Abstract: A method for making a resistive heater for a planar lightwave circuit. The method includes the step of depositing a resistive layer on a top clad of a planar lightwave circuit. An interconnect layer is subsequently deposited over the resistive layer. The resistive layer can be tungsten and the interconnect layer can be aluminum. The interconnect layer is then etched to define a heater interconnect, wherein the heater interconnect is disposed over the resistive layer and has a first width. The heater interconnect is then masked, and the resistive layer is etched to define a resistive heater. The resistive heater is disposed beneath the heater interconnect and has a second width larger than the first width.

Abstract: A method of making an optical waveguide structure for an active PLC device having a reduced dn/dt birefringence. The method includes the step of forming a waveguide core layer on a bottom cladding, the waveguide core layer having a higher refractive index than the bottom cladding. The waveguide core layer is then etched to define a waveguide core. A top cladding is subsequently formed over the waveguide core and the bottom cladding. The top cladding also has a lower refractive index than the waveguide core. The top cladding is then etched to define a first trench and a second trench parallel to the waveguide core. The first trench and the second trench are configured to relieve a stress on the waveguide core. This stress can be induced by a heater, as in a case where the active PLC is a thermo-optic PLC. The first trench and the second trench can extend from an upper surface of the top cladding to an upper surface of the bottom cladding.

Abstract: A method of forming a localized oxidation having reduced bird's beak encroachment in a semiconductor device by providing an opening in the silicon substrate that has sloped sidewalls with a taper between about 10° and about 75° as measured from the vertical axis of the recess opening and then growing field oxide within the tapered recess opening for forming the localized oxidation.

Abstract: A method for making a resistive heater for a planar lightwave circuit. The method includes the step of depositing a resistive layer on a top clad of a planar lightwave circuit. An interconnect layer is subsequently deposited over the resistive layer. The resistive layer can be tungsten and the interconnect layer can be aluminum. The interconnect layer is then etched to define a heater interconnect, wherein the heater interconnect is disposed over the resistive layer and has a first width. The heater interconnect is then masked, and the resistive layer is etched to define a resistive heater. The resistive heater is disposed beneath the heater interconnect and has a second width larger than the first width.

Abstract: A method of making an optical waveguide structure for an active PLC device having a reduced dn/dt birefringence. The method includes the step of forming a waveguide core layer on a bottom cladding, the waveguide core layer having a higher refractive index than the bottom cladding. The waveguide core layer is then etched to define a waveguide core. A top cladding is subsequently formed over the waveguide core and the bottom cladding. The top cladding also has a lower refractive index than the waveguide core. The top cladding is then etched to define a first trench and a second trench parallel to the waveguide core. The first trench and the second trench are configured to relieve a stress on the waveguide core. This stress can be induced by a heater, as in a case where the active PLC is a thermo-optic PLC. The first trench and the second trench can extend from an upper surface of the top cladding to an upper surface of the bottom cladding.

Abstract: In a planar lightwave circuit, a method of making an optical waveguide that resists core deformation. The method includes a step of forming a core layer on a bottom clad. A waveguide core is formed from the core layer using an etching process. The waveguide core is fabricated to have a higher refractive index than the bottom clad. A silica glass cap layer is then formed over the waveguide core and the bottom clad. A top clad is then formed over the waveguide core, the silica glass cap layer, and the bottom clad. The waveguide core has a higher refractive index than the top clad. The silica glass cap layer maintains the shape of the waveguide core during an anneal process of the top clad. The silica glass cap layer can be deposited using PECVD (plasma enhanced chemical vapor deposition). The silica glass cap layer can be between 0.3 to 2 microns thick. The silica glass cap layer can be undoped silica glass.

Abstract: A method of etching openings in oxide layers is disclosed. A hard mask layer is formed on the oxide layer. The hard mask layer is then patterned by a photoresist layer and an etch is performed to form openings in the hard mask. Next, the patterning layer may be removed and an etch is performed to remove the oxide in the regions defined by the hard mask layer openings. The etch with hard mask has minimized aspect ratio dependency, so that openings of different sizes may be formed simultaneously. An etch that may be carried out with Freon 134a (C.sub.2 H.sub.2 F.sub.4) to provide superior oxide:nitride selectivity is also disclosed. Additionally, the etch may be carried out at high temperature for improved wall profile without loss of selectivity. For deep openings, a two step etch process is disclosed, with a polymer clean step between the etches to remove polymer build up from first etch, and allow the etch to proceed to an increased depth.