目的 在实验室自制的2.45 GHz环形天线多模腔微波等离子体化学气相沉积装置中进行直径100 mm基片台上单晶金刚石的均匀批量生长。方法 通过建立一个二维氢等离子体模型研究了不同尺寸基片台对等离子体环境的影响。采用发射光谱（OES）诊断金刚石生长过程中的等离子体环境,利用红外测温仪测量基片台的温度,采用拉曼光谱表征生长得到金刚石质量。结果 基片台的尺寸增大会导致等离子体向中心集中,边缘效应的影响逐渐减弱,造成基片台温度的不均匀分布。通过减小底部Mo块尺寸,加强直径100 mm基片台的边缘效应,实现了温度的均匀分布,并成功在直径100 mm的基片台上制备了一批质量均匀的单晶金刚石。结论 增强直径100 mm基片台的边缘效应可以提升边缘温度,改善温度分布的均匀性,在合适的工艺条件下能够批量制备质量均匀的单晶金刚石。
Abstract
It is a large-area diamond preparation technology. By improving the structure of the substrate stage, the uniform batch growth of single crystal diamonds on a Ф100 mm substrate stage has been achieved in a 2.45 GHz MPCVD device. The plasma generated by the 2.45 GHz MPCVD system usually cannot completely cover the Ф100 mm substrate stage. The non-uniform plasma distribution above the substrate leads to heterogeneous diamond growth across different regions, accumulation of internal stress within the diamond, and even crack formation, all of which hinder the high-quality batch growth of single-crystal diamonds. By using a 2D hydrogen plasma model, the work aims to investigate environmental variations of plasma across substrate stages of different sizes, identify crucial factors for controlling uniform diamond growth, and determine the optimal process conditions for homogeneous growth on a Φ100 mm substrate.
A batch growth experiment of diamond was conducted with a batch of single-crystal diamond seed crystals with an orientation of <100> and a size of 8 mm×8 mm×0.2 mm. Before growth, the seed crystals were cleaned with a mixed solution of concentrated sulfuric acid and concentrated nitric acid at 150 ℃ for 2 hours. The mixing ratio of concentrated sulfuric acid to concentrated nitric acid was 3:1. Afterwards, the seed crystals were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 minutes respectively. After drying in the N2 environment, they were placed in the chamber. The plasma environment during the diamond growth process was diagnosed by emission spectroscopy, the temperature of the substrate stage was measured by an infrared thermometer, and the quality of the diamond was characterized by Raman spectroscopy.
The increase in the size of the substrate stage will cause the plasma to concentrate towards the center, and the impact of the edge effect will gradually weaken, resulting in an uneven temperature distribution of the substrate stage. By simply increasing the size of the substrate stage, the maximum coverage range of the plasma is basically around Ф80 mm, which cannot guarantee the quality of single-crystal diamond growth in batches placed on it. This should be related to the distribution state of the plasma above the substrate stage and the distribution state of the substrate temperature. The edge effect of the substrate stage can be appropriately enhanced to improve the temperature distribution. By reducing the size of the molybdenum (Mo) block beneath the Φ100 mm Mo substrate holder, a gap is introduced to enhance edge effects, suppress peripheral heat dissipation, and significantly improve temperature uniformity. Under the conditions of microwave power of 9 kW, working pressure of 15.6 kPa, and 5% methane, a batch of single-crystal diamonds with uniform quality has been prepared on a 100 mm diameter substrate stage. Spectral tests show that the electron temperature and electron density distribution above the substrate stage are relatively uniform. The temperature difference between the center and the edge of the substrate stage during the growth process is 50-60 ℃. The Raman spectra of diamonds from radial positions exhibits consistent diamond characteristic peaks at 1 332 cm-1, with full width at half maximum (FWHM) values around 6.89 cm-1, demonstrating high uniformity in crystal quality.
Temperature is identified as a critical parameter for controlling the growth of diamonds. Enhancing the edge effect of the Ф100 mm substrate stage can improve the uniformity of temperature distribution, enabling large-area homogeneous batch fabrication of single-crystal diamonds under appropriate process conditions. This work provides a practical pathway for scaling up high-quality diamond production via MPCVD technology.
关键词
MPCVD /
单晶金刚石 /
模拟 /
等离子体
Key words
MPCVD /
single-crystal diamond /
simulation /
plasma
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基金
湖北省教育厅基金项目（Q20201512）; 湖北省自然科学基金（联合基金）（2025AFD307）
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