Simulation optimization of physical field of diamond particles deposited by multi-piece substrates HFCVD system
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摘要: 探索热丝化学气相沉积(hot filament chemical vapor deposition, HFCVD)合成高效优质的金刚石已成为研究热点。采用可提高金刚石颗粒单次沉积产量的新型多片式栅状衬底,应用FLUENT流体仿真软件,在原有单个出气口数量及进气总流量保持不变的情况下,优化传统模型,将单个进气口拆分成5个大小相等的进气口,对影响金刚石单晶颗粒均匀性的进气口数量和排布方式工艺参数进行仿真,对比分析HFCVD系统内气体的物理场。结果显示:4组优化模型均提高了衬底温度及流速的均匀性,有利于金刚石单晶颗粒的均匀生长,但对其沉积速率影响不显著;进一步分析优化模型的温度场,发现5个进气口及单个出气口分别位于反应腔体顶部和底部的中间位置时系统的温度差最低,最满足金刚石单晶颗粒在多片式硅衬底上均匀生长的条件。HFCVD金刚石单晶颗粒沉积试验验证了仿真结果的正确性。
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关键词:
- 热丝化学气相沉积法 /
- FLUENT仿真软件 /
- 优化模型 /
- 金刚石颗粒均匀生长
Abstract: Hot filament CVD method, which is used to synthesize high efficiency and high quality superhard abrasives, has become a research hotspot. Based on a new multi-piece grid substrate, which can increase the single deposition yield of micro-powder, and FLUENT, the fluid simulation software, the traditional model is optimized with unchanged number of single outlet and stable total intake flow but the single inlet is split into five equally sized inlet. The number and the arrangement of inlets that affect the process uniformity are simulated. The physical field of gas in the HFCVD system is compared and analyzed. Results show that the four optimized models all perform improved uniformity of substrate temperature and flow rate, which is conducive to the uniform growth of diamond single crystal particles, but the effect of diamond deposition rate is not significant. Further analysis on the temperature field of the optimized model indicates that the temperature difference of the system is the lowest with five inlets located in the middle top and a single outlet in the middle bottom of the reaction chamber, which satisfies the condition of uniform growth of diamond single crystal particles on multi-piece silicon substrate. Finally, CVD single crystal diamond particles are deposited to verify the reliability of the simulation. -
表 1 材料属性
Table 1. Material properties
材料 密度 ρ /
(kg·m−3)热导率 λ /
(W·m−1·K−1)热容 c /
(J·kg−1·K−1)H2 不可压缩气体 0.167 2 14 283 Si 2 330 149.000 0 703 Ta(热丝) 15 500 63.000 0 185 Cu (衬底支撑台) 8 978 388.000 0 381 表 2 进出气口不同分布位置的参数设置
Table 2. Parameter setting of different distribution positions of the inlet and outlet
编号 模型 进气口数量 单个进气口直径 D / mm 单个进气口流速 v /(m·s−1) 进气口的分布位置 出气口的分布位置 0 传统模型 1 10.000 0.169 反应腔体左底部 反应腔体右底部 1 优化模型 5 4.472 0.849 反应腔体左侧壁 反应腔体右底部 2 优化模型 5 4.472 0.849 反应腔体顶端 反应腔体底部中间 3 优化模型 5 4.472 0.849 反应腔体左侧壁 反应腔体左底部 4 优化模型 5 4.472 0.849 反应腔体左侧壁 反应腔体底部中间 注:进出气口的分布位置均在xz平面内进行观测。 表 3 传统模型—适宜金刚石微粉生长的衬底上的温度极值
Table 3. Traditional model: temperature extremum on the substrate suitable for the growth of diamond powder
硅片序号 最高温度 Tmax / K 最低温度 Tmin / K 温差 ΔT /K 2 1 191.60 1 127.46 64.14 5 1 201.82 1 129.00 72.82 8 1 198.84 1 129.06 69.78 11 1 200.64 1 128.20 72.44 14 1 186.58 1 123.91 62.67 表 4 优化模型—适宜金刚石微粉生长的衬底上的温度极值
Table 4. Optimization model: Temperature extremum on the substrate suitable for the growth of diamond powder
硅片序号 优化模型1 优化模型2 优化模型3 优化模型4 最高温度
Tmax / K最低温度
Tmin / K温差
ΔT / K最高温度
Tmax / K最低温度
Tmin / K温差
△T / K最高温度
Tmax / K最低温度
Tmin / K温差
ΔT / K最高温度
Tmax / K最低温度
Tmin / K温差
ΔT / K2 1 196.46 1 133.1 63.36 1 198.54 1 135.41 63.13 1 199.23 1 135.88 63.35 1 196.57 1 133.15 63.42 5 1 207.41 1 134.92 72.49 1 209.87 1 137.62 72.25 1 210.71 1 137.74 72.97 1 208.00 1 135.08 72.92 8 1 205.04 1 135.35 69.69 1 207.18 1 137.67 69.51 1 208.4 1 138.16 70.24 1 205.49 1 135.54 69.95 11 1 207.78 1 134.9 72.88 1 209.82 1 137.43 72.39 1 210.57 1 137.68 72.89 1 207.88 1 135.07 72.81 14 1 195.83 1 133.02 62.81 1 198.54 1 136.28 62.26 1 198.38 1 135.76 62.62 1 195.63 1 133.11 62.52 表 5 CVD金刚石单晶颗粒沉积参数
Table 5. CVD single crystal diamond particle deposition parameters
沉积参数 形核参数 生长参数 丙酮与氢气的比例 1.5% 2.0% 硼碳摩尔比率 [B]/[C]gas / 10−6 5 000 5 000 压强 p / Pa 3 000 3 000 偏流强度 B /A 4.0 4.0 衬底温度 $ {T}_{\mathrm{c}} $ /℃ 700 950 热丝温度 $ {T}_{\mathrm{r}} $ /℃ 2 000±200 2 2 200±200 沉积时间 t / min 40 80 -
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