Browse Prior Art Database

Laser Ablation Wall Angle Enhancement

IP.com Disclosure Number: IPCOM000113491D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Doany, F: AUTHOR [+4]

Abstract

Laser Ablation can presently be used to pattern the polymer layers in polymer/metal (e.g., polyimide/copper) multi-layer circuit boards. Typical optical projection systems today use excimer lasers at fluence levels <= 300mJ/cm sup(2) which produce maximum wall angles of about 60-70º (where 90º denotes vertical walls). Steeper wall angles can be obtained at much higher laser fluence levels (> J/cm sup(2)), although these fluence levels are generally too high and will damage the underlying metal/polymer circuitry. When the wall angle becomes shallower, the bottom dimension of the ablated features decreases relative to the top surface dimension; if the polymer thickness is of the same order as the ablated feature dimensions, the bottom can be completely closed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 78% of the total text.

Laser Ablation Wall Angle Enhancement

      Laser Ablation can presently be used to pattern the polymer
layers in polymer/metal (e.g., polyimide/copper) multi-layer circuit
boards.  Typical optical projection systems today use excimer lasers
at fluence levels <=  300mJ/cm sup(2)  which produce maximum wall angles of
about 60-70º  (where 90º  denotes vertical walls).  Steeper
wall angles can be obtained at much higher laser fluence levels (>
J/cm sup(2)), although these fluence levels are generally too high and will
damage the underlying metal/polymer circuitry.  When the wall angle
becomes shallower, the bottom dimension of the ablated features
decreases relative to the top surface dimension; if the polymer
thickness is of the same order as the ablated feature dimensions, the
bottom can be completely closed.  In applications requiring maximum
feature (circuit) density, near 90º  wall angles are desirable.

      Laser ablation of features using contact masks typically
produces steeper wall angles than ablation using projection optics.
It has been found experimentally that when an intimate contact mask
is used in conjunction with projection laser ablation, a sharper edge
image results with a steeper wall angle in the ablated feature.

      A thin metal layer (e.g., few 100A chromium) is deposited on
the surface of the polymer (e.g., polyimide).  When the metal is thin
enough and has sufficient absorption, the first laser pulse will
remove the metal...