| 摘要: | 隨著5G通訊系統、再生能源系統、雲端機房、電動車/自駕車、人工智慧、機器人與物聯網的普及，氮化鎵(GaN)電子元件的市場規模預期可逐年快速成長。然而目前GaN元件大多製作於SiC，GaN-on-Si與GaN基板上，各自受限於磊晶厚度、品質、基板價格、尺寸等因素，造成元件規格與成本的瓶頸。本計畫擬以有機金屬化學蒸氣沉積法進行凡德瓦磊晶，成長GaN於有石墨烯或氮化硼二維材料覆蓋之多晶AlN基板、(111)與(100)矽基板，以突破前述基板所引起的瓶頸，在GaN材料領域開創新局。將使用的多晶AlN基板具有高絕緣性、高導熱性，國內可以量產，尺寸可達200 mm以上之優點，更可大幅降低因熱膨脹係數差異所引起的磊晶應力，可以容許GaN磊晶厚度大幅增加，而不會有磊晶龜裂或晶圓翹區的問題。毫米波電晶體性能也會因為用此高絕緣、高導熱之基板而明顯提升。選用(111)與(100)晶面矽基板，除可突破傳統GaN-on-Si的磊晶厚度限制，也希望將目前矽晶圓廠主流的(100)基板整合入GaN-on-Si製程，不僅可降低成本，亦可為GaN未來應用在邏輯與混和信號晶片奠定基礎。 ;With the advancements and growth of 5G mobile communications, renewable energy, cloud computing, electric/autonomous vehicles, artificial intelligence, robots, internet of things, a rapid growth of GaN-based power electronics and RF devices in the next few years is foreseen. However, current GaN RF devices are mainly developed on SiC substrate, which is insulating but limited by size and cost. As to the power electronics sector, GaN-on-Si is considered a competitive platform, on which lateral devices are developed and have been deployed. Due to the mismatch in thermal expansion coefficient between GaN and Si, the thickness of GaN is limited, therefore lateral devices are limited to applications below 900 V. For higher power applications, vertical devices on GaN substrate are under extensive development. However, the cost and size of GaN substrates available currently make these devices even more expensive than their SiC counterpart. This project aims at a new approach to resolve the aforementioned issues caused by the substrates. We plan to grow GaN films on poly-AlN substrates and (111)/(100) Si substrates, which are covered by graphene and/or h-BN 2D materials, using metal-organic vapor deposition. This is a van der Waals epitaxy process, a very challenging task while giving us an opportunity create a disruptive technology in the GaN device field. The poly-AlN substrate has not only high resistivity, high thermal conductivity, large wafer size up to 200 mm produced in a mass production scale by a local vendor, but also low thermal expansion coefficient mismatch with GaN, which allows a the growth of GaN up to several tens of um as required for high blocking voltage devices. Millimeter wave transistors are expected to perform better when this substrate is used. Growth parameters for GaN grown on both (111) and (100) Si substrates will also be explored in this work. The adoption of mainstream (100) Si substrates used current CMOS fab is expected to lower the cost as well as pave a way for heterogeneous integration with logic and mixed signal microchips. |
