Structures including a photonic device and an undercut
Structures including a photonic device, such as a spot-size converter, and an undercut, and related methods. The structure comprises a photonic device, a semiconductor substrate, and a dielectric layer disposed between the photonic device and the semiconductor substrate. The dielectric layer includes a plurality of D-shaped openings that are laterally offset from the photonic device, and each of the plurality of D-shaped openings has a first sidewall portion that is curved and a second sidewall portion that is substantially planar.
1 . A structure comprising:
a photonic device;
a semiconductor substrate; and
a dielectric layer disposed between the photonic device and the semiconductor substrate, the dielectric layer including a first plurality of D-shaped openings that are laterally offset from the photonic device, and each of the first plurality of D-shaped openings having a first sidewall portion that is curved and a second sidewall portion that is substantially planar.
2 . The structure of claim 1 wherein the semiconductor substrate includes a cavity beneath the photonic device, and the first plurality of D-shaped openings intersect the cavity in the semiconductor substrate.
3 . The structure of claim 1 wherein the dielectric layer includes a second plurality of D-shaped openings that are laterally offset from the photonic device, each of the second plurality of D-shaped openings has a first sidewall portion that is curved and a second sidewall portion that is substantially planar, and the photonic device is laterally disposed between the first plurality of D-shaped openings and the second plurality of D-shaped openings.
4 . The structure of claim 3 wherein the semiconductor substrate includes a cavity beneath the photonic device, and the first plurality of D-shaped openings and the second plurality of D-shaped openings intersect the cavity in the semiconductor substrate.
5 . The structure of claim 3 wherein the first plurality of D-shaped openings are arranged in a first row, and the second plurality of D-shaped openings are arranged in a second row.
6 . The structure of claim 3 wherein the photonic device is disposed between a first outer edge of a keep-out lane and a second outer edge of a keep-out line, the second sidewall portion of each of the first plurality of D-shaped openings coincides with the first outer edge of the keep-out lane, and the second sidewall portion of each of the second plurality of D-shaped openings coincides with the second outer edge of the keep-out lane.
7 . The structure of claim 1 wherein the semiconductor substrate includes a cavity beneath the photonic device, and the first plurality of D-shaped openings intersect the cavity in the semiconductor substrate.
8 . The structure of claim 1 wherein the photonic device is a spot-size converter.
9 . The structure of claim 1 wherein each of the first plurality of D-shaped openings has a cross-sectional profile that is a disk segment.
10 . The structure of claim 9 wherein each of the first plurality of D-shaped openings has a height, the first sidewall portion of each of the first plurality of D-shaped openings is an arc of the disk segment projected over the height, and the second sidewall portion of each of the first plurality of D-shaped openings is a chord of the disk segment projected over the height.
11 . The structure of claim 10 wherein the arc has an arc length that is greater than 180°.
12 . The structure of claim 1 wherein each of the first plurality of D-shaped openings has a cross-sectional profile that is an elliptical segment.
13 . The structure of claim 1 wherein the second sidewall portion of each of the first plurality of D-shaped openings is closer to the photonic device than the first sidewall portion.
14 . The structure of claim 1 wherein the first plurality of D-shaped openings are arranged in a row.
15 . The structure of claim 14 wherein the photonic device includes a waveguide core having a section with a longitudinal axis, and the row is aligned parallel to the longitudinal axis.
16 . The structure of claim 15 wherein the second sidewall portion of each of the first plurality of D-shaped openings is spaced from the longitudinal axis of the section of the waveguide core.
17 . The structure of claim 14 wherein the photonic device includes a waveguide core having a section with a longitudinal axis, and the row is tilted at an angle relative to the longitudinal axis.
18 . A method comprising:
forming a photonic device, wherein a dielectric layer is disposed between the photonic device and a semiconductor substrate; and
forming a first plurality of D-shaped openings in the dielectric layer that are laterally offset from the photonic device, wherein each of the first plurality of D-shaped openings has a first sidewall portion that is curved and a second sidewall portion that is substantially planar.
19 . The method of claim 18 further comprising:
forming a second plurality of openings in the dielectric layer, wherein the second plurality of openings are round and have a diameter greater than or equal to 10 micrometers.
20 . The method of claim 19 further comprising:
forming a groove in the semiconductor substrate at a location of the second plurality of openings.