Transmission electron microscopy of cross-sections of magnetoresistive read heads

Cross-sectional images of the multilayered structures of magnetoresistive ( MR) read heads showing the nanostructure,of individual layers are desirable for process evaluation and failure analysis. We have successfully prepared thin cross-sections of MR read heads with soft-adjacent-layer transverse-b iased sensor and pattern exchange longitudinal biasing for study by transmi ssion electron microscopy (TEM). The perfection and defects of individual s tructural layers (about 10-20 nm thick) of the MR head an clearly visible i n cross-sectional TEM images. Two very thin defect layers due to residual p hotoresist materials have been observed at the MR sensor-exchange layer int erface and exchange-conducting layer interface. The origin of the defect la yers is the incomplete removal of residual photoresist materials by ion-bea m etching during processing. Deeper etching by ion-beam milling reduces the size of the defect layers. The dummy resistance of the MR sensor is substa ntially reduced after deeper etching. This is the first study of the nanost ructure of MR heads and the first demonstration of process evaluation using TEM in magnetic disc-drive technology.