柔性HfO2/Ta2O5叠层栅介质ZnO薄膜晶体管

为了有效提高柔性薄膜晶体管的电学性能,室温条件下,在聚酰亚胺(PI)衬底上使用H_fO₂、Ta₂O₅两种高介电常数材料相结合的叠层结构代替单层Ta₂O₅作为栅电介质,探究其对器件电学性能的影响。采用磁控溅射法制备薄膜,研究了叠层栅电介质结构中Ta₂O₅层在不同溅射时长、不同氧氩比条件下对于器件电学性能的影响,并进行H_fO₂/Ta₂O₅叠层栅电介质器件与Ta₂O₅单层栅电介质器件的比较。结果表明,Ta₂O₅栅电介质层在溅射时长为1 h、氧氩比为10∶90时,器件电学性能达到最佳。叠层栅电介质结构的引入显著提高了器件电学性能,电流开关比为1.27×10⁶,阈值电压为9.1 V,亚阈值摆幅为0.54 V/decade,载流子迁...     

有机/无机/有机结构的封装薄膜水汽透过率研究

为了减少原子层沉积(ALD)方法在氧化物薄膜制备过程中ALD反应气对有机电致发光器件(OLED)性能的影响,利用旋涂光交联聚合物技术,直接在OLED上形成有机/无机/有机3层结构的保护薄膜。通过扫描电子显微镜(SEM)、原子力显微镜(AFM)的表面形貌分析表明,3层结构的封装薄膜表面平滑且致密,减少水(H2O)汽在氧化物表面积聚,降低H2O对氧化物薄膜的腐蚀作用,且成膜过程对OLED的各功能层没有伤害。经Ca薄膜的电学方法测量证明,这种3层结构的封装薄膜对气体有极高的阻隔作用,其H2O汽透过率(WVTR)可以达到9.0×10-5 g/(m2·day),从而实现了对OLED的有效保护。     

有机电致发光器件的新型薄膜封装技术研究

针对有机电致发光器件(OLED)在空气中水汽和O2作用下寿命下降的问题,提出一种对OLED进行薄膜封装方法。封装薄膜由电子束蒸镀Al2O3薄膜和原子层沉积(ALD,atomic layer deposition)Al2O3薄膜相结合形成。利用Ca薄膜电学测试方法测定封装薄膜的水汽透过率(WVTR)。具体实现方法是,采用玻璃作为衬底,在100nm的Al电极上蒸镀200nm的Ca膜,然后对整个系统进行薄膜封装,只留出Al电极的一部分作为探针接触电极。实验发现,采用电子束蒸镀结合ALD的Al2O3薄膜封装,Ca薄膜变成透明的时间比未封装或采用单一结构封装得到了延长。为了检验薄膜封装效果,制作了一组绿光OLED,器件结构为ITO/MoOX(5nm)/mMTDATA(20nm)/NPB(30nm)/Alq3(50nm)/LiF(1nm)/Al,实验结果表明,本文提出的薄膜封装方法对器件进行封装,器件的寿命得到了延长。     

基于MIS电容器的Al2O3与In0.74Al0.26As的界面特性

采用In_0.74Al_0.26As/In_0.74Ga_0.26As/In_xAl_1-xAs异质结构多层半导体作为半导体层,制备了金属-绝缘体-半导体（MIS）电容器。其中,SiN_x和SiN_x/Al₂O₃分别作为MIS电容器的绝缘层。高分辨率透射电子显微镜和X射线光电子能谱的测试结果表明,与通过电感耦合等离子体化学气相沉积生长的SiN_x相比,通过原子层沉积生长的Al2_O3可以有效地抑制Al₂O₃和In_0.74Al_0.26As界面的In₂O₃的含量。根据MIS电容器的电容-电压测量结果,计算得到SiN_x/Al₂O₃/In...     

磁控溅射工作压强对β-Ga2O3薄膜特性的影响

作为新兴的第三代半导体材料,β-Ga₂O₃高质量薄膜是制备高效Ga₂O₃基器件的基础,β-Ga₂O₃薄膜的制备、表征及光电特性的研究具有深刻的意义。通过分析研究磁控溅射工作压强变化对薄膜性能和形貌的影响,为制备更高质量的薄膜提供了一种新的方法。基于射频磁控溅射方法,在单晶c面蓝宝石(Al₂O₃)衬底上沉积生长Ga₂O₃薄膜,并进行900℃、90min的氮气退火处理,以得到β-Ga₂O₃薄膜。沉积过程不改变其他实验参数,仅改变工作压强,研究工作压强对β-Ga₂O₃薄膜特性的影响。X射线衍射仪(XRD)和原子力显微镜(AFM)表征结果显示,β-Ga₂O₃薄膜具有不同取向的衍射峰,沿着■晶向择优生长,薄膜呈多晶状态。适当增大工作压强可使β-Ga<...     

