacial thermal matching can be improved by utilizing the closer thermal expansion coefficients of tungsten and diamond. During deposition and subsequent cooling, the tungsten ring 3 can constrain the deformation of the substrate edge, reducing excessive tensile stress at the diamond film edge caused by the large difference in thermal expansion coefficients between the molybdenum substrate 4 and diamond, thereby effectively suppressing the risk of film cracking.
[0045] The copper sheet 5, installed within the heat dissipation groove structure inside the molybdenum substrate 4, enhances the lateral thermal diffusion capability of the substrate stage by utilizing the high thermal conductivity of copper (approximately 400 W·m⁻¹·K⁻¹). The heat generated during deposition can be rapidly transferred laterally through the copper sheet 5, significantly reducing the radial temperature gradient (from the center to the edge) on the substrate stage surface and providing a uniform temperature field for achieving uniform diamond growth.
[0046] By employing a tight fit between the tungsten ring 3, the molybdenum base 4, and the copper sheet 5, good thermal contact and mechanical stability between the components can be ensured. This tight fit reduces interfacial thermal resistance, allowing for efficient heat conduction between the molybdenum, copper, and tungsten materials, fully leveraging the advantages of composite material design and synergistically regulating the overall thermal and stress fields.
[0047] By controlling the height difference between the mating surfaces of the tungsten ring 3, the molybdenum base 4, and the copper sheet 5 to within 0.1 mm, the contact thermal resistance can be minimized, ensuring excellent thermal consistency and mechanical stability of the composite structure at high temperatures, and achieving efficient thermal management and stress matching. The flat surface avoids warping or additional stress caused by uneven support of the substrate, while ensuring good thermal conductivity contact between the substrate and the substrate stage.
[0048] The design was further optimized so that the side surface of the frustum-shaped arc is a smoothly transitioning curved surface.
[0049] By designing the side of the frustum-shaped structure as a smoothly transitioning arc surface, the electric field transition can be further smoothed, the electric field abrupt change or the effect of local excessive plasma intensity that may occur at sharp corners can be eliminated, and the uniform and stable distribution of plasma above the substrate can be promoted. This avoids local field distortion and plasma instability caused by sharp corners or abrupt interfaces, making the plasma sphere shape more regular and the spatial distribution of active particles on the substrate surface more uniform.
[0050] The scheme was further optimized by using copper sheet 5 made of high thermal conductivity pure copper material, and the thermal conductivity of copper sheet 5 is higher than that of molybdenum base 4; the thermal expansion coefficient of tungsten ring 3 is between that of molybdenum base 4 and diamond.
[0051] By using high thermal conductivity pure copper material to manufacture copper sheet 5, its lateral heat diffusion efficiency can be maximized. High purity ensures that the copper material has a high thermal conductivity close to the theoretical value, thus optimizing its function as a "heat diffuser" and effectively homogenizing the temperature of the substrate mesa.
[0052] By setting the thermal conductivity of copper sheet 5 to be higher than that of molybdenum base 4, the lateral heat transfer efficiency inside the substrate stage can be significantly enhanced, which is the key to rapidly homogenizing the radial temperature gradient.
[0053] By setting the thermal expansion coefficient of the tungsten ring 3 to be between that of the molybdenum substrate 4 and the diamond, a gradient transition layer with a thermal expansion coefficient can be formed at the edge of the substrate stage, which can more effectively buffer and match the thermal stress generated by the diamond film during deposition and cooling, and reduce the risk of interface cracking.
[0054] Further optimization of the design: the tungsten ring 3 has a ring structure, with an outer diameter of no more than 50.4 mm and a thickness of no less than 1 mm.
[0055] By limiting the outer diameter of the tungsten ring 3 to no more than 50.4 mm and its thickness to no less than 1 mm, sufficient structural strength and heat capacity can be ensured. This allows the tungsten ring 3 to effectively cover and constrain the edge area of a typical-sized (e.g., 2-inch) silicon substrate 2, providing adequate mechanical strength. The appropriate size ensures that the tungsten ring 3 can effectively cover and support the edge area of the silicon substrate 2, while its sufficient thickness guarantees its structural stability at high temperatures and its effective constraint on edge stress, preventing thermal deformation or failure due to excessively large or thin dimensions.
