DFL Read Head Decoupling Layer for RSB Patterning Consistency
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Solution Overview
Problem
The patterning process of rear soft bias (RSB) and tunnel magneto resistance (TMR) sensor in dual free layer (DFL) read heads is hindered by the use of a cap layer, leading to inadequate removal of RSB material and inconsistent bias performance due to hard-to-pattern materials like Ni80Fe20, Ni45Fe55, and CoFe.
Innovation Solution
A decoupling layer is applied after patterning the RSB and TMR sensor, allowing for flexible optimization of its width to fully decouple the RSB and TMR sensor from the top shield while maintaining partial coupling of side shields, eliminating the need for a cap layer during patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cap layer is disposed on the RSB prior to patterning, then the RSB is decoupled from the shield, but the patterning process is impeded and RSB width consistency deteriorates
Solution Approach 1:
The cap layer is deposited beforehand to provide magnetic decoupling protection, but the critical patterning step is performed first on the RSB and TMR sensor before the cap layer is finalized. This preliminary action sequence allows the pattern definition to occur when the cap layer is still removable, solving both the decoupling need and the patterning impediment.
Solution Approach 2:
The cap layer is selectively removed (taken out) after the RSB and TMR sensor patterning is complete. This extraction allows the pattern definition to be achieved without the cap layer's interfering presence during the critical patterning step, while maintaining the decoupling function where needed.
2Reliability
If hard-to-pattern materials like Ni80Fe20, Ni45Fe55, and CoFe are used for RSB to provide sufficient bias, then bias performance improves, but patterning difficulty increases
Solution Approach 1:
The RSB and TMR sensor are patterned beforehand while the cap layer is still present but removable. This preliminary patterning action is performed when the material stack is most amenable to pattern definition, before subsequent processing steps make patterning more difficult. This allows hard-to-pattern materials to be used without compounding the patterning difficulty.
Solution Approach 2:
The cap layer serves as an intermediary that protects the RSB material during deposition and initial processing, then is selectively removed to allow clean pattern definition of the hard-to-pattern RSB material. This intermediary approach enables the use of high-performance materials while managing their patterning challenges.
3Productivity
If the RSB is patterned at the same time as the TMR sensor for manufacturing efficiency, then productivity improves, but the cap layer prevents proper RSB shape definition
Solution Approach 1:
The simultaneous patterning of RSB and TMR sensor is performed as a preliminary action before the cap layer is finalized or removed. This timing allows both structures to be defined together in a single patterning step (maintaining productivity) while the cap layer's presence at this stage does not prevent proper pattern transfer to the underlying layers.
Solution Approach 2:
The cap layer is selectively extracted after the simultaneous patterning step. This extraction removes the cap layer's interfering effect on the final pattern definition, allowing both RSB and TMR sensor to achieve their intended shapes and widths without the cap layer's detrimental influence on material removal during patterning.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures proper decoupling and stabilization of the RSB and TMR sensor, improving manufacturing efficiency and bias consistency without the limitations of traditional cap layers.
Implementation Method 1
a decoupling layer disposed on the TMR sensor, the RSB, and at least a portion of the SB side shields... the decoupling layer's extra width will help it completely decouple the RSB and TMR sensor from the top shield
Implementation Method 2
The RSB is stabilized by shape anisotropy which arises from its long, slender and needle-like shape
Implementation Method 3
the two free layers are within a tunnel magneto resistance (TMR) sensor stack and are individually stabilized longitudinally by an anti-ferromagnetically coupled (AFC) soft bias (SB)
Data Source
AI summary
Rather than disposing a cap layer on a rear soft bias (RSB) of a DFL read head prior to the patterning of the RSB and TMR sensor, disclosed is a decoupling layer disposed on the RSB and TMR sensor after they undergo patterning, with the decoupling layer undergoing its own subsequent patterning. The RSB and the TMR sensor can thus be patterned (defined) together without a RSB cap layer adversely affecting the patterning. As the decoupling layer undergoes its separate patterning, its cross-track width can be flexibly optimized to be greater than that of both the RSB and the TMR sensor. In some embodiments, the decoupling layer's extra width will help it completely decouple the RSB and TMR sensor from the top shield. The side shields will be partially decoupled from the top shield due to the extra width, but will still retain partial coupling to the top shield.