具有栅介质电场屏蔽作用的新型GaN纵向槽栅MOSFET器件设计

Design of Novel Vertical GaN-Based Trench Gate MOSFET with Electric Field Shielding Function of Gate Dielectric

摘要:

基于氮化镓(GaN)等宽禁带(WBG)半导体的金氧半场效应晶体管(MOSFET)器件在关态耐压下,栅介质中存在与宽禁带半导体临界击穿电场相当的大电场,致使栅介质在长期可靠性方面受到挑战。为了避免在GaN器件中使用尚不成熟的p型离子注入技术,提出了一种基于选择区域外延技术制备的新型GaN纵向槽栅MOSFET,可通过降低关态栅介质电场来提高栅介质可靠性。提出了关态下的耗尽区结电容空间电荷竞争模型,定性解释了栅介质电场p型屏蔽结构的结构参数对栅介质电场的影响规律及机理,并通过权衡器件性能与可靠性的关系,得到击穿电压为1200V、栅介质电场仅0.8MV/cm的具有栅介质长期可靠性的新型GaN纵向槽栅MOSFET。

Abstract:

Metal-oxide-semiconductor field effect transistor (MOSFET) devices based on wide bandgap (WBG) semiconductors such as gallium nitride (GaN) have a high electric field equivalent to the critical breakdown electric field of WBG semiconductor in the gate dielectric under the off-state voltage, which dampens the long-term reliability of the gate dielectric. In order to avoid using the immature p-type ion implantation technology in GaN devices, a new type of vertical GaN-based trench gate MOSFET based on selective area epitaxy is proposed, which can improve the gate dielectric reliability by reducing the off-state gate dielectric electric field. And a process preparation based on selective region epitaxy is designed to avoid the etching damage of MOS interface. The space charge competition model of the depletion region junction capacitance in the off-state is proposed, and the influence law and mechanism of the structural parameters of p-type shielding structure on the gate dielectric electric field are qualitatively explained. By trade off the relationship between device performance and reliability, a novel vertical GaN-based trench gate MOSFET with long-term reliability of gate dielectric is obtained with the breakdown voltage of 1200V and gate dielectric electric field of 0.8MV/cm.