本文研究了0.8μm SOI NMOS晶体管,经剂量率为50rad(Si)/s的60Coγ射线辐照之后的总剂量效应,分析了器件在不同辐照条件和测量偏置下的辐照响应特性.研究结果表明:器件辐照时的栅偏置电压越高,辐照后栅氧化层中积累的空穴陷阱电荷越多,引起的漏极泄漏电流越大.对于漏偏置为5V的器件,当栅电压大于阈值电压时,前栅ID-VG特性曲线中的漏极电流因碰撞电离而突然增大,体电极的电流曲线呈现倒立的钟形.
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.
A comparative study of two kinds of oxidants（H2O and O3） with the combinations of two metal precursors [trimethylaluminum（TMA） and tetrakis（ethylmethylamino） hafnium（TEMAH）] for atomic layer deposition（ALD） hafnium aluminum oxide（HfAlOx） films is carried out.The effects of different oxidants on the physical properties and electrical characteristics of HfAlOx films are studied.The preliminary testing results indicate that the impurity level of HfAlOx films grown with both H2O and O3 used as oxidants can be well controlled,which has significant effects on the dielectric constant,valence band,electrical properties,and stability of HfAlOx film.Additional thermal annealing effects on the properties of HfAlOx films grown with different oxidants are also investigated.
In this paper the influences of the metal-gate and high-k/SiO 2 /Si stacked structure on the metal-oxide-semiconductor field-effect transistor（MOSFET） are investigated.The flat-band voltage is revised by considering the influences of stacked structure and metal-semiconductor work function fluctuation.The two-dimensional Poisson＇s equation of potential distribution is presented.A threshold voltage analytical model for metal-gate/high-k/SiO 2 /Si stacked MOSFETs is developed by solving these Poisson＇s equations using the boundary conditions.The model is verified by a two-dimensional device simulator,which provides the basic design guidance for metal-gate/high-k/SiO 2 /Si stacked MOSFETs.
HfO2 films are deposited by atomic layer deposition（ALD） using tetrakis ethylmethylamino hafnium（TEMAH） as the hafnium precursor,while O3 or H2O is used as the oxygen precursor.After annealing at 500℃ in nitrogen,the thickness of Ge oxide＇s interfacial layer decreases,and the presence of GeO is observed at the H2 O-based HfO2 interface due to GeO volatilization,while it is not observed for the O3-based HfO2.The difference is attributed to the residue hydroxyl groups or H2 O molecules in H2 O-based HfO2 hydrolyzing GeO2 and forming GeO,whereas GeO is only formed by the typical reaction mechanism between GeO2 and the Ge substrate for O3-based HfO2 after annealing.The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing,which has effects on the variation of valence band offset and the C-V characteristics of HfO2 /Ge after annealing.The results are confirmed by X-ray photoelectron spectroscopy（XPS） and electrical measurements.
本文对PD SOI NMOS器件进行了60Coγ射线总剂量辐照的实验测试,分析了不同的栅长对器件辐射效应的影响及其物理机理.研究结果表明,短沟道器件辐照后感生的界面态密度更大,使器件跨导出现退化.PD SOI器件的局部浮体效应是造成不同栅长器件辐照后输出特性变化不一致的主要原因.短沟道器件输出特性的击穿电压更低.在关态偏置条件下,由于背栅晶体管更严重的辐射效应,短沟道SOI器件的电离辐射效应比同样偏置条件下长沟道器件严重.
We present an AIInN/AlN/GaN MOS-HEMT with a 3 nm ultra-thin atomic layer deposition （ALD） Al2O3 dielectric layer and a 0.3 μm field-plate （FP）-MOS-HEMT. Compared with a conventional AIInN/AlN/GaN HEMT （HEMT） with the same dimensions, a FP-MOS-HEMT with a 0.6 μm gate length exhibits an improved maximum drain current of 1141 mA/mm, an improved peak extrinsic transconductance of 325 mS/mm and effective suppression of gate leakage in both the reverse direction （by about one order of magnitude） and the forward direction （by more than two orders of magnitude）. Moreover, the peak extrinsic transconductance of the FP-MOS-HEMT is slightly larger than that of the HEMT, indicating an exciting improvement of transconductance performance. The sharp transition from depletion to accumulation in the capacitance-voltage （C-V） curve of the FP-MOS-HEMT demonstrates a high-quality interface of Al2O3/AlInN. In addition, a large off-state breakdown voltage of 133 V, a high field-plate efficiency of 170V/#m and a negligible double-pulse current collapse is achieved in the FP-MOS-HEMT. This is attributed to the adoption of an ultra-thin Al2O3 gate dielectric and also of a field-plate on the dielectric of an appropriate thickness. The results show a great potential application of the ultra-thin ALD-Al2O3 FP-MOS-HEMT to deliver high currents and power densities in high power microwave technologies.
