Blind via formation in a photoimageable dielectric material

Abstract

A blind via structure, and associated laser ablation methods of formation, that includes a blind via within a photoimageable dielectric (PID) layer on a substrate, such that the sidewall of the blind via makes an obtuse angle with the blind end of the blind via. The obtuse-angled sidewall may be formed by executing two processes in sequence. In the first process, photoimaging of the PID layer, with selective exposure to ultraviolet light, results in one or more blind vias having acute-angled sidewalls. The photoimaging cross links the PID material that had been selectively exposed to ultraviolet light such that a subsequent developing step removes PID material not cross linked, or weakly cross linked, to simultaneously form multiple blind vias having different sized openings. In the second process, laser ablation is selectively employed to remove the acute-angled sidewalls from particular blind vias in a way that forms replacement obtuse-angled sidewalls in the laser-ablated blind vias. Alternatively, the first process involving photoimaging may be omitted such that the second step involving laser ablation forms the entire obtuse-angled blind via. The resultant blind via structure includes at least one blind via having an obtuse-angled sidewall, and optionally, at least one blind via having an acute-angled sidewall.