Method for Production of a Radiation-Emitting Semiconductor Chip

• US 20080093611A1
• Filed: 04/29/2004
• Published: 04/24/2008
• Est. Priority Date: 04/29/2004
• Status: Active Grant

• Current Assignee: OSRAM OLED GMBH (Ams-Osram AG)
• Original Assignee: Osram Opto Semiconductors GmbH (Ams-Osram AG)
• Inventors: Hahn, Berthold, Kaiser, Stephan, Harle, Volker
• Granted Patent: US 7,897,423 B2
• Time in Patent Office: Days
• US Class Current: 257/95
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

A method for micropatterning a radiation-emitting surface of a semiconductor layer sequence for a thin-film light-emitting diode chip. The semiconductor layer sequence is grown on a substrate. A mirror layer is formed or applied on the semiconductor layer sequence, which reflects back into the semiconductor layer sequence at least part of a radiation that is generated in the semiconductor layer sequence during the operation thereof and is directed toward the mirror layer. The semiconductor layer sequence is separated from the substrate by means of a lift-off method, in which a separation zone in the semiconductor layer sequence is at least partly decomposed in such a way that anisotropic residues of a constituent of the separation zone, in particular a metallic constituent of the separation layer, remain at the separation surface of the semiconductor layer sequence, from which the substrate is separated. The separation surface—provided with the residues—of the semiconductor layer sequence with a dry etching method, a gaseous etchant or a wet-chemical etchant, wherein the anisotropic residues are at least temporarily used as an etching mask. A semiconductor chip is produced according to such a method.

Claims

1. A method for micropatterning a radiation-emitting surface of a semiconductor layer sequence for a thin-film light-emitting diode chip comprising the steps of:

(a) growing the semiconductor layer sequence on a substrate;

(b) forming or applying a mirror layer on the semiconductor layer sequence, which reflects back into the semiconductor layer sequence at least part of a radiation that is generated in the semiconductor layer sequence during operation thereof and is directed toward the mirror layer;

(c) separating the semiconductor layer sequence from the substrate with a lift-off method, in which a separation zone in the semiconductor layer sequence is at least partly decomposed in such a way that anisotropic residues of a constituent of the separation zone remain at a separation surface of the semiconductor layer sequence, from which the substrate is separated; and

(d) etching the separation surface—

provided with the residues—

of the semiconductor layer sequence with a dry etching method, a gaseous etchant or a wet-chemical etchant, wherein the residues are at least temporarily used as an etching mask.

2. The method as claimed in claim 1, wherein in step (d) both residues of the separation zone and the semiconductor layer sequence are etched in material-removing fashion at the separation surface thereof.

3. The method as claimed in claim 1, wherein in step (d) different crystal facets of the semiconductor layer sequence are uncovered.

4. The method as claimed in claim 1, wherein the wet-chemical etchant contains KOH or the gaseous etchant contains a corrosive gas.

5. The method as claimed in claim 1, wherein after method step (d) the etched separation surface is treated with a further wet-chemical or gaseous etchant which predominantly etches at crystal defects and selectively etches different crystal facets at the separation surface of the semiconductor layer sequence.

6. The method as claimed in claim 5, wherein the further wet-chemical etchant contains KOH, or the gaseous etchant contains a corrosive gas.

10. The method as claimed in claim 1, wherein the semiconductor layer sequence is a radiation-emitting semiconductor layer sequence based on nitride compound semiconductor material, and wherein in step (c) nitride compound semiconductor material of the semiconductor layer sequence is decomposed in the separation zone in such a way that gaseous nitrogen arises.

11. The method as claimed in claim 1, wherein the lift-off method is a laser lift-off method.

12. The method as claimed in claim 1, wherein the semiconductor layer sequence has at the separation surface an increased defect density in comparison with a part of the semiconductor layer sequence that is disposed further than the separation surface from the substrate.

13. The method as claimed in claim 12, wherein the region of the semiconductor layer sequence in which the separation zone is situated is a buffer layer.

14. The method as claimed in claim 1, wherein the semiconductor layer sequence contains at least one material from the system In_xAl_yGa_1-x-yN where 0≦

x≦

1, 0≦

y≦

1 and x+y≦

1.

15. The method as claimed in claim 1, wherein the semiconductor layer sequence contains at least one material from the system In_xAl_yGa_1-x-yN where 0≦

x≦

1, 0≦

y≦

1 and x+y≦

1, and wherein the separation zone substantially has GaN and anisotropic residues made of metallic Ga remain on the separation surface of the semiconductor layer sequence.

16. The method as claimed in claim 1, wherein the semiconductor layer sequence has a dopant concentration of between 1*10¹⁸ cm⁻

3 and 1*10²⁰ cm<sup>−

3</sup> inclusive at its separation surface.

17. The method as claimed in claim 16, wherein the dopant is Si.

18. The method as claimed in claim 1, wherein the separation zone contains AlGaN, the Al content of which is chosen in such a way that it is decomposed in step (c), and Al is sintered into the semiconductor layer sequence.

19. The method as claimed in claim 18, wherein the Al content lies between approximately 1% and approximately 10% Al.

20. The method as claimed in claim 18, wherein in step (c) Al is melted and sintered into the semiconductor layer sequence.

21. The method as claimed in claim 18, wherein the separation zone has a GaN layer adjoined by an AlGaN layer as seen from the substrate, and in step (c) the entire GaN layer and part of the AlGaN layer are decomposed.

