Method for fabricating a plurality of electromagnetic radiation emitting semiconductor chips

• US 7,655,488 B2
• Filed: 10/27/2008
• Issued: 02/02/2010
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: OSRAM GmbH (Ams-Osram AG)
• Original Assignee: OSRAM GmbH (Ams-Osram AG)
• Inventors: Hahn, Berthold, Kaiser, Stephan, Eisert, Dominik, Bader, Stefan
• Primary Examiner(s): Tran; Minh-Loan T
• Application Number:
  US12/290,097
• Publication Number:
  US 20090130787A1
• Time in Patent Office: 463 Days
• Field of Search: 438/29, 438/33, 438/46, 257/E33.068, 257/E33.074
• US Class Current: 438/29
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Method for fabricating a semiconductor chip which emits electromagnetic radiation, wherein to improve the light yield of semiconductor chips which emit electromagnetic radiation, a textured reflection surface is integrated on the p-side of a semiconductor chip. The semiconductor chip has an epitaxially produced semiconductor layer stack based on GaN, which comprises an n-conducting semiconductor layer, a p-conducting semiconductor layer and an electromagnetic radiation generating region which is arranged between these two semiconductor layers. The surface of the p-conducting semiconductor layer which faces away from the radiation-generating region is provided with three-dimensional pyramid-like structures. A mirror layer is arranged over the whole of this textured surface. A textured reflection surface is formed between the mirror layer and the p-conducting semiconductor layer.

Claims

1. Method for fabricating a plurality of semiconductor chips which emit electromagnetic radiation, comprising the following method steps:

(a) provision of a growth substrate wafer;

(b) epitaxial growth of a semiconductor layer sequence on the growth substrate wafer, which includes a p-conducting semiconductor layer, an n-conducting semiconductor layer and an electromagnetic radiation generating region which is arranged between these two semiconductor layers, the n-conducting semiconductor layer being first of all grown on the growth substrate wafer, and a plurality of planar sub-surfaces, which are positioned obliquely with respect to a main plane of the radiation-generating region and each form an angle of between 10° and

50°

with this plane, being formed on the p-conducting semiconductor layer surface;

(c) application of a mirror layer to the p-conducting semiconductor layer;

(d) production or application of a base on or to the mirror layer;

(e) removal of at least part of the growth substrate wafer from the semiconductor layer stack;

(f) application of a contact layer to the n-conducting semiconductor layer; and

(g) separation of the wafer produced in steps (a) to (f) into individual semiconductor chips.

2. The method according to claim 1, wherein after method step (e) the remaining part of the growth substrate wafer is at least partially patterned for the purpose of electrically contacting the n-conducting semiconductor layer.

3. The method according to claim 2, wherein before step (f) the n-conducting semiconductor layer or the remaining part of the growth substrate wafer is patterned by means of an etching process or mechanical patterning in such a way that a plurality of planar sub-surfaces, which are positioned obliquely with respect to a main plane of the radiation-generating region and each form an angle of between 15°

and 70°

with this plane, are formed on the n-conducting semiconductor layer surface or on the growth substrate wafer surface.

4. The method according to claim 1, wherein the planar sub-surfaces form pyramid-like structures.

5. The method according to claim 1, wherein the mirror layer is produced with a plurality of layers.

6. The method according to claim 1, wherein the mirror layer is produced by at least one of applying a highly reflective layer to the p-conducting semiconductor layer, applying a protective layer to the highly reflective layer or, if the highly reflective layer is not present, to the p-conducting semiconductor layer, applying a joining layer to the protective layer or, if the joining layer is not present, to the highly reflective layer or, if the highly reflective layer is not present, to the p-conducting semiconductor layer.

7. The method according to claim 6, wherein at least one of the highly reflective layer, the protective layer and the joining layer is applied by vapour deposition or sputtering.

8. The method according to claim 1, wherein according to method step (d), the base is soldered or adhesively bonded to the mirror layer.

9. The method according to claim 1, wherein, before method step (f), at least one trench is patterned in the semiconductor layer stack, extending at least through the n-conducting semiconductor layer and the electromagnetic radiation generating region and thereby defining a plurality of individual semiconductor layer elements.

10. The method according to claim 9, wherein the at least one trench is filled with an electrically insulating material which transmits radiation generated by the radiation-generating region.

11. The method according to claim 9, wherein the at least one trench is patterned by at least one of photolithography and etching.

12. Method for fabricating a plurality of semiconductor chips which emit electromagnetic radiation, comprising the following method steps:

(a) provision of a growth substrate wafer;

(b) epitaxial growth of a semiconductor layer sequence on the growth substrate wafer, which includes a p-conducting semiconductor layer, an n-conducting semiconductor layer and an electromagnetic radiation generating region which is arranged between these two semiconductor layers, the n-conducting semiconductor layer being first of all grown on the growth substrate wafer;

(c) application of a mirror layer to the surface of the p-conducting semiconductor layer;

(d) production or application of a base on or to the mirror layer;

(e) removal of at least part of the growth substrate wafer from the semiconductor layer stack;

(ea) etching or mechanical patterning of the exposed n-conducting semiconductor layer or of the remaining part of the growth substrate wafer, so that a plurality of planar sub-surfaces, which are positioned obliquely with respect to a main plane of the radiation-generating region and each form an angle of between 15° and

70°

with this plane, are formed on the n-conducting semiconductor layer surface or on the growth substrate wafer surface;

(f) application of a contact layer to the n-conducting semiconductor layer; and

(g) separation of the wafer produced in step a to f into individual semiconductor chips.

13. The method according claim 12, wherein the planar sub-surfaces form pyramid-like structures.

14. The method according to claim 12, wherein the mirror layer is produced by at least one of applying a highly reflective layer to the conducting semiconductor layer, applying a protective layer to the highly reflective layer or, if the highly reflective layer is not present, to the p-conducting semiconductor layer;

and applying a joining layer to the protective layer or, if the protective layer is not present, to the highly reflective layer or, if the highly reflective layer is not present, to the p-conducting semiconductor layer.

15. The method according to claim 12, wherein, before method step (f), at least one trench is patterned in the semiconductor layer stack, extending at least through the n-conducting semiconductor layer and the electromagnetic radiation generating region and thereby defining a plurality of individual semiconductor layer elements.