Inventors:
Sukhbir Singh Dulay - San Jose CA, US
Justin Jia-Jen Hwu - San Jose CA, US
Thao John Pham - San Jose CA, US
Assignee:
Hitachi Global Storage Technologies Netherlands B.V. - Amsterdam
International Classification:
G11B 5/127, H04R 31/00
US Classification:
2960316, 2960313, 2960315, 2960318, 216 62, 216 65, 216 66, 20419234, 360122, 360317, 451 5, 451 41
Abstract:
A method for measuring recession in a wafer undergoing an asymmetrical ion mill process. The method includes the formation of first and second reference features and possibly a dummy feature. The reference features are constructed such that the location of the midpoint between them is unaffected by the asymmetrical ion mill. By measuring the distance between a portion of the dummy feature and the midpoint between the reference features, the amount of recession of the dummy feature can be measured. The measurement can be used to calculate the relative location of the flare to the read sensor rear edge through overlay information. By keeping the angles of the sides of the features steep (ie. nearly parallel with the direction in which the ion mill is asymmetrical) the amount of material consumed on each of the reference features is substantially equal and the midpoint between the reference features is substantially stationary.