22. The method as claimed in claim 18, wherein an aluminum n-contact is produced at the separation surface of the semiconductor layer sequence.

23. The method as claimed in claim 1, wherein a sapphire substrate is used.

24. The method as claimed in claim 1, wherein a contact pad, in particular a contact metallization for electrical connection of the semiconductor layer sequence, is applied to the micropatterned separation surface of the semiconductor layer sequence.

25. The method as claimed in claim 1, wherein through the micropatterning at the separation surface of the semiconductor layer sequence a roughening is produced on a scale which corresponds to a wavelength range of an electromagnetic radiation emitted by the semiconductor layer sequence during operation thereof.

26. The method as claimed in claim 25, wherein the roughening structures are of the order of magnitude of half an internal wavelength.

27. The method as claimed in claim 1, wherein the semiconductor layer sequence is grown overall from hexagonal GaN-based material on the substrate, wherein the 000-1 crystal face (N face of the hexagonal nitride lattice) faces toward the substrate.

28. The method as claimed in claim 10, wherein a laser radiation source having a wavelength in the range of between 350 nm and 360 nm or a shorter wavelength is used in step (c).

29. The method as claimed in claim 1, wherein a Bragg mirror is applied in step (b).

30. The method as claimed in claim 1, wherein step (b) involves producing a mirror layer having a reflective layer disposed further than a radiation-transmissive layer from the semiconductor layer sequence.

31. The method as claimed in claim 1, wherein the mirror layer has a reflection layer with a plurality of windows toward the semiconductor layer sequence and a current transport layer that is different from the reflection layer is arranged in the windows.

32. An electromagnetic-radiation-emitting semiconductor chip comprising:

an epitaxially produced semiconductor layer sequence having an n-conducting semiconductor layer, a p-conducting semiconductor layer and an electromagnetic-radiation-generating region arranged between these two semiconductor layers, at least one of the semiconductor layers having a nitride compound semiconductor material, and

a carrier body, on which the semiconductor layer stack is arranged,

wherein

at least one semiconductor layer of the semiconductor layer sequence is micropatterned by means of a method as claimed in claim 1.

33. The semiconductor chip as claimed in claim 32,

wherein the mirror layer is patterned.

7. A method for micropatterning a radiation-emitting surface of a semiconductor layer sequence for a thin-film light-emitting diode chip comprising the steps of:

(a) growing the semiconductor layer sequence on a substrate;

(b) forming or applying a mirror layer on the semiconductor layer sequence, which reflects back into the semiconductor layer sequence at least part of a radiation that is generated in the semiconductor layer sequence during the operation thereof and is directed toward the mirror layer;

(c) separating the semiconductor layer sequence from the substrate, wherein a separation zone made of compound semiconductor material of the semiconductor layer sequence is at least partly decomposed, and

(d) etching a separation surface of the semiconductor layer sequence, from which the substrate is separated, by means of an etchant which predominantly etches at crystal defects and selectively etches different crystal facets at the separation surface.

8. The method as claimed in claim 7,

wherein in step (d) the etchant contains KOH.

9. The method as claimed in claim 7,

wherein in step (d) the etchant contains a corrosive gas.

34. The method as claimed in claim 7, wherein the semiconductor layer sequence is a radiation-emitting semiconductor layer sequence based on nitride compound semiconductor material, and wherein in step (c) nitride compound semiconductor material of the semiconductor layer sequence is decomposed in the separation zone in such a way that gaseous nitrogen arises.

35. The method as claimed in claim 7, wherein the lift-off method is a laser lift-off method.

36. The method as claimed in claim 7, wherein the semiconductor layer sequence has at the separation surface an increased defect density in comparison with a part of the semiconductor layer sequence that is disposed further than the separation surface from the substrate.

37. The method as claimed in claim 7, wherein the semiconductor layer sequence contains at least one material from the system In_xAl_yGa_1-x-yN where 0≦

x≦

1, 0≦

y≦

1 and x+y≦

1.

38. The method as claimed in claim 7, wherein the semiconductor layer sequence has a dopant concentration of between 1*10¹⁸ cm⁻

3 and 1*10²⁰ cm<sup>−

3</sup> inclusive at its separation surface.

39. The method as claimed in claim 7, wherein the separation zone contains AlGaN, the Al content of which is chosen in such a way that it is decomposed in step (c), and Al is sintered into the semiconductor layer sequence.

40. The method as claimed in claim 7, wherein a sapphire substrate is used.

41. The method as claimed in claim 7, wherein a contact pad, in particular a contact metallization for electrical connection of the semiconductor layer sequence, is applied to the micropatterned separation surface of the semiconductor layer sequence.

42. The method as claimed in claim 7, wherein through the micropatterning at the separation surface of the semiconductor layer sequence a roughening is produced on a scale which corresponds to a wavelength range of an electromagnetic radiation emitted by the semiconductor layer sequence during operation thereof.

43. The method as claimed in claim 7, wherein the semiconductor layer sequence is grown overall from hexagonal GaN-based material on the substrate, wherein the 000-1 crystal face (N face of the hexagonal nitride lattice) faces toward the substrate.

44. The method as claimed in claim 7, wherein a Bragg mirror is applied in step (b).

45. The method as claimed in claim 7, wherein step (b) involves producing a mirror layer having a reflective layer disposed further than a radiation-transmissive layer from the semiconductor layer sequence.

46. The method as claimed in claim 7, wherein the mirror layer has a reflection layer with a plurality of windows toward the semiconductor layer sequence and a current transport layer that is different from the reflection layer is arranged in the windows.