Optical interconnect modules with polymer waveguide on silicon substrate
An optical interconnect device on a silicon substrate is disclosed which includes a trench having two slanted side walls opposite to each other, a number of polymer waveguides formed in the trench, each including a straight portion and two end reflectors formed on the slanted side walls of the trench, a light source and an optical receiver disposed on an insulated layer on the silicon surface outside the trench. Conductive lines are patterned on the insulating layer and connects to the light source and the optical receiver. The light source and the optical receiver are aligned respectively to the two end reflectors of each polymer waveguide such that an optical path is formed from the light source device through the plurality of polymer waveguides to the optical receiver device, via reflection by the two end reflectors. A fabrication method to build the device is disclosed thereof.
1. A method of fabricating an optical interconnect apparatus, comprising:
providing a silicon substrate having a top silicon surface;
forming a trench on the top silicon surface;
patterning a first and a second slanted side walls of the trench, wherein the first and second slanted sidewalls are opposite to each other;
forming a plurality of polymer waveguides in the trench, comprising:
depositing a first polymer cladding layer in the trench covering a bottom of the trench, the first and second slanted side walls, followed by depositing a polymer core layer on the first polymer cladding layer;
patterning the polymer core layer and covering the patterned polymer core layer with a second polymer cladding layer, wherein the plurality of polymer waveguides each has one straight portion and two angled end reflectors, wherein the two angled end reflectors are formed on the first and second slanted sidewalls;
depositing an insulating layer on the silicon top surface outside the trench;
patterning conductive lines in the insulating layer;
growing solder bumps on conductive lines for flip chip mounting with bond pads;
connecting a light source device with one of the conductive lines near the first slanted side wall of the trench and an optical receiver device with another one of the conductive lines near the second slanted side wall of the trench; and
aligning the light source device and the optical receiver device with the slanted end reflectors of the plurality of polymer waveguides.
2. A method of fabricating an optical interconnect apparatus in claim 1 , wherein the light source device comprises a vertical cavity surface emitting laser (VCSEL) and wherein the optical receiver device comprises a photodetector (PD).
3. A method of fabricating an optical interconnect apparatus in claim 1 , wherein patterning the first and second slanted side walls of the trench comprises applying a variable lithography exposure energy to achieve smooth and accurate slanted angles.
4. A method of fabricating an optical interconnect apparatus in claim 1 , wherein the slanted end reflectors have approximately 45 degree slanted angles.
5. The method of fabricating an optical interconnect apparatus in claim 1 , wherein patterning the plurality of conductive lines comprises forming trenches and filling a metal in the trenches, followed by removing excess metal by polishing (CMP) or by selective etch to clean up the metal outside the trenches.
6. The method of fabricating an optical interconnect apparatus in claim 1 , wherein patterning the plurality of conductive lines comprises depositing a metal layer, patterning the metal layer into lines by selective etch, electroplating, or laser writing.
7. The method of fabricating an optical interconnect apparatus in claim 6 , wherein the metal layer includes a metal from one of aluminum, tungsten, stainless steel, copper.