Patent ID: 7325419

Claim:
A method of forming an optical waveguide, the method comprising: forming an undercladding layer over a substrate; depositing a phosphorus-doped silicate glass core layer over the undercladding layer with a plasma-enhanced chemical-vapor-deposition process, wherein depositing the core layer comprises: disposing the substrate in a substrate processing chamber; flowing a process gas into the substrate processing chamber, the process gas comprising a silicon source, a first oxygen source, and a phosphorus source; forming a first plasma from the process gas to deposit the phosphorus-doped silicate glass core over the undercladding layer, wherein the phosphorus-doped silicate glass core has a thickness with a thickness greater than 4.5 μm; and exposing the phosphorus-doped silicate glass core layer to a second plasma, wherein the second plasma is formed from gas that includes a second oxygen source and does not include a silicon source; etching the phosphorus-doped silicate glass core layer to produce a plurality of phosphorus-doped silicate glass cores separated by at least 1 μm; and depositing an uppercladding layer over the phosphorus-doped silicate glass cores and in gaps between the phosphorus-doped silicate glass cores.