Methods of processing of gallium nitride

• US 20050042845A1
• Filed: 07/14/2004
• Published: 02/24/2005
• Est. Priority Date: 07/14/2003
• Status: Active Grant

• Current Assignee: Allegis Technologies Incorporated
• Original Assignee: Allegis Technologies Incorporated
• Inventors: Urbanek, Wolfram
• Granted Patent: US 7,015,117 B2
• Time in Patent Office: Days
• US Class Current: 438/483
• CPC Class Codes: B23K 2103/172 wherein at least one of the layers is non-metallic
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/10253 Silicon [Si]
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/641 characterized by the materials

Abstract

A method for improving thermal dissipation in large gallium nitride light emitting diodes includes replacing sapphire with a better thermal conductor resulting in more efficient removal of thermal energy. A method for achieving a reliable and strong temporary bond between a GaN epitaxial layer and a support wafer. A method for transferring an epitaxial film from a growth substrate to a secondary substrate. An excimer laser initiates film delamination from the growth substrate. The laser beam is shaped by a shadow mask and aligned to an existing pattern in the growth substrate. A method for fabricating a LED that radiates white spectrum light. A phosphor that radiates a white spectrum after excitation in the blue or UV spectrum onto the GaN epitaxial wafer prior to die separation and packaging. A method for depositing a metal substrate onto a GaN epitaxy layer.

Claims

1. A method of processing GaN comprising:

(a) growing a GaN epitaxial layer on a top surface of a sapphire substrate;

(b) patterning said GaN layer;

(c) attaching a support structure to said GaN layer;

(d) radiating with a laser directed at a bottom surface of said sapphire substrate, wherein a wavelength of said laser is selected to cause energy of said laser to be substantially absorbed near an interface of said GaN layer with said sapphire so as to delaminate said GaN and create an exposed GaN surface;

(e) removing said sapphire substrate;

(f) depositing a secondary substrate onto said exposed GaN surface.

2. A method as recited in claim 1 wherein said secondary substrate is electrically conductive.

3. A method as recited in claim 1 wherein said secondary substrate includes:

(a) a first contact layer selected from the group consisting of Ti/Al and Ag;

(b) a second layer of Cr/Au on said first layer; and

(c) a third layer of metal on said second layer.

4. A method as recited in claim 1 wherein said support structure includes:

(a) a first adhesive layer on said GaN; and

(b) a second support layer on said first layer.