Yang Shun-Kai, Mazumder Soumen, Wu Zhan-Gao, Wang Yeong-Her
Department of Electrical Engineering, Institute of Microelectronics, National Cheng Kung University, Tainan 701, Taiwan.
Materials (Basel). 2021 Mar 21;14(6):1534. doi: 10.3390/ma14061534.
In this paper, we have demonstrated the optimized device performance in the Γ-shaped gate AlGaN/AlN/GaN metal oxide semiconductor high electron mobility transistor (MOS-HEMT) by incorporating aluminum into atomic layer deposited (ALD) HfO and comparing it with the commonly used HfO gate dielectric with the N surface plasma treatment. The inclusion of Al in the HfO increased the crystalline temperature (~1000 °C) of hafnium aluminate (HfAlO) and kept the material in the amorphous stage even at very high annealing temperature (>800 °C), which subsequently improved the device performance. The gate leakage current (I) was significantly reduced with the increasing post deposition annealing (PDA) temperature from 300 to 600 °C in HfAlO-based MOS-HEMT, compared to the HfO-based device. In comparison with HfO gate dielectric, the interface state density (D) can be reduced significantly using HfAlO due to the effective passivation of the dangling bond. The greater band offset of the HfAlO than HfO reduces the tunneling current through the gate dielectric at room temperature (RT), which resulted in the lower I in Γ-gate HfAlO MOS-HEMT. Moreover, I was reduced more than one order of magnitude in HfAlO MOS-HEMT by the N surface plasma treatment, due to reduction of N vacancies which were created by ICP dry etching. The N plasma treated Γ-shaped gate HfAlO-based MOS-HEMT exhibited a decent performance with I of 870 mA/mm, G of 118 mS/mm, threshold voltage (V) of -3.55 V, higher I/I ratio of approximately 1.8 × 10, subthreshold slope (SS) of 90 mV/dec, and a high V of 195 V with reduced gate leakage current of 1.3 × 10 A/mm.
在本文中，我们通过将铝掺入原子层沉积（ALD）的HfO中，并将其与经过N表面等离子体处理的常用HfO栅极电介质进行比较，展示了Γ形栅极AlGaN/AlN/GaN金属氧化物半导体高电子迁移率晶体管（MOS-HEMT）的优化器件性能。HfO中Al的加入提高了铝酸铪（HfAlO）的结晶温度（约1000°C），即使在非常高的退火温度（>800°C）下，材料仍保持非晶态，这随后改善了器件性能。与基于HfO的器件相比，基于HfAlO的MOS-HEMT中，随着沉积后退火（PDA）温度从300°C升高到600°C，栅极漏电流（I）显著降低。与HfO栅极电介质相比，由于有效钝化了悬空键，使用HfAlO可显著降低界面态密度（D）。HfAlO比HfO更大的能带偏移降低了室温（RT）下通过栅极电介质的隧穿电流，这导致Γ形栅极HfAlO MOS-HEMT中的I更低。此外，由于电感耦合等离子体（ICP）干法蚀刻产生的N空位减少，通过N表面等离子体处理，HfAlO MOS-HEMT中的I降低了一个多数量级。经N等离子体处理的Γ形栅极HfAlO基MOS-HEMT表现出良好的性能，I为870 mA/mm，G为118 mS/mm，阈值电压（V）为 -3.55 V，更高的I/I比约为1.8×10，亚阈值斜率（SS）为90 mV/dec，高V为195 V，栅极漏电流降低至1.3×10 A/mm。
