Abstract We have studied the development of intrinsic stress and microstructure of copper (Cu) films deposited under energetic ion bombardment. Stress evolution during growth of ∼150 nm thick Cu films on Si(001) substrates has been investigated by in situ measurements in a high power impulse magnetron sputtering (HiPIMS) process for different substrate bias voltages (from 0 to −160 V) and benchmarked with conventional direct current magnetron sputtering (DCMS). The microstructure and crystal orientation of the studied films have been examined by various ex situ methods. For HiPIMS, we found that the substrate bias voltage (energy of Cu ions) strongly affects the film continuity during the early growth stages and the compressive stress developed during the post-coalescence stage. Contrarily to common expectations, the stress magnitude can be significantly reduced despite the energy increase of the bombarding particles when using HiPIMS. These results are discussed based on a recent kinetic model taking into account the grain size-dependent defect incorporation due to energetic particle bombardment. Reversible stress relaxations are observed upon growth interrupts, with characteristic time constants of tens of seconds, which suggests that the stress and microstructure development are mainly mediated by surface diffusion processes. In addition, polycrystalline films [111]-textured are obtained for negative bias voltages from 0 to −100 V, while for even higher negative bias voltages (up to −160 V), epitaxial growth of Cu(001) is achieved. For the DCMS samples, there is no significant change in film continuity and crystal orientation when varying the bias voltage.

中文翻译：

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高能离子轰击在 Cu 薄膜生长过程中调整应力和微观结构演变的好处

摘要 我们研究了在高能离子轰击下沉积的铜 (Cu) 薄膜的内应力和微观结构的发展。通过在高功率脉冲磁控溅射 (HiPIMS) 工艺中针对不同的衬底偏置电压（从 0 到 -160 V）进行原位测量，研究了在 Si(001) 衬底上生长 150 nm 厚的 Cu 膜期间的应力演变并进行了基准测试使用传统的直流磁控溅射 (DCMS)。已通过各种非原位方法检查了所研究薄膜的微观结构和晶体取向。对于 HiPIMS，我们发现衬底偏置电压（Cu 离子的能量）强烈影响早期生长阶段的膜连续性和后聚结阶段产生的压应力。与普遍预期相反，尽管使用 HiPIMS 时轰击粒子的能量增加，但应力大小可以显着降低。这些结果是基于最近的动力学模型讨论的，考虑到由于高能粒子轰击导致的晶粒尺寸依赖性缺陷掺入。在生长中断时观察到可逆应力松弛，特征时间常数为数十秒，这表明应力和微观结构的发展主要由表面扩散过程介导。此外，对于从 0 到 -100 V 的负偏压，获得了多晶膜 [111] 纹理，而对于更高的负偏压（高达 -160 V），实现了 Cu(001) 的外延生长。对于 DCMS 样本，