Investigation of Copper Etching with a Ferric Nitrate Solution.

Abstract

Copper has unique properties, such as low electrical resistivity, that are exploited in a number of applications, including an interconnect layer in integrated circuits and microelectronic devices. Etching techniques are essential for the fabrication of fine structures, devices, and circuits. This article addresses the methods of copper etching with an emphasis on approaches using ferric nitrate. Potentiodynamic polarization tests using benzotriazole as an inhibitor showed that ferric nitrate has higher inhibition efficiency than conventional etchants. This is because benzotriazole in a ferric nitrate solution is adsorbed on the copper surface to a greater extent than in a ferric chloride and cupric chloride solution, as confirmed by Fourier transform infrared analysis. Quantitative atomic force microscopy characterization showed that good surface quality with significantly lower surface roughness can be obtained from a copper film etched in a ferric nitrate solution, which has potential use in microelectronics manufacturing.