Patent ID: 11860417
Assignee: CISCO TECHNOLOGY, INC.
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method of fabricating an optical apparatus, the method comprising:
doping a first semiconductor layer to increase a doping level of the first semiconductor layer to a first doping level;
after doping the first semiconductor layer to the first doping level, applying a hard mask layer above the first semiconductor layer, wherein the hard mask layer includes a plurality of features;
after applying the hard mask layer, etching a first trench and a second trench partly through the first semiconductor layer to form a first optical waveguide that includes (i) a first ridge beneath a first feature of the plurality of features and between the first trench and the second trench, (ii) a second ridge beneath a second feature of the plurality of features, and (iii) a third ridge beneath a third feature of the plurality of features, wherein the first trench is between the first ridge and the second ridge, wherein the second trench is between the first ridge and the third ridge, wherein a first bottom of the first trench is exposed, and wherein a second bottom of the second trench is exposed;
after etching the first trench and the second trench, conformally depositing a spacer layer on the plurality of features, the first trench, and the second trench such that spacers are formed on sidewalls of the first trench and the second trench;
after depositing the spacer layer, etching through the spacer layer to expose the first bottom and the second bottom, wherein a width of an exposed portion of the first bottom is defined by the spacers formed on the sidewalls of the first trench, and a width of an exposed portion of the second bottom is defined by the spacers formed on the sidewalls of the second trench;
after etching the spacer layer, doping the exposed portion of the first bottom and the exposed portion of the second bottom to a second doping level greater than the first doping level while the first feature keeps the first ridge at the first doping level; and
depositing a first dielectric layer above the first optical waveguide such that the first dielectric layer extends to the first bottom and the second bottom.