Fabrication methods

1. A method of selectively patterning a device structure, the method comprising:

forming, on a substrate, a hollow shadow wall having a hollow interior cavity with no wall material, the hollow shadow wall being formed of a base lying on a surface of the substrate, and one or more side walls connected to the base, the one or more side walls extending away from the surface of the substrate and around the base to define an internal cavity of the hollow shadow wall;

selectively patterning a device structure supported by the substrate adjacent to the shadow wall, by using a deposition beam to selectively deposit a layer of deposition material on the device structure, the deposition beam having a non-zero angle of incidence relative to a normal to the surface of the substrate and an orientation in a plane of the substrate's surface, such that the shadow wall prevents deposition on a surface portion of the device structure within a shadow region defined by the shadow wall; and

removing the one or more side walls of the hollow shadow wall once the device structure has been selectively patterned.

2. The method of claim 1 , wherein the hollow shadow wall is formed by deposition of at least one wall material in an area of the substrate's surface left exposed by a partial resist layer on the substrate's surface, the partial resist layer having a top-surface and at least one inner side-surface extending from the top-surface to the substrate's surface, so as to create a boundary of an exposed area, wherein the partial resist layer is removed once the hollow shadow wall has been formed.

3. The method of claim 2 , wherein the hollow shadow wall is formed from at least one deposited layer of the wall material, which covers the top-surface of the partial resist layer, the inner side-surface of the partial resist layer and the exposed area of the substrate's surface, the one or more side walls of the hollow shadow wall comprising the wall material covering the inner side-surface of the partial resist layer prior to its removal and the base of the hollow shadow wall comprising the wall material covering the exposed area of the substrate's surface, wherein the wall material covering the top-surface of the partial resist layer is removed with the partial resist layer leaving the hollow shadow wall supported by the substrate.

4. The method of claim 3 , wherein the inner-side surface of the partial resist layer has at least one serrated region, such that a corresponding region of the one or more side walls exhibits corresponding serrations, which increase the rigidity of the one or more side walls.

5. The method of claim 1 , wherein the one or more side walls surround the entirety of the base in a plane in which the surface of the substrate substantially lies.

6. The method of claim 1 , wherein the one or more side walls are removed via a mechanical process.

7. The method of claim 2 , wherein a mask layer is formed on the substrate, the mask layer leaving at least one device region of the substrate exposed in which the device structure is to be grown, the partial resist layer being deposited on the mask layer with the exposed area of the substrate's surface for forming the hollow shadow wall being adjacent to the exposed device region, the device being grown from device material in the exposed region via selective area growth of the device material.

8. A method of selectively patterning a device component, the method comprising:

forming on a surface of a substrate a partial layer of resist so as to form at least one exposed area of a substrate surface exposed, the partial resist layer having a top-surface lying substantially parallel to the surface of the substrate and an inner side-surface extending from the top-surface to the surface of the substrate, so as to create a boundary of the at least one exposed area where the inner side-surface meets the substrate's surface;

forming a shadow wall having a hollow interior cavity with no wall material in the exposed area from wall material deposited on the inner side-surface of the partial resist layer, the wall material extending to the exposed area of the substrate surface for supporting the shadow wall after the resist layer is removed;

removing the partial resist layer from the substrate thereby leaving the shadow wall supported by the substrate; and

using a deposition beam to selectively deposit a layer of deposition material on a device component supported by the substrate adjacent to the shadow wall, the deposition beam having a non-zero angle of incidence relative to a normal to the surface of the substrate and an orientation in a plane of the substrate's surface, such that the shadow wall prevents deposition on a surface portion of the device component within a shadow region defined by the shadow wall.

9. A method according to claim 8 , wherein the wall material only partially fills a cavity defined by the inner side-surface, such that the shadow wall has an internal cavity.

10. A method according to claim 9 , wherein the wall material forms a layer over the exposed area.

11. A method according to claim 9 , wherein at least a portion of the inner-side surface is serrated so as to increase a rigidity of the shadow wall.

12. A method according to claim 8 , comprising a step of removing one or more side walls of the shadow wall after the selective deposition of the deposition material, the one or more side walls extending away from the surface of the substrate prior to their removal to define the internal cavity.

13. A method according to claim 12 , wherein the one or more shadow walls are removed mechanically.

14. A method according to claim 8 , wherein the boundary of the exposed area has two edges which taper inwards towards each other in a plane lying substantially parallel to the substrate's surface.

15. A method according to claim 14 , wherein the edges taper inwardly to an elongated tip region of the exposed area.

16. A method according to claim 15 , wherein the elongated tip region extends along a tip axis and defines the shadow region during selective deposition of the deposition material, the shadow region having a width dependent on a width of the elongated tip region perpendicular to the tip axis.

17. A method according to claim 8 , wherein the deposition material is a superconductor and/or the device component formed of a semiconductor material.

18. A method of selectively patterning a device structure, the method comprising:

forming a shadow wall having a hollow interior cavity with no wall material on a surface of a substrate, the shadow wall comprising one or more side walls extending away from the surface of the substrate, the one or more side walls having at least one serrated region that increases a rigidity of the one or more side walls;

using a deposition beam to selectively deposit a layer of deposition material on a device structure supported by the substrate adjacent to the shadow wall, the deposition beam having a non-zero angle of incidence relative to a normal to the surface of the substrate and an orientation in a plane of the substrate's surface, such that the shadow wall prevents deposition on a surface portion of the device structure within a shadow region defined by the shadow wall, thereby selectively patterning the device structure.

19. The method of claim 18 , wherein the shadow wall is a hollow shadow wall comprising a base on the substrate's surface connected to the one or more side walls.

20. The method of claim 19 , wherein the one or more side walls extend around the base to define an internal cavity of the shadow wall.