Electromagnetic radiation generating semiconductor chip and method for making same

• US 20060011923A1
• Filed: 06/16/2005
• Published: 01/19/2006
• Est. Priority Date: 06/30/2004
• Status: Active Grant

• Current Assignee: Osram Opto Semiconductors GmbH (Ams-Osram AG)
• Original Assignee: Osram Opto Semiconductors GmbH (Ams-Osram AG)
• Inventors: Strauss, Uwe, Eisert, Dominik
• Granted Patent: US 8,330,175 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/387 with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer
• CPC Class Codes: H01L 33/405 Reflective materials

Abstract

An electromagnetic radiation generating semiconductor chip is disclosed. A semiconductor layer sequence suitable for generating electromagnetic radiation is grown on a first main face of a radioparent, electrically conductive growth substrate, for example, a SiC growth substrate. Provided on a second main face of said growth substrate that faces away from said semiconductor layer sequence is a roughening that acts as a diffuser for an electromagnetic radiation emitted into said growth substrate by said semiconductor layer sequence and that in particular has a scattering factor higher than 0.25. A layer or layer sequence reflective of the electromagnetic radiation is applied to said roughening. A method for making the semiconductor chip is also disclosed.

Claims

1. An electromagnetic radiation generating semiconductor chip comprising:

a radioparent, electrically conductive growth substrate;

a semiconductor layer sequence suitable for generating electromagnetic radiation grown on a first main face of the growth substrate;

a roughening provided on a second main face of said growth substrate that faces away from said semiconductor layer sequence, wherein the roughening acts as a diffuser for the electromagnetic radiation emitted into said growth substrate by said semiconductor layer sequence, and wherein the roughening produces a scattering factor higher than 0.25; and

a layer or layer sequence reflective to the electromagnetic radiation applied to said roughening.

3. The semiconductor chip as specified in claim 1, wherein said growth substrate has a thickness that is between 50 μ

m inclusive and 150 μ

m inclusive.

4. The semiconductor chip as specified in claim 3, wherein said growth substrate has a thickness of about 100 μ

m.

5. The semiconductor chip as specified in claim 1, wherein said electromagnetic radiation generating semiconductor layer sequence is based on nitride III/V compound semiconductor material.

6. The semiconductor chip as specified in claim 5, wherein said electromagnetic radiation generating semiconductor layer sequence contains at least one semiconductor layer based on In_xAl_yGa_1-x-yN, where 0≦

x≦

1, 0≦

y≦

1 and x+y≦

1.

7. The semiconductor chip as specified in claim 1, wherein said growth substrate is a SiC growth substrate implanted with a nitrogen dopant adjacent said reflective layer to increase the majority charge carrier density and provide increased electrical conductivity.

8. The semiconductor chip as specified in claim 1, wherein said reflective layer contains a metal that is reflective to the electromagnetic radiation emitted by said semiconductor layer sequence.

9. The semiconductor chip as specified in claim 8, wherein said metal contains one or more of Al, Ag, Ru, and Ir.

10. The semiconductor chip as specified in claim 1, wherein said roughening is a diffuse roughening of said second main face.

11. The semiconductor chip as specified in claim 1, wherein said second main face is provided with a pyramid structure to roughen it.

12. The semiconductor chip as specified in claim 1, wherein a roughening is also provided on a side confronting the side on which said reflective layer or layer sequence is disposed.

14. The semiconductor chip as specified in claim 1, further comprising a transparent or semitransparent, electrically conductive front-side contact layer disposed on a front side facing away from said reflective layer or layer sequence and through which said semiconductor chip emits electromagnetic radiation when it is operating.

15. A method for making a semiconductor chip as specified in claim 1, comprising:

growing said electromagnetic radiation generating semiconductor layer sequence on said growth substrate,

forming a transparent or semitransparent, electrically conductive front-side contact layer on said electromagnetic radiation generating semiconductor layer sequence,

forming mesas in said electromagnetic radiation generating semiconductor layer sequence,

thinning said growth substrate,

roughening the second main face of said growth substrate,

applying said reflective layer or said reflective layer sequence to said second main face of said growth substrate.

17. The method as specified in claim 15, wherein a bonding pad is disposed on said transparent or semitransparent, electrically conductive front-side contact layer.

18. The method as specified in claim 15, wherein a passivation layer is applied to said mesas before the thinning of said growth substrate.

19. The method as specified in claim 15, wherein said roughening is produced by means of a laser process or by means of a wet chemical etching process or a dry etching process.

20. The method as specified in claim 15, wherein said transparent or semitransparent, electrically conductive front-side contact layer comprises a radioparent first metal layer and a second metal layer disposed thereafter, viewed from said semiconductor layer sequence, said first metal layer being applied to said growth substrate or to said semiconductor layer sequence, as the case may be, substantially over the entire area thereof, and said second metal layer being retracted with respect to said first metal layer.

21. The method as specified in claim 20, wherein said first metal layer is a Pt layer or a Pt-based layer and said second metal layer an Au layer or an Au-based layer.

22. The method as specified in claim 15, wherein said transparent or semitransparent, electrically conductive front-side contact layer is an indium/tin layer.

23. The method as specified in claim 15, wherein the thickness of said growth substrate after thinning is smaller than an edge length of said semiconductor chip.

24. The semiconductor chip as specified in claim 1, wherein the growth substrate comprises SiC.

2. An electromagnetic radiation generating semiconductor chip comprising:

a radioparent, electrically conductive growth substrate;

a semiconductor layer sequence suitable for generating electromagnetic radiation grown on a first main face of the growth substrate;

a roughening provided on a main face of said semiconductor layer sequence that faces away from said growth substrate, wherein the roughening acts as a diffuser for the electromagnetic radiation emitted to said main face of said semiconductor layer sequence by said semiconductor layer sequence, and wherein the roughening produces a scattering factor higher than 0.25; and

a layer or layer sequence reflective to the electromagnetic radiation applied to said roughening.

16. A method for making a semiconductor chip as specified in claim 2, comprising:

growing said electromagnetic radiation generating semiconductor layer sequence on said growth substrate,

roughening the main face of said semiconductor layer sequence that faces away from said growth substrate,

applying said reflective layer or layer sequence to the roughened main face of said semiconductor layer sequence,

forming mesas in said electromagnetic radiation generating semiconductor layer sequence,

thinning said growth substrate, and

forming a transparent or semitransparent, electrically conductive front-side contact layer on said electromagnetic radiation generating semiconductor layer sequence.

25. The semiconductor chip as specified in claim 2, wherein the growth substrate comprises SiC.

13. An electromagnetic radiation generating semiconductor chip comprising:

a radioparent, electrically conductive growth substrate;

a semiconductor layer sequence suitable for generating electromagnetic radiation grown on a first main face of the growth substrate;

a layer or layer sequence reflective to the electromagnetic radiation applied to a second main face of said growth substrate that faces away from said semiconductor layer sequence; and

a roughening provided on a front side facing away from said reflective layer or layer sequence and through which said semiconductor chip emits electromagnetic radiation when it is operating, wherein the roughening produces a scattering factor higher than 0.25.

26. The semiconductor chip as specified in claim 13, wherein the growth substrate comprises SiC.