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A Method to Remove Magnetic Particle Contamination Disclosure Number: IPCOM000016194D
Original Publication Date: 2002-Oct-28
Included in the Prior Art Database: 2003-Jun-21

Publishing Venue



Sliders bearing the write head, the shields and the GMR sensor, have to be lapped in a controlled fashion to achieve a desirable GMR sensor stripe height for optimal electrical output. Very fine particles of all exposed materials in the write/read sensors and the slider body are generated in this chemical-mechanical process. It was determined that magnetic particles, mostly iron, adhere to the GMR sensor and the hard bias layer on both sides of the GMR sensor after the lapping process. The adhesion is apparently caused by magnetic attraction, since the iron particles would only adhere to the CoPtCr hard bias layer and the GMR sensor. It was further determined that the iron particles primarily came from the iron-rich shields in the immediate vicinity of the hard bias layer and the GMR sensor. The problem with this iron particle contamination is that it is sitting on top of the sensor surface, with a height of up to around 20nm. This contamination, if not removed, prevents the protective carbon overcoat from adhering to the GMR sensor surface and thus causes a sensor corrosion problem in the storage file. It was found that this iron particle contamination adheres to the magnetic layers underneath quite strongly and can survive all the subsequent aqueous cleaning processes. This invention discloses the use of lapping coolant instead of water in a brushing operation to clean off the iron particles immediately after the lapping process. The lapping coolant is preferably composed of either 100% ethylene glycol or 90% ethylene glycol and 10% water. In multiple experimental and pilot line trials, this cleaning method has proven effective in removing all the contamination on top of the GMR sensor and the hard bias layer. 1