Mathematical modeling and measurement of etching profile for junction shape control in MR read heads

A computer model was used to predict the junction profile between magnetoresistive (MR) read sensor and hard bias element which is known to have an influence on head performance. Ion beam etching (IBE) rates as a function of incident beam angle for each material were experimentally determined for this model. Key process parameters such as stencil structure (e.g. height, shape, and etch rate of the photoresist), ion beam angle, and MR element structure were varied. A series of experiments have been performed to confirm the model prediction by employing atomic force microscopy. When the sidewall of stencil was vertical, the junction angle became small resulting from the shadowing of incident ion beams. It is also found that when a thin Ta layer was inserted between the MR element and bottom gap layer, the junction angle was increased.