Fabrication ultra-thin bonded semiconductor layers

• US 6,323,108 B1
• Filed: 07/27/1999
• Issued: 11/27/2001
• Est. Priority Date: 07/27/1999
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Kub, Francis J., Hobart, Karl D.
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): Simkovic, Viktor
• Application Number:
  US09/373,031
• Time in Patent Office: 854 Days
• Field of Search: 438/406, 438/455, 438/456, 438/457, 438/458, 438/459, 156/344, 156/584
• US Class Current: 438/458
• CPC Class Codes: H01L 21/76254 with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond

Abstract

The invention uses implantation, typically hydrogen implantation or implantation of hydrogen in combination with other elements, to a selected depth into a wafer with that contains one or more etch stops layers, treatment to split the wafer at this selected depth, and subsequent etching procedures to expose etch stop layer and ultra-thin material layer.

A method for making an ultra-thin material layer bonded to a substrate, has the steps: (a) growing an etch stop layer on a first substrate; (b) growing an ultra-thin material layer on the etch stop layer; (c) implanting an implant gas to a selected depth into the first substrate; (d) bonding the ultra-thin material layer to a second substrate; (e) treating the first substrate to cause the first substrate to split at the selected depth; (f) etching remaining portion of first substrate to expose the etch stop layer, and (g) etching the etch stop layer to expose the ultra-thin material layer.

Claims

1. A method for making an ultra-thin material bonded to a substrate, comprising the steps:

growing an etch stop layer on a first substrate;

growing an ultra-thin material layer on said etch stop layer;

implanting an implant ion to a selected depth into said first substrate;

bonding said ultra-thin material layer to a second substrate;

splitting said first substrate at said selected depth;

thereby forming a freestanding portion of said first substrate, separated from a remaining portion of said first substrate; and

heating to a temperature less than 650°

C.

2. The method of claim 1, wherein said implant ion comprises a ion selected from the group consisting of hydrogen, helium, and combinations thereof.

3. The method of claim 2, wherein said implant ion comprises hydrogen, and further comprises boron.

4. The method of claim 1, wherein said splitting further comprises heating said first substrate having implanted ions to a temperature wherein said implant ion expands, causing said first substrate to split at said selected depth.

5. The method of claim 1, wherein said method further comprises the step of:

etching said remaining portion of said first substrate, thereby exposing said etch stop layer.

6. The method of claim 5, wherein said method further comprises the step of:

etching said etch stop layer, thereby exposing said ultra-thin material layer.

7. The method of claim 1, wherein said ultra-thin material is an ultra-thin semiconductor.

8. The method of claim 7, further comprising the step of:

forming an oxide on said ultra-thin semiconductor, prior to said bonding step.

9. The method of claim 1, further comprising the step of:

depositing an additional material layer on said ultra-thin material, prior to said bonding step, and either before or after said implanting step.

10. The method of claim 9, wherein said deposited additional layer is low in viscosity.

11. The method of claim 1, wherein said step of bonding said ultra-thin material layer to said second substrate comprises direct bonding said ultra-thin material layer to said second substrate.

12. The method of claim 11, wherein said ultra-thin material layer has a hydrophilic face and said second substrate has a hydrophilic face.

13. The method of claim 12, wherein said hydrophilic face on second substrate is an oxide face.

14. The method of claim 13, wherein said oxide face is a native oxide face.

15. The method of claim 11, wherein said ultra-thin material layer has a hydrophobic face and said second substrate has a hydrophobic face.

16. The method of claim 11, wherein said ultra-thin material layer has a hydrophilic face and said second substrate has a hydrophobic face.

17. The method of claim 11, wherein said ultra-thin material layer has a hydrophobic face and said second substrate has a hydrophilic face.

18. The method of claim 1, wherein said step of bonding said ultra-thin material layer to said second substrate comprises bonding said ultra-thin material layer to said second substrate with an adhesive.

19. The method of claim 18, wherein said adhesive is a solder.

20. The method of claim 19, wherein said solder is selected from the group consisting of indium, tin, other metals, and combinations thereof.

21. The method of claim 1, wherein said selected depth for implanting said hydrogen is between about 500 Å

and about 22,000 Å

.

22. The method of claim 1, wherein said second substrate has one or more of the properties selected from the group consisting of thermal conductivity, microwave insulation, optical transparency, and thermal expansion coefficient matched to the thermal expansion coefficient of said ultra-thin material.

45. The method of claim 1, further including the step of removing said remaining portion of said first substrate and said etch stop layer and wherein said material layer has a surface roughness of <

10 Å

rms.

23. A method of making an ultra-thin material bonded to a substrate, comprising the steps:

implanting an etch stop material in a first substrate, thereby forming an ultra-thin doped layer on said substrate;

implanting hydrogen to a selected depth into said first substrate below said doped layer;

bonding said ultra-thin doped layer to a second substrate;

splitting said first substrate at said selected depth;

thereby forming a freestanding portion of said first substrate, separated from a remaining portion of said first substrates; and

heating to a temperature less than 650°

C.

