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Control Etch Profile in Ablative Photodecomposition by Optical Methods

IP.com Disclosure Number: IPCOM000038698D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Braren, BE: AUTHOR [+3]

Abstract

Ablative photodecomposition (APD) is the rapid photodecomposition and etching of a material by the irradiation of the material with far ultraviolet (UV) light, via an effect which is not purely thermal and in which adverse thermal effects are not produced. Application of APD as a technology for the dry etching of polymer films depends greatly on the profile of the etch pattern that can be achieved. Optical methods can be used to allow the etch angle (which is always overcut) to vary from 0Œ to 33Œ. These results apply to free-standing films or films which are laid on surfaces which do not reflect or scatter the ultra (Image Omitted) violet light. In films on substrates which do not undergo etching (e.g., polyimide on ceramic), the etch profiles are similar but not exactly the same.

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Control Etch Profile in Ablative Photodecomposition by Optical Methods

Ablative photodecomposition (APD) is the rapid photodecomposition and etching of a material by the irradiation of the material with far ultraviolet (UV) light, via an effect which is not purely thermal and in which adverse thermal effects are not produced. Application of APD as a technology for the dry etching of polymer films depends greatly on the profile of the etch pattern that can be achieved. Optical methods can be used to allow the etch angle (which is always overcut) to vary from 0OE to 33OE. These results apply to free-standing films or films which are laid on surfaces which do not reflect or scatter the ultra

(Image Omitted)

violet light. In films on substrates which do not undergo etching (e.g., polyimide on ceramic), the etch profiles are similar but not exactly the same. Small overcut angles (0OE - 7OE) are achieved by concentrating the beam from an excimer laser 10 (cavity length 1 meter) with a lens 12 of (f= 10 - 100 cm) focal length and exposing the polymer surface 14 through a contact (or near contact) metal mask 16 with the desired pattern on it, as shown in Fig. 1. Smaller overcut angles are obtained with longer focal lengths (50 - 100 cm) and larger overcut angles with shorter focal lengths. Generally the target 14 is positioned within a few cm of the beam focus. Figs. 2 and 3 illustrate etch profiles (openings 17) in a resist layer of 500-micrometer thickness. Small or zero overcut angles are important in lift-off metallurgy where absence of contact between the evaporated metal at the surface of an organic film and at the bottom of a pattern cut in it is essential. A direct application is in the repair o...