Characterization of Al and Ni-P Films as Hardmasks for the ICP-RIE Plasma Etching Bosch Process

The high-performance mechanical resistance has attracted intensive scientific interest in Hardmasks (HMs) films applicable via the Bosch etching process for Silicon Micro-Channels (SiMCs) fabrication. This manuscript compares different film deposition methods and metal film behavior as HMs during the dry etching for the Bosch process in the Inductively Coupled Plasma and Reactive Ion Etching system. The HMs were deposited by thermal evaporation Aluminum (Alev), DC Sputtering Aluminum (Alspu), and bath chemical Nickel-phosphorus (Ni-P). The 500nm, $1\mu $ m and $1\mu $ m thick layers of Alspu, Alev and Ni-P films, respectively, were deposited on the Si wafer (p-type (100) orientation, $400\mu $ m thick layer, and 3-inch diameter). The Four Point Probe Measurements and Atomic Force Microscopy (AFM) analyses extract the resistivity and grain size values, respectively. For this work, the HM patterns consist of parallel metallic lines ranging from 175 to $220~\mu $ m in width with spacing between 230 and $500~\mu $ m. The pattern transfer technique was carried out by lithography and wet etching. All samples were cleaved on $10\times 10$ mm squares with a $400~\mu $ m thick layer. The Bosch etching process was applied for time variations between 40sec and 60sec per cycle, using SF ${}_{6}+$ Ar and C4F ${}_{8}+$ Ar, to obtain the SiMCs, with anisotropic etching and depth values between $66~\mu $ m and $104~\mu $ m. The SiMC depth values were measured using Scanning Electron Microscopy (SEM) and Scan Profile analyses. The Al and Ni-P film analyses of the resistivity and grain size were related to the HM performance during the Bosch process. Key Words: ICP-RIE, Si Microchannel, Bosch process.[2024-0149]