Method and system for fabricating fiducials for processing of semiconductor devices
A method of forming alignment marks, each alignment mark including a plurality of fiducials, includes providing a III-V compound substrate having a device region and an alignment mark region. The method also includes forming a first hardmask in the device region and a hardmask structure in the alignment mark region, etching a first surface portion of the III-V compound substrate to form a plurality of trenches in the device region, and epitaxially regrowing a semiconductor layer in the trenches. The method further includes forming a second mask in the device region and a patterned structure in the alignment mark region. The patterned structure includes a set of masked regions corresponding to the plurality of fiducials and a second set of openings. The method also includes forming the plurality of fiducials.
1. A method of forming alignment marks, each alignment mark including a plurality of fiducials, the method comprising:
providing a III-V compound substrate having a device region and an alignment mark region, wherein the III-V compound substrate is characterized by a processing surface;
forming a first hardmask having a first set of openings in the device region exposing a first surface portion of the processing surface of the III-V compound substrate and a hardmask structure in the alignment mark region;
etching the first surface portion of the III-V compound substrate using the first hardmask as a mask to form a plurality of trenches in the device region;
epitaxially regrowing a semiconductor layer in the trenches;
forming a second mask having one or more openings in the device region and a patterned structure in the alignment mark region, wherein the patterned structure includes a set of masked regions corresponding to the plurality of fiducials and a second set of openings; and
removing, using the second mask, the first hardmask in the device region and a portion of the hardmask structure in the alignment mark region corresponding to the second set of openings to form the plurality of fiducials.
2. The method of claim 1 wherein each of the plurality of fiducials correspond to one of the set of masked regions.
3. The method of claim 1 wherein the second set of openings in the patterned structure are positioned between masked regions of the set of masked regions.
4. The method of claim 1 wherein the III-V compound substrate comprises a GaN substrate and a plurality of epitaxial III-V layers.
5. The method of claim 4 wherein the plurality of epitaxial III-V layers comprises an n-GaN epitaxial layer and a p-GaN epitaxial layer.
6. The method of claim 1 wherein the trenches each have a depth of about 0.8 μm and a width of about 1.8 μm.
7. The method of claim 1 wherein the plurality of fiducials each have a width between 0.1 μm and 1 μm and a pitch between 0.2 μm and 1.2 μm.
8. The method of claim 1 wherein the trenches in the device region are characterized by a first pitch and the plurality of fiducials are characterized by a second pitch less than the first pitch.
9. The method of claim 1 wherein the device region includes an array of FinFETs and wherein:
a set of fiducials of the plurality of fiducials is characterized by a first pitch between each of the plurality of fiducials in the set of fiducials; and
a second pitch associated with the array of FinFETs is greater than the first pitch.
10. The method of claim 1 wherein a set of the plurality of fiducials in the alignment mark region form an alignment mark.
11. The method of claim 1 wherein each of the plurality of fiducials are elongated and a length of each of the plurality of fiducials is parallel to an m-plane of the III-V compound substrate.
12. The method of claim 1 wherein the first set of openings comprise an array of elongated openings arranged in parallel to each other configured to form a plurality of semiconductor fins.
13. The method of claim 12 wherein the elongated openings each have a width in a range between about 0.2 μm and about 0.3 μm, a length in a range between about 10 μm and about 1000 μm, and a pitch between two adjacent elongated openings is in a range between about 1.9 μm and about 10 μm.