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Single Level Metallurgy Process for Fabrication of Bubble Overlays

IP.com Disclosure Number: IPCOM000088540D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Romankiw, LT: AUTHOR

Abstract

This article describes a process for the fabrication of bubble domain propagation, control and sense circuits which includes only one photoresist application, two exposures which use critical alignment, and three through-mask plating steps.

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Single Level Metallurgy Process for Fabrication of Bubble Overlays

This article describes a process for the fabrication of bubble domain propagation, control and sense circuits which includes only one photoresist application, two exposures which use critical alignment, and three through-mask plating steps.

The fabrication process consists of the following steps: (1) Sputter SiO(2) separator (or evaporate SCHOTT* 8329 glass). (If SCHOTT glass is used, only one pump-down is required). (2) Evaporate 200 Angstroms magnetoresistive (MR) film [*]. (3) Apply SHIPLEY** 1350H resist or electron(E)-beam resist, expose, and develop all patterns (i.e., T and I bars and/or chevron patterns, control lines, and MR conductor lines). (4) Deposit about one half the desired thickness of permalloy approx.2000 Angstroms to 3000 Angstroms), approx. 1000 Angstroms to 1500 Angstroms of Au or Cu, then the second half of the permalloy thickness (approx. 2250 Angstroms to 3250 Angstroms; the extra thickness is to compensate for permalloy removal in step (6)). (5) Expose the remaining resist except for the MR sensors, and develop in a suitable developer.
(6) Sputter-etch 200 Angstroms of background MR defining the the MR sensors.
(7) Remove SHIPLEY resist, using KERN DECONTAM*** or prolonged exposure to acetone in an ultrasonic field, and protect circuits by sputtering on approx. 7000 Angstroms to 10,000 Angstroms of SiO(2) (sputtered). When using E- beam resist, use a suitable resist removal solvent. Alternatively, remove the resist by ashing in O(2) containing plasma. (8) Etch holes in SIO(2) for contact to control lines and MR sensors.

In step (3) SHIPLEY 1350H can be replaced by E-beam resist.

In step (4) the separator metallic layer of Au or Cu is approx. 8 times as conductive as permalloy; at the same time it is thin enough so that removal of edge domains in the T and I bars is accomplished. To remove the edge domains, the Au or Cu layer need be only ~ 200 Angstroms to 300 Angstroms thick. The remaining thickness is used to provide conductivity. The exact thickness of this layer will depend on the desired balance between the maximum allowable resistance of the lines and the magnetic coupling of the two permalloy films. In this step, the three layers can be electroplated in succession or can be evaporated through a resist mask.

In some cases, to improve adhesion of Au, it may be necessary...