Manufacturability of Gmr Heads: 10Gb/in 2 and Beyond
- PDF / 168,815 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 57 Downloads / 153 Views
MANUFACTURABILITY OF GMR HEADS: 10Gb/in2 AND BEYOND S. SAHU, JIAN CHEN, V. TALGHADER, S. COOL AND S. MAO Seagate Recording Heads, 7801 Computer Avenue South, Minneapolis, MN 55435-5489 ABSTRACT Consistency of spin-valve stack deposition, both wafer-to-wafer and within a wafer, is key to the manufacturability of GMR heads. For typical GMR heads, film thicknesses are now in the range of 5Å-150Å and process control is becoming a challenge. This paper discusses the importance of characterizing the thickness and uniformity of each material in the spin-valve stack within the context of single layer sheet films. For this study, single layer sheet films and full multilayer spin-valve stacks were deposited in a multi-target cluster tool. The sheet resistance and thickness of the single layer sheet films were measured using a 4-point probe and ellipsometry, respectively. Results were then correlated to the sheet resistance and magnetic performance (i.e., GMR ratio, exchange field, and magneto-static coupling field) of the full spin-valve stacks with a synthetic antiferromagnet as the pinned layer. The 1σ < 2% uniformity, wafer-to-wafer and within wafer, realized for the full stacks is a strong indicator of a manufacturable process. Model calculations of the sheet resistance and GMR were carried out to provide theoretical understanding of the film thickness dependence. The calculated results are well correlated with the experimental measurements. The model is based on band structures and implicitly includes the momentum-dependent reflection and transmission coefficients at the interfaces. Results from both experiments and calculations show that process control and repeatability (both within a wafer and from wafer to wafer) are crucial to the spin-valve manufacturability, offering a critical challenge to the disc drive industry as it heads into the next generation of GMR heads. INTRODUCTION The read sensor currently used in high areal density magnetic recording heads (10Gb/in2 and higher) is a multilayer spin valve structure consisting of a stack of thin films with thicknesses in the range of a few to a few hundred Angstroms. Spin valves are fabricated with a ferromagnetic “free layer” separated from a ferromagnetic “pinned layer” by a conducting “spacer layer”. In response to an external magnetic field, the free layer magnetization rotates with respect to that of the pinned layer. This change in relative moment directions leads to a large change in the sensor resistance, known as the giant-magnetoresistance (GMR) effect [1] and makes the spin valve structure an excellent magnetic field sensor. With increasing areal densities and subsequently smaller dimensions of the sensor, the thicknesses of the layers in the sensor stack are also decreasing. Hence, it is important to
F7.4.1
consider manufacturability of the sensor stack – namely, the measurement as well as process capability [2] and repeatability, all of which contribute to the final “yield” of the sensor. [3] This paper addresses two main areas: (1) existing process cap
Data Loading...
