BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a symbolic illustration of selected components in a prior art disk drive.
FIG. 2 is a symbolic illustration of a section, taken parallel to the air-bearing surface, of a prior art read sensor with overlaid leads.
FIG. 3 is a symbolic illustration of a section, taken perpendicular to the surface of a wafer after initial steps in a method of fabricating a sensor according to the invention.
FIG. 4 is a symbolic illustration of a section, taken perpendicular to the surface of a wafer subsequent to FIG. 3, after the DLC layer has been milled and the photoresist mask has been stripped in a method of fabricating a sensor according to the invention.
FIG. 5 is a symbolic illustration of a section, taken perpendicular to the surface of a wafer subsequent to FIG. 4, after lead layers over the active region of the sensor have been milled and the DLC mask layer has been removed in a method of fabricating a sensor according to the invention.
FIG. 6 is a symbolic illustration of a section, taken perpendicular to the surface of a wafer subsequent to FIG. 5, after the photoresist mask for the full width of the sensor has been patterned and the excess lead and sensor material has been milled away in a method of fabricating a sensor according to the invention.
FIG. 7 is a symbolic illustration of a section, taken perpendicular to the surface of a wafer subsequent to FIG. 6, after the layers for the hard bias structures have been deposited in a method of fabricating a sensor according to the invention.
FIG. 8 is a symbolic illustration of a section, taken perpendicular to the surface of a wafer subsequent to FIG. 7, after the photoresist has been removed in a method of fabricating a sensor according to the invention.
FIG. 9 is a symbolic illustration of a section, taken perpendicular to the surface of a wafer in an embodiment using ruthenium for lead-1 layer in a method of fabricating a sensor according to the invention.
FIG. 10 is a flowchart of a method according to the invention.
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS
A first embodiment of the invention is a read head with overlaid leads that only contact the top of the sensor along a confined area. FIG. 3 is a symbolic illustration of a plan view of a wafer 40 at a first stage in a process of fabricating a sensor with overlaid leads according to the first embodiment of the invention. The figures are not according to scale, since the large range of sizes would make the drawings unclear. Except were noted the dimensions are according to the prior art. The invention deposits the GMR and lead layers full film on the wafer before milling away the unwanted material. The stack of sensor material layers 43 has been deposited on the gap layer 41 according to the prior art. The leads preferably include two layers of electrically conductive material: lead-145 and lead-247. The first lead layer 45 is an electrically conductive material such as tantalum or ruthenium. Use of ruthenium for lead-1 is a special embodiment that will discussed further below. A conductive metal such as rhodium is preferably used for the lead-247 material. A mask layer 49 preferably of DLC is deposited full film over the wafer onto the upper lead-2 layer. The patterned photoresist 51 includes a hole that defines the active area of the sensor where the lead layers will be removed.
An oxygen-based RIE process is used to mill through the DLC 49 in the exposed area of the photoresist mask 51, then the photoresist mask 51 is stripped off. This leaves the DLC to serve as a mask for milling one or both of the two lead layers 45, 47 as shown in FIG. 4. The choice of material for the mask layer is constrained by the need for resistance to etching process used to remove the metallic materials used for the leads. Any appropriate material can be used including silicon dioxide.
The state of the wafer after the two lead layers 45, 47 have been milled through according to the first embodiment that is not using ruthenium for lead-1 is shown in FIG. 5. After the lead layer or layers have been milled the DLC 49 is been removed by RIE.
The next step is to pattern a photoresist pad 53 over the full width of the sensor as shown in FIG. 6. The excess lead and sensor material around the pad 53 has been milled away exposing the sides of the leads and the GMR layer stack as shown in FIG. 6.
The hardbias structures are deposited next as show in FIG. 7. The layers in the hardbias structures are selected according to the prior art. For example a layer of rhodium 55 is deposited followed by one or more layers for the magnetic material 57 for the bias. The photoresist 53 is then removed using a chemical-mechanical polishing (CMP) process with the result being shown in FIG. 8.
The prior process of fabricating a sensor can be resumed at this point. The exposed lead-2 material 47 and the hardbias structure 57 are in electrical contact with the sensor 43. The further development of the lead connections can be performed according to the prior art.
FIG. 10 is a flowchart of a method according to the invention. The layers for the sensor and the leads are deposited sequentially on the wafer 81. The leads will preferably include two layers with the upper layer preferably being rhodium. The lower layer can optionally be ruthenium which can also serve as the cap layer for the sensor. Tantalum is another option for the first lead layer. A mask layer, preferably DLC, is deposited 82. A photoresist mask with a hole defining the active area of the sensor is patterned 83. The exposed area of the DLC mask over the active area of the sensor is removed by a RIE process that does not affect the metallic lead-2 layer 84. The photoresist is then stripped 85. A selected portion of the exposed lead material is then removed using the DLC as a mask 86. In the first embodiment of the invention, the first and second lead layers will be removed completely from the surface sensor exposed through the DLC mask. The DLC mask is then removed 87. A photoresist mask pad is patterned to define the full sensor width 88. The excess sensor and lead material exposed around the mask is milled away 89. The layers for the hardbias structure are deposited 91. The first layer of the hardbias structure can be rhodium followed by the remaining layers for the hard bias structure according to the prior art 91. The mask is then removed using a CMP-assisted liftoff 92.
The prior art can be resumed at this point. The typical process would deposit a material for the next gap layer, then the seed layer for the S2 shield for the read head.
In an alternative embodiment the use of ruthenium for the first lead layer 45 is preferred since it protects against oxidation of the sensor layers when the DLC mask layer 49 is ultimately removed by oxygen RIE. The ruthenium oxide, which is formed on the surface of the ruthenium layer during the RIE, is conductive, so it provides conductivity, as well as, corrosion protection. In the alternative embodiment, it is preferable to remove only the lead-2 layer 47 in the active area of the sensor. If the sensor has a ruthenium cap, it can serve as the first lead layer. When the first lead layer is ruthenium, then the second lead layer 47 will be removed completely in the active area of the sensor, but the ruthenium layer 45 can be left at least partially in place as shown in FIG. 9, which illustrates the structure of the wafer for the alternative embodiment using ruthenium for lead-1 layer 45. In this embodiment the ruthenium lead-1 layer is not completely removed, so it remains in the final structure, but otherwise the process in the alternative embodiment is the same.
The invention has been described with respect to particular embodiments, but other uses and applications for the thin film structures and methods according to the invention will be apparent to those skilled in the art.
Patent Application
20070266550
