(Invited) Status of Room-Temperature Mass-Production Capability Plasma-Based Copper Etch Process
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Copper (Cu) dominate interconnect applications in advanced ICs, large-area flat panel displays, and other microelectronics for its high conductivity, long lifetime, and plenty of raw material supply at the low cost. It is preferable that Cu arrow lines are prepared with the plasma etching method. However, due to the low volatility of the Cu halide or organic compound in the plasma reaction, there is lack of practical manufacturable etching process that satisfies requirements on large-area, high-throughput, room-temperature, simple, and low cost.Since IBM introduced the CMP Cu etching method (1), it has been widely adopted in IC production. This a tedious process that involves sputter and electroplating depositions, dielectric etching, mechanical polishing, and environmental unfriendly slurry solutions. There are challenges in endpoint detection, dishing, and preparing very fine lines.We first reported a 2-step plasm-based Cu etch process that could be conducted at room temperature under the typical plasm etching condition without requiring high-density plasma or extra power source (2,3). Instead of spontaneously removing the plasma-Cu reaction product, the Cu film is converted into a compound at a high rate, which is then dissolved in an acid or alkaline solution. Being described as a disruptive technology, this process has been successfully demonstrated in the fabrication of CMOS hips, TFT LCD panels, and sub 0.5 lines (4,5).Recently, we published a new process that replaces the corrosive chlorine- or bromine-containing feed gas with oxygen (6). The new process can reduce the production cost, e.g., no need of corrosion-resistant tubes, valves, flow controllers, and pumps. The large-area and high throughput advantages are maintained in the new process.In this talk, the principle of the oxygen or halogen plasma-based Cu etch process will be discussed with respect to the reaction mechanism, material properties, and limitations. Possible future development of this technology will be examined. https://www.chiphistory.org/ibm-s-development-of-copper-interconnect-for-icsKuo and S. Lee, ECS Proc.9930, 328 (1999).Kuo and S. Lee, Jpn. J. Appl. Phys.39, L188 (2000).Kuo, Proc. 16th Intl. Workshop AM-FPD Dev, 211 (2009).Kuo, ECS Trans.66, 139 (2015).Y. Kuo and J. Q. Su, Jpn. J. Appl. Phys.61, 030902 (2022).
