SOI substrate for integration of opto-electronics with SiGe BiCMOS

1. A structure comprising:

a silicon-on-insulator substrate comprising a buried oxide layer having a first thickness situated over a bulk silicon substrate and a silicon layer having a second thickness situated directly on said buried oxide layer;

a trench situated in said silicon layer and said buried oxide layer, said trench having a bottom surface and a first and a second sidewall, said trench being situated adjacent to an optical region of said silicon-on-insulator substrate, wherein said optical region comprises at least one optical component;

an epitaxial layer situated in said trench and situated on said bulk silicon substrate, said epitaxial layer and said bulk silicon substrate forming a bulk silicon electronic region of said silicon-on-insulator substrate;

a base of a bipolar transistor situated on said epitaxial layer, said base comprising silicon-geranium;

wherein said optical region of said silicon-on-insulator substrate is optimized for said at least one optical component by controlling said first thickness of said buried oxide layer and said second thickness of said silicon layer.

2. The structure of claim 1 further comprising a first spacer and a second spacer, said first spacer being situated between said first sidewall of said trench and said epitaxial layer said second spacer being situated between said second sidewall of said trench and said epitaxial layer.

3. The structure of claim 1 further comprising an interlayer dielectric layer situated over said silicon-on-insulator substrate.

4. The structure of claim 3 further comprising a first interconnect metal segment and a second interconnect metal segment situated on said interlayer dielectric layer, said first interconnect metal segment connected to said optical region by a first contact and said second interconnect metal segment connected to said base of said bipolar transistor by a second contact.

5. The structure of claim 1 further comprising an emitter of said bipolar transistor situated on said base.

6. The structure of claim 1 wherein said base is situated over a collector of said bipolar transistor, said collector being situated in said epitaxial layer.

7. The structure of claim 1 wherein said base comprises single-crystal silicon-germanium.

8. The structure of claim 1 wherein said silicon-on-insulator substrate has a planar surface, said planar surface including a top surface of said silicon layer and a top surface of said epitaxial layer.

9. The structure of claim 1 wherein said trench has a depth of between approximately 1.5 microns and approximately 2.0 microns.

10. The structure of claim 1 wherein said second thickness of said silicon layer is between approximately 3000.0 Angstroms and approximately 6000.0 Angstroms.

11. A method comprising:

providing a silicon-on-insulator substrate comprising a buried oxide layer having a first thickness situated over a bulk silicon substrate and a silicon layer having a second thickness situated directly on said buried oxide layer;

forming a trench in said silicon layer and said buried oxide layer, said trench exposing a portion of said bulk silicon substrate, said trench being situated adjacent to an optical region of said silicon-on-insulator substrate, wherein said optical region comprises at least one optical component;

forming an epitaxial layer on said exposed portion of said bulk silicon substrate in said trench, said epitaxial layer and said bulk silicon substrate forming a bulk silicon electronic region of said silicon-on-insulator substrate;

forming a base of a bipolar transistor on said epitaxial layer in said bulk silicon electronic region;

wherein said base of said bipolar transistor comprises silicon-germanium, wherein said optical region of said silicon-on-insulator substrate is optimized for said at least one optical component by controlling said first thickness of said buried oxide layer and said second thickness of said silicon layer.

12. The method of claim 11 further comprising a step of forming a spacer adjacent to a sidewall of said trench after said step of forming said trench and prior to said step of forming said epitaxial layer.

13. The method of claim 11 further comprising steps of:

forming an interlayer dielectric layer over said silicon-on-insulator substrate;

forming a first and a second contact in said interlayer dielectric layer, said first contact being situated over said optical region and said second contact being situated over said bipolar transistor.

14. The method of claim 13 further comprising steps of:

forming a first and a second interconnect metal segment on said interlayer dielectric layer, said first interconnect metal segment being situated over said first contact and said second interconnect metal segment being situated over said second contact.

15. The method of claim 11 wherein said step of forming said base of said bipolar transistor comprises steps of:

forming a first and a second field oxide region in said bulk silicon electronic region;

growing said base of said bipolar transistor on said epitaxial layer between said first field oxide region and said second field oxide region.

16. The method of claim 11 wherein a top surface of said epitaxial layer and a top surface of said silicon layer form a substantially planar surface.

17. The method of claim 11 further comprising a step of forming an emitter on said base of said bipolar transistor.

18. The method of claim 11 wherein said step of forming said epitaxial layer comprises using a selective epitaxial process to grow said epitaxial layer on said exposed portion of said bulk silicon substrate.

19. The method of claim 11 wherein said trench has a depth of between approximately 1.5 microns and approximately 2.0 microns.

20. The method of claim 11 wherein said second thickness of said silicon layer is between approximately 3000.0 Angstroms and approximately 6000.0 Angstroms.