Vertical optical via and method of fabrication

A method for providing a vertical optical via for a semiconductor substrate having a front surface and a back side, the method comprising:

• providing a hard mask on the front surface of the semiconductor substrate, the hard mask having an aperture therein, a first portion of the semiconductor substrate being exposed by the aperture;
• removing the first portion of the semiconductor substrate to form a via hole in the semiconductor substrate, the via hole having a sidewall, a bottom and a diameter of at least twenty micrometers and not more than one hundred micrometers;
• providing a cladding layer in the via hole, the step of providing the cladding layer including thermally oxidizing the sidewall, the cladding layer having a first index of refraction;
• depositing a core layer, a portion of the core layer residing in the via hole, the core layer having a second index of refraction greater than the first index of refraction;
• performing a planarization;
• oxidizing the core layer;
• depositing a first oxide layer on the front surface of the semiconductor substrate;
• forming at least a first photonic device on first oxide layer and aligned with the at least one core layer;
• depositing a second oxide layer on the at least one photonic device;
• removing a second portion of the semiconductor substrate including the back side and the bottom of the via hole to expose a bottom portion of the at least one core layer and a bottom surface of the semiconductor substrate, the vertical optical via including the at least one cladding layer and the at least one core layer, the vertical optical via extending from the front surface of the semiconductor substrate to the bottom surface;
• depositing a third oxide layer on the bottom surface after the step of removing the second portion of the semiconductor substrate;
• providing at least a second photonic device on the third oxide layer, the at least the second photonic device being aligned with the at least one core layer;
• and
• depositing a third oxide layer on the second photonic device.