Semiconductor fabrication equipment extensively uses Al alloys which form an AlF layer when exposed to fluorine gas used in semiconductor processing. The AlF layer can flake off, rendering the chamber components unfit for semiconductor manufacturing. With the goal of resisting fluorine attack, the growth of protective AlN coatings on Al-6061 substrates was investigated, and this paper reports on the effects of process parameters on coating quality. It was found that Mg powders in a powder bed placed before the sample along the gas flow path can supply a rapid burst of magnesium vapor to the sample during exothermal nitridation (combustion) of Mg powders. This burst of supersaturated magnesium vapor can convert the native protective Al2O3 to non-protective MgO on the sample surface if the extent of magnesium supersaturation, the temperature of the sample, and the residence time of the vapor around the sample are high enough. At the same time, the magnesium supersaturation should not be so high as to get significant gas phase nucleation of Mg3N2 particulates that can stick to the front edge of the sample causing a ‘front edge anomaly’. This balance is achieved by using a bimodal distribution of magnesium powders. Conversion of Al2O3 to MgO is accompanied by the formation of a Mg3N2 layer above the MgO layer, with incomplete surface coverage. Microstructural analysis suggests that AlN nucleation is preferred on this Mg3N2 layer, with uncovered areas being regions of outward Al diffusion from the alloy. The coating grows outward with the AlN dendrites growing outwards and laterally leading to a dense coating with a dendritic network of AlN in an Al matrix. Even a small concentration of oxygen or water vapor in the reaction chamber leads to excessive MgO formation on the AlN coating surface, particularly during the sample cooldown. Excessive MgO formation on the coating surface, termed as ‘MgO poisoning’, inhibits further coating growth. The residual Mg and Mg3N2 in the powder bed getter the oxygen and moisture, respectively, thereby keeping the oxygen content sufficiently low to avoid MgO poisoning provided the chamber has good hermetic integrity.

中文翻译：

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工艺参数对Al基合金上AlN涂层生长的影响


半导体制造设备广泛使用 Al 合金，当暴露于半导体加工中使用的氟气体时，会形成 AlF 层。AlF 层会剥落，使腔室元件不适合半导体制造。为了抵抗氟的侵蚀，研究了 Al-6061 基材上保护性 AlN 涂层的生长，本文报告了工艺参数对涂层质量的影响。研究发现，在镁粉末的放热氮化（燃烧）过程中，沿气流路径放置在样品前的粉末床中的 Mg 粉末可以向样品提供镁蒸气的快速爆发。如果镁过饱和度的程度、样品的温度和蒸汽在样品周围的停留时间足够高，这种过饱和镁蒸气的爆发可以将样品表面的天然保护性 Al2O3 转化为非保护性 MgO。同时，镁过饱和度不应太高，以免 Mg3N2 颗粒发生明显的气相成核，这些颗粒可能会粘附在样品的前缘，从而导致“前缘异常”。这种平衡是通过使用镁粉的双峰分布来实现的。Al2O3 转化为 MgO 伴随着 MgO 层上方形成 Mg3N2 层，表面覆盖不完全。微观结构分析表明，AlN 成核在该 Mg3N2 层上是优选的，未覆盖的区域是 Al 从合金向外扩散的区域。涂层向外生长，AlN 枝晶向外和横向生长，导致在 Al 基体中形成具有 AlN 树枝状网络的致密涂层。 即使反应室中氧气或水蒸气浓度较低，也会导致 AlN 涂层表面形成过量的 MgO，尤其是在样品冷却期间。涂层表面形成过多的 MgO，称为“MgO 中毒”，会抑制涂层的进一步生长。粉末床中残留的 Mg 和 Mg3N2 分别吸收氧气和水分，从而保持足够低的氧含量以避免 MgO 中毒，前提是粉末床具有良好的气密完整性。