[0056] Further optimization of the design: copper sheet 5 is a boss structure, the top diameter of copper sheet 5 matches the inner diameter of the heat dissipation groove structure, and the overall thickness of copper sheet 5 is no more than 5mm.
[0057] By designing the copper sheet 5 as a boss structure that matches the inner diameter of the heat sink structure, and with an overall thickness not exceeding 5mm, the contact area between it and the molybdenum base 4 can be maximized within a limited space, optimizing the heat transfer interface while controlling the overall component height. This good matching ensures a tight fit and efficient heat conduction path, while the appropriate thickness balances thermal conductivity with structural compactness. Controlling the overall height and thermal inertia of the composite substrate stage, while ensuring sufficient thermal conductivity cross-section, facilitates rapid response to temperature control during deposition.
[0058] This invention provides a controllable preparation method for polycrystalline diamond, comprising the following steps: S1, mounting a tungsten ring 3 and a copper sheet 5 on a molybdenum base 4 respectively, and pre-treating the composite substrate stage and the silicon substrate 2 by cleaning, polishing, and diamond micron powder inoculation; S2, placing the pre-treated silicon substrate 2 in the support position of the composite substrate stage and inserting it into the deposition chamber 1 of the diamond preparation device; S3, introducing a base atmosphere and an auxiliary gas into the deposition chamber 1, and generating plasma under high-power microwave excitation for deposition; S4, after deposition, removing the sample by programmed cooling.
[0059] By using the aforementioned composite substrate stage device for polycrystalline diamond fabrication, an optimized hardware platform can be combined with the deposition process. This substrate stage provides a uniform plasma environment and temperature field for the deposition process, reducing intrinsic thermal stress and laying a stable and controllable physical foundation for subsequent fine-tuning of performance using process gases.
[0060] The scheme was further optimized, with the base atmosphere consisting of hydrogen and methane; the auxiliary gases consisting of nitrogen, argon, and carbon dioxide; and the performance of polycrystalline diamond was directionally controlled by adjusting the volume fraction ratio of argon and carbon dioxide in the total gas flow rate.
[0061] By introducing a multi-component auxiliary gas consisting of nitrogen, argon, and carbon dioxide, and precisely controlling their concentration ratios, the physicochemical effects of different gases can be comprehensively utilized to synergistically and directionally regulate the growth kinetics and final properties of diamond. Nitrogen (N2) primarily promotes the growth rate and may affect crystal orientation; argon (Ar) increases plasma density, affecting surface morphology and crystal quality; carbon dioxide (CO2) has the function of chemically etching non-diamond carbon phases and potentially supplementing carbon sources. In the stable growth environment created by the composite substrate stage, by adjusting the ratio of the three gases, the growth process can be selectively guided towards different goals such as high growth rate, high quality, large grains, or low stress, achieving controllable performance preparation.
[0062] To further optimize the scheme, in step S3, the volume fraction of nitrogen in the total gas flow rate is fixed at 1%.
[0063] By fixing the nitrogen gas integral at 1%, a stable and repeatable baseline framework can be provided for the entire process. While utilizing nitrogen to promote the growth rate, the uncontrollable negative impact of its concentration fluctuations on crystal quality can be avoided, thus simplifying the complexity of process control.
[0064] To further optimize the scheme, in step S3, the volume fraction of argon is adjusted to a range of 0.1% to 0.8%, and the volume fraction of carbon dioxide is adjusted to a range of 0.1% to 0.8%.
[0065] By adjusting the volume fractions of argon and carbon dioxide to 0.1%–0.8%, a broad and effective process operation window can be defined. Adjustments within this range can significantly affect the deposition results, providing ample room for fine-tuning the process for different application objectives.
