摘要 近年來為了追求固態照明用之高功率發光二極體，將散熱性差的sapphire基板移除是一個重要發展的方向。而過去5-10年發展出的thin-GaN LED結構即是用以解決這個難題所製作而成的高功率發光二極體。在thin-GaN LED製程當中，把氮化鎵薄膜從sapphire轉移到有較好熱傳導性和導電性的矽基板上，必須使用wafer bonding的技術。而先前研究指出，在磊晶過程中，會因為sapphire和矽基板的熱膨脹係數(Coefficient of Thermal Expansion)不同而產生熱應力殘留在GaN磊晶層內[1][2]，由於熱應力會導致GaN epi-layer內部量子效率降低[3]，近而影響LED的發光效率。因此本研究將利用Cu/Sn/Ag晶圓鍵合製作Thin-GaN LED，並用此一技術將GaN磊晶層的應力降低。本實驗藉由Cu/Sn/Ag材料於低溫150 ℃成功的進行晶圓鍵結，並於GaN薄膜轉移後，比較不同鍵結金屬系統、溫度、時間的應力釋放量。最後探討經由晶圓鍵結程序後，可降低MQW因晶格不匹配所造成的極化效應，並由文獻[14]指出降低極化場效應對LED的light-output power、External quantum efficiency、發光波長的改善。 Abstract To pursuit higher output power of LED for general lighting applications, the poor thermal and electrical conduction of the sapphire substrate is a hurdle to be solved. For the last few years, peoples believe that Thin-GaN LED is the one having a great potential to be the solution of high-power LED applications. To fabricate Thin-GaN LED, wafer bonding is often used to transfer the GaN epilayer onto the thermal conductive substrate, i.e., Si wafer in this work. Previous researches indicate that a high thermal stress would be resulted from the difference of the coefficient of thermal expansions between sapphire substrate and the transferring Si substrate. The thermal stress would cause serious cracking on the GaN epi-layer. Therefore, a low- temperature wafer bonding is the key step for a successful process of Thin-GaN LED. In this work, a low-temperature wafer bonding process using Cu-Sn-Ag solid diffusion bonding is successfully developed. The primary results show that an uniform bonding interface can be achieved at 150 ℃. Using Cu-Sn-Ag solid diffusion wafer bonding, GaN MOCVD epi-layer was transferred on the Si wafer, then, thin-GaN LED was processed. Then, the stress relief of thin-GaN LEDs was measured and compared with different bonding temperatures, systems, and process ambient.
