Fabrication process for a semiconductor substrate

• US 6,294,478 B1
• Filed: 02/27/1997
• Issued: 09/25/2001
• Est. Priority Date: 02/28/1996
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Sakaguchi, Kiyofumi, Yonehara, Takao
• Primary Examiner(s): Powell, William
• Application Number:
  US08/807,604
• Time in Patent Office: 1,671 Days
• Field of Search: 438/747, 438/753, 438/756, 438/FOR.106, 216/2, 216/90, 216/99, 148/33.2, 148/33.3, 148/33.4, 148/33.5
• US Class Current: 438/753
• CPC Class Codes: H01L 21/76259 with separation/delamination along a porous layer

Abstract

SOI substrates are fabricated with sufficient quality and with good reproducibility. At the same time, conservation of resources and reduction of cost are realized by reuse of the wafer and the like.

Carried out to achieve the above are a step of bonding a principal surface of a first substrate to a principal surface of a second substrate, the first substrate being Si substrate in which at least one layer of non-porous thin film is formed through a porous Si layer, a step of exposing the porous Si layer in a side surface of a bonding substrate comprised of the first substrate and the second substrate, a step of dividing the porous Si layer by oxidizing the bonding substrate, and a step of removing the porous Si and oxidized porous Si layer on the second substrate separated by the division of the porous Si layer.

Claims

1. A fabrication process for a semiconductor film comprising:

a step of preparing a first substrate having at least one layer of non-porous thin film on a porous Si layer;

a step of forming a bonding substrate by bonding said first substrate to a second substrate such that said non-porous thin film is located in an inside of a laminate comprised of these substrates;

a step of exposing said porous Si layer in a side surface of said bonding substrate comprised of said first substrate and said second substrate;

a step of dividing said bonding substrate in said porous Si layer by oxidizing said bonding substrate; and

a step of removing a porous Si and oxidized porous Si layer on said second substrate separated by the division of said bonding substrate in said porous Si layer.

6. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein after removing the porous Si and oxidized porous Si layer on the first substrate separated by said division of the porous Si layer, the first substrate is again used as a raw material for said first substrate before bonding.

7. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein after removing the porous Si and oxidized porous Si layer on the first substrate separated by said division of the porous Si layer, the first substrate is again used as a raw material for said second substrate before bonding.

8. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein at least one layer of non-porous thin film is formed through a porous Si layer on each of two principal surfaces of said first substrate and said second substrate is bonded to each of said two principal surfaces.

9. The fabrication process semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said non-porous thin film is a single-crystal Si layer.

10. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said non-porous thin film comprises an oxidized Si layer and a single-crystal Si layer.

11. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said non-porous thin film is a single-crystal compound semiconductor layer.

12. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said second substrate is an Si substrate.

13. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said second substrate is an Si substrate in which an oxidized Si film is formed at least on a principal surface to be bonded.

14. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said second substrate is a light transparent substrate.

15. The fabrication process of semiconductor film according to claim 8, wherein said second substrates respectively bonded to the two principal surfaces of said first substrate are those selected from Si substrate, Si substrate with an oxidized Si film formed at least on a principal surface to be bonded, and light transparent substrate.

16. The fabrication process of semiconductor film according to claim 15, wherein the second substrate bonded to one principal surface of said first substrate and the second substrate bonded to the other principal surface thereof are made of respective materials different from each other.

17. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein a surface flattening process in a direction spreaded with the principal surface of the second substrate is carried out after removing said porous Si and oxidized porous Si layer.

18. The fabrication process of semiconductor film according to claim 17, wherein said surface flattening process is annealing in an ambient containing hydrogen.

19. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein removal of said porous Si and oxidized porous Si layer is selectively carried out by soak in either one of hydrofluoric acid, a mixture solution in which at least one of alcohol and hydrogen peroxide solution is added to hydrofluoric acid, buffered hydrofluoric acid, and a mixture solution in which at least one of alcohol and hydrogen peroxide solution is added to buffered hydrofluoric acid.

20. The fabrication process of semiconductor film according to claim 11, wherein removal of said porous Si and oxidized porous Si layer is carried out by selective chemical etching of porous Si with an etchant having a faster etch rate of porous Si against a compound semiconductor.

21. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein removal of said porous Si and oxidized porous Si layer is carried out by polishing the layer, using said non-porous thin film as a stopper.

22. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein bonding of said first substrate to said second substrate is making the substrates into close contact with each other.

23. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein bonding of said first substrate to said second substrate is carried out by a method selected from anodic bonding, pressing, annealing, and combinations thereof.

24. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein formation of the non-porous thin film on the porous Si layer is carried out by performing anodization of an Si substrate to form porous Si and thereafter forming a non-porous thin film on said porous Si.

25. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein formation of the non-porous thin film on the porous Si layer is carried out by implanting ions of at least one element of rare gases, hydrogen, and nitrogen into an Si substrate to form a porous layer in a certain depth from a surface thereof.

26. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein formation of the non-porous thin film on the porous Si layer is carried out by anodizing an Si substrate to form a porous Si layer, thereafter forming a non-porous thin film on said porous Si layer, and then implanting ions of at least one element of rare gases, hydrogen, and nitrogen through the non-porous thin film into said porous Si layer so as to have a projected range thereof in said porous Si layer.

27. The fabrication process of semiconductor film according to claim 24, wherein said anodization is carried out in an HF solution.

28. The fabrication process of semiconductor film according to claims 1, 2, 3, 4 or 5, wherein prior to the oxidation of said bonding substrate, a layer of a material having a smaller coefficient of thermal expansion than Si is formed on at least one of outer surfaces of said bonding substrate.

35. The fabrication process for a semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said first substrate is obtained by a process comprised of:

a step of forming a porous Si layer by anodizing a silicon substrate;

a step of forming an oxidized film on a pore wall of the porous Si layer;

a step of forming said non-porous thin film on said silicon substrate.

36. The fabrication process for a semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said step of forming the bonding substrate is a step of bonding said substrates through an insulating layer.

37. The fabrication process for a semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said step of dividing the bonding substrate in said porous Si layer is carried out by oxidizing said porous Si layer.

38. The fabrication process for a semiconductor film according to claims 1, 2, 3, 4 or 5, wherein said oxidizing is carried out by pyro-oxidizing.

43. A fabrication process for a semiconductor film according to claims 1, 2 or 32, wherein after said removing step, said non-porous thin film is heat-treated under an atmosphere containing hydrogen.

44. A fabrication process for a semiconductor film according to claims 26, 33 or 34, wherein after said separating step, said non-porous thin film is heat-treated under an atmosphere containing hydrogen.

2. A fabrication process for a semiconductor film comprising:

a step of preparing a first substrate having at least one layer of non-porous thin film on a porous Si layer;

a step of forming a bonding substrate by bonding said first substrate to a second substrate such that said non-porous thin film is located in an inside of a laminate comprised of these substrates in which said porous Si layer is exposed in a side surface thereof;

a step of dividing said bonding substrate in said porous Si layer by oxidizing a bonding substrate comprised of said first substrate and said second substrate; and

a step of removing a porous Si and oxidized porous Si layer on said second substrate separated by the division of said bonding substrate in said porous Si layer.

3. A fabrication process for a semiconductor film comprising:

a step of preparing a first substrate having at least one layer of non-porous thin film on a separating layer;

a step of forming a bonding substrate by bonding said first substrate to a second substrate such that said non-porous thin film is located in an inside of a laminate comprised of these substrates;

a step of separating said non-porous thin film from said bonding substrate by oxidizing said bonding substrate; and

a step of removing the separating and oxidized separating layer on said second substrate separated by the division of said bonding substrate in said separating layer.

4. A fabrication process for a semiconductor film comprising:

a step of preparing a first substrate having at least one layer of non-porous thin film on a separating layer;

a step of forming a bonding substrate by bonding said first substrate to a second substrate such that said non-porous thin film is located in an inside of a laminate comprised of these substrates;

a step of exposing said separating layer in a side surface of said bonding substrate comprised of said first substrate and said second substrate; and

a step of separating said non-porous thin film from said bonding substrate by oxidizing said bonding substrate.

5. A fabrication process for a semiconductor film comprising:

a step of preparing a first substrate having at least one layer of non-porous thin film on a separating layer;

a step of forming a bonding substrate by bonding said first substrate to a second substrate such that said non-porous thin film is located in an inside of a laminate comprised of these substrates; and

a step of separating said non-porous thin film from said bonding substrate comprising oxidizing said bonding substrate.

29. A fabrication process for a semiconductor film comprising:

anodizing a surface of a single-crystal silicon substrate by changing a current density to form a porous region comprised of three porous layers,

forming at least one layer of non-porous thin film on the porous region, and

separating the non-porous thin film from the single-crystal silicon substrate.

30. A fabrication process for a semiconductor film according to claim 29, wherein the anodizing step comprises:

anodizing the surface of the single-crystal silicon substrate at a first current density, then anodizing the surface at a second current density higher than the first current density, and thereafter anodizing the surface at a third current density lower than the second current density.