[0066] To further optimize the scheme, when aiming for a high growth rate, the argon gas fraction should be controlled to be no more than 0.3% and the carbon dioxide volume fraction no more than 0.3%; when aiming for high crystal quality, the argon gas fraction should be controlled between 0.5% and 0.8% and the carbon dioxide volume fraction no more than 0.2% to 0.5%; when aiming for a comprehensive performance that balances growth rate, grain size, and crystal quality, the argon gas fraction should be controlled between 0.3% and 0.5% and the carbon dioxide volume fraction between 0.3% and 0.5%, and the absolute value of the difference between the volume fractions of argon and carbon dioxide should not exceed 0.1%.
[0067] By setting a process window oriented towards high growth rates, it is possible to minimize physical sputtering or intense chemical etching of the growth surface by the auxiliary gas while maintaining basic plasma activity. This allows the carbon source to primarily contribute to diamond network construction, thereby maximizing the deposition rate. By setting a process window oriented towards high crystal quality, a higher concentration of argon gas can be used to increase plasma density and electron energy, promoting the generation of more active carbon-containing groups. Simultaneously, a small amount of carbon dioxide can be used to selectively etch weakly bonded non-diamond carbon phases. The synergistic effect of these two methods significantly improves the crystal integrity and purity of diamond.
[0068] The composite substrate stage and its fabrication method for polycrystalline diamond deposition provided by this invention are implemented as follows: First, a dedicated substrate stage composed of a molybdenum base 4, a tungsten ring 3, and a copper sheet 5 is designed and fabricated. The frustum-shaped arc side of the molybdenum base 4 optimizes the electric field distribution within the microwave cavity, resulting in a uniform sheath and plasma. The internally embedded high thermal conductivity copper sheet 5 acts as an efficient lateral heat diffuser, significantly reducing the radial temperature gradient of the deposition surface. The top tungsten ring 3, with its thermal expansion coefficient similar to that of diamond, effectively constrains edge deformation and alleviates interfacial thermal mismatch stress. The bottom heat dissipation groove structure further enhances axial heat dissipation capability. Precision machining ensures a tight fit between the components, guaranteeing synergy between thermal and mechanical properties. Based on this hardware optimization, during polycrystalline diamond deposition, the substrate and device undergo standard pretreatment processes such as cleaning, polishing, and seeding. The pretreated substrate is placed on the composite substrate stage and inserted into the MPCVD deposition chamber 1. In the core stage of deposition, nitrogen, argon, and carbon dioxide in specific proportions are introduced as auxiliary gases into a hydrogen- and methane-based atmosphere. By precisely adjusting the concentration ratio of these three auxiliary gases, the plasma chemical environment and surface reaction process can be flexibly controlled. For example, a low Ar / low CO2 ratio tends to achieve a higher growth rate; a high Ar / moderate CO2 ratio tends to achieve high crystallinity; and a balanced Ar / CO2 ratio is beneficial for balancing growth rate, grain size, and stress. Deposition is carried out in an optimized and stable thermal and plasma field, and the sample is removed after programmed cooling.
[0069] This invention systematically solves the key technical challenge of simultaneously optimizing deposition uniformity, growth rate, crystal quality, and residual stress in the MPCVD method for preparing polycrystalline diamond by deeply integrating and synergistically innovating hardware structure (composite substrate stage) and software process (multi-component gas control). It provides an efficient and reliable solution for the controllable preparation of high-performance polycrystalline diamond materials for different application needs.
[0070] 1. Simulation verification of the plasma environment optimization effect:
[0071] Figure 5 (Flat panel) Figure 6 (Frustum shape) and Figure 7 A clear comparison of the electric field distribution cloud maps (for the frustum-shaped arc-side design of this invention) shows that, under the same microwave power and cavity conditions, the frustum-shaped arc-side design of this invention can effectively eliminate electric field concentration in the edge region, obtaining the most uniform sheath electric field distribution. Similarly, Figure 8 , Figure 9 and Figure 10The electron density cloud map comparison shows that the structure of this invention can achieve a more uniform and concentrated high-density plasma region, which in principle lays an optimized physical basis for uniform deposition. This part of the simulation verifies the dominant control effect of the substrate stage's external geometry on plasma properties.