h-BN/Al2O3栅介质氢终端金刚石场效应晶体管

金刚石是实现高频大功率器件的理想候选材料,但是其较低的载流子迁移率制约了器件的性能,六方氮化硼(h-BN)作为氢终端金刚石场效应晶体管(FET)的栅介质材料有望提升金刚石材料的载流子迁移率。利用商业化大面积h-BN材料,制备了h-BN/Al₂O₃栅介质的氢终端金刚石FET,h-BN/Al₂O₃/氢终端金刚石材料的载流子迁移率得到提升,达到186 cm²/(V·s)。相较于Al₂O₃栅介质的金刚石FET,h-BN/Al₂O₃栅介质的金刚石FET最大饱和电流密度和最大跨导均得到提升,分别为141 mA/mm和9.7 mS/mm。通过电容-电压(C-V)测试计算了栅介质和金刚石间界面固定电荷密度和陷阱密度,h-BN/Al₂O₃栅介质的金刚石FET界面负固定电荷密度为5.4×10¹² cm^-2·eV^-1...     

Al2O3厚度对SAW传感器声波模式及性能的影响

该文采用多物理场耦合的有限元模型,探究了保护层Al₂O₃厚度对以LGS为压电基底、Pt为电极的声表面波(SAW)高温传感器中声波特性及器件性能的影响。结果表明,随着Al₂O₃保护层厚度的增加,声表面波在L波方向的振动位移增加,在SH波和SV波方向的振动位移减弱,当保护层归一化厚度为6.25%时,其能量向衬底内部扩散;当保护层归一化厚度为18.75%时,Rayleigh波消失,此时为体波BAW模式;增加Al₂O₃保护层,波速v、机电耦合系数K²显著升高;一阶频率温度系数τ_f,1和转换温度随保护层厚度的增加而升高。利用Al₂O₃薄膜对SAW温度传感器进行结构优化,为了获得良好的综合性能,归一化厚度应该在0.94%附近。     

波浪形界面结构的Al2O3/PMMA交叠薄膜设计与力学性能仿真

文章以Al₂O₃/PMMA交叠薄膜为例,在其交叠界面处引入波浪形结构,通过增加Al₂O₃在弯曲方向的实际长度改善其力学性能。采用有限元仿真方法对Al₂O₃/PMMA交叠薄膜结构进行建模,分别研究了波浪形结构形貌、周期、深度和PMMA厚度等参数对交叠薄膜弯曲性能的影响规律。仿真结果表明,波浪形界面结构能较大提高交叠薄膜的弯曲性能,当波浪形结构的周期在500～1 500 nm,深度在600～1 600 nm范围内,PMMA厚度为6μm时,交叠薄膜具有较好的弯曲性能,相比于没有引入界面结构的交叠薄膜,同等条件下产生的最大应力下降了超过70%,有效提升了封装薄膜的弯曲性能,对后续无机/有机交叠薄膜的制备工艺具有指导意义。     

不同介电层对HfxZr1-xO2薄膜铁电性能影响的研究进展

近年来,铁电Hf_xZr_1-xO₂(HZO)薄膜受到越来越多的关注,但是铁电层与电极材料层以及铁电层与半导体衬底层之间的界面问题并没有得到解决,阻碍了HZO薄膜的进一步应用。总结了通过引入不同介电层材料,如Al₂O₃、ZrO₂、HfO₂、Ta₂O₅等,调节HZO薄膜铁电性能的方法及其机理;详细介绍了各种介电层材料作为封盖层对HZO薄膜铁电性能的影响,如对HZO薄膜提供平面内应力、控制铁电层的晶粒尺寸及作为铁电层形核核心的作用;最后,总结并展望了利用介电层调控HZO薄膜铁电性能的一般规律,为后续相关研究的开展提供了指导。     

一种具有高能量分辨率Al2O3钝化结区的PIN探测器

提出了一种Al₂O₃钝化结区的PIN探测器，与传统PIN探测器不同的是，在器件正面的pn结和背面的高低结处沉积了10 nm厚的Al₂O₃薄膜。经TCAD仿真结果表明，该探测器具有更低的漏电流和保护环处的电子电流密度，能对高能粒子射线入射产生良好的响应。设计了两种探测器的制备步骤并制备了器件，通过薄膜少子寿命的表征、器件的暗态I-V测试和²⁴¹Am元素能谱测试对其进行了评估。测试结果表明，与传统的PIN探测器相比，Al₂O₃钝化结区的PIN探测器的少子寿命提升至1 061μs,漏电流降低至5 nA,能量分辨率提升至521 eV,表现出更好的探测性能。     

