氮气含量对射频磁控溅射法制备的AlN薄膜微观结构与力学性能的影响

Effect of nitrogen concentration on microstructure and mechanical properties of reactive radio frequency magnetron sputtered AlN thin films

用Ar气和N2气分别作为溅射气体和反应气体，采用射频反应磁控溅射法，通过调节工作气体（Ar气与N2气的混合气体）中N2的含量（体积分数）φ（N2），在硅（100）衬底上制备一系列六方结构AlN多晶薄膜，利用X射线衍射（XRD）、扫描电镜（SEM）、原子力显微镜（AFM）和纳米压痕仪等对薄膜特性进行测试与分析。结果表明，φ（N2）对AlN薄膜的择优取向、结晶性、沉积速率与力学性能的影响都十分显著，对薄膜的微观结构和表面粗糙度也有一定影响：随φ（N2）增大，薄膜的厚度和沉积速率逐渐减小，结晶性也发生显著变化；较高的φ（N2）有利于AlN薄膜沿（002）晶面择优生长；φ（N2）对AlN薄膜的硬度影响较大，而对弹性模量影响较小。实验制备的AlN薄膜具有良好的纳米力学性能，硬度平均值在12.0～29.3 GPa之间，弹性模量平均值在184.0～209.8 GPa之间。

The wurtzite structural aluminum nitride （AlN） films were deposited on Si（100） wafers by reactive radio frequency （RF） magnetron sputtering system, using a gas mixture of Ar（sputtering gas）and N2 （reactive gas） with varying nitrogen flow ratio. The properties of aluminum nitride thin films were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, atomic force microscopy （AFM） and nanoindentation techniques. The results show that the preferred orientation, crystallinity, deposition rate and nanomechanical properties significantly depend upon the nitrogen flow ratio. The microstructure and the surface roughness are also influenced by the nitrogen flow ratio. As the nitrogen flow ratio increases, the thickness and deposition rate of the film decrease, and the crystallinity of the films changes obviously. The growing of AlN films along preferred orientation （002） is improved under higher nitrogen flow ratio. The nitrogen concentration has little influence on the elastic modulus but obviously affects the hardness of AlN films. The AlN films fabricated in this study have excellent nano-mechanics properties with hardness in the range of 12.0～29.3 GPa and elastic modulus in the range of 184.0～209.8 GPa.