METHOD OF FORMING THREE DIMENSIONAL FEATURES ON LIGHT EMITTING DIODES FOR IMPROVED LIGHT EXTRACTION

• US 20080135866A1
• Filed: 02/13/2008
• Published: 06/12/2008
• Est. Priority Date: 04/01/2004
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: DONOFRIO, MATTHEW
• Granted Patent: US 7,829,906 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/066 by using masks
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: Y10S 438/94 Laser ablative material removal

Abstract

A method is disclosed for obtaining a high-resolution lenticular pattern on the surface of a light emitting diode. The method comprises imprinting a patterned sacrificial layer of etchable material that is positioned on a semiconductor surface that is in turn adjacent a light emitting active region, and thereafter etching the imprinted sacrificial layer and the underlying semiconductor to transfer an imprinted pattern into the semiconductor layer adjacent the light emitting active region.

Claims

1. An LED precursor structure comprising:

at least one Group III nitride active layer;

a photoresist layer on said Group III nitride-layer; and

an embossing stamp pressed into said photoresist layer.

2. An LED precursor according to claim 1 wherein said photoresist layer is heated to a temperature sufficient to soften the photoresist but below the temperature at which the photoresist would lose structural integrity.

3. An LED precursor according to claim 1 heated to a temperature of between about 50 and 100°

C.

4. An LED precursor according to claim 1 further comprising a conductive substrate supporting said Group III nitride layer.

5. An LED comprising:

a conductive substrate;

at least one light-emitting active layer on said substrate; and

a patterned semiconductor lenticular surface on said active layer opposite said substrate with no more than 25 microns of non-lenticular material between said patterned lenticular surface and said active layer.

6. An LED according to claim 5 wherein said lenticular surface comprises a plurality of lenticular features that are smaller than 10 microns in their individual footprints.

7. An LED according to claim 5 wherein said lenticular surface comprises a plurality of substantially identical lenticular features.

8. An LED according to claim 5 wherein said lenticular surface comprises a plurality of lenticular features that are smaller than 6 microns in their individual footprints.

9. An LED according to claim 5 wherein said active layer comprises a Group III nitride.

10. An LED according to claim 9 wherein said lenticular surface comprises silicon carbide.