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Rework Process for Copper Conductor Layers

IP.com Disclosure Number: IPCOM000042813D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Anderson, NC: AUTHOR [+5]

Abstract

Current practice requires that a thin film head wafer, found to be defective (coil shorting, improper electrical resistance, or incorrect thickness), be stripped back to the Al2O3 undercoat and restarted through the fabrication process. Since the conductor deposition is approximately at the midpoint of the fabrication process, such failures are costly to rework. This technique facilitates rework of copper conductor materials without damage to the permalloy, gap, or insulation layer. The key is a selective etchant which dissolves only the copper layer. The etchant is a solution of about 20% ammonium persulfate (NH4)2 S208 adjusted to a pH of about 8. After the defective copper layer has been removed, the wafer can be remetalized with copper, coated with photoresist, exposed, developed, and plated with copper.

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Rework Process for Copper Conductor Layers

Current practice requires that a thin film head wafer, found to be defective (coil shorting, improper electrical resistance, or incorrect thickness), be stripped back to the Al2O3 undercoat and restarted through the fabrication process. Since the conductor deposition is approximately at the midpoint of the fabrication process, such failures are costly to rework. This technique facilitates rework of copper conductor materials without damage to the permalloy, gap, or insulation layer. The key is a selective etchant which dissolves only the copper layer. The etchant is a solution of about 20% ammonium persulfate (NH4)2 S208 adjusted to a pH of about 8. After the defective copper layer has been removed, the wafer can be remetalized with copper, coated with photoresist, exposed, developed, and plated with copper.

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