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Process for Preventing Contaminant Formation During Metal Etching

IP.com Disclosure Number: IPCOM000037453D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Albrechta, SM: AUTHOR [+3]

Abstract

Particle contaminants that form between circuit lines cause failures of electronic circuits by providing a pathway for current leakage. They may also contain materials which corrode circuitry. The following process prevents formation of copper-containing contaminant particles that form when circuit lines are produced by subtractive etching of copper films bonded to polyimide or other polymer supports.

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Process for Preventing Contaminant Formation During Metal Etching

Particle contaminants that form between circuit lines cause failures of electronic circuits by providing a pathway for current leakage. They may also contain materials which corrode circuitry. The following process prevents formation of copper-containing contaminant particles that form when circuit lines are produced by subtractive etching of copper films bonded to polyimide or other polymer supports.

The circuitry addressed by this process can be produced by bonding a thin film, consisting of copper sandwiched between two layers of chromium, to polyimide or another polymer. Then, after application of a patterned photoresist to protect the desired metal circuit lines, the unwanted metal between the lines is removed by a metal etching process consisting of the following steps: 1) alkaline potassium permanganate solution removes the top chromium; 2) ferric chloride etchant solution is used to remove the copper; 3) alkaline potassium permanganate solution removes the bottom chromium; 4) oxalic acid removes traces of potassium permanganate.

Each of these steps is followed by a water rinse. Step 4 is necessary to remove traces of permanganate that are not removed by water rinsing after step 3; otherwise the circuitry corrodes over time. However, this oxalic acid rinse reacts with residues left on the sides of the copper lines after ferric chloride etch (step 3). This produces copper- containing particle...