Wafer-Level Packaging of Micromechanical Resonators

An approach to low-cost, wafer-level packaging of microelectromechanical systems (MEMS), e.g., microresonators, is reported. The process does not require wafer-to-wafer bonding and can be applied to a wide range of MEMS devices. A sacrificial polymer-placeholder is first patterned on top of the MEMS component of interest, followed by overcoating with a low dielectric constant polymer overcoat. The sacrificial polymer decomposes at elevated temperature, and the volatile products from the sacrificial material permeate through the overcoat polymer leaving an embedded air-cavity around the MEMS structure. Thus, the device is released from the sacrificial polymeric material, housed in a protective overcoat. The protected MEMS device can then be handled and packaged like an integrated circuit. The electrical characteristics of the microresonators before and after packaging were essentially the same, showing the packaging scheme does not alter the device performance. This approach is applicable to both surface and bulk micromachined devices     

Oscillatory Potentials in Achromatopsia as a Tool for Understanding Cone Retinal Functions

Achromatopsia (ACHM) is an inherited autosomal recessive disease lacking cone photoreceptors functions. In this study, we characterize the time-frequency representation of the full-field electroretinogram (ffERG) component oscillatory potentials (OPs), to investigate the connections between photoreceptors and the inner retinal network using ACHM as a model. Time-frequency characterization of OPs was extracted from 52 controls and 41 achromat individuals. The stimulation via ffERG was delivered under dark-adaptation (DA, 3.0 and 10.0 cd·s·m⁻²) to assess mixed rod-cone responses. The ffERG signal was subsequently analyzed using a continuous complex Morlet transform. Time-frequency maps of both DA conditions show the characterization of OPs, disclosing in both groups two distinct time-frequency windows (~70–100 Hz and >100 Hz) within 50 ms. Our main result indicates a significant cluster (p < 0.05) in both conditions of reduced relative power (dB) in ACHM people compared to controls, mainly at the time-frequency window >100 Hz. These results suggest that the strongly reduced but not absent activity of OPs above 100 Hz is mostly driven by cones and only in small part by rods. Thus, the lack of cone modulation of OPs gives important insights into interactions between photoreceptors and the inner retinal network and can be used as a biomarker for monitoring cone connection to the inner retina.     

Air-Gaps for High-Performance On-Chip Interconnect Part I: Improvement in Thermally Decomposable Template

The incorporation of air-cavities (i.e., air-gaps) as the intralevel dielectric in integrated circuits (ICs) can provide an ultralow-k solution, especially at the 32 nm technology node and beyond. Air-gaps can be created by the templating method using norbornene (NB)-based sacrificial polymers. However, it has been found that the hardness and modulus of the templating material is critical to achieving mechanical fidelity of the structure during processing. As a result, stiffer sacrificial polymers lead to higher yield. In this study, tetracyclododecene (TD)-based sacrificial polymers were investigated and compared with norbornene-based (NB)-based polymers. Nanoindentation experiments showed that thin films of TD-based sacrificial polymers were harder than NB-based sacrificial polymers. The effect of the modulus and hardness on the process repeatability was quantitatively evaluated by comparing the straightness of 50-nm-wide lines of TD- and NB-based sacrificial polymers. It was shown that the TD-based polymer structures were straighter and had better reproducibility than those of NB-based polymers due to an increase in hardness and modulus. The thermal decomposition properties of TD-based polymers were similar to their NB-based counterparts. Both TD- and NB-based polymers were thermally stable at 300°C and the decomposition residues were less than 1% of the original weight. The thickness of the residue (solid reaction byproducts) from thin TD films was as low as 2.1 nm (depending on the atmosphere quality) and the residue was hydrophobic.     

Aqueous-Develop,Photosensitive Polynorbornene Dielectric: Properties and Characterization

The properties of a new aqueous-base-develop, negative-tone photosensitive polynorbornene have been characterized. High-aspect-ratio features of 7:1 (height:width) were produced in 70-μm-thick films in a single coat with straight side-wall profiles and high fidelity. The polymer films studied had contrast of 12.2 and low absorption coefficient. To evaluate the polymer’s suitability to microelectronics applications, epoxy crosslinking reactions were studied as a function of processing condition through Fourier-transform infrared spectroscopy, nanoindentation, and dielectric measurements. The fully crosslinked films had an elastic modulus of 2.9 GPa and hardness of 0.18 GPa.     

Connective‐Tissue Fibroblasts Established on Micropillar Interfaces are Pivotal for Epithelial‐Tissue Morphogenesis

Polydimethylsiloxane (PDMS) pillar arrays are applied as a biomechanical microenvironment to establish gingival connective‐tissue fibroblasts (GCTFs) and to further analyze the pivotal role of GCTFs in epithelial‐tissue morphogenesis. GCTFs are known to exert successful adhesion and growth on fibronectin immobilized on pillar heads, over time, concomitant with the increased gene expression of vimentin and collagen type‐I. GCTF‐populated pillar arrays clearly reveal that epithelial‐tissue morphogenesis of immortalized human gingival keratinocytes (IHGKs), co‐cultured for 7 and 14 days, parallels the in vivo phenotype more closely, when compared with GCTF‐free control arrays. This in vivo‐like phenotype is substantiated by higher mRNA levels for keratin 1, involucrin and filaggrin differentiation markers. Furthermore, it is reflected by a tissue‐specific protein orientation of the aforementioned molecules, and also of the cell‐to‐cell contact forming desmoplakin and the basement membrane constituents, laminin‐5, laminin‐1/10, and collagen type‐IV. These experiments suggest that the in vivo‐like phenotype of the IHGK is governed by the GCTFs growing on the micropillar interfaces. Moreover, they form the basis for the optimization or neogeneration of biomaterials by varying predefined microenvironmetal parameters to achieve an in vivo‐like cell growth and differentiation, indispensable for tissue morphogenesis during regeneration.     

实现更高速以太网络的需求与考虑的解决方案

10 GbE的关键驱动要素之一就是对链接合并通信协议的使用加以限制,以便将多重的1 GbE链接合并起来.LAG通常是在现有以太网络技术的速度与下一阶段以太网络技术的更高速度,对两者之间所存在的落差作为桥接之用的过渡阶段.     

Die Prüfung der Zunderbeständigkeit hitzebeständiger Walz- und Schmiedestähle

Untersuchung der Brauchbarkeit gängiger Entzunderungsmittