Techniques and apparatus for elongation patterning using angled ion beams

1. A method of patterning a substrate including a plurality of layers disposed atop a substrate base, the method comprising:

providing a cavity in the plurality of layers, the cavity extending to a first depth in the plurality of layers, and the cavity having a first length along a first direction and a first width along a second direction, perpendicular to the first direction;

directing first angled ions in a first exposure to the cavity, wherein after the first exposure the cavity has a second length, greater than the first length;

directing normal-incidence ions in a second exposure to the cavity, wherein the cavity retains the second length after the second exposure, wherein a topmost layer of the plurality of layers is removed, and wherein the cavity is extended to a second depth to expose the substrate base; and

directing second angled ions to the cavity in a third exposure, subsequent to the second exposure, wherein the cavity has a third length, greater than the second length, after the third exposure;

wherein the first angled ions form a first ribbon beam having a first long axis, parallel to the second direction and a first short axis, parallel to the first direction, and wherein the second angled ions form a second ribbon beam having a second long axis parallel to the second direction and a second short axis parallel to the first direction.

2. The method of claim 1 , wherein the plurality of layers comprises at least three layers, and wherein the cavity is disposed in a first layer and in a second layer, subjacent the first layer, before the first exposure.

3. The method of claim 2 , wherein the cavity is extended into a third layer, subjacent the second layer, after the second exposure.

4. The method of claim 3 , wherein the first layer is removed after the second exposure.

5. The method of claim 1 , wherein the first angled ions are directed in a presence of a first reactive ambient, along a first trajectory at a first non-zero angle of incidence with respect to a perpendicular to a plane of the substrate, the first trajectory being aligned with the first direction, and wherein the second angled ions are directed in a presence of a second reactive ambient, along a second trajectory at a second non-zero angle of incidence with respect to the perpendicular to the plane of the substrate, the second trajectory being aligned with the first direction.

6. The method of claim 5 , wherein the first non-zero angle of incidence comprises at least 10 degrees, and the second non-zero angle of incidence comprises at least 10 degrees.

7. The method of claim 1 , wherein the normal-incidence ions are directed along a perpendicular to a plane of the substrate in the presence of a third reactive ambient.

8. The method of claim 1 , wherein the plurality of layers comprises at least two layers, and wherein the cavity is disposed in a first layer before the first exposure, and wherein the cavity is extended into a second layer after the second exposure.

9. The method of claim 1 , wherein the second length exceeds the first length by 20 nm to 50 nm, and wherein the third length exceeds the first length by 60 nm to 80 nm.

10. The method of claim 1 , wherein the first width does not increase after the first exposure, and wherein the first width does not increase after the second exposure.