Non Local Strain Gradient Cohesive Zone Formulation for Microvia Corner Step Debonding
Non-local strain gradient cohesive zone modeling eliminates mesh-dependent stress singularities at microvia corner steps to accurately predict reflow debonding.
Copper Seed Layer
Meaning
Conductive thin films provide the electrical foundation for electroplating processes on non-metallic substrates in semiconductor packaging. A copper seed layer facilitates the deposition of bulk copper into trenches and vias through a physical vapor deposition process. This layer must remain continuous to prevent voids during the subsequent plating cycle.
Deposition Method
Physical vapor deposition or chemical vapor deposition creates the initial metal coating by bombarding a target material in a vacuum environment. Presence of the copper seed layer ensures that the electrolytic solution can distribute current evenly across the entire surface of the wafer or panel. Uniformity of this coating determines the final thickness accuracy of the circuit traces.
Interface Integrity
Adhesion between the barrier layer and the metal deposit relies on the morphology of the contact surface. Because a copper seed layer is prone to oxidation, manufacturing facilities must control the time between deposition and plating to prevent the formation of resistive oxides. Failures in this interface lead to delamination or high contact resistance in the finished electronic component.
Operational Limit
Maintaining a narrow operating window for the deposition equipment ensures high yields in advanced nodes. If the copper seed layer is too thin, the high current density during plating may cause the film to dissolve before the bulk metal arrives. If it is too thick, the overhang at the top of high-aspect-ratio features might block the entry of the plating solution.
The step coverage capabilities of the deposition tool determine whether the film reaches the bottom of deep features without thinning out.