Development of Embedded Three-Dimensional 35-nF/mm2 MIM Capacitor and BiCMOS Circuits Characterization

This paper summarizes the electrical characterization of MIM capacitor realized in three dimensions. Manufacturing of the device is described, as well as an electrical comparison of three dielectrics, Si₃N₄, Al₂O₃, Ta₂O₅ and two deposition methods, metal organic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). Selecting Al₂O₃ deposited by ALD, high density of 35 nF/mm² is obtained with low leakage current. Statistical measurements put forward the industrial robustness of the device integrated in BiCMOS technology. Three circuits embedding this new device are characterized: a high-pass filter, a voltage-controlled oscillator (VCO), and a phase-locked loop (PLL). They demonstrate excellent performances with significant area and assembly costs savings.     

Low-frequency noise in Si0.7Ge0.3 surface channel pMOSFETs with ALD HfO2/Al2O3 gate dielectrics

Low-frequency noise was characterized in Si_0.7Ge_0.3 surface channel pMOSFETs with ALD Al₂O₃/HfO₂/Al₂O₃ stacks as gate dielectrics. The influences of surface treatment prior to ALD processing and thickness of the Al₂O₃ layer at the channel interface were investigated. The noise was of the 1/f type and could be modeled as a sum of a Hooge mobility fluctuation noise component and a number fluctuation noise component. Mobility fluctuation noise dominated the 1/f noise in strong inversion, but the number fluctuation noise component, mainly originating from traps in HfO₂, also contributed closer to threshold and in weak inversion. The number fluctuation noise component was negligibly small in a device with a 2 nm thick Al₂O₃ layer at the SiGe channel interface, which reduced the average 1/f noise by a factor of two and decreased the device-to-device variations.     

Submicrometer Inversion-Type Enhancement-Mode InGaAs MOSFET With Atomic-Layer-Deposited Al2O3 as Gate Dielectric

High-performance inversion-type enhancement-mode n-channel In_0.53Ga_0.47As MOSFETs with atomic-layer-deposited (ALD) Al₂O₃ as gate dielectric are demonstrated. The ALD process on III-V compound semiconductors enables the formation of high-quality gate oxides and unpinning of Fermi level on compound semiconductors in general. A 0.5-mum gate-length MOSFET with an Al₂O₃ gate oxide thickness of 8 nm shows a gate leakage current less than 10^-4 A/cm² at 3-V gate bias, a threshold voltage of 0.25 V, a maximum drain current of 367 mA/mm, and a transconductance of 130 mS/mm at drain voltage of 2 V. The midgap interface trap density of regrown Al₂O₃ on In_0.53Ga_0.47As is ~1.4 x 10¹²/cm² ldr eV which is determined by low-and high-frequency capacitance-voltage method. The peak effective mobility is ~1100 cm² / V ldr s from dc measurement, ~2200 cm²/ V ldr s after interface trap correction, and with about a factor of two to three higher than Si universal mobility in the range of 0.5-1.0-MV/cm effective electric field.     

Two-step annealing technique for leakage current reduction inchemical-vapor-deposited Ta2O5 film

A capacitor technology developed to obtain extremely thin Ta₂ O₅ dielectric film with an effective SiO₂ film thickness down to 3 nm (equivalent to 11 fF/μm²) for a 1.5-V, low-power, high-density, 64-Mb DRAM is discussed. The Ta₂ O₅ has low leakage current, low defect density, and excellent step coverage. The key process is two-step annealing after the deposition of the film by thermal chemical vapor deposition (CVD). The first step involves ozone (O₃) annealing with ultraviolet light irradiation, which reduces the leakage current. The second step is dry oxygen (O₂) annealing, which decreases the defect density. A more significant reduction in the leakage current is attained by the combination of the two annealing steps     

Good High-Temperature Stability of TiN/ Al2O3/WN/TiN Capacitors

For the first time, good thermal stability up to an annealing temperature of 1000degC has been demonstrated for a new TiN/Al₂O₃/WN/TiN capacitor structure. Good electrical performance has been achieved for the proposed layer structure, including a high dielectric constant of ~ 10, low leakage current of 1.2times10^-7 A/cm² at 1 V, and excellent reliability. A thin WN layer was incorporated into the metal-insulator-metal capacitor between the bottom TiN electrode and the Al₂O₃ dielectric suppressing of interfacial-layer formation at Al₂ O₃/TiN interfaces and resulting in a smoother Al₂O₃/TiN interface. This new layer structure is very attractive for deep-trench capacitor applications in DRAM technologies beyond 50 nm.     