24. The method of claim 23, wherein said etch stop material and said first substrate are selected from the group consisting of (a) an SiGe etch stop layer and an Si first substrate, and (b) an InAs etch stop layer with a cap layer over said etch stop layer, and a GaSb first substrate.

25. The method of claim 23, wherein said etch stop material is selected from the group consisting of boron, carbon, nitrogen, and combinations thereof.

26. The method of claim 23, wherein said etch stop material is implanted to a concentration on the order of 10²⁰ atoms/cm³.

27. The method of claim 23, wherein said etch stop material is implanted to a depth of between about 40 Å

and about 60 Å

.

46. The method of claim 23, further including the step of removing said remaining portion of said first substrate and said etch stop layer and wherein said material layer has a surface roughness of <

10 Å

rms.

28. A method for making an ultra-thin material compliantly bonded to a substrate, comprising the steps:

preparing a first layer of a first, a second substrate or material layer for a weak bond;

growing an etch stop layer on said first substrate;

growing an ultra-thin material layer on said etch stop layer;

implanting hydrogen to a selected depth into said first substrate;

compliantly bonding said ultra-thin material layer to said second substrate; and

splitting said first substrate at said selected depth;

thereby forming a freestanding portion of said first substrate, separated from a remaining portion of said first substrate, said remaining portion being compliantly bonded to said second substrate.

29. The method of claim 28, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate is preceded by a step of cleaning said second substrate and said ultra-thin material layer to remove organics.

30. The method of claim 28, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate comprises bonding said material layer to said second substrate by van der Waals forces.

31. The method of claim 30, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate is preceded by a step of chemically modifying said second substrate and said ultra-thin material layer so that both are hydrophilic, both are hydrophobic, or one is hydrophilic and one is hydrophobic.

32. The method of claim 28, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate comprises binding said material layer to said second substrate by ionic bonding.

33. The method of claim 28, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate comprises bonding said material layer to said second substrate by covalent bonds selected from the group of Ge—

O bonds, Ga—

O bonds, and bonds that are weaker than Ge—

O or Ga—

O.

34. The method of claim 28, further comprising the step of etching away said remaining portion of said first substrate to expose said etch stop layer.

35. The method of claim 34, further comprising the step of etching away said etch stop layer.

36. The method of claim 28, further comprising the step of forming grooves in said etch stop layer, for permitting said etch stop layer to laterally expand without buckling during heating.

47. The method of claim 28, further including the step of removing said remaining portion of said first substrate and said etch stop layer and wherein said material layer has a surface roughness of <

10 Å

rms.

37. A method for making a structure with an ultra-thin lattice matched relaxed layer between a material layer and a substrate, comprising the steps:

growing a lateral selective pseudomorphic epitaxial layer on a first substrate, to a thickness less than a critical thickness for defect formation;

implanting ions to a selected depth into said first substrate;

compliantly bonding said pseudomorphic opitaxial layer to a second substrate;

splitting said first substrate at said selected depth;

thereby forming a freestanding portion of said first substrate, separated from a remaining portion of said first substrate, said remaining portion being compliantly bonded to said second substrate;

etching said remaining portion of said first substrate, thereby exposing said pseudomorphic epitaxial layer;

forming grooves at selected lateral separations through said pseudomorphic epitaxial layer; and

heating said pseudomorphic epitaxial layer to a temperature to relax strain in said pseudomorphic epitaxial layer.

38. The method of claim 37, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate is preceded by a step of cleaning said second substrate and said ultra-thin material layer to remove organics.

39. The method of claim 37, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate comprises binding said material layer to said second substrate by van der Waals bonds.

40. The method of claim 39, wherein said step of compliantly bonding said ultra-thin material layer to said second substrate is preceded by a step of chemically modifying said second substrate and said ultra-thin material layer so that both are hydrophilic, both are hydrophobic, or one is hydrophilic and one is hydrophobic.

41. The method of claim 37, further comprising the step of:

growing an etch stop layer on said substrate, prior to said step of growing a pseudomorphic epitaxial layer on said substrate.

48. The method of claim 37, further including the step of removing said remaining portion of said first substrate and said etch stop layer and wherein said material layer has a surface roughness of <

10 Å

rms.

42. A method for making material layer bonded to a substrate comprising the step:

selecting a substrate with surface roughness of less than 10 Å

;

growing an etch stop layer on a first substrate,

growing a material layer on said etch stop layer;

implanting an implant ion to a selected depth into said first substrate;

bonding said material layer to a second substrate;

splitting said first substrate at said selected depth thereby forming a freestanding portion of said first substrate, separated from a remaining portion of said first substrate; and

removing said remaining portion of said first substrate and said etch stop layer, wherein said material layer has a surface roughness of 10 Å

rms.

43. The method of claim 42, further including the step of annealing at a temperature of 400°

C. or below.

44. The method of claim 42, wherein said material layer has a thickness less than 500 Å

.