Bottom leads chemical mechanical planarization for TMR magnetic sensors
Abstract:
A Wheatstone bridge array comprising a tunneling magnetoresistive (TMR) sensor and a method for manufacturing is disclosed. The bottom lead for the TMR sensor has a very small surface roughness due to not only chemical mechanical planarization (CMP) but also due to forming the bottom lead from multiple layers. The multiple layers include at least a bottom first metal layer and a top second metal layer disposed on the first metal layer. The second metal layer generally has a lower surface roughness than the first metal layer. Additionally, the second metal layer has a slower polishing rate. Therefore, not only does the second metal layer reduce the surface roughness simply be being present, but the slower polishing rate enables the top second metal film to be polished to a very fine surface roughness of less than or equal to ˜2 Angstroms.
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