Polymer Via Profile Control With Laser Etching
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Profiles of via holes in a polymer substrate can be varied from nearly vertical to very much tapered in the proximity printing mode, wherein a metal mask with openings is placed close to the substrate and an excimer laser beam is directed onto the substrate so that the profiles are controllably tapered by laser etching. In order to achieve the various tapers, the near-field diffraction (Fresnel diffraction) effect is utilized to tailor the incident fluence at the edge of polyimide vias. This effect is coupled with the etch rate dependence on the laser fluence to achieve maximum controllability. It is known that the laser intensity or fluence varies across the mask opening on the substrate due to the diffraction effect.