Method of making photonic devices with SOG interlayer

1. A method of making a photonic device including an optical waveguide, comprising:

depositing a first optical layer over a substrate by plasma enhanced chemical vapor deposition;

depositing a first thin spin-on glass interlayer over said first optical layer to smooth out surface roughness in said first optical layer; and

depositing a second optical layer over said thin spin-on glass interlayer by plasma enhanced chemical vapor deposition;

wherein said first and second optical layers form part of said waveguide; and

wherein said optical waveguide comprises a buffer layer, a core layer, and a cladding layer, said first and second optical layers providing respectively said buffer layer and said core layer, and wherein said method further comprises:

depositing a second spin-on glass interlayer over said core layer to smooth out surface roughness in said core layer, and

depositing a third optical layer over said second thin spin-on glass interlayer by plasma enhanced chemical vapor deposition to form said cladding layer.

2. A method as claimed in claim 1 , wherein said first and second spin-on glass interlayers have a thickness in the range of 0.01 μm to 2.0 μm.

3. A method as claimed in claim 1 , wherein after forming each said spin-on glass interlayer, said substrate is subjected to thermal treatment to cause densification of said spin-on glass interlayer and the underlying optical layer.

4. A method as claimed in claim 3 , wherein said thermal treatment takes place at a temperature in the range between 400° C. and 1200° C.

5. A method as claimed in claim 1 , wherein an additional buffer layer is first deposited on a backside of said substrate to prevent warpage.

6. A method as claimed in claim 1 , wherein each said spin-on glass interlayer is inorganic phosphosilicate spin-on glass.

7. A method as claimed in claim 1 , wherein each said spin-on glass interlayer is a silicate-based solution containing one or more of the following elements: Boron, Aluminum, Gallium, Indium, Thallium, Carbon, Germanium, Lead, Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Titanium, Zirconium, Hafnium, or any other rare earths elements (atomic numbers 57 to 71).

8. A method as claimed in claim 1 , wherein each said spin-on glass interlayer is a siloxane-based solution containing one or more of the following elements: Boron, Aluminum, Gallium, Indium, Thallium, Carbon, Germanium, Lead, Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Titanium, Zirconium, Hafnium, or any other rare earths elements (atomic numbers 57 to 71).

9. A method as claimed in claim 1 , wherein each said spin-on glass interlayer is made of another precursor leading to an inorganic or a semi-organic layer containing one or more of the following elements: Carbon, Silicon, Boron, Aluminum, Gallium, Indium, Thallium, Carbon, Germanium, Lead, Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Titanium, Zirconium, Hafnium, or any other rare earths elements (atomic numbers 57 to 71).

10. A method as claimed in claim 1 , wherein each said spin-on glass interlayer comprises a plurality of sublayers, a bottom said sublayer providing a refractive index matching layer with the underlying optical layer and a top one of said sublayers providing a refractive index matching layer with an overlying optical layer.

11. A method as claimed in claim 1 , wherein said optical layers are made of silica.

12. A method of making a photonic device including an optical waveguide, comprising:

depositing an optical buffer layer on the front side of a wafer;

forming a first thin spin-on glass layer over said optical buffer layer;

subjecting the wafer to a first stabilizing thermal treatment;

depositing an optical core layer over said first thin spin-on glass layer;

forming a second thin spin-on glass layer over said core layer;

subjecting the wafer to a second stabilizing thermal treatment;

depositing an optical cladding layer over said second thin spin-on glass layer; and

subjecting said wafer to a third stabilizing thermal treatment; and

wherein said buffer layer, said core layer, and said cladding layer form said optical waveguide.

13. A method as claimed in claim 12 , wherein prior to depositing said optical buffer layer an anti-warping buffer layer is deposited on the backside of said wafer, and said wafer is subject to a further stabilizing thermal treatment.

14. A method as claimed in claim 12 , wherein said stabilizing thermal treatments take place between 400° C. and 1200° C.

15. A method as claimed in claim 12 , wherein said stabilizing thermal treatments take place at a temperature of at least 600° C.

16. A method as claimed in claim 12 , wherein said stabilizing thermal treatments take place at a temperature of about 800° C.

17. A method as claimed in claim 12 , wherein said optical layers are deposited by plasma enhanced vapor deposition.

18. A method as claimed in claim 12 , wherein said optical layers are fabricated by a technique selected from the group consisting of: Flame Hydrolysis, Low Pressure Chemical Vapor Deposition (LPCVD), Electron Cyclotron Resonance Deposition (ECRD), Bias Sputtering Deposition (BSD). and Metal-Organic Chemical Vapor Deposition (MOCVD).

19. A method as claimed in claim 12 , further comprising the steps of depositing a hard mask after said second thermal treatment, patterning said mask, etching core layer through said hard mask, and removing said hard mask prior to depositing said cladding layer.

20. A method as claimed in claim 12 , wherein said spin-on glass is inorganic phosphosilicate spin-on glass.

21. A method as claimed in claim 20 , wherein said optical layers are made of silica.

22. A method as claimed in claim 12 , wherein said spin-on glass is a silicate-based solution containing one or more of the following elements: Boron, Aluminum, Gallium, Indium, Thallium, Carbon, Germanium, Lead, Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Titanium, Zirconium, Hafnium, or any other rare earths elements (atomic numbers 57 to 71).

23. A method as claimed in claim 12 , wherein said spin-on glass is a siloxane-based solution containing one or more of the following elements: Boron, Aluminum, Gallium, Indium, Thallium, Carbon, Germanium, Lead, Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Titanium, Zirconium, Hafnium, or any other rare earths elements (atomic numbers 57 to 71).

24. A photonic device comprising:

an optical buffer layer;

an optical core layer over said buffer layer; and

an optical cladding layer over said optical core layer;

said optical buffer layer, said optical core layer, and said optical cladding layer forming part of an optical waveguide; and

a thin spin-on glass interlayer to smooth out surface roughness formed between at least one pair of said optical layers; and

wherein said spin-on glass interlayer is formed at an interface between said buffer layer and said core layer, and between said core layer and said cladding layer.

25. A photonic device as claimed in claim 24 , wherein said spin-on glass is inorganic phosphosilicate spin-on glass.

26. A photonic device claimed in claim 24 , wherein said spin-on glass is a silicate-based solution containing one or more of the following elements: Boron, Aluminum, Gallium, Indium, Thallium, Carbon, Germanium, Lead, Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Titanium, Zirconium, Hafnium, or any other rare earths elements (atomic numbers 57 to 71).

27. A photonic device as claimed in claim 24 , wherein said spin-on glass is a silicate-based solution containing one or more of the following elements: Boron, Aluminum, Gallium, Indium, Thallium, Carbon, Germanium, Lead, Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth, Titanium, Zirconium, Hafnium, or any other rare earths elements (atomic numbers 57 to 71).

28. A photonic device as claimed in claim 24 , wherein said optical layers are made of silica.

29. A photonic device as claimed in claim 28 , wherein said core layer comprises phosphorus doped silica.

30. A photonic device as claimed in claim 24 , wherein said optical buffer layer is deposited on a substrate and further comprising an anti-warping buffer layer deposited on a backside of said substrate.

31. A photonic device as claimed in claim 30 , wherein said anti-warping buffer layer is made silica.

32. A photonic device as claimed in claim 24 , wherein the thickness of said at least one spin-on glass interlayer lies in the range of 0.01 μm to 2.01 μm.

33. A photonic device as claimed in claim 24 , wherein said at least one spin-on glass interlayer comprises a plurality of sublayers including a refractive index matching sublayer.