31. A fabrication process for a semiconductor film according to claim 29, wherein an inner surface of each pore of the porous region is coated with a thermally oxidized film prior to the step of forming the non-porous thin film on the porous region.

39. A fabrication process for a semiconductor film according to claim 29, wherein a structure resulting from forming said non-porous thin film is bonded to a second substrate to permit said non-porous thin film to be located inside before separating said non-porous thin film from said single-crystal silicon substrate.

40. A fabrication process for a semiconductor film according to claim 39, wherein said structure is bonded to permit an insulating layer to be interposed between said structure and said second substrate.

41. A fabrication process for a semiconductor film according to claim 29, wherein an anodization solution for forming each of said three porous layers, comprises identical components in identical proportion.

42. A fabrication process for a semiconductor film according to claim 29, wherein the anodizing step comprises:

anodizing the surface of the single-crystal silicon substrate at a first current density, then anodizing the surface at a second current density higher than the first current density.

32. A semiconductor substrate having a non-porous thin film and a single-crystal region with a porous region comprised of three porous layers sandwiched therebetween, wherein a porosity of an intermediate porous layer among the three porous layers of the porous region is higher than a porosity of either of the other porous layers contiguous to the intermediate porous layer and a thickness of the intermediate porous layer is larger than a thickness of either of the other contiguous porous layers.

45. The fabrication process for a semiconductor film according to claims 32, 33 or 34, wherein said separating layer is formed by anodization of a surface of an Si substrate or by implanting hydrogen ions into a certain region of an Si substrate.

33. A bonding substrate comprised of a first substrate and a second substrate, the first substrate comprising a non-porous thin film, a single-crystal region and a porous region comprised of three porous layers sandwiched between the non-porous thin film and the single-crystal region, wherein the second substrate is bonded to the first substrate such that the non-porous thin film is sandwiched between the second substrate and the porous region, wherein a porosity of an intermediate porous layer among the three porous layers of the porous region is higher than a porosity of either of the other porous layers contiguous to the intermediate porous layer and a thickness of the intermediate porous layer is larger than a thickness of either of the other contiguous porous layers.

34. A bonding substrate according to claim 33, wherein the first substrate and the second substrate are bonded to each other through an insulating layer.

46. The fabrication process for a semiconductor film according to claim 34, wherein said separating step comprises separation at said separating layer.

47. A fabrication process for a semiconductor film comprising:

a step of preparing a first substrate having at least one layer of non-porous thin film on a separating layer;

a step of forming a bonding substrate by bonding said first substrate to a second substrate such that said nonporous thin film is located in an inside of a laminate comprised of these substrates; and

a step of separating said non-porous thin film from said bonding substrate comprising heating said bonding substrate in an oxidizing atmosphere.

48. The fabrication process for a semiconductor film according to claim 47, wherein said step of preparing the first substrate is comprised of implanting hydrogen ions into a Si substrate to a certain depth from a surface of the Si substrate.

49. The fabrication process for a semiconductor film according to claim 47, wherein said separating layer is an ion-implanted layer.

50. The fabrication process for a semiconductor film according to claim 47, wherein said separating step is conducted by separating said bonding substrate at said separating layer.

51. The fabrication process for a semiconductor film according to claim 47, further comprising a step of heat-treating a part of said first substrate transferred on said second substrate in a hydrogen atmosphere after said separating step.

52. A fabrication process for a semiconductor film containing a step of separating a bonding substrate formed by bonding a first substrate having an ion-implanted layer in a certain region thereof to a second substrate at the ion-implanted layer, wherein said separating step is comprised of allowing the separation in the bonding substrate to proceed from a side face of the bonding substrate toward the center of the bonding substrate and then heat-treating a part of the first substrate transferred on the second substrate in an atmosphere containing hydrogen.

53. The fabrication process for a semiconductor film according to claim 52, wherein said first substrate is formed by implanting hydrogen ions into a Si substrate.

54. The fabrication process for a semiconductor film according to claim 52, wherein said bonding substrate has an insulating layer between said first substrate and said second substrate.

55. The fabrication process for semiconductor film according to claim 52, wherein said heat-treatment is carried out in hydrogen.

56. A fabrication process for a semiconductor film comprising:

anodizing a surface of a single-crystal silicon substrate by changing a current density to form a porous region comprised of at least two porous layers;

forming at least one layer of non-porous thin film on the porous region;

separating the non-porous thin film from the single crystal silicon substrate; and

heating the non-porous thin film under an atmosphere containing hydrogen.

57. The fabrication process according to claim 56, wherein said anodizing step is carried out by changing the current density but without changing a composition of a solution used in the anodizing step.