本文研究了原子层化学气相淀积ALCVD(atom layer chemical vapor deposition)方法淀积的HfO2/SiO2/p-SiMOS电容的电特性.高频时,积累电容出现了频率色散现象.针对双频C-V法测量超薄HfO2/SiO2堆栈栅MOS电容中制备工艺和测量设备引入的寄生效应,给出了改进的等效电路模型,消除了频率色散.研究发现,高k介质中存在的缺陷和SiO2/Si处的界面态,使高频C-V特性发生漂移.对禁带中界面态的分布进行归纳,得到C-V曲线形变的规律.研究了形变的C-V曲线与理想C-V特性的偏离,给出了界面态电荷密度的分布,得到了相对于实测C-V曲线的矫正线.通过比较理想C-V曲线和矫正线,提取了平带电压、栅氧化层电荷、SiO2/Si界面的界面态密度等典型的电学参数.
本文提出了一个新型的SOI埋层结构SOANN(silicon on aluminum nitride with nothing),用AIN代替传统的SiO2材料,并在SOI埋氧化层中引入空洞散热通道.分析了新结构SOI器件的自加热效应.研究结果表明:用AIN做为SOI埋氧化层的材料,降低了晶格温度,有效抑制了自加热效应.埋氧化层中的空洞,可以进一步提供散热通道,使埋氧化层的介电常数下降,减小了电力线从漏端通过埋氧到源端的耦合,有效抑制了漏致势垒降低DIBL(drain Induced barrier lowering)效应.因此,本文提出的新型SOANN结构可以提高SOI器件的整体性能,具有优良的可靠性.
A GaN/A10.3Ga0.TN/A1N/GaN high-electron mobility transistor utilizing a field plate （with a 0.3 μm overhang towards the drain and a 0.2 μm overhang towards the source） over a 165-nm sputtered HfO2 insulator （HfO2-FP- HEMT） is fabricated on a sapphire substrate. Compared with the conventional field-plated HEMT, which has the same geometric structure but uses a 60-nm SiN insulator beneath the field plate （SiN-FP-HEMT）, the HfO2-FP-HEMT exhibits a significant improvement of the breakdown voltage （up to 181 V） as well as a record field-plate efficiency （up to 276 V/μm）. This is because the HfO2 insulator can further improve the modulation of the field plate on the electric field distribution in the device channel, which is proved by the numerical simulation results. Based on the simulation results, a novel approach named the proportional design is proposed to predict the optimal dielectric thickness beneath the field plate. It can simplify the field-plated HEMT design significantly.
High performance 150-nm gate-length metamorphic Al0.48In0.52As/Ga0.47In0.53 As high electron mobility transistors(mHEMTs) with very good device performance have been successfully fabricated.A T-shaped gate is fabricated by using a combined technique of optical and e-beam photolithography,which is beneficial to decreasing parasitic capacitance and parasitic resistance of the gate.The ohmic contact resistance R c is as low as 0.03 mm when using a novel ohmic contact metal system(Ni/Ge/Ti/Au).The devices exhibit excellent DC and RF performance.A peak extrinsic transconductance of 775 mS/mm and a maximum drain current density of 720 mA/mm are achieved.The unity current gain cut-off frequency(fT) and the maximum oscillation frequency(f max) are 188.4 and 250 GHz,respectively.
WU XiaoFengLIU HongXiaLI HaiOuLI QiHU ShiGangXI ZaiFangZHAO Jin
