Influence of Rapid Thermal Processing on the Machining Properties of Copper Thin Films for Nano/Micro Pattern Fabrication

Abstract

The semiconductor and display industries employ microfabrication and high-density technology to enhance the performance of IT products. Current micro-patterning methods primarily rely on photolithography. However, photolithography is a complex and expensive process, with limited freedom of pattern design, and involves dry etching methods that use toxic substances, which are harmful to humans and the environment. To address these issues, new alternative patterning technologies are being researched. This study proposes precision mechanical machining as an alternative to photolithography. Machining is an all-in-one process that allows pattern creation using only tools and equipment. It is ecofriendly thanks to its simple and non-chemical process and offers a high degree of pattern freedom. However, machining can be problematic and destructive when processing brittle materials. This study attempted to find optimal processing conditions by analyzing machining properties based on the mechanical properties of copper metal, which is commonly used in semiconductor wiring. A post-deposition rapid thermal process was used to induce changes in the mechanical properties of a copper thin film, and processing was performed to find the optimal conditions. The study found that copper films annealed at 400°C had an approximately two-fold increase in crystal size, a 2.8% increase in density, and a 20.4% decrease in hardness. This is because sufficient heat energy promotes crystal growth and removes residual stress, thereby increasing ductility and improving machinability. As a result, fine patterning of thin films with clean cut surfaces was possible. Consequently, copper wires can be annealed at over 400°C for precise patterning. Additionally, not only is the machining depth adjustable, but it is also possible to remove the entire thin film using a critical load. The results of this study confirmed the applicability of nanoscale machining technology as an alternative to photolithography, and suggest its use in repair processes. These findings provide a foundation for future research aimed at optimizing processing conditions and exploring the broader potential of this technology across various high-value-added industries beyond semiconductors and displays.