Method and apparatus for increasing uniformity in ion mill process

1. A method for increasing etch depth uniformity in ion mill etching of a wafer during its manufacturing process, said method comprising:

loading designated regions of a production pallet with carriers containing wafers to be ion milled, wherein said designated regions have been predetermined to exhibit similar and preferred depths of etching, wherein said loading designated regions comprises:

performing multiple process runs;

determining HDD yield loss per HDD head based on said performing multiple process runs; and

determining locations of said designated regions exhibiting similar and preferred depths of etching based on said determining HDD yield loss and results of said multiple process runs;

loading non-designated regions of said production pallet with dummy carriers based on said determining locations of said designated regions; and

performing said ion milling on said wafers.

2. The method as recited in claim 1 wherein loading non-designated regions of said production pallet with dummy carriers further comprises:

for a pallet containing 20 regions in a four-by-five array, loading four corner regions and six central regions with said dummy carriers.

3. The method as recited in claim 1 , wherein said wafers comprise hard disk drive heads.

4. The method as recited in claim 3 , wherein said increasing etch depth uniformity in ion milling process for wafers further comprises:

improving fly height control for said hard disk drive heads.

5. The method as recited in claim 1 , wherein said increasing etch depth uniformity further comprises:

increasing both run-to-run uniformity and within-run uniformity.

6. An apparatus for increasing etch depth uniformity in an ion mill process, said apparatus comprising:

a production pallet;

a plurality of wafer carriers, said wafer carriers disposed within designated regions of said production pallet, wherein wafers to be ion milled are loaded into said designated regions, said designated regions having been predetermined to exhibit similar and preferred depths of etching, wherein said loading designated regions comprises:

performing multiple process runs;

determining HDD yield loss per HDD head based on said performing multiple process runs; and

determining locations of said designated regions exhibiting similar and preferred depths of etching based on said determining HDD yield loss and results of said multiple process runs;

and wherein dummy wafers are loaded into non-designated regions based on said determining locations of said designated regions.

7. The apparatus as described in claim 6 wherein non-designated regions in a pallet containing 20 regions in a four-by-five array comprise four corner regions and six central regions.

8. The apparatus as described in claim 6 , wherein said wafers to be ion milled comprise sliders for hard disk drive heads.

9. The apparatus as described in claim 8 , wherein said increasing etch depth uniformity in ion milling process results in improved fly height control for said sliders.

10. A ion mill etch depth uniformity increaser comprising:

designated region determinor means for determining designated regions for loading carriers comprising wafers to be ion mill etched into a production pallet, wherein said designated regions exhibit similar and preferred depths of etching, wherein said determining designated regions for loading carriers comprises:

performing multiple process runs;

determining HDD yield loss per HDD head based on said performing multiple process runs; and

determining locations of said designated regions exhibiting similar and preferred depths of etching based on said determining HDD yield loss and results of said multiple process runs;

carrier loading means, receiving output from said designated region determinor means, for loading said carriers comprising wafers to be ion mill etched into said designated regions of said production pallet based on said output and for loading carriers containing dummy wafers into non-designated regions of said production pallet based on said determining locations of said designated regions; and

ion milling means coupled to said carrier loading means for ion mill etching said wafers to be ion milled.

11. The ion mill etch depth uniformity increaser as described in claim 10 , wherein said wafers to be ion milled comprise sliders for hard disk drive heads.

12. The ion mill etch depth uniformity increaser as described in claim 11 , wherein said exhibiting similar and preferred depths of etching results in improved fly height control for said hard disk drive heads.