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Etching of Polyimide Using the 9.2-Micron Wavelength of Pulsed CO2 Laser Radiation

IP.com Disclosure Number: IPCOM000060374D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 183K

Publishing Venue

IBM

Related People

Brannon, JH: AUTHOR [+2]

Abstract

In the manufacture of semiconductor devices polyimide (PI) films are etched to produce holes larger than N 30 mm. This is commonly done by using oxygen plasma or an excimer laser. This article proposes using a CO2 laser for etching which is much simpler and more efficient than the other methods. Several methods have evolved for etching surface relief features into PI. These features range from a couple of microns to over one millimeter in size. Oxygen plasma has a relatively slow etch rate and requires lithographic processing for surface mask definition. The pulsed excimer laser method produces fairly large etch rates and by projection etching is able to eliminate the need for surface masking by lithography.

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Etching of Polyimide Using the 9.2-Micron Wavelength of Pulsed CO2 Laser Radiation

In the manufacture of semiconductor devices polyimide (PI) films are etched to produce holes larger than N 30 mm. This is commonly done by using oxygen plasma or an excimer laser. This article proposes using a CO2 laser for etching which is much simpler and more efficient than the other methods. Several methods have evolved for etching surface relief features into PI. These features range from a couple of microns to over one millimeter in size. Oxygen plasma has a relatively slow etch rate and requires lithographic processing for surface mask definition. The pulsed excimer laser method produces fairly large etch rates and by projection etching is able to eliminate the need for surface masking by lithography. However, it does require toxic halogen gases, such as F2 or HCl, for operation and the use of intense ultraviolet beams. The pulsed CO2 laser has been available for some time but was not considered for use with PI because its accepted wavelength of 10.6 mm is such that the quality of polyimide absorption is poor at this wavelength. However, because of its broad spectral transmission, the pulsed CO2 laser can be made to work at any of a number of discrete wavelengths between 9 and 11 microns by use of a diffraction grating. This article suggests a specific wavelength for use with PI. The infrared transmission spectrum of PI is displayed in Fig. 1. This is based on a 5.3 mm thick film of fully-cured PI vs. air, and shows a series of discrete absorption bands. By...