Ammonium Persulfate Etchant for Copper Wiring Stability

The patent changes the chemical parameters of the etchant by replacing hydrogen peroxide with ammonium persulfate as the primary oxidizing agent, and by adjusting pH using organic acids and ammonium salts. This parameter change maintains effective etching speed while dramatically improving storage stability, as ammonium persulfate does not decompose rapidly like hydrogen peroxide.

The patent eliminates the need for expensive peroxide solution stabilizers by using a different chemical system (ammonium persulfate-based) that inherently provides both stability and etching capability without requiring additional stabilizing additives.

The patent uses a fundamentally different etchant chemistry (ammonium persulfate-based) that achieves stability without requiring expensive stabilizer additives. The etchant formulation uses readily available chemicals (ammonium persulfate, organic acids, ammonium salts) that are more cost-effective than peroxide stabilizers.

The patent extracts and eliminates the problematic hydrogen peroxide component from the etchant formulation, replacing it with a more stable alternative. This removes the root cause of decomposition and the associated need for expensive stabilizers.

The patent substitutes the chemical etching mechanism with a more controlled and uniform process. The ammonium persulfate-based etchant provides consistent etching rates that produce smoother wire profiles and better dimensional control, enabling thinner copper layers to be manufactured with controlled resistance characteristics.

The patent changes the etching chemistry parameters to achieve more uniform etching profiles. The ammonium persulfate system, combined with organic acids and ammonium salts, provides controlled etching that maintains wire integrity even at reduced thicknesses, thereby managing electrical resistance in thinner conductors.

The patent develops a universal etchant formulation (ammonium persulfate, organic acid, ammonium salt, fluorine-containing compound) that can etch both titanium and copper layers in the multilayer structure with a single process step, eliminating the need for separate etching processes for each metal layer.

The patent uses a composite etchant system combining multiple chemical components (ammonium persulfate as oxidizer, organic acid for pH control, ammonium salt for buffering, fluorine-containing compound for titanium etching) that works synergistically to etch both titanium and copper layers effectively in a unified process.