Laboratoire de Physique des Gaz et des Plasmas (LPGP), UMR 8578 CNRS, Université Paris-Sud, Université Paris-Saclay, 91405, Orsay, France.
Institut Pprime, Département Physique et Mécanique des Matériaux, UPR 3346 CNRS, Université de Poitiers, 86962, Chasseneuil-Futuroscope, France.
Sci Rep. 2017 May 10;7(1):1655. doi: 10.1038/s41598-017-01755-8.
We report on a new route to grow epitaxial copper (Cu) ultra-thin films (up to 150 nm thick) at ambient temperature on Si(001) wafers covered with native oxide without any prior chemical etching or plasma cleaning of the substrate. It consists of a single-step deposition process using high power impulse magnetron sputtering (HiPIMS) and substrate biasing. For a direct current (DC) substrate bias voltage of -130 V, Cu/Si heteroepitaxial growth is achieved by HiPIMS following the Cu(001) [100]//Si(001) [110] orientation, while under the same average deposition conditions, but using conventional DC magnetron sputtering, polycrystalline Cu films with [111] preferred orientation are deposited. In addition, the intrinsic stress has been measured in situ during growth by real-time monitoring of the wafer curvature. For this particular HiPIMS case, the stress is slightly compressive (-0.1 GPa), but almost fully relaxes after growth is terminated. As a result of epitaxy, the Cu surface morphology exhibits a regular pattern consisting of square-shaped mounds with a lateral size of typically 150 nm. For all samples, X-ray diffraction pole figures and scanning/transmission electron microscopy reveal the formation of extensive twinning of the Cu {111} planes.
我们报告了一种在不进行任何预处理化学蚀刻或等离子体清洁的情况下，在覆盖有本征氧化物的 Si(001) 晶片上，在环境温度下生长外延铜（Cu）超薄薄膜（厚度可达 150nm）的新途径。它由一个使用高功率脉冲磁控溅射（HiPIMS）和基底偏置的单步沉积工艺组成。对于-130V 的直流（DC）基底偏置电压，HiPIMS 之后实现了 Cu/Si 外延生长，其取向为 Cu(001) [100]//Si(001) [110]，而在相同的平均沉积条件下，但使用传统的直流磁控溅射，沉积了具有[111]择优取向的多晶 Cu 薄膜。此外，通过实时监测晶片曲率，在生长过程中原位测量了本征应力。对于这种特殊的 HiPIMS 情况，应力略为压缩（-0.1GPa），但在生长结束后几乎完全松弛。由于外延，Cu 表面形貌呈现出由具有典型横向尺寸为 150nm 的方形丘组成的规则图案。对于所有样品，X 射线衍射极图和扫描/透射电子显微镜揭示了 Cu{111}面的广泛孪晶形成。
