Self aligned undercut structure using tungsten hard mask
Original Publication Date: 2003-Aug-22
Included in the Prior Art Database: 2003-Aug-22
With increasing areal density, read track widths have been decreasing. In the widely used contiguous junction design, the hard bias field necessary to stabilize the sensor is strong enough to pin the "free" layer at the hard bias/sensor interface (track edges). As read track widths decrease, a larger fraction of the "free" layer is getting pinned. In other words, less and less of the sensor is free to read, reducing amplitude. Actual sensor designs on wafer level have the disadvantage, that the sensor width typically is realized using a resist dual apply mode. This is done to get a so-called undercut structure, enabling an easier lift off of the remaining resist structure. The undercut structure and the applied follow on processes, like ion milling and/or sputter deposition, does have the disadvantages, that we create re-deposition along the resist wall. The re-deposition, also called fencing, can later on create short cuts to upper layers. Our approach would have the benefit, to eliminate fencing. Another beneficial feature of the process discussed below, certainly is, that we would be able to get around a second photo step as well as the related alignment. The under layer structure can be controlled to a certain extend in size, using the upper imaging layer and well defined etch processes.