垂直式LED元件光電特性之研究

Abstract

發光二極體(Light-Emitting Diode)具有潛力發展成新世代固態照明的主流元件，目前對於LED的研究，主要著重於高功率的大面積(1×1 mm2以上)的 LED[1]，功率大代表LED產生的熱能也大，因此在散熱的研究上也是大家研究的重點。 相較於傳統Sapphire-based LED 如 Face-up LED 與 Flip-chip LED 的共平面p型與n型電極，垂直式 LED (Vertical LED)結構最新穎，擁有較佳的電流分布以及散熱能力，相同的 chip size 下電極遮蔽面積較低、發光面積最大，最具有發展大面積(大於 40 mils 以上)高功率 LED 的技術優勢，兼具高流明輸出與高效率，為未來 LED 照明產業最關鍵的光源技術之一。 目前垂直式 LED 或 Thin GaN LED 的封裝單體，包括兩道高溫 Bonding 製程，其一為晶粒製造時的基板轉移製程，其二為後續封裝時的高溫固晶製程，至少兩次的高溫結合產生的雙結合面，除了增加介面熱阻，也降低封裝良率與可靠度。因此，創新的垂直式 LED 結構與其製造技術，可提升垂直式 LED 光熱特性、良率及可靠度，成為未來照明級 LED 光源的關鍵技術方向。以 LED 的封裝角度來看，除了需提供 LED 晶片保護與電氣特性外，良好的導熱與高信賴度也是高功率 LED 封裝元件關鍵特性， LED 晶圓級構裝技術(wafer-level package，WLP) 已嶄露頭角，提供半導體業者進入固態照明產業最佳技術管道，勢必成為下一波固態照明爆發成長的重要關鍵技術。

Light-Emitting Diode has the potential to be developed into the mainstream device of cutting edge solid state lighting. Currently, research on LED has its focus on high power and large area (above 1×1 mm2) LED [1]. High power means the heat generated by LED is also of large amount, hence, the research on heat dissipation is also the focus of research. As compared to the traditional sapphire-based LED, for example, the co-planar p type and n type electrodes of Face-up LED and Flip-chip LED, vertical LED has the newest structure, and it also owns better current distribution and heat dissipation capability. Under the same chip size, the electrode masking area is lower, the light-emitting area is the largest, hence, it has the most advantage to be developed into large area (larger than 40 mils) and high power LED. It has both high lumen output and high efficiency, and it is the most crucial optical source technology in the future LED lighting industry. Currently, the package unit of vertical LED or thin GaN LED includes two high temperature bonding processes, one is the substrate transfer process during the chip processing, and the second is the subsequent high temperature die bonding during the packaging process. Double bonding surface is generated by at least two times of high temperature bonding, it not only increases the interface heat resistance, but also reduces packaging yield and reliability. Therefore, innovative vertical LED structure and its manufacturing technology can enhance the photo-thermal property, yield and reliability of the vertical LED, and it will become the key technology of future lighting grade LED optical source. If we take a look from the view point of LED packaging, in addition to providing LED chip protection and electric characteristic, the package’s good thermal conduction and high reliability is also key characteristic of high power LED packaged device. LED wafer-level package (WLP) has its niche today, it is the best technical channel for a semiconductor players to get into the field of solid state lighting industry, hence, it is going to become key crucial technology in the eruption and growth of the next wave solid date lighting.