| CPC H01L 21/32 (2013.01) [G03F 7/70283 (2013.01); H01L 21/027 (2013.01)] | 20 Claims |

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1. A method comprising:
forming a first layer over a substrate;
forming a second layer over the first layer;
exposing the second layer to a first ion beam, wherein the substrate is tilted at a tilt angle with respect to an axis of the first ion beam, the tilt angle being measured between the axis of the first ion beam and an upper surface of the substrate, wherein the tilt angle is greater than 0°; and
moving the substrate with respect to the first ion beam while exposing the second layer to the first ion beam, wherein the substrate moves along a scan line, wherein a scan angle between the scan line and a line perpendicular to the axis of the first ion beam, wherein the scan angle is greater than 0°.
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