Techniques and apparatus for selective shaping of mask features using angled beams

1. A method of patterning a substrate, comprising:

providing a set of features in a mask layer, the mask layer being disposed on a layer of the substrate, wherein a given feature comprises a first dimension along a first direction, a second dimension along a second direction, orthogonal to the first direction, and a first thickness;

directing an angled ion beam to a first side region of the set of features in a first exposure, wherein the first side region is etched a first amount along the first direction;

directing an angled deposition beam to a second side region of the set of features in a second exposure, wherein a protective layer is formed on the second side region, the second side region being oriented perpendicularly with respect to the first side region; and

directing the angled ion beam to the first side region in a third exposure, wherein the first side region is etched a second amount along the first direction.

2. The method of claim 1 , the directing the angled ion beam comprising:

forming a reactive plasma in a plasma chamber;

applying a bias voltage between the substrate and the plasma chamber; and

extracting the angled ion beam from the reactive plasma through an extraction assembly, and directing the angled ion beam as an angled reactive ion beam to the substrate at a non-zero angle of incidence with respect to a perpendicular to a main plane of the substrate.

3. The method of claim 2 , the directing the angled deposition beam comprising:

after the first exposure, setting the substrate and plasma chamber to a same potential while the reactive plasma is present in the plasma chamber; and

rotating the substrate through ninety degrees about the perpendicular, wherein the angled deposition beam is directed to the substrate through the extraction assembly at the non-zero angle of incidence.

4. The method of claim 2 , wherein the first exposure comprises scanning the substrate with respect to the extraction assembly along the first direction through a first set of etching scans.

5. The method of claim 2 , wherein the second exposure comprises scanning the substrate with respect to the extraction assembly along the first direction through a first set of deposition scans.

6. The method of claim 2 , the directing the angled deposition beam comprising:

forming a second reactive plasma in a second plasma chamber, the second plasma chamber comprising a second extraction assembly;

setting the substrate and the second plasma chamber to a same potential while the second reactive plasma is present in the second plasma chamber; and

transporting the substrate from a first adjacent the extraction assembly to a second position adjacent the second extraction assembly,

wherein the substrate and the second extraction assembly are arranged such that the angled deposition beam is extracted through the second extraction assembly and is directed to the second side region.

7. The method of claim 6 , the directing the angled deposition beam comprising directing the angled deposition beam at a second non-zero angle of incidence with respect to the perpendicular, different from the non-zero angle of incidence.

8. The method of claim 6 , wherein the reactive plasma comprises a first reactive chemistry, and wherein the second reactive plasma comprises a second reactive chemistry.

9. The method of claim 1 , wherein the set of features comprises a set of cavities, wherein, after the third exposure, the set of cavities has a second dimension, greater than the first dimension along the first direction, and retains the second dimension along the second direction.

10. The method of claim 1 , wherein the protective layer and the mask layer comprise a same material.

11. The method of claim 1 , wherein the set of features comprises a plurality of cavities, wherein after the third exposure, the plurality of cavities are merged to form one cavity.

12. A method of patterning a substrate, comprising:

providing a set of features in a mask layer, the mask layer being disposed on a surface of the substrate and comprising a first material, wherein a given feature comprises a first dimension along a first direction, a second dimension along a second direction, orthogonal to the first direction, and a first thickness; and

repeatedly performing an etch cycle to selectively etch the set of features, the etch cycle comprising:

directing an angled ion beam to the set of features in a first exposure, when the substrate is oriented at a first twist angle, wherein the set of features is etch a first amount along the first direction;

rotating the substrate to a second twist angle after the directing the angled ion beam;

and

directing an angled deposition beam to the set of features in a second exposure, wherein a protective layer is formed on a protected portion of the set of features.

13. The method of claim 12 , the directing the angled ion beam comprising:

forming a reactive plasma in a plasma chamber;

applying a bias voltage between the substrate and the plasma chamber; and

extracting the angled ion beam from the reactive plasma through an extraction assembly, and directing the angled ion beam as an angled reactive ion beam to the substrate at a non-zero angle of incidence with respect to a perpendicular to a main plane of the substrate.

14. The method of claim 13 , the directing the angled deposition beam comprising:

after the first exposure, setting the substrate and plasma chamber to a same potential while the reactive plasma is present in the plasma chamber; and

rotating the substrate through ninety degrees about the perpendicular, wherein the angled deposition beam is directed to the substrate through the extraction assembly at the non-zero angle of incidence.

15. The method of claim 12 , wherein the set of features comprise a set of structures that define at least one cavity, wherein after the first exposure, the set of structures are characterized by a depletion zone in a plane orthogonal to the first direction where mask material is removed,

and wherein after the second exposure the protective layer fills the depletion zone.

16. The method of claim 15 , wherein before a given etch cycle, the set of structures are characterized by a given shape, a height and a spacing, and wherein after the given etch cycle the given shape, the height and the spacing are restored for the set of structures.