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

• Published in: Journal of microelectromechanical systems Vol. 34; no. 3; pp. 244 - 251
• Main Authors: Ruiz, Camila Sola, Salles do Nascimento, Valter, Fischer, Clovis, Hummel Cioldin, Frederico, Roberto Silva, Audrey, Alexandre Diniz, Jose
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2025; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum; dry etching; Electrical resistivity; Etching; etching rate; Evaporation; Grain size; heating transfer; Inductively coupled plasma; Metal films; Microchannels; Microscopy; Nickel; Photovoltaic cells; pillar structure; Plasma etching; Plasmas; Reactive ion etching; Scanning electron microscopy; Si microchannel; Silicon; solar cells; Sputtering; Substrates; thermal evaporation
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2025.3535688

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, <inline-formula> <tex-math notation="LaTeX">1\mu </tex-math></inline-formula>m and <inline-formula> <tex-math notation="LaTeX">1\mu </tex-math></inline-formula>m thick layers of Alspu, Alev and Ni-P films, respectively, were deposited on the Si wafer (p-type (100) orientation, <inline-formula> <tex-math notation="LaTeX">400\mu </tex-math></inline-formula>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 <inline-formula> <tex-math notation="LaTeX">220~\mu </tex-math></inline-formula>m in width with spacing between 230 and <inline-formula> <tex-math notation="LaTeX">500~\mu </tex-math></inline-formula>m. The pattern transfer technique was carried out by lithography and wet etching. All samples were cleaved on <inline-formula> <tex-math notation="LaTeX">10\times 10 </tex-math></inline-formula>mm squares with a <inline-formula> <tex-math notation="LaTeX">400~\mu </tex-math></inline-formula>m thick layer. The Bosch etching process was applied for time variations between 40sec and 60sec per cycle, using SF<inline-formula> <tex-math notation="LaTeX">{}_{6}+ </tex-math></inline-formula>Ar and C4F<inline-formula> <tex-math notation="LaTeX">{}_{8}+ </tex-math></inline-formula>Ar, to obtain the SiMCs, with anisotropic etching and depth values between <inline-formula> <tex-math notation="LaTeX">66~\mu </tex-math></inline-formula>m and <inline-formula> <tex-math notation="LaTeX">104~\mu </tex-math></inline-formula>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]