Chloride-mediated morphology control in acidic cupric chloride copper etching: Mechanistic insights and process implications

This study investigates the role of chloride ion concentration in dictating surface morphology during acidic cupric chloride etching of copper from a surface science perspective. It demonstrates that Cl − governs the etching process by mediating a dynamic balance between formation and complexation-induced dissolution of a surface CuCl layer. A critical threshold concentration of approximately 257 g L − is identified, marking the transition where soluble [CuCl 3 ] 2− becomes dominant, fundamentally altering interfacial properties and etching mode. Surface analysis (SEM, AFM, XPS, XRD) directly correlates this transition with evolution from non-uniform to highly anisotropic morphology, providing evidence for the transient CuCl layer's mediating role. While this homogeneous chemical approach enables practical tuning of etch rates and uniformity, its inherent limitation is clarified: the mechanism ensuring uniformity fundamentally restricts achievable anisotropy. These findings establish a fundamental surface chemical principle for etching control, define the strategy's boundary and underscore the necessity of integrating functional additives for applications requiring extreme anisotropy.