Method of fabricating a three dimensional electronic structure
The present disclosure provides methods for fabricating multi-layered electronic architectures in silicon and/or germanium. In particular the disclosure provides an advanced marker design and a methodology for aligning devices on multiple layers of a multi-layered electronic architecture. The disclosure also provides a process for growing a semiconductor material with high quality surfaces.
1. An alignment marker for aligning electronic devices arranged on different planes of a multi-layered semiconductor architecture, the marker having a trenched structure comprising:
a central region arranged to host at least a portion of an electronic device, wherein the central region is located at a bottom of the trenched structure; and
a plurality of elongate regions radially extending from the central region, the plurality of elongate regions being arranged to host a plurality of conductive electrodes for control of the electronic device,
wherein the trenched structure is arranged in a manner such that, when a layer of semiconductor material is grown onto the marker, a further trenched structure is replicated on a surface of the grown layer of semiconductor material.
2. The alignment marker of claim 1 , wherein the replicated trenched structure has a shape that is substantially similar to the shape of the original trenched structure.
3. The alignment marker of claim 1 , wherein the trenched structure further comprises peripheral contact regions at end portions of the elongate regions, the contact regions being arranged to host contact pads.
4. The alignment marker of claim 1 , wherein the wall portion has a depth and a slope such that the marker is replicated with enough accuracy on a surface of the grown layer of semiconductor material when the thickness of the grown layer of semiconductor material is more than 100 nm.
5. The alignment marker of claim 1 , wherein the trenched structure that forms in the grown layer of semiconductor material is located above the marker, with an accuracy of about 20 nm.
6. The alignment marker of claim 1 , wherein the central region of the marker has a surface suitable to host an electronic device fabricated using the lithographic capabilities of an STM or SEM.
7. The alignment marker of claim 1 , wherein the trenched structure has a depth between about 100 nm and about 200 nm.
8. The alignment marker of claim 1 , wherein the width of the trenched structure at half depth is between about 50 nm and about 200 nm.
9. The alignment marker of claim 1 , wherein the trenched structure has a substantially flat region at the bottom of the trenches and the flat region has a width between about 100 nm and about 150 nm.
10. The alignment marker of claim 1 , wherein the semiconductor material is crystalline silicon, crystalline germanium or a silicon-germanium alloy.
11. A method for aligning electronic elements on different planar surfaces of a multi-layered architecture with respect to each other, the method comprising the steps of:
providing a first planar surface of a semiconductor material comprising at least one marker in accordance with any one of the preceding claims and a first electronic element formed on the bottom of the trenched structure of the marker;
imaging the at least one marker with the electronic element;
determining the position of a reference point on the marker by using image data;
determining an offset between the reference point and the electronic element;
growing a further layer of the semiconductor material on the first planar surface in a manner such that the at least one marker is reproduced on a second planar surface; the second planar surface being a planar surface of the grown layer of the semiconductor material; and
forming a second electronic element in the reproduced marker whereby the position of the second electronic element in the reproduced marker is based on the position of the reference point and offset of the first electronic element.
12. The method of claim 11 , wherein the step of forming a second electronic element in the reproduced marker comprises the steps of:
imaging the reproduced marker;
determining the position of the reference point on the reproduced marker by using image data;
determining the position of the second electronic element based on the position of the reference point on the reproduced marker and the offset;
forming the second electronic element at the position of the second electronic element.
13. The method of claim 11 , wherein the position of a reference point on the marker, on the first planar surface or the grown surface, is determined by finding an intersection region of the central axis of each of the elongate trenched regions.
14. The method of claim 11 , wherein the second planar surface is the surface of an epitaxial silicon layer formed on the first planar surface.
15. The method of claim 11 , wherein the method comprises the step of forming a narrower neck portion in one of the elongate regions of the trenched structure and using the neck portion as a reference for positioning the electronic element.
16. The method of claim 11 , wherein the semiconductor material is crystalline silicon, crystalline germanium or a silicon-germanium alloy.
17. A multi-layered electronic architecture comprising a plurality of electronic elements distributed on two or more planes of the architecture, the electronic elements being vertically aligned across planes with an accuracy below 20 nm using a marker in accordance with claim 1 .
18. The multi-layered electronic architecture of claim 17 , wherein the architecture comprises a silicon layer.
19. The multi-layered electronic architecture of claim 17 , wherein the architecture comprises:
a plurality of qubit elements disposed in a two-dimensional matrix arrangement across the architecture; and
a plurality of control members, each control member being arranged to control a plurality of qubits of the architecture.