High-performance polycrystalline SiGe thin-film transistors usingAl2O3 gate insulators

The use of aluminum oxide as the gate insulator for low temperature (600°C) polycrystalline SiGe thin-film transistors (TFTs) has been studied. The aluminum oxide was sputtered from a pure aluminum target using a reactive N₂O plasma. The composition of the deposited aluminum oxide was found to be almost stoichiometric (i.e., Al₂O₃), with a very small fraction of nitrogen incorporation. Even without any hydrogen passivation, good TFT performance was measured an devices with 50-nm-thick Al₂O₃ gate dielectric layers. Typically, a field effect mobility of 47 cm²/Vs, a threshold voltage of 3 V, a subthreshold slope of 0.44 V/decade, and an on/off ratio above 3×10⁵ at a drain voltage of 0.1 V can be obtained. These results indicate that the direct interface between the Al₂ O₃ and the SiGe channel layer is sufficiently passivated to make Al₂O₃ a better alternative to grown or deposited SiO₂ for SiGe field effect devices     

High-density MIM capacitors using Al2O3 andAlTiOx dielectrics

We have investigated the electrical characteristics of Al₂ O₃ and AlTiO_x MIM capacitors from the IF (100 KHz) to RF (20 GHz) frequency range. Record high capacitance density of 0.5 and 1.0 μF/cm² are obtained for Al₂ O₃ and AlTiO_x MIM capacitors, respectively, and the fabrication process is compatible to existing VLSI backend integration. However, the AlTiO_x MIM capacitor has very large capacitance reduction at increasing frequencies. In contrast, good device integrity has been obtained for the Al₂O₃ MIM capacitor as evidenced from the small frequency dependence, low leakage current, good reliability, small temperature coefficient, and low loss tangent     

Improved gain performance in Yb3+-sensitized Er3+-doped alumina (Al2O3) channel opticalwaveguide amplifiers

Small-signal amplification in short, Yb³⁺-sensitized, Er³⁺-doped alumina (Al₂O₃) channel optical waveguides with high Er³⁺ concentrations is analyzed. Taking into account uniform up conversion, excited state absorption (ESA) from the Er³⁺ metastable level (⁴I_13/2 ), and Yb³⁺→Er³⁺ energy transfer by cross relaxation, the obtainable gain improvements compared to Yb³⁺ -free Er³⁺-doped Al₂O₃ optical waveguides are investigated. The amplifier model is based on propagation and population rate equations and is solved numerically by combining finite elements and the Runge-Kutta algorithm. The analysis predicts that 5-cm long Yb³⁺/Er³⁺ co-doped Al₂O ₃ waveguides show 13-dB net signal gain for 100 mW pump power at λ_p=980 nm     

Effects of Al2O3 Dielectric Cap and Nitridation on Device Performance, Scalability, and Reliability for Advanced High- κ/Metal Gate pMOSFET Applications

A pFET threshold-voltage (Vt) reduction of about 200 mV is demonstrated by inserting a thin Al₂O₃ layer between the high-k dielectric and the TiN gate without noticeable degradation of other electrical properties. HfSiO_propcapped with 9 Aring of thin Al₂O₃obtains a low long-channel Vt of -0.37 V (the lowest among those with TiN gate), a high mobility of 59 cm² /V ldr s at 0.8 MV/cm (92% of universal value), a negligible equivalent- oxide-thickness (EOT) increase of 0.1 Aring (compared to the uncapped reference), and a low Vt instability of 4.8 mV at 7 MV/cm. It also passes the ten-year negative-bias-temperature-instability (NBTI) lifetime specification with a gate overdrive of -0.7 V. This indicates that thin Al₂O₃obtains caps are beneficial to the pFET applications. In contrast, nitrogen incorporation in the Al₂O₃-capped HfSiO_prop is not favorable because it increases the Vt by 50-140 mV, degrades the mobility by 10%-22%, increases the EOT by 0.5-0.8 Aring and the Vt instability by 5-13 mV, and reduces the NBTI lifetime by four to five orders of magnitude. Compared to postcap nitridation, high-k nitridation results in more severe degradation of these properties by incorporating nitrogen closer to the Si/SiO₂ interface.     

Er3+ –Y3+-Codoped Al 2O3 for High-Temperature Sensing

Optical high-temperature sensing using the fluorescence intensity ratio (FIR) technique of green up-conversion emissions at 523 and 546 nm in Er³⁺-Y³⁺-codoped Al₂O₃ was studied in a wide temperature range of 295 K-973 K. The maximum sensitivity and the temperature resolution derived from the FIR technique are approximately 0.0035 K^-1 and 0.3 K, respectively, which indicated that Er³⁺-Y³⁺-codoped Al₂O₃ plays an important role for applications in the optical high-temperature sensing.