Optical waveguide structure and method for fabricating the same

• US 20040151463A1
• Filed: 02/03/2003
• Published: 08/05/2004
• Est. Priority Date: 02/03/2003
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Voight, Steven A., Talin, Albert Alec
• Granted Patent: US 7,020,374 B2
• Time in Patent Office: Days
• US Class Current: 385/131
• CPC Class Codes: G02B 6/132 by deposition of thin films

Abstract

An optical waveguide structure (10) is provided. The optical waveguide structure (10) has a monocrystalline substrate (12), an amorphous interface layer (14) overlying the monocrystalline substrate (12) and an accommodating buffer layer (16) overlying the amorphous interface layer (14). An optical waveguide layer (20) overlies the accommodating buffer layer (16).

Claims

1. An optical waveguide structure comprising:

a monocrystalline substrate;

an amorphous interface layer overlying said monocrystalline substrate;

an accommodating buffer layer overlying said amorphous interface layer; and

an optical waveguide layer overlying said accommodating buffer layer.

2. The optical waveguide structure of claim 1, further comprising an optical buffer layer overlying said accommodating buffer layer and underlying said optical waveguide layer.

3. The optical waveguide structure of claim 1, further comprising a cladding layer overlying said accommodating buffer layer, said optical waveguide layer disposed at least partially within said cladding layer.

4. The optical waveguide structure of claim 3, wherein said optical waveguide layer is disposed within a window formed in said cladding layer.

5. The optical waveguide structure of claim 3, wherein said cladding layer overlies said optical waveguide layer.

6. The optical waveguide structure of claim 1, said monocrystalline substrate comprising one of silicon, germanium, a combination of silicon and germanium, a combination of silicon and carbon, a combination of silicon, germanium and carbon, and a silicon-on-insulator.

7. The optical waveguide structure of claim 1, said accommodating buffer layer comprising one of alkaline earth metal titanates, alkaline earth metal zirconates, alkaline earth metal hafnates, alkaline earth metal tantalates, alkaline earth metal ruthenates, alkaline earth metal niobates, alkaline earth metal vanadates, alkaline earth metal tin-based perovskites, lanthanum aluminate, lanthanum scandium oxide, gadolinium oxide, gallium nitride, aluminum nitride, and boron nitride.

8. The optical waveguide structure of claim 2, wherein said optical buffer layer comprises a dielectric material that has an index of refraction smaller than an index of refraction of a material that comprises said optical waveguide layer.

9. The optical waveguide structure of claim 8, wherein said optical waveguide layer comprises a dielectric material having a first index of refraction and said optical buffer layer comprises a dielectric material having a second index of refraction and a difference between said first index of refraction and said second index of refraction is at least 0.1%.

10. The optical waveguide structure of claim 2, wherein said optical buffer layer comprises one of SrTiO₃, BaTiO₃, Sr_xBa₁₋

xTiO₃, Sr_xZr<sub>1−

x</sub>TiO₃, where (0<

x<

1), PbTiO₃, Pb_xLa<sub>1−

x</sub>(Zr_yTi<sub>1−

y</sub>)O₃ where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

11. The optical waveguide structure of claim 1, wherein said optical waveguide layer comprises one of BaTiO₃, PbTiO₃, Pb_xLa₁₋

x(Zr_yTi<sub>1−

y</sub>)O₃, where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

12. The optical waveguide structure of claim 3, wherein said cladding layer comprises a dielectric material that has an index of refraction that is smaller than an index of refraction of a material that comprises said optical waveguide layer.

13. The optical waveguide structure of claim 12, wherein said optical waveguide layer comprises a dielectric material having a first index of refraction and said cladding layer comprises a dielectric material having a second index of refraction and a difference between said first index of refraction and said second index of refraction is at least 0.1%.

14. The optical waveguide structure of claim 3, wherein said cladding layer comprises one of SrTiO₃, BaTiO₃, Sr_xBa₁₋

xTiO₃, Sr_xZr<sub>1−

x</sub>TiO₃, where (0<

x<

1), PbTiO₃, Pb_xLa<sub>1−

x</sub>(Zr_yTi<sub>1−

y</sub>)O₃ where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

15. The optical waveguide structure of claim 1, said accommodating buffer layer having a thickness in the range of about 2 to about 100 nm.

