Pulsed Laser Generation of Vias in Thin Polyimide Layers
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
A method is disclosed for forming vias through a polyimide insulating layer between wiring planes using a pulsed laser. Vias through a polyimide layer have typically been formed by reactive ion or wet chemical etching. Each of these processes requires additional masking steps. Wet chemical etching also produces openings with sloping walls and is limited to openings greater than 50 mm in diameter. This method comprises exposing the polyimide layer to a pulsed laser beam having an output wavelength which is absorbed in the layer. Suitable lasers include a frequency-doubled Nd:YAG laser and dye lasers. Typically, the pulse is between 10 and 50 nanoseconds long. Longer pulse lengths produce thermal spreading in the layer, resulting in an opening which is larger than desired.