ANALYSIS OF THE X-RAY PHOTOELECTRON SPECTRA OF a-SiOCF FILMS PREPARED BY PLASMA-ENHANCED CHEMICAL VAPOUR DEPOSITION

The preparation of a-SiOCF films from Si(OC₂H₅)₄, C₄F₈ and/or Ar using the plasma-enhanced chemical vapour deposition method is reported. The chemical bonding structures of the films are analysed by x-ray photoelectron spectroscopy (XPS). In the case of the films deposited from the mixture with and without Ar, the configurations of F-Si-O-Si, Si-OH, Si-O-Si, C-CF and C-F are contained. However, there is also the C-C configuration in the film prepared from the mixture with Ar. Moreover, it is found that the photoelectron peaks of Si 2p, O 1s and F 1s for the film deposited from the feeding gas with Ar show the same shift of about 1eV toward high binding energy in comparison with those for the film prepared from the feeding gas without Ar. No evidence reveals the presence of an Si-C bond in the films.     

四角晶相HfO2(001)表面原子和电子结构研究

采用基于第一性原理的密度泛函理论研究了四角晶相二氧化铪(t-HfO₂)体相及 其(001)表面的原子几何与电子结构.理论计算结果表明，t-HfO₂(001)表面不会 产生重构现象.与体相电子结构相比, t-HfO₂(001)表面态密度明显高于体相态 密度.其次，表面原子的态密度更靠近费米能级(E_F)，价带往低能量处移动，并 有表面态产生.计算结果表明了t-HfO₂表面禁带宽度明显低于体相的禁带宽度. t-HfO₂(001)的表面态产生以及表面禁带宽度减小是由于Hf原子与O原子的配位 数减少，表面原子周围的环境发生变化而引起的. 关键词： 密度泛函理论 2(001)')" href="#">t-HfO₂(001) 表面电子结构     

Electrical Characterization of Metal-Insulator-Metal Capacitors with Atomic-Layer-Deposited HfO2 Dielectrics for Radio Frequency Integrated Circuit Application

Metal-insulator-metal （MIM） capacitors with atomic-layer-deposited HfO2 dielectric and TaN electrodes are investigated for rf integrated circuit applications. For 12nm HfO2, the fabricated capacitor exhibits a high capacitance density of 15.5fF/μm2 at 100kHz, a small leakage current density of 6.4 × 10^-9 A/cm^2 at 1.8V and 125℃, a breakdown electric field of 2.6 MV//cm as well as voltage coefficients of capacitance （VCCs） of 2110ppm/V^2 and -824 ppm/V at 100kHz. Further, it is deduced that the conduction mechanism in the high field range is dominated by the Poole-Frenkel emission, and the conduction mechanism in the low field range is possibly related to trap-assisted tunnelling. Finally, comparison of various HfO2 MIM capacitors is present, suggesting that the present MIM capacitor is a promising candidate for future rf integrated circuit application.     

Band Structures of Metal-Oxide Capped Graphene： A First Principles Study

We perform a first-principles calculation based on density functional theory to investigate the interface between single layer graphene and metal oxides. Our study reveals that the monolayer graphene becomes semiconducting by single crystal SiO2 and Al2O3 contact, with energy gaps to - 0.9 and - 1.8 eV, respectively. We find the gap originates from the breakage of π bond integrity, whose extent is related to the interface atom configuration. We believe that our results highlight a promising direction for the feasibility to apply large scale graphene layers as building blocks in future electronics devices.     

Low voltage program-erasable Pd-Al_2O_3-Si capacitors with Ru nanocrystals for nonvolatile memory application

Pd-Al2O3-Si capacitors with Ru nanocrystals are fabricated and electrically characterized for nonvolatile memory application.While keeping the entire insulator Al2O3thickness fixed,the memory window has a strong dependence on the tunneling layer thickness under low operating voltages,whereas it has weak dependence under high operating voltages.As for the optimal configuration comprised of 6-nm tunneling layer and 22-nm blocking layer,the resulting memory window increases from 1.5 V to 5.3 V with bias pulse increasing from 10 5s to 10 2s under±7 V.A ten-year memory window as large as 5.2 V is extrapolated at room temperature after±8 V/1 ms programming/erasing pulses.     

