Vertical silicon membrane arrays patterned with tri-level e-beam resist

A high resolution, tri-level e-beam resist process has been developed which has produced, by liftoff, planar metal features as fine as 25 nm wide by 5 Μm long on thick Si substrates. The metal features have been used as masks for transfer of the pattern into the substrate itself, producing arrays of Si membranes, 50 nm wide, 0.3 pm high and extending 5 Μm in length. We compare the resolution of the tri-level system with that obtained for a previously reported bi-level system of similar composition.     

Electron beam induced current investigations of active electrical defects in silicon due to reactive ion etching and reactive ion beam etching processes

Reactive ion etching and reactive ion beam etching are common tools for anisotropic etch processes in silicon microdevice fabrication; but, unfortunately, they also create radiation damage in the etched surface. We have studied the electrically active defects by measuring the recombination of carriers with the help of the electron beam induced current (EBIC) mode of a secondary electron microscope. We have measured the temperature behavior of the samples by annealing studies and the temperature dependent EBIC signal for several p-doped silicon wafers and obtained different shaped curves. Theoretical EBIC models developed with the assumption of a reduced net carrier concentration in the etched areas agree with our experimental results.     

The effect of cathode materials on reactive ion etching of silicon and silicon dioxide in a CF4 plasma

Silicon and silicon dioxide have been Reactive Ion Etched in a CF₄ plasma using a diode sputtering configuration to achieve etching. Pressures ranged from 20 to 100 millitorr and power densities to the RF cathode were between 0.1 and 1.0 W/cm². The effect of cathode material on the quality of etched surfaces and on etch rates has been investigated. It has been observed that the etch rate of silicon decreases as the area of silicon exposed to the plasma is increased and that this silicon loading effect is strongly influenced by the material covering the balance of the cathode. For instance, the silicon loading effect is much more pronounced when silicon dioxide rather than aluminum is used to cover the balance of the cathode. This silicon loading effect was investigated further by varying RF power. It was found that loading a silicon dioxide covered cathode with silicon wafers decreases the dependence of silicon etch rate on power. The silicon dioxide etch rate and its dependence on RF power are the same whether silicon, silicon dioxide or aluminum is used to cover the balance of the cathode. Possible explanations for these experimental results will be discussed.     

黑硅无掩模反应离子刻蚀法制备及光学性能研究

采用无掩模反应离子刻蚀法制备了黑硅.利用扫描电子显微镜及紫外-可见-近红外分光光度计研究了黑硅的微结构和光学特性.结果表明,黑硅微结构高度为2.0～3.5 μm,径向尺寸90～400 nm,间距200～610 nm.在400～1 000 nm光谱范围内黑硅吸收率为94％,是单晶硅的1.5倍;在1 200～1 700 nm光谱范围吸收率为55％～60％,是B掺杂单晶硅的20倍.制备的黑硅的光学带隙为0.600 6 eV,吸收光谱明显向红外方向偏移.     

Electrical characterization of very-low energy (0-30 eV) CI-Radical/Ion-beam-etching induced damage using two-dimensional electron gas heterostructures

Damage induced by very low energy (30 eV) Cl reactive ion beam etching (RIBE) and radical etching (RE) has been electrically characterized. GaAs/n-AlGaAs two-dimensional electron gas heterostructures were used as damage sensitive probes. Sheet carrier concentrations and Hall mobilities were measured at 77 K, under dark as well as illuminated conditions. By carefully designing the sample structure, the damaged layer thickness could be estimated by comparing dark and illuminated data. In case of RE, no degradation was detected at depths as shallow as 25 nm from the etched surface. For 30 eV-RIBE, the damage was detected but found to be reasonably small (38% decrease in electron mobility) and shallow (<50 nm). Electrical and optical damage are compared briefly.     

反应离子深刻蚀中硅/玻璃结构footing效应的实验研究

针对反应离子深刻蚀中硅/玻璃键合结构的footing效应问题,用实验方法进行了研究.通过2～4和0.01～0.03Ω·cm两种不同电导率的硅结构过刻蚀的对比,以及对50,20和5μm三组不同间隙高度的器件结构过刻蚀的对比,揭示了单晶硅结构的电导率及器件结构和玻璃衬底间隙高度对footing效应的影响.实验结果显示电导率为2～4Ω·cm的硅结构比电导率为0.01～0.03Ω·cm的硅结构footing效应严重;硅结构和玻璃衬底的间隙为5μm的比间隙为20和50μm的footing效应严重, 对这一现象的理论分析认为,被刻蚀的硅的电导率越高, 硅结构与玻璃衬底的间隙越大,footing效应越不明显.本文中不同电导率和不同间隙高度的实验对比结果可以为硅微传感器材料类型的选取和器件的优化设计提供参考.     

反应离子深刻蚀中硅/玻璃结构footing效应的实验研究

针对反应离子深刻蚀中硅/玻璃键合结构的footing效应问题,用实验方法进行了研究.通过2～4和0.01～0.03Ω·cm两种不同电导率的硅结构过刻蚀的对比,以及对50,20和5μm三组不同间隙高度的器件结构过刻蚀的对比,揭示了单晶硅结构的电导率及器件结构和玻璃衬底间隙高度对footing效应的影响.实验结果显示电导率为2～4Ω·cm的硅结构比电导率为0.01～0.03Ω·cm的硅结构footing效应严重;硅结构和玻璃衬底的间隙为5μm的比间隙为20和50μm的footing效应严重, 对这一现象的理论分析认为,被刻蚀的硅的电导率越高, 硅结构与玻璃衬底的间隙越大,footing效应越不明显.本文中不同电导率和不同间隙高度的实验对比结果可以为硅微传感器材料类型的选取和器件的优化设计提供参考.     

Lattice‐Registered Two‐Photon Polymerized Features within Colloidal Photonic Crystals and Their Optical Properties

In this work we demonstrate a significant advance in the introduction of embedded defects in 3D photonic crystals by means of two‐photon polymerization. We have developed the ability to precisely position embedded defects with respect to the lattice of 3D photonic crystals by imaging the structure concurrently with two‐photon writing. Defects are written with near‐perfect lattice registration and at specifically defined depths within the crystal. The effect of precise defect position on the optical response is investigated for embedded planar cavities written in a photonic crystal. The experimental data are compared to spectra calculated using the Scalar Wave Approximation (SWA).     

Liquid‐Crystalline Electrolytes for Lithium‐Ion Batteries: Ordered Assemblies of a Mesogen‐Containing Carbonate and a Lithium Salt

Thermotropic liquid‐crystalline (LC) electrolytes for lithium‐ion batteries are developed for the first time. A rod‐like LC molecule having a cyclic carbonate moiety is used to form self‐assembled two‐dimensional ion‐conductive pathways with lithium salts. Electrochemical and thermal stability, and efficient ionic conduction is achieved for the liquid crystal. The mixture of the carbonate derivative and lithium bis(trifluoromethylsulfonyl)imide is successfully applied as an electrolyte in lithium‐ion batteries. Reversible charge–discharge for both positive and negative electrodes is observed for the lithium‐ion batteries composed of the LC electrolyte.