Semiconductor optical modulator and method for manufacturing semiconductor optical modulator

1. A semiconductor optical modulator, comprising:

a substrate having a principal surface;

a waveguide disposed on the principal surface of the substrate, the waveguide extending in a first direction;

a first electrode disposed on the waveguide, the first electrode being in contact with an upper surface of the waveguide;

a first wiring connected to the first electrode, the first wiring extending in a second direction intersecting the first direction;

a build-up portion connected to the first wiring;

a second wiring connected to the build-up portion, the second wiring extending in a plane parallel to the principal surface of the substrate;

a first resin layer disposed between the first wiring and the substrate, the first resin layer embedding the waveguide; and

a second resin layer disposed between the first resin layer and the second wiring, the Second resin layer embedding the first electrode and the build-up portion, wherein

the build-up portion extends along a third direction, the third direction intersecting the principal surface of the substrate,

the second wiring is disposed on the resin layer, and

the resin layers embed the first wiring.

2. The semiconductor optical modulator according to claim 1 ,

wherein the build-up portion is arranged on the first wiring by being spaced apart from the first electrode.

3. The semiconductor optical modulator according to claim 1 , further comprising:

another waveguide disposed on the substrate to form a pair of said waveguides extending in the first direction;

an optical coupler disposed on the substrate, the optical coupler optically connecting said waveguides of the pair; and

another second wiring disposed on the resin layer to form a pair of said second wirings extending in the first direction,

wherein the pair of said waveguides is arranged between said second wirings of the pair thereof.

4. The semiconductor optical modulator according to claim 1 , further comprising:

a plurality of first electrodes disposed on the waveguide,

a plurality of first wirings connected to corresponding of the first electrodes, and

a plurality of build-up portions connected to corresponding of the first electrodes, wherein

the first electrodes are spaced apart from each other, and

the build-up portions are each connected with the second wiring.

5. The semiconductor optical modulator according to claim 1 , further comprising a first insulating film composed of an inorganic silicon compound, the first insulating film disposed between the first resin layer and the second resin layer,

wherein the first wiring is disposed on the first insulating film.

6. The semiconductor optical modulator according to claim 5 , further comprising a second insulating film composed of an inorganic silicon compound, the second insulating film being disposed on the second resin layer,

wherein the second wiring is disposed on the second insulating film.

7. The semiconductor optical modulator according to claim 1 , wherein

the build-up portion includes a barrier metal layer and an inner metal layer,

the barrier metal layer is in contact with the resin layer, and

the inner metal layer is in contact with a surface of the barrier metal layer.

8. The semiconductor optical modulator according to claim 1 ,

wherein the waveguide includes a lower contact layer disposed on the principal surface of the substrate, a lower cladding layer disposed on the lower contact layer, a core layer disposed on the lower cladding layer, and an upper cladding layer disposed on the core layer, and

wherein the lower contact layer has a larger width than a width of the core layer.

9. The semiconductor optical modulator according to claim 8 , further comprising:

an isolation mesa disposed on the principal surface of the substrate, the isolation mesa including the lower contact layer;

a second electrode connected to an upper surface of the isolation mesa;

a third wiring connected to the second electrode;

a ground build-up portion connected to the third wiring; and

a fourth wiring connected to the ground build-up portion,

wherein the ground build-up portion extends along a fourth direction intersecting the principal surface of the substrate, and

wherein the fourth wiring is disposed on the resin layer.

10. A method for manufacturing a semiconductor optical modulator, comprising the steps of:

forming a waveguide on a principal surface of a substrate, the waveguide extending in a first direction;

forming a first resin layer on the principal surface of the substrate, the first resin layer embedding the waveguide;

forming a first opening in the first resin layer on the waveguide h etching the first resin layer;

forming a first electrode in the first opening, the first electrode being in contact with an upper surface of the waveguide;

forming a first wiring on the first electrode and on the first resin layer, the first wiring having a portion extending in a second direction intersecting the first direction;

forming a second resin layer on the first wiring and on the first resin layer, the second resin layer embedding the first wiring;

forming a second opening in the second resin layer on the first wiring by etching the second resin layer, the second opening extending in a third direction intersecting the principal surface of the substrate; and

forming a build-up portion in the second opening, and a second wiring on the second resin layer, simultaneously.

11. The method according to claim 10 , wherein, in the step of forming the second opening, the second opening has a width smaller than a width of the first wiring.

12. The method according to claim 10 , wherein, in the step of forming the second opening, the second opening is arranged on the first wiring by being spaced apart from the first electrode.