Memory Effect of Metal--Insulator--Silicon Capacitors with SiO2/HfO2/Al2O3 Dielectrics

Charge trapping characteristics of the metal-insulator-silicon （MIS） capacitors with Si02/HfO2//A12O3 stacked dielectrics are investigated for memory applications＇. A capacitance-voltage hysteresis memory window as large as 7.3 V is achieved for the gate voltage sweeping of ±12 V, and a fiat-band voltage shift of 1.5 V is observed in terms of programming under 5 V and I ms. Furthermore, the time- and voltage-dependent charge trapping characteristics are also demonstrated, the former is related to charge trapping saturation and the latter is ascribed to variable tunnelling barriers for electron injecting and discharging under different voltages.     

四角晶相HfO2(001)表面原子和电子结构研究

采用基于第一性原理的密度泛函理论研究了四角晶相二氧化铪(t-HfO2)体相及其(001)表面的原子几何与电子结构.理论计算结果表明,t-HfO2(001)表面不会产生重构现象.与体相电子结构相比, t-HfO2(001)表面态密度明显高于体相态密度.其次,表面原子的态密度更靠近费米能级(EF),价带往低能量处移动,并有表面态产生.计算结果表明了t-HfO2表面禁带宽度明显低于体相的禁带宽度. t-HfO2(001)的表面态产生以及表面禁带宽度减小是由于Hf原子与O原子的配位数减少,表面原子周围的环境发生变化而引起的.     

POROUS AMORPHOUS FLUOROPOLYMER FILMS WITH ULTRALOW DIELECTRIC CONSTANT

With the development of ultralarge scale integrated circuit, new interlayer dielectrics with low dielectric constant for multilevel interconnections are required, instead of conventional SiO₂ films. For the sake of seeking perfect dielectrics, amorphous fluoropolymer (AF) thin film with a thickness of about 0.9μm has been prepared by spin-coating method, following the principle of phase separation. By capacitance-voltage (C-V) measurements the dielectric constant of the thin film is equal to 1.57 at 1 MHz, which is attributed to numerous pores contained in the film matrix. X-ray photoelectron spectroscopy (XPS) spectra show that after annealing, about 71% CF₃ groups in the AF film have decomposed into CF₂, CF, etc. This leads to the increase of CF₂ groups by three times and CF groups by 8% in the AF film. In a word, compared with the film without being annealed, about 25% carbon, 7% fluorine and 12% oxygen atoms will be lost after annealing at 400℃ for 30min.     

热退火对等离子体增强化学气相沉积SiCOH薄膜结构与性能的影响

热退火是多孔低介电常数薄膜制备过程中的重要一环, 对薄膜结构及性能具有重要影响. 本文以四乙氧基硅烷和双戊烯为前驱体, 采用等离子体增强化学气相沉积方法制备了SiCOH薄膜, 对其进行了氮气氛围下的热退火处理, 分析了热退火对薄膜结构与性能的影响, 探究了退火过程中薄膜结构变化的可能的反应机理. 傅里叶变换红外光谱和固体核磁共振谱结果表明, 沉积薄膜是一种有机无机杂化薄膜. 退火过程中, 薄膜中的-CH₂, -CH₃等有机组分被分解除去, 形成了以稳定的Si-O-Si等无机组分为骨架的多孔结构, 并通过氮气吸附/脱附等温线测试得到了验证. 在此期间, 薄膜骨架微结构亦发生一系列调整, C=C, Si-C含量增加, Si、O、C等元素间发生进一步键合. C=C 含量的提高, 使得薄膜的消光系数和漏电流密度增大. 实验证明, 退火后薄膜具有低折射率、低介电常数特性, 是一类具有优异的介电性能和力学性能的材料, 作为芯片后端互连层间介质具有极大的应用潜力.     

非平衡定态相图在含氮体系低压金刚石沉积中的应用

０前言最近几年低压金刚石制备研究中,出现了一类以含氮气相混合物为原料的制备方法,正逐渐被人们所重视：少量氮原子的存在（甚至是ｐｐｍ级）可以显著提高金刚石薄膜的淀积速率,改善薄膜质量［１,７］。本文报道根据非平衡热力学耦合理论［１０］,首次计算得到了含...