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

1. A method of patterning a substrate, comprising:

generating a plasma in a plasma chamber;

providing a substrate, on a substrate stage adjacent the plasma chamber, the substrate comprising a layer having a set of features;

providing an extraction assembly along a side of the plasma chamber, between the plasma and the substrate stage;

sending a first control signal to apply a first bias voltage between the plasma chamber and the substrate while the substrate stage is arranged at a first twist angle, wherein an angled ion beam is directed at a first energy to the substrate in a first exposure;

sending a second control signal to apply a second bias voltage between the plasma chamber and the substrate; and

sending a third control signal to perform rotation of the substrate stage to a second twist angle, wherein the angled ion beam is directed at a second energy to the substrate in a second exposure, when the substrate stage is arranged at the second twist angle,

wherein the angled ion beam performs a first etch of a first side region of the set of features to a first amount along a first direction, during the first exposure, and

wherein the angled ion beam performs a deposit of a protective layer on a second side region of the set of features, the second side region being oriented perpendicularly with respect to the first side region, during the second exposure.

2. The method of claim 1 , further comprising

sending a further control signal to apply the first bias voltage between the plasma chamber and the substrate; and

sending concurrently with the further control signal, an additional control signal to rotate the substrate stage to the first twist angle,

wherein in a third exposure the reactive angled ion beam performs a second etch of the first side region of the set of features to a second amount along the first direction, after the reactive angled ion beam deposits the protective layer on the second side region.

3. The method of claim 1 , wherein the first bias voltage is a negative bias, and wherein the second bias voltage is zero bias.

4. The method of claim 1 , wherein the angled ion beam has a ribbon beam shape.

5. The method of claim 1 , wherein the plasma chamber is a cylindrical plasma chamber, and wherein the extraction assembly comprises an elongated extraction aperture, the elongated extraction aperture being bounded by a nozzle structure that extends radially outwardly from the plasma chamber.

6. The method of claim 1 , wherein the first etch of the first side region and the deposit of the protective layer on the second side region constitute an etch cycle, the method further comprising: repeating the etch cycle.

7. A method of patterning a substrate, comprising:

providing a set of cavities in a mask layer, the mask layer being disposed on a layer of the substrate, the set of cavities comprising an endwall and a sidewall;

directing an angled ion beam in a plurality of exposures to the mask layer to elongate the set of cavities along a first direction within a main plane of the substrate,

wherein the angled ion beam is directed to the endwall at a first ion energy in a first exposure of the plurality of exposures, and

wherein the angled ion beam is directed to the sidewall in a second exposure of the plurality of exposures at a second ion energy less than the first ion energy, wherein a protective layer is formed on the sidewall during the second exposure.

8. The method of claim 7 , wherein a tip-to-tip spacing between adjacent cavities of the plurality of cavities is reduced after the plurality of directional etch operations.

9. The method of claim 7 , wherein the angled ion beam is provided as an angled reactive ion beam to the substrate at a non-zero angle of incidence with respect to a perpendicular to the main plane of the substrate.