16. The optical waveguide structure of claim 1, said monocrystalline substrate comprising silicon and said amorphous interface layer comprising a silicon oxide.

17. The optical waveguide structure of claim 2, wherein said optical buffer layer has a first lattice constant and said accommodating buffer layer has a second lattice constant, said second lattice constant being substantially matched to said first lattice constant.

18. The optical waveguide structure of claim 1, wherein said monocrystalline substrate has a first lattice constant and said accommodating buffer layer has a second lattice constant, said second lattice constant being substantially matched to said first lattice constant.

19. The optical waveguide structure of claim 2, wherein said optical waveguide layer has a first lattice constant and said optical buffer layer has a second lattice constant, said second lattice constant being substantially matched to said first lattice constant.

20. The optical waveguide structure of claim 1, wherein said amorphous interface layer has a thickness in the range of about 0.5 to 5 nm.

21. A method for forming an optical waveguide structure, the method comprising the steps of:

providing a monocrystalline substrate;

depositing a monocrystalline accommodating buffer layer overlying said monocrystalline substrate;

forming an amorphous interface layer between said monocrystalline substrate and said monocrystalline accommodating buffer layer; and

forming an optical waveguide layer overlying said accommodating buffer layer.

22. The method of claim 21, further comprising the step of forming an optical buffer layer overlying said monocrystalline accommodating buffer layer before the step of forming an optical waveguide layer.

23. The method of claim 21, further comprising the step of forming a cladding layer overlying said optical waveguide layer.

24. The method of claim 21, wherein said step of forming a monocrystalline accommodating buffer layer comprises forming said accommodating buffer layer by molecular beam epitaxy.

25. The method of claim 22, wherein the step of forming an optical buffer layer comprises forming said optical buffer layer by one selected from the group comprising MBE, CVD, MOCVD, MEE, ALE, PVD, CSD, PLD, and MOD.

26. The method of claim 21, wherein the step of forming an optical waveguide layer comprises forming said optical waveguide layer by one selected from the group comprising MBE, CVD, MOCVD, MEE, ALE, PVD, CSD, PLD, and MOD.

27. The method of claim 23, wherein the step of forming a cladding layer comprises forming said cladding layer by one selected from the group comprising MBE, CVD, MOCVD, MEE, ALE, PVD, CSD, PLD, and MOD.

28. The method of claim 21, wherein the step of providing a monocrystalline substrate comprises providing a monocrystalline silicon substrate and the step of forming an amorphous interface layer comprises forming an amorphous silicon oxide layer.

29. The method of claim 21, wherein the step of depositing a monocrystalline accommodating buffer layer comprises depositing a monocrystalline accommodating buffer layer having a thickness in the range of about 2 to 100 nm.

30. The method of claim 21, wherein the step of forming an amorphous interface layer comprises forming an amorphous interface layer having a thickness in the range of about 0.5 to 5 nm.

31. The method of claim 21, the step of depositing a monocrystalline accommodating buffer layer comprising depositing a monocrystalline accommodating buffer layer of a material selected from the group comprising alkaline earth metal titanates, alkaline earth metal zirconates, alkaline earth metal hafnates, alkaline earth metal tantalates, alkaline earth metal ruthenates, alkaline earth metal niobates, alkaline earth metal vanadates, alkaline earth metal tin-based perovskites, lanthanum aluminate, lanthanum scandium oxide, gadolinium oxide, gallium nitride, aluminum nitride, and boron nitride.

32. The method of claim 21, the step of forming an optical waveguide layer comprising forming an optical waveguide layer of a material selected from the group comprising BaTiO₃, PbTiO₃, Pb_xLa₁₋

x(Zr_yTi<sub>1−

y</sub>)O₃, where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

33. The method of claim 22, the step of forming an optical buffer layer comprising forming an optical buffer layer of a material selected from the group comprising SrTiO₃, BaTiO₃, Sr_xBa₁₋

xTiO₃, Sr_xZr<sub>1−

x</sub>TiO₃, where (0<

x<

1), PbTiO₃, Pb_xLa<sub>1−

x</sub>(Zr_yTi<sub>1−

y</sub>)O₃, where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

34. The method of claim 23, the step of forming a cladding layer comprising forming a cladding layer of a material selected from the group comprising SrTiO₃, BaTiO₃, Sr_xBa₁₋

xTiO₃, Sr_xZr<sub>1−

x</sub>TiO₃, where (0<

x<

1), PbTiO₃, Pb_xLa<sub>1−

x</sub>(Zr_yTi<sub>1−

y</sub>) where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

35. A method for forming an optical waveguide structure, the method comprising the steps of:

providing a monocrystalline substrate;

depositing a monocrystalline accommodating buffer layer overlying said monocrystalline substrate;

forming an amorphous interface layer between said monocrystalline substrate and said monocrystalline accommodating buffer layer;

forming a cladding layer overlying said monocrystalline accommodating buffer layer;

forming a trench in said cladding layer; and

forming an optical waveguide layer within said trench.

36. The method of claim 35, further comprising the step of forming an optical buffer layer overlying said monocrystalline accommodating buffer layer before the step of forming a cladding layer.

37. The method of claim 35, wherein said step of forming said accommodating buffer layer comprises forming said accommodating buffer layer by molecular beam epitaxy.

38. The method of claim 36, wherein the step of forming said optical buffer layer comprises forming said optical buffer layer by one selected from the group comprising MBE, CVD, MOCVD, MEE, ALE, PVD, CSD, PLD, and MOD.

39. The method of claim 35, wherein the step of forming said optical waveguide layer comprises forming said optical waveguide layer by one selected from the group comprising MBE, CVD, MOCVD, MEE, ALE, PVD, CSD, PLD, and MOD.

40. The method of claim 35, wherein the step of forming said cladding layer comprises forming said cladding layer by one selected from the group comprising MBE, CVD, MOCVD, MEE, ALE, PVD, CSD, PLD, and MOD.

41. The method of claim 35, wherein the step of providing a monocrystalline substrate comprises providing a monocrystalline silicon substrate and the step of forming an amorphous interface layer comprises forming an amorphous silicon oxide layer.

42. The method of claim 35, wherein the step of depositing a monocrystalline accommodating buffer layer comprises depositing a monocrystalline accommodating buffer layer having a thickness in the range of about 2 to 100 nm.

43. The method of claim 35, wherein the step of forming an amorphous interface layer comprises forming an amorphous interface layer having a thickness in the range of about 0.5 to 5 nm.

44. The method of claim 35, the step of depositing a monocrystalline accommodating buffer layer comprising depositing a monocrystalline accommodating buffer layer of a material selected from the group comprising alkaline earth metal titanates, alkaline earth metal zirconates, alkaline earth metal hafnates, alkaline earth metal tantalates, alkaline earth metal ruthenates, alkaline earth metal niobates, alkaline earth metal vanadates, alkaline earth metal tin-based perovskites, lanthanum aluminate, lanthanum scandium oxide, gadolinium oxide, gallium nitride, aluminum nitride, and boron nitride.

45. The method of claim 35, the step of forming an optical waveguide layer comprising forming an optical waveguide layer of a material selected from the group comprising BaTiO₃, PbTiO₃, Pb_xLa₁₋

x(Zr_yTi<sub>1−

y</sub>)O₃, where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

46. The method of claim 36, the step of forming an optical buffer layer comprising forming an optical buffer layer of a material selected from the group comprising SrTiO₃, BaTiO₃, Sr_xBa₁₋

xTiO₃, Sr_xZr<sub>1−

x</sub>TiO₃, where (0<

x<

1), PbTiO₃, Pb_xLa<sub>1−

x</sub>(Zr_yTi<sub>1−

y</sub>)O₃, where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.

47. The method of claim 35, the step of forming a cladding layer comprising forming a cladding layer of a material selected from the group comprising SrTiO₃, BaTiO₃, Sr_xBa₁₋

xTiO₃, Sr_xZr<sub>1−

x</sub>TiO₃, where (0<

x<

1), PbTiO₃, Pb_xLa<sub>1−

x</sub>(Zr_yTi<sub>1−

y</sub>)O₃, where (0.7<

x<

1.0, 0<

y<

1.0), Pb(Mg_1/3Nb_2/3)O₃, KNbO₃, LiNbO₃, LiTaO₃, Sr_xBa<sub>1−

x</sub>Nb₂O₆, Pb_xBa<sub>1−

x</sub>Nb₂O₆, Bi₄Ti₃O₁₂, Pb₂KNb₅O₁₅, K₃Li₂Nb₅O₁₅, and substituted derivatives thereof.