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SELF ALIGNED LEAD OVERLAY PROCESS

IP.com Disclosure Number: IPCOM000015652D
Original Publication Date: 2002-Jun-23
Included in the Prior Art Database: 2003-Jun-20
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Abstract

Lead overlay design provides significant amplitude improvement over contiguous junctions. In order to maximize the amplitude and retain good stability, the length of the lead overlay region requires a tight control. This control is very difficult to achieve for trackwidths around or below 0.15 ┬Ám using a conventional dual photoresist process.

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SELF ALIGNED LEAD OVERLAY PROCESS

Lead overlay design provides significant amplitude improvement over contiguous junctions. In order to maximize the amplitude and retain good stability, the length of the lead overlay region requires a tight control. This control is very difficult to achieve for trackwidths around or below 0.15 µm using a conventional dual photoresist process.

We disclose a new method whereby a single photo step is used to define separate hard bias and leads junctions. This self-aligned method ensures excellent control of the overlay length. In one version, hard bias material is ion beam deposited at a near perpendicular angle (80 or 85 degrees). Then a conductor lead such as gold is ion beam sputtered at a lower angle (60 to 70 degrees). Use of gold material may be critical since this material penetrates well into the undercut region compared to hard magnet materials or Ta. Given this property of gold material and the deposition angle differences, we can obtain lead overlap region of 500 Å or more. The photoresist/undercut dimensions can be adjusted to maximize this overlap region.

In a second version, hard bias and a ~400 Å Ta film is deposited at near normal incident angle followed by a low angle ion milling step (the angle between the beam and the wafer normal can be ~70 degrees). The sidewall coverage from hard bias is expected to be reduced due to high angle deposition. But the ion milling step will clean the re-deposited material and reduce...