Process complexity of magnetoresistive sensors: a review

Abstract

Magnetoreslstive (MR) thin film sensors are presently used In a variety of hard disk and tape storage devices. Review papers [1,2] have detailed the various methods and configurations required to linearize and stabilize the output slgnal characterlstlcs of the MR thin film transducer. However, little emphasis has been placed on describing the complexity of such configurations with respect to materials and fabrication requlrements. Speciflcally this review will examine MR sensor configurations from the perspective of the thin film processing technology required to Implement the sensor design into a thin film head environment. The general trend Is that the process complexity for MR sensors has increased In the areas of magnetic materlals and patterning as the areal density performance of the sensor has Improved.

Influence of stress and unidirectional field annealing on structural and magnetic performance of PtMn bottom spin-filter spin valves

“…However, in asdeposited, sputtered stoichiometric PtMn thin films a post-deposition annealing, the so-called unidirectional annealing (UDA), is necessary to induce a phase transformation from the asdeposited, paramagnetic FCC phase to the antiferromagnetic FCT phase. Additional to the UDA, several thermal annealing steps up to 250 C are required in the process of device fabrication for curing organic insulators coated on the metal surfaces [5]. The degree of FCC-FCT transformation, the H ex and the resulting GMR performance of top or bottom SVs are affected by annealing temperature, PtMn thickness and seed layers [2,[6][7][8][9].…”

Fabrication of magnetic recording heads and dry etching of head materials

“…As feature dimensions shrink, the semiconductor industry has replaced liftoff processing with a combination of reactive ion etching and chemical-mechanical polishing (CMP) processes. However, liftoff processing is still widely used in MR and GMR recording-head fabrication [2] because the films to be lifted off are typically thinner than those in a semiconductor device, and the features are wider than those in a semiconductor device. For the fabrication of increasingly higher-density recording heads, however, the applicability of the liftoff technique will become questionable.…”

“…In contrast, electroplating is still commonly used in recording-head fabrication (for the copper coil, copper leads, nickel-iron magnetic shields, and nickel-iron write pole pieces). Up to seven plating process steps are used in wafer fabrication [2], As an example, the upper pole piece of Figure 2 is usually fabricated by defining the pole-tip feature in a relatively thick photoresist layer over topography, followed by plating several microns of a magnetic material into the resist-defined mask. Electroplating offers a cost-effective approach to metal deposition.…”

“…The processes used to fabricate a recording head comprise a combination of lithography, deposition (vacuum or plating), and etching steps. Review papers describing the details of recordinghead fabrication have been published io the Uterature [1,2]. Recording heads are usually fabricated on AlfiJ'TiC ceramic wafers, which provide excellent mechanical and tribological properties.…”

An enhanced physics-based model to estimate the displacement of piezoelectric actuators

“…In the early 1930s, the Preisach model was introduced to model the nonlinear behaviour of ferromagnetic materials placed in a magnetic field (Hegewald et al, 2008, Fontana, 1995. Similarity between the behaviour of ferromagnetic materials and piezoelectric actuators resulted in introducing the Preisach model for piezoelectric actuators (Wolf et al, 2011, Zelinka et al, 1987.…”