Read sensors and methods of making same with back-edge milling and refilling
View Patent ↗Methods and apparatus provide a refill configuration adjacent a back-edge that defines a height of a magnetoresistive read sensor. Milling through layers of the sensor forms the back-edge and may be initially conducted at a first angle of incidence greater than a second angle of incidence. In combination, an insulating material and a polish resistant material, such as a non-magnetic metal, disposed on the insulating material fills a void created by the milling. The sensor further includes first and second magnetic shields with the layers of the sensor along with the polish resistant material and insulating material disposed between the first and second magnetic shields.
1. A method of forming a magnetoresistive (MR) read sensor, comprising:
providing a MR sensor stack on a first magnetic shield;
removing a portion of the MR sensor stack to form a back-edge of the MR sensor stack, wherein the back-edge defines a height of the MR sensor stack in a direction perpendicular to a track width direction;
depositing an insulating layer on the back-edge of the MR sensor stack;
depositing a non-magnetic polish resistant layer on the insulating layer, wherein the non-magnetic polish resistant layer has a slower polishing rate than the insulating layer; and
depositing a second magnetic shield over the MR sensor stack and the polish resistant layer.
2. The method of claim 1 , further comprising chemical mechanical polishing to remove material of the polish resistant and insulating layers deposited on the MR sensor stack.
3. The method of claim 1 , wherein the non-magnetic polish resistant layer is a metal.
4. The method of claim 1 , wherein the non-magnetic polish resistant layer is selected from one of chromium, rhodium, tantalum, tungsten, and zirconium.
5. The method of claim 1 , wherein removing the portion of the MR sensor comprises milling at a first angle and then milling at a second angle smaller than the first angle.
6. The method of claim 1 , wherein removing the portion of the MR sensor comprises milling at a first angle of 50° and then milling at a second angle of 30°.
7. The method of claim 1 , wherein removing the portion of the MR sensor comprises milling to a barrier layer at a first angle and then milling, at a second angle smaller than the first angle, to a first magnetic shield.
8. The method of claim 1 , wherein the insulating layer comprises alumina.
9. The method of claim 1 , wherein depositing the insulating layer forms a layer of alumina that is greater than 10 nanometers thick.
10. The method of claim 1 , wherein depositing the insulating layer occurs by atomic layer deposition.
11. A method of forming a magnetoresistive (MR) read sensor, comprising:
providing a MR sensor stack disposed on a first magnetic shield;
initially milling a portion of the MR sensor stack at a first angle;
further milling the portion of the MR sensor stack at a second angle smaller than the first angle to form a back-edge of the MR sensor stack, wherein the further milling removes part of the first magnetic shield;
depositing an insulating layer on the back-edge of the MR sensor stack to partially fill a void created by the milling;
depositing a metallic non-magnetic layer on the insulating layer to complete filling of the void, wherein the metallic non-magnetic layer has a slower polishing rate than the insulating layer; and
depositing a second magnetic shield over the MR sensor stack and the polish resistant layer.
12. The method of claim 11 , wherein the further milling commences once the initial milling is stopped upon reaching a barrier layer of the MR sensor stack.
13. The method of claim 11 , wherein the first angle is about 50° and the second angle is about 30°.
14. The method of claim 11 , wherein the non-magnetic polish resistant layer is selected from at least one of chromium, rhodium, tantalum, tungsten, and zirconium.