[0072] 2. Simulation verification of thermal management and stress control effects:
[0073] To evaluate the effectiveness of material composite and heat dissipation design within the substrate stage, a thermo-mechanical coupling simulation model was established. Figure 11 Two-dimensional cross-sectional structures of different substrate stages are shown for comparison. The thermal distribution simulation sets the equivalent thermal load on the substrate stage surface at the steady state of deposition, simulating its steady-state temperature field at a deposition temperature of approximately 850°C. The stress distribution simulation simulates the final residual stress distribution after the diamond is uniformly cooled to room temperature (25°C) at a cooling rate of 15°C / min, starting from the deposition temperature of 850°C.
[0074] Figure 12 Temperature distribution curve and Figure 13 The stress distribution curves visually compare the performance differences of the aforementioned structures under the same boundary conditions. Combined with the specific simulation data in Table 1, it can be seen that compared to the traditional pure molybdenum plate structure, the composite substrate stage of this invention (corresponding to the optimized structure in the attached figure) significantly reduces the simulated temperature difference (ΔT) from the center to the edge of the silicon substrate 2 surface; simultaneously, it significantly reduces the peak value of the simulated residual tensile stress at the diamond edge. It should be noted that the simulations were conducted under ideal conditions, and the specific values are intended to reveal and compare the clear trends and relative advantages and disadvantages of different structural design schemes in improving temperature uniformity and reducing thermal stress. In actual processes, due to the complexity of the environment, the absolute values may differ, but the improvement trend exhibited by the structural design of this invention is clear and predictable.
[0075] Table 1 shows... Figure 11-13 Comparison table of key simulation temperature and stress data for different composite substrate stage structures
[0076]
[0077] To illustrate this more clearly, three non-limiting specific embodiments are provided below, in which the gas ratios are calculated based on the total gas flow rate and the N2 concentration is fixed at 1%.
[0078] Example 1 (Higher Rate Orientation):
[0079] During the growth stage, the following gas ratio was used: CH4 / H2 = 4%, N2 1%, Ar 0.2%, and CO2 0.2%. Other process conditions were: total gas flow rate 500 sccm, chamber pressure 140 Torr, silicon substrate temperature 850℃, microwave power 4800W, and deposition time 10 hours. After deposition, the cross-section of the polycrystalline diamond was characterized by scanning electron microscopy (SEM). The thickness of the main deposited layer was measured in the center, middle, and edge regions, which were approximately 33.7 μm, 34.1 μm, and 34.5 μm, respectively, with an average thickness of approximately 34.1 μm. Based on a total deposition time of 10 hours, the average growth rate of the polycrystalline diamond was approximately 3.53 μm / h.
[0080] Example 2 (High-Quality Orientation):
[0081] During the growth stage, the gas ratio was: CH4 / H2 = 4%, N2 1%, Ar 0.6%, and CO2 0.4%. Other process conditions were: total flow rate 500 sccm, pressure 130 Torr, silicon substrate temperature 850℃, microwave power 4800W, and growth time 10 hours. Under these conditions, the Raman spectrum of the polycrystalline diamond obtained showed a full width at half maximum (FWHM) of approximately 3.31 cm⁻¹ near 1332 cm⁻¹, indicating high crystal purity. Its XRD (111) peak FWHM was approximately 0.168 cm⁻¹. -1 .
[0082] Example 3 (Comprehensive Performance Orientation):
[0083] During the growth stage, the gas composition was: CH4 / H2 = 4%, N2 1%, Ar 0.4%, and CO2 0.4%. Other conditions were: total flow rate 500 sccm, pressure 150 Torr, silicon substrate temperature 850℃, microwave power 4800W, and growth time 10 hours. The growth rate of the prepared polycrystalline diamond was approximately 2.47 μm / h. Scanning electron microscopy (SEM) showed that its average grain size was approximately 8.49 μm, and the full width at half maximum (FWHM) of the diamond characteristic peak near 1332 cm⁻¹ was approximately 4.04 cm⁻¹.
