Improving the reliability of eutectic bonding vertical power light-emitting diodes by a Mo buffer layer

• Published in: Thin solid films 2014-11, Vol.570, p.500-503
• Main Authors: Chang, Liann-Be, Yen, Chia-I, You, Ting-Wei, Jeng, Ming-Jer, Wu, Chun-Te, Hu, Sung-Cheng, Kuo, Yang-Kuao
• Format: Article
• Language: English
• Subjects: Ag-paste; Applied sciences; Bonding; Buffer layers; Condensed matter: structure, mechanical and thermal properties; Copper; Cu–Sn; Design. Technologies. Operation analysis. Testing; Devices; Electronics; Eutectic bonding; Eutectic temperature; Exact sciences and technology; Integrated circuits; LED; Light-emitting diodes; Microelectronic fabrication (materials and surfaces technology); Optoelectronic devices; Physical properties of thin films, nonelectronic; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silver; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thermal shock; Thermal stability; thermal effects; Wafers
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2014.03.029

As a major step in the conduction of heat dissipation, wafer bonding significantly contributes to device reliability. This work presents the Cu–Sn eutectic bonding with a Mo buffer layer for light emitting diodes to increase its reliability. The conventional Ag-paste bonding and Cu–Sn bonding (without Mo top layer) are also studied for comparison. Their reliability is measured using thermal shock treatments ranging from −40 to 120°C (200cycles). Experimental results indicate that the eutectic bonding with a Mo buffer layer demonstrates a better device performance than the other two counterparts. Following thermal shock treatment, the light droops for the Ag-paste, Cu–Sn, and Mo/Cu–Sn bonding samples are 15, 11 and 7%, respectively. Additionally, the increasing ratios of thermal resistance are 26, 33 and 19%, respectively. Moreover, adding the Mo buffer layer can relieve the thermal stress problem, owing to the thermal expansion mismatch in Gallium–Nitride/Cu–Sn/submount wafer bonding structures. •Eutectic bonding with a Mo buffer layer is investigated in Cu–Sn eutectic bonding.•Thermal shock treatments (−40–120°C, 200cycles) were used to test reliability.•Light droop for the Ag-paste, Cu–Sn, and Mo/Cu–Sn bonding was ~15, 11 and 7%.•A Mo buffer layer can effectively relieve thermal stress.