MULTIPLE FREQUENCY PROCESSING TO IMPROVE ELECTRICAL RESISTIVITY OF BLIND MICRO-VIAS

摘要

A method of forming a blind-via in a laminated substrate by forming a first conductive layer. A dielectric layer is then formed on the first conductive layer. An exposed second conductive layer is formed on the dielectric layer, with the second conductive layer having a preformed aperture. The dielectric layer is laser drilled through to the first conductive layer to form a blind-via at a location within the preformed aperture of the second conductive layer using a plurality of laser pulses. Each laser pulse has a first energy density per pulse that is greater than an ablation threshold of the dielectric layer and less than an ablation threshold of the first conductive layer. The first conductive layer is then laser drilled for a predetermined number of pulses. Each of the predetermined number of pulses has a second energy density per pulse that is greater than an ablation threshold of the first conductive layer. The predetermined number of pulses cause the surface of the first conductive layer exposed by the laser drilling to become molten.