Development of fine pattern wet etching methods of copper circuits

Research Project

Project/Area Number	12650707
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Material processing/treatments
Research Institution	Tohoku University
Principal Investigator	MATSUMOTO Katsutoshi Tohoku Univ., Grad. School of Eng., Research Associate, 大学院・工学研究科, 助手 (70190519)
Co-Investigator(Kenkyū-buntansha)	TANIGUCHI Shoji Tohoku Univ., Grad. School of Eng., Professor, 大学院・工学研究科, 教授 (00111253)
Project Period (FY)	2000 – 2001
Project Status	Completed (Fiscal Year 2001)
Budget Amount *help	¥3,000,000 (Direct Cost: ¥3,000,000) Fiscal Year 2001: ¥1,500,000 (Direct Cost: ¥1,500,000) Fiscal Year 2000: ¥1,500,000 (Direct Cost: ¥1,500,000)
Keywords	copper / etching / printed circuit boards / mass transfer / cavity
Research Abstract	Wet etching of copper foil was studied using an agitated vessel containing aqueous solutions composed of CuCl_2 and HCl. To confirm the rate-limiting species, dissolution rate of CuCl plate was measured and compared with that of copper. From those results, the liquid-phase-mass transfer is the rate-limiting step of the etching reaction. And it was concluded that CuCl is precipitated on the solid surface during the etching of copper, and the rate is controlled by the diffusion rate of CuCl_2. Etching rates at low CuCl_2 concentration were analyzed using a model for the liquid-phase-mass transfer based on the film theory in which electrical interactions between ions are taken into account. The calculated etching rates agreed well with the experimental values in this concentration region of CuCl_2. The cavity shape evolution during wet etching of copper in an agitated vessel has been developed using a mass-transfer model by the use of observed diffusivity. The calculated cavity shapes were in good agreement with the observed ones. Therefore, it is found that this model is reliable to evaluate the pattern etching with cavity formation.