Method and system for fabricating regrown fiducials for semiconductor devices
A method of forming regrown fiducials includes providing a III-V compound substrate having a device region and an alignment mark region. The III-V compound substrate is characterized by a processing surface. The method also includes forming a hardmask layer 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 second set of openings in the alignment mark region exposing a second surface portion of the processing surface and etching the first surface portion and the second surface portion of the III-V compound substrate using the hardmask layer as a mask to form a plurality of trenches. The method also includes epitaxially regrowing a semiconductor layer in the trenches to form the regrown fiducials extending to a predetermined height over the processing surface in the alignment mark region.
1 . A method of forming regrown 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 hardmask layer 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 second set of openings in the alignment mark region exposing a second surface portion of the processing surface of the III-V compound substrate;
etching the first surface portion and the second surface portion of the III-V compound substrate using the hardmask layer as a mask to form a plurality of trenches; and
epitaxially regrowing a semiconductor layer in the plurality of trenches to form the regrown fiducials extending to a predetermined height over the processing surface of the III-V compound substrate in the alignment mark region.
2 . The method of claim 1 wherein the III-V compound substrate comprises a GaN substrate and a plurality of epitaxial III-V layers.
3 . The method of claim 1 wherein the each of the plurality of trenches comprise a depth of about 0.8 μm.
4 . The method of claim 1 wherein the plurality of trenches in the device region each have a width of about 2 μm.
5 . The method of claim 1 wherein a width of the regrown fiducials is between 0.1 μm and 1 μm and a pitch of the regrown fiducials is between 0.2 μm and 1.2 μm.
6 . The method of claim 5 wherein the width is between 0.4 μm and 0.6 μm and the pitch is between 0.5 μm and 1.2 μm.
7 . The method of claim 1 wherein the plurality of trenches in the device region are characterized by a first pitch and the regrown fiducials are characterized by a second pitch less than the first pitch.
8 . The method of claim 1 wherein a set of regrown fiducials in the alignment mark region forms an alignment mark.
9 . The method of claim 1 wherein the regrown fiducials are elongated and a length of the regrown fiducials is parallel to an m-plane of the III-V compound substrate.
10 . The method of claim 1 wherein the first set of openings comprises an array of elongated openings arranged in parallel to each other configured to form a plurality of semiconductor fins.
11 . The method of claim 10 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.
12 . The method of claim 1 wherein the III-V compound substrate comprises an n-GaN epitaxial layer and the semiconductor layer comprises a p-GaN epitaxial layer.
13 . The method of claim 1 wherein epitaxially regrowing the semiconductor layer is self-limiting in the alignment mark region.