晶片黏貼技術應用於三/五族化合物半導體元件效率提升之研究

Abstract

本文主旨是以晶片黏貼的技術製作三五族化合物半導體光電元件之光電特性探討，利用晶片黏貼技術可以達到異質磊晶的需求，也因此克服了三五族化合物光電元件因先天晶格匹配的物理限制下無法製作出的結構並達到較好的光電特性。第一部份是探討將塑膠光纖所用的650nm共振腔發光二極體以兩次晶片黏貼之技術，將傳統的砷化鎵基板以高導熱的矽基板取代，並維持與原先相同結構中的正極朝上與上下布拉格反射鏡之化合物半導體材料，所製作出元件的電特性與原先結構相近，而元件光特性上具有較高的光功率輸出、元件對環境溫度與高電流注入影響較低、較低的接面溫度，此外元件於資料傳輸的測試中可達到622Mbit/sec。第二部分則是介紹晶片黏貼之技術應用在磷化鋁銦鎵的發光二極體元件，前半部份是利用膠合黏貼與溼蝕刻的技術，將傳統吸光且導熱差的砷化鎵基板以高透光的藍寶石基板取代，並以高溫濕蝕刻方式將藍寶石基板側壁做非等相性蝕刻，此具有基板側壁導角的元件將可以大幅增加光淬取效率，另外考量藍寶石基板的散熱特性較差，元件亦製作出覆晶型式且具有側壁導角之發光二極體元件，由於發光區接近矽基板且具有很厚的窗口層於元件表面，因此覆晶型式結構的發光效率與元件特性相較於前者可以大幅提升；而後半段則是利用金屬黏貼技術將砷化鎵基板以矽基板取代，藉此能提高元件在高溫或高電流注入之效率，此外為了提升光淬取效率在元件的表面製作出結構化，其中包含了微米尺寸之碗狀陣列結構，以及在微米碗狀結構中以奈米球塗佈與乾蝕刻方式製作出奈米尺寸之柱狀結構，這相較於傳統表面平整之元件可增加兩倍光淬取效率。第三部分則是介紹將金屬黏貼技術應用在氮化鎵材料之藍綠光發光二極體元件，搭配雷射剝離技術將傳統藍寶石基板以高導熱矽基板取代，首先晶片黏貼前以雷射挖取溝槽將可提升雷射剝離之良率；將優化的鋁銀合金做為歐姆接觸材料與反射層的技術運用結構中，鋁銀合金不但具有高反射率且有較好高溫穩定性，另外為了解決氮表面歐姆接觸不易，高濃度摻雜與清洗方式將可大幅降低接觸電阻，此外優化後氫氧化鉀溶液將可以大幅提升光淬取效率，最後元件相較於傳統藍寶石基板之氮化物發光二極體具有較佳的光電特性、較低的熱阻抗與穩定的可靠度。

This dissertation is study of wafer bonding technique applied for III-V compound semiconductor optoelectronic devices. The wafer bonding technique overcomes hetero-epitaxy growth and achieving better electrical and optical performances which are restricted by physical barrier of lattice match requirement. Firstly, the conventional 650nm RCLEDs for plastic optical fiber with GaAs substrate is replaced with a high thermal conductivity Si substrate by glue bonding and metal bonding technique. This MBRCLEDs is maintained p-side up and DBRs materials structure and without sacrificing electrical performances. The MBRCLEDs has higher output power, high temperature insensitivity, less decay in high current injection, lower junction temperature as compared with conventional RCLEDs. Furthermore, the MBRCLEDs have superior reliability and achieve 622Mbit/ sec. Second, the glue bonding technique is applied to AlGaInP-based LEDs. The conventional GaAs substrate, having inherent drawbacks of poor thermal conductivity and absorbed, is replaced with a transparent sapphire substrate. The sapphire substrate sidewall has geometric shaping by using high temperature chemical etchant. This geometric sapphire shaping LEDs provide superior light extraction efficiency as compared to without one. In order to improve thermal issue in sapphire substrate, the flip-chip structure is applied for improving. The flip-chip AlGaInP-based LEDs have thick window layer of sapphire, which has geometric sidewall shaping, p-side layer close to Si submount for thermal dispersion. This flip-chip structure provides an excellent light extraction efficiency and stable reliability. Furthermore, the metal bonding technique is implemented in AlGaInP-based LEDs, and the GaAs substrate is replaced with Si substrate. The metal bonding LEDs have textured surface for increasing light extraction efficiency. Several textures of micro scale bowls array and nano scale rods added in micro bowls are implemented by anisotropic chemical etching and nano-spheres spin-coating with dry-etching. Comparing to conventional plane surface, the nano-rods added in micro-bowls surface LEDs has two magnitudes output power due to less total internal reflection effect. Finally, the vertical thin film GaN-based LEDs are fabricated by metal bonding and laser-lift-off technique. In order to release internal stress and improve yield after laser lift-off process, a laser cut trench before metal bonding process is used. The optimized Al an Ag composition to form AlAg alloy for p-ohmic contact and high reflector application is applied. The AlAg alloy provides not only high reflectivity but also high thermal stable property. In order to solve n-ohmic contact at N-face n-GaN layer, higher doped n-GaN layer and chemical cleaning at N-face are also implemented. The optimized KOH chemical etchant for surface roughing is applied for enhancing light extraction efficiency. Comparing to conventional sapphire-based GaN-LEDs, the vertical thin film GaN-based LEDs has higher output power under equal current density, lower forward voltage, less wavelength shift under high current injection and high ambient temperature, lower thermal impendence, and higher reliability over 1000hr.