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Generation of Vias in Polymide by Rapid Heating and Controlled Evaporation of Underlying Metallurgy with a Pulsed Laser

IP.com Disclosure Number: IPCOM000048880D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Bhattacharyya, A: AUTHOR [+4]

Abstract

A focussed laser beam with very short pulses (10-50 ns) has been used to create vias in polyimide overlying a metallurgy layer by controlled surface evaporation of underlying metal.

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Generation of Vias in Polymide by Rapid Heating and Controlled Evaporation of Underlying Metallurgy with a Pulsed Laser

A focussed laser beam with very short pulses (10-50 ns) has been used to create vias in polyimide overlying a metallurgy layer by controlled surface evaporation of underlying metal.

The underlying metallization may be part of a signal line, a capping layer over another via in a multilayer ceramic structure or a mesh plane for power distribution. Vias may be formed in an overlying polyimide layer in a single step, automated, maskless process with only one (possibly automated) registration step.

The figure illustrates the method in which vias are generated:
(1) Use a laser wavelength at which the polyimide is highly

transparent, so that very little of the incident light energy

is absorbed in the polyimide.
(2) Use a very short laser pulse with appropriate energy per

pulse so that the power density in the laser focal spot is of

the order of 10/8/ to 10/9/ watts/cm/2/. Under such

circumstances,

even though the energy is very low (of the order of tens of

microjoules), the extremely high rate of supplying the energy

over a very small area causes the exposed metallurgy to be

heated rapidly and evaporate. The depth of the exposed

surface

evaporated is determined by the pulse energy and can be

controlled

precisely. This controlled micro-evaporation of the

surface metallurgy causes the polyimide above the laser

exposed

area to blow out, leaving a via in t...