[0084] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A composite substrate stage for polycrystalline diamond deposition, characterized in that, The device includes a molybdenum base (4), a tungsten ring (3), and a copper sheet (5). The external geometry of the molybdenum base (4) is a frustum arc-shaped structure. The interior of the molybdenum base (4) is provided with an installation groove and a heat dissipation groove structure. The tungsten ring (3) is installed in the installation groove at the top of the molybdenum base (4). The copper sheet (5) is embedded in the heat dissipation groove structure at the bottom of the molybdenum base (4). The tungsten ring (3), the molybdenum base (4), and the copper sheet (5) are tightly fitted together, and the height difference between each mating surface of the tungsten ring (3), the molybdenum base (4), and the copper sheet (5) is controlled within 0.1 mm.
2. The composite substrate stage for polycrystalline diamond deposition according to claim 1, characterized in that, The side surface of the frustum-shaped arc is a smoothly transitioning arc surface.
3. The composite substrate stage for polycrystalline diamond deposition according to claim 1, characterized in that, The copper sheet (5) is made of high thermal conductivity pure copper material, and the thermal conductivity of the copper sheet (5) is higher than that of the molybdenum base (4); the thermal expansion coefficient of the tungsten ring (3) is between that of the molybdenum base (4) and diamond.
4. The composite substrate stage for polycrystalline diamond deposition according to claim 1, characterized in that, The tungsten ring (3) has a ring structure, with an outer diameter of no more than 50.4 mm and a thickness of no less than 1 mm.
5. The composite substrate stage for polycrystalline gold deposition according to claim 1, characterized in that, The copper sheet (5) has a boss structure, the top diameter of the copper sheet (5) matches the inner diameter of the heat dissipation groove structure, and the overall thickness of the copper sheet (5) is no more than 5mm.
6. A method for controllable preparation of polycrystalline diamond using the composite substrate stage according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. The tungsten ring (3) and the copper sheet (5) are respectively installed on the molybdenum base (4), and the composite substrate stage and the silicon substrate (2) are pretreated by cleaning, polishing and diamond micro powder inoculation. S2. Place the pretreated silicon substrate (2) in the support position of the composite substrate stage and load it into the deposition chamber (1) of the diamond preparation device; S3. Introduce a basic atmosphere and auxiliary gas into the deposition cavity (1), and generate plasma under high-power microwave excitation for deposition; S4. After deposition is complete, the sample is removed by cooling the sample using a programmed process.
7. The method for controllable preparation of polycrystalline diamond according to claim 6, characterized in that, The base atmosphere includes hydrogen and methane; the auxiliary gas includes nitrogen, argon and carbon dioxide; the performance of polycrystalline diamond is directionally controlled by adjusting the volume fraction ratio of argon and carbon dioxide in the total gas flow rate.
8. The method for controllable preparation of polycrystalline diamond according to claim 7, characterized in that, In step S3, the volume fraction of nitrogen in the total gas flow rate is fixed at 1%.
9. The method for controllable preparation of polycrystalline diamond according to claim 7, characterized in that, In step S3, the volume fraction of argon is adjusted within the range of 0.1% to 0.8%, and the volume fraction of carbon dioxide is adjusted within the range of 0.1% to 0.8%.
10. The method for controllable preparation of polycrystalline diamond according to claim 9, characterized in that, When aiming for a high growth rate, the argon gas fraction should be controlled to be no more than 0.3% and the carbon dioxide volume fraction should be no more than 0.3%. When aiming for high crystal quality, the argon gas fraction should be controlled to be between 0.5% and 0.8% and the carbon dioxide volume fraction should be no more than 0.2% and 0.5%. When aiming for a comprehensive performance that balances growth rate, grain size, and crystal quality, the argon gas fraction should be controlled to be between 0.3% and 0.5% and the carbon dioxide volume fraction should be between 0.3% and 0.5%, and the absolute value of the difference between the volume fractions of argon and carbon dioxide should not exceed 0.1%.