Polished polymide substrate

• US 6,563,998 B1
• Filed: 04/15/1999
• Issued: 05/13/2003
• Est. Priority Date: 04/15/1999
• Status: Expired due to Fees

• Current Assignee: Opticomp Networks Incorporated
• Original Assignee: Opticomp Networks Incorporated
• Inventors: Sudarshanam, Venkatapuram S., Farah, John
• Primary Examiner(s): Ullah, Akm E.
• Application Number:
  US09/292,432
• Time in Patent Office: 1,489 Days
• Field of Search: 216/18, 216/20, 216/83, 216/102, 216/2, 438/691, 438/753, 438/756, 438/757, 438/977, 526/245, 385/122, 385/132, 385/142, 385/143, 349/137, 349/201, 349/569, 349/570, 349/571
• US Class Current: 385/131
• CPC Class Codes: G02B 2006/12176 Etching
• CPC Class Codes: G02B 6/138 by using polymerisation
• CPC Class Codes: G02B 6/30 for use between fibre and thin-film device
• CPC Class Codes: G02B 6/3636 the mechanical coupling means being grooves G02B6/3652 takes precedence
• CPC Class Codes: G02B 6/364 inverted grooves, e.g. dovetails
• CPC Class Codes: G02B 6/3652 the additional structures being prepositioning mounting areas, allowing only movement in one dimension, e.g. grooves, trenches or vias in the microbench surface, i.e. self aligning supporting carriers
• CPC Class Codes: G02B 6/3688 using laser ablation
• CPC Class Codes: G02B 6/3692 with surface micromachining involving etching, e.g. wet or dry etching steps surface micromachining involving subtractive techniques B81C1/00055

Abstract

Polymer substrates, in particular polyimide substrates, and polymer laminates for optical applications are described. Polyimide substrates are polished on one or both sides depending on their thickness, and single-layer or multi-layer waveguide structures are deposited on the polished polyimide substrates. Optical waveguide devices are machined by laser ablation using a combination of IR and UV lasers. A waveguide-fiber coupler with a laser-machined groove for retaining the fiber is also disclosed.

Claims

1. A substrate for a circuit structure comprising:

a planar substrate mass of polyimide material having a first side and a second side, said first side being polished to a surface smoothness between about 0.5 μ

inch and 100 μ

inch, capable of receiving a circuit structure.

2. The substrate for a circuit structure of claim 1, wherein said surface smoothness is between about 1 μ

inch and 50 μ

inch.

3. The substrate for a circuit structure of claim 1, wherein said surface smoothness is between about 1 μ

inch and 20 μ

inch.

4. The substrate for a circuit structure of claim 1, wherein said second side is polished.

5. The substrate for a circuit structure of claim 1, further comprising a first polymer layer applied to said first polished side of said planar substrate mass.

6. The substrate for a circuit structure of claim 5, further comprising an adhesion layer between said first polymer layer and said first polished side.

7. The substrate for a circuit structure of claim 5, wherein said first polymer layer has a refractive index that is greater than the refractive index of said polyimide substrate material.

8. The substrate for a circuit structure of claim 5, further comprising a second polymer layer applied over said first polymer layer, wherein the index of refraction of said second polymer layer is greater than the index of refraction of said first polymer layer.

9. The substrate for a circuit structure of claim 8, wherein said first polymer layer and said second polymer layer comprise an optical waveguide.

10. The substrate for a circuit structure of claim 8, further comprising a third polymer layer applied over said second polymer layer, wherein the index of refraction of said second polymer layer is greater than the index of refraction of said third polymer layer.

11. The substrate of claim 10, wherein the index of refraction of said third polymer layer is about equal to the index of refraction of said first polymer layer.

12. The substrate for a circuit structure of claim 10, wherein said first polymer layer, said second polymer layer and said third polymer layer comprise an optical waveguide.

13. The substrate for a circuit structure of claim 12, wherein said optical waveguide is a single mode waveguide.

14. The substrate for a circuit structure of claim 12, wherein said optical waveguide is a channel waveguide.

15. The substrate for a circuit structure of claim 10, wherein said first polymer layer and said second polymer layer, and said third polymer layer are polyimides.

16. The substrate for a circuit structure of claim 10, wherein said polyimide substrate material, said first polymer layer, said second polymer layer and said third polymer layer have coefficients of thermal expansion of between about 20×

10<sup>−

6</sup>/°

C. and 75×

10<sup>−

6</sup>/°

C.

17. The substrate for a circuit structure of claim 10 wherein said planar substrate mass, said first polymer layer, said second polymer layer and said third polymer layer are cut to form at least one cantilever member having a connected end and a free end opposite said connected end, said free end having a first edge, and an air gap between said free end and said substrate, said substrate having a second edge opposite said first edge, said first edge and said second edge are separated by said air gap.

18. The substrate for a circuit structure of claim 17 wherein said first edge and said second edge are substantially parallel.

19. The substrate for a circuit structure of claim 17 wherein said first edge and said second edge are inclined at an acute angle relative to a normal of said first side of said planar mass.

20. The substrate for a circuit structure of claim 17 wherein said first edge and said second edge are substantially parallel to a normal of said first side of said planar substrate mass.

21. The substrate for a circuit structure of claim 17 wherein said planar substrate mass, said first polymer layer, said second polymer layer and said third polymer layer are diced.

22. The substrate for a circuit structure of claim 17 wherein said planar substrate mass, said first polymer layer, said second polymer layer and said third polymer layer are ablated with a laser.

23. The substrate for a circuit structure of claim 1, wherein said first polished side is highly reflective.

24. The substrate for a circuit structure of claim 23, further comprising a highly reflective layer applied to said first polished side.

25. The substrate for a circuit structure of claim 24, wherein said planar substrate mass and said highly reflective layer are cut to form at least one movable member.

26. A method of preparing a substrate for a circuit structure comprising:

providing a planar substrate mass of polyimide material having a first side and a second side; and

polishing said first side to a surface smoothness between about 0.5 μ

inch and 100 μ

inch.

27. The method of claim 26 further comprising:

polishing said second side of said planar substrate mass.

28. The method of claim 26 further comprising:

applying a first polymer layer to said first polished side of said planar mass;

applying a second polymer layer over said first polymer layer; and

applying a third polymer layer over said second polymer layer, wherein the index of refraction of said second polymer layer is larger than the index of refraction of said first polymer layer and of said third polymer layer.

29. The method of claim 27 further comprising:

applying a first polymer layer to said first polished side of said planar mass;

applying a second polymer layer over said first polymer layer; and

applying a third polymer layer over said second polymer layer, wherein the index of refraction of said second polymer layer is larger than the index of refraction of said first polymer layer and of said third polymer layer.

30. The method of claim 28, wherein said first polymer layer, said second polymer layer and said third polymer layers form a single mode waveguide.

31. The method of claim 29, wherein said first polymer layer, said second polymer layer and said third polymer layers form a single mode waveguide.

32. The method of claim 30, wherein said single mode waveguide is a channel waveguide.

33. The method of claim 31, wherein said single mode waveguide is a channel waveguide.

34. The method of claim 28 further comprising:

shaping said polyimide substrate mass, said first polymer layer, said second polymer layer and said third polymer layer using at least one laser to form at least one movable member.

35. The method of claim 29 further comprising:

shaping said polyimide substrate mass, said first polymer layer, said second polymer layer and said third polymer layer using at least one laser to form at least one movable member.

36. The method of claim 34 wherein said movable member further comprises a cantilever member having a connected end and a free end opposite said connected end, said free end having a first edge, and an air gap between said free end and said substrate, said substrate having a second edge opposite said first edge, said first edge and said second edge are separated by said air gap.

37. The method of claim 35 wherein said movable member further comprises a cantilever member having a connected end and a free end opposite said connected end, said free end having a first edge, and an air gap between said free end and said substrate, said substrate having a second edge opposite said first edge, said first edge and said second edge are separated by said air gap.

38. The method of claim 36 wherein said step of shaping using a laser further includes:

partially cutting said second side of said planar substrate mass, said first polymer layer, said second polymer layer and said third polymer layer using a first laser emitting in the infrared spectral range; and

completing said cutting of said planar substrate mass, said first polymer layer, said second polymer layer and said third polymer layer using a second laser emitting in the ultraviolet spectral range.

39. The method of claim 37 wherein said step of shaping using a laser further includes:

partially cutting said second side of said planar substrate mass, said first polymer layer, said second polymer layer and said third polymer layer using a first laser emitting in the infrared spectral range; and

completing said cutting of said planar substrate mass, said first polymer layer, said second polymer layer and said third polymer layer using a second laser emitting in the ultraviolet spectral range.

40. The method of claim 38 wherein said first laser is a CO₂ laser and said second laser is an excimer laser.

41. The method of claim 39 wherein said first laser is a CO₂ laser and said second laser is an excimer laser.

42. The method of claim 38 wherein said first laser is a CO₂ laser and said second laser is a quadrupled YAG laser.

43. The method of claim 39 wherein said first laser is a CO₂ laser and said second laser is a quadrupled YAG laser.

44. The method of claim 41 further comprising:

forming a groove in said planar substrate mass having a depth, said depth capable of receiving an optical fiber wherein said fiber aligns with said channel waveguide.

45. The method of claim 42 further comprising:

forming a groove in said planar substrate mass having a depth, said depth capable of receiving an optical fiber wherein said fiber aligns with said channel waveguide.

46. The method of claim 44 wherein said step of forming a groove comprises ablating with a pulsed laser having a pulse width.

47. The method of claim 46 wherein said pulsed laser is an excimer laser.

48. The method of claim 46 wherein said pulse width is about a picosecond.

49. The method of claim 46 wherein said pulse width is about a femtosecond.

50. The method of claim 45 wherein said step of forming a groove comprises ablating with a pulsed laser having a pulse width.

51. The method of claim 50 wherein said pulsed laser is an excimer laser.

52. The method of claim 50 wherein said pulse width is about a picosecond.

53. The method of claim 50 wherein said pulse width is about a femtosecond.

54. A method of forming a groove having a precise depth and width in a planar substrate mass of polyimide material comprising:

providing a planar substrate mass of polyimide material having a first side and a second side;

polishing said first side to a surface smoothness between about 0.5 μ

inch and 100 μ

inch; and

cutting said first side of said planar substrate mass using a pulsed laser, said pulsed laser outputting a predetermined number of pulses to form a groove having a depth and a width capable of receiving an optical fiber.