High temperature gold-free wafer bonding for light emitting diodes

• Main Authors: HAMAGUCHI NORIHITO, LIN CHAO-KUN, YANG LONG, CHUANG CHIH-WEI
• Format: Patent
• Language: English
• Published: 22.09.2015
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR; ELECTRICITY; SEMICONDUCTOR DEVICES

A vertical GaN-based LED is made by growing an epitaxial LED structure on a silicon wafer. A silver layer is added and annealed to withstand >450° C. temperatures. A barrier layer (e.g., Ni/Ti) is provided that is effective for five minutes at >450° C. at preventing bond metal from diffusing into the silver. The resulting device wafer structure is then wafer bonded to a carrier wafer structure using a high temperature bond metal (e.g., AlGe) that melts at >380° C. After wafer bonding, the silicon is removed, gold-free electrodes (e.g., Al) are added, and the structure is singulated. High temperature solder (e.g., ZnAl) that is compatible with the electrode metal is used for die attach. Die attach occurs at >380° C. for ten seconds without melting the bond metal or otherwise damaging the device. The entire LED contains no gold, and consequently is manufacturable in a high-volume gold-free semiconductor fabrication facility.