METHOD OF ACHIEVING A TF HEAD WITH NO ALUMINA PROTRUSION
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2003-Jun-19
Published is a method of building a Thin Film Head with No Alumina Protrusion. Current process capabilities for Pole Tip Recession are currently limited by process steps that influence trailing edge alumina protrusion. This publication provides a method for eliminating this material as a part of the wafer build up, allowing for improved pole tip recession capability. Current wafer build processes encapsulate the read write elements of a TF head in a thick alumina encapsulation layer. This has been a historical part of the TF head structure for many years, but does not play a direct role in the magnetic performance of the device. This layer is known to expand and protrude beyond the plane of the air bearing surface of the head, as the head flies over a disk surface. It is considered to be a mechanical reliability issue and had required changes in the head fabrication process to reduce its impact. These processes have had a negative impact on pole tip recession, a critical parameter in the magnetic performance of the head. Therefore the elimination of the cause of head protrusion would allow significant improvements in pole tip recession. The solution to the problem posed above is based in the wafer fabrication process. Rather than depositing a single, thick film of alumina over the pole tips, this method would deposit a thin layer of non-etchable material over the pole pieces. Then the remaining encapsulating material would be deposited as it is done today. A low cost wet etch process could then be used to etch away the larger encapsulation layer, leaving only a thin layer of etch barrier over the pole pieces. This could be done selectively over the pole pieces at the air bearing surface or over the entire head surface, depending on cost or other considerations. The wafer could then be processed exactly as it is today in current production processes. The only exception to this would be in the processes used creating the final pole tip recession geometries. These could be optimised specifically for a more repeatable recession value with a mean very closely approaching the air bearing surface. The processes to do this are known within the engineering community. There are several methods and material choices for the etch barrier material. The prime candidate is a modified Alumina material currently used as the gap alumina in current head structures. It is well characterised and is known to have good etch resistance. As this material is already interlaced in the current head structure with standard alumina in several layers, the structural integrity of the interface is already a tested and known quantity. The process parameters for creating this material are already well known as well. As this method does not introduce a material not before used in heads such as these, the corrosion and reliability risks are low. If another material is required, there are other choices that would meet these requirements as well, but would require additional testing for reliability performance.