The present study covers the processes that govern the incorporation of nitrogen in the film during atomic layer deposition (ALD) of cobalt and cobalt nitride prepared from cobaltocene (CoCp₂) and NH₃ plasma. It is demonstrated that nitrogen incorporation is strongly temperature-dependent; at temperatures of 260 °C and below, the deposited films consist primarily of Co₂N, whereas increasing the temperature to 300 °C leads to a mixture of Co₃N and Co, and at 350 °C, nominally pure Co is obtained. The sample temperature clearly has a very strong effect on the composition of the deposited film, and in order to understand this temperature dependence, the thermal stability of the CoN_x species formed during the interaction between a sample consisting of pure Co and an NH₃ plasma is analyzed. X-ray photoemission spectroscopy depth profiling reveals that this plasma treatment converts the top 4 nm of the Co film into CoN_x. Temperature-programmed desorption experiments show that this nitride layer starts to decompose at a temperature of approximately 290 °C, which eventually leads to complete removal of all nitrogen from the film. Based on this, a reaction scheme for ALD of Co is proposed; the interaction between the NH₃ plasma and the adsorbed CoCp₂-derived species leads to the formation of cobalt nitride. At temperatures below 290 °C, the resulting film primarily consists of Co₂N, whereas at 300 °C, partial decomposition takes place, resulting in the formation of a mixture of Co₃N and pure Co. At 350 °C, decomposition is effectively complete, leading to pure Co with nitrogen contents below 4 at %. Finally, it is argued that the aforementioned mechanism could potentially play a role in plasma-enhanced ALD of other elements that form metastable nitrides such as Ni, Cu, Re, and Ru.

中文翻译：

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钴和氮化钴的等离子体增强原子层沉积：什么控制氮的掺入？

本研究涵盖了控制钴和由钴茂（CoCp ₂）和NH ₃等离子体制备的氮化钴的原子层沉积（ALD）过程中膜中氮掺入的过程。结果表明，氮的掺入与温度密切相关。在260°C和更低的温度下，沉积的薄膜主要由Co ₂ N组成，而将温度提高到300°C会导致Co ₃ N和Co的混合物，并在350°C时获得名义上纯的Co。样品温度显然对沉积膜的组成有非常强的影响，并且为了理解这种温度依赖性，CoN _x的热稳定性分析了由纯Co和NH ₃等离子体组成的样品之间的相互作用过程中形成的杂质。X射线光电子能谱深度剖析表明，这种等离子体处理将Co膜的顶部4 nm转换为CoN _x。程序升温解吸实验表明，该氮化物层在大约290°C的温度下开始分解，最终导致薄膜中所有氮的完全去除。在此基础上，提出了钴的ALD反应方案。NH ₃等离子体与吸附的CoCp ₂衍生的物种之间的相互作用导致形成氮化钴。在低于290°C的温度下，所得薄膜主要由Co _2组成N，而在300°C时会发生部分分解，从而形成Co ₃ N和纯Co的混合物。在350°C时，分解有效完成，导致纯Co的氮含量低于4 at％。最后，有人认为上述机制可能在其他形成亚稳态氮化物（如Ni，Cu，Re和Ru）的元素的等离子体增强ALD中发挥作用。