Non-reactive barrier metal for eutectic bonding process

• US 9,343,641 B2
• Filed: 08/02/2011
• Issued: 05/17/2016
• Est. Priority Date: 08/02/2011
• Status: Expired due to Fees

• Current Assignee: Toshiba Corporation
• Original Assignee: Manutius IP, Inc.
• Inventors: Lin, Chao Kun
• Primary Examiner(s): Naraghi, Ali
• Application Number:
  US13/196,870
• Publication Number:
  US 20130032846A1
• Time in Patent Office: 1,750 Days
• Field of Search: 257 98-100
• US Class Current: 1/1
• CPC Class Codes: H01L 2224/2929 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/29339 Silver [Ag] as principal constituent
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/32 of an individual layer connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/73 Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/0655 Polyacetal
• CPC Class Codes: H01L 2924/10253 Silicon [Si]
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/12042 LASER
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/207 : Diameter ranges
• CPC Class Codes: H01L 2933/0066 : relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 33/0093 : Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/40 : Materials therefor
• CPC Class Codes: H01L 33/62 : Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

A eutectic metal layer (e.g., gold/tin) bonds a carrier wafer structure to a device wafer structure. In one example, the device wafer structure includes a silicon substrate upon which an epitaxial LED structure is disposed. A layer of silver is disposed on the epitaxial LED structure. The carrier wafer structure includes a conductive silicon substrate covered with an adhesion layer. A layer of non-reactive barrier metal (e.g., titanium) is provided between the silver layer and the eutectic metal to prevent metal from the eutectic layer (e.g., tin) from diffusing into the silver during wafer bonding. During wafer bonding, the wafer structures are pressed together and maintained at more than 280° C. for more than one minute. Use of the non-reactive barrier metal layer allows the total amount of expensive platinum used in the manufacture of a vertical blue LED manufactured on silicon to be reduced, thereby reducing LED manufacturing cost.

Claims

1. An apparatus comprising:

a carrier;

an adhesion layer next to the carrier, the adhesion layer comprising a first titanium layer that prevents migration of tin;

a bonding metal layer next to the adhesion layer, the bonding metal layer comprising a tin layer;

a non-reactive barrier metal layer next to the bonding metal layer, the non-reactive barrier metal layer comprising a second titanium layer that prevents migration of tin;

an encapsulation layer next to the non-reactive barrier metal layer, the encapsulation layer comprising a platinum layer that prevents migration of silver;

a reflective layer encapsulated by the encapsulation layer, the reflective layer comprising a silver layer;

a current blocking layer next to the reflective layer; and

a light emitting structure next to the current blocking layer and the reflective layer, the light emitting structure comprising an active layer between a p-type layer and an n-type layer;

wherein the n-type layer comprises a first gallium-nitride (GaN) layer, a second GaN layer, and an intervening sublayer between the first GaN layer and the second GaN layer;

wherein the intervening sublayer comprises an aluminum-gallium-nitride layer doped with silicon (AlGaN;

Si);

wherein the intervening sublayer is thinner than the first GaN layer, and the intervening sublayer is thinner than the second GaN layer.

2. The apparatus of claim 1, wherein the active layer comprises indium and gallium, and wherein the bonding metal layer further comprises a gold layer.

3. The apparatus of claim 1, wherein a sum of thicknesses of all platinum layers between the light emitting structure and the carrier is less than 200 nanometers.

4. The apparatus of claim 1, wherein there is one and only one layer of platinum between the light emitting structure and the carrier.

5. The apparatus of claim 1, wherein the encapsulation layer comprises at least one layer of nickel and a layer of rhodium.

6. The apparatus of claim 1, wherein the non-reactive barrier metal layer comprises substantially no platinum.

7. The apparatus of claim 1, wherein the non-reactive barrier metal layer comprises substantially no tungsten.

8. The apparatus of claim 1, wherein the bonding metal layer comprises a plurality of layers, one of which is an alloy layer including the tin and a first metal material that is different from the tin.

9. The apparatus of claim 8, wherein:

the bonding metal layer comprises a second layer of the first metal material, a third layer of the first metal material, and

the alloy layer is between the second layer and the third layer.

10. The apparatus of claim 1, wherein the bonding metal layer comprises a eutectic metal layer.

11. The apparatus of claim 1, wherein the non-reactive barrier metal layer is greater than fifty nanometers thick.

12. The apparatus of claim 1, wherein the carrier comprises a silicon substrate.

13. The apparatus of claim 1, wherein the intervening sublayer has a bandgap that is less than 6.2 eV.

14. The apparatus of claim 1, wherein the intervening sublayer has a bandgap that is less than 4 eV.

15. The apparatus of claim 1, wherein the n-type layer comprises a plurality of the intervening sublayers.