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Ultrasonic Copper Lift-Off Prior to Additive Plating

IP.com Disclosure Number: IPCOM000039687D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Baehrle, D: AUTHOR [+3]

Abstract

A process is described for the selective removal of a thin copper layer. Copper, sputtered on a photolithographically structured permanent resist, is removed from the resist surface by wet rotating brush rolls. Ultrasound and an alkaline solution of a complexing agent also remove the copper layer from the vertical walls of photoresist channels to prevent overplating in the additive bath. The process for producing an embedded conductor structure for multilayer circuit boards, as previously disclosed in the IBM Technical Disclosure Bulletin 27, 3086-3087 (October 1984), is improved by removing excess copper from the vertical walls of photoresist channels, using 1.

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Ultrasonic Copper Lift-Off Prior to Additive Plating

A process is described for the selective removal of a thin copper layer. Copper, sputtered on a photolithographically structured permanent resist, is removed from the resist surface by wet rotating brush rolls. Ultrasound and an alkaline solution of a complexing agent also remove the copper layer from the vertical walls of photoresist channels to prevent overplating in the additive bath. The process for producing an embedded conductor structure for multilayer circuit boards, as previously disclosed in the IBM Technical Disclosure Bulletin 27, 3086-3087 (October 1984), is improved by removing excess copper from the vertical walls of photoresist channels, using 1. a computer-controlled ultrasonic bath in which the

ultrasonic power, the reflected power, the wobble

frequency and the amplitude are automatically

adapted to the respective laminate, so that

optimum conditions are invariably obtained;

2. an alkaline solution of tetrasodium salt of

ethylenediamine tetraacetic acid (tetrasodium

EDTA) containing, if necessary, a wetting agent,

and

3. maintaining the bath temperature at about 60oC. Example: It was found in tests that sputtered copper is removed from smooth resist surfaces in an

alkaline solution of tetrasodium EDTA with a

concentration of about 35 g/l and containing a wetting

agent, such as GAFAC*. An additional ultrasonic

treatment, in which power adaptation, frequency

optimization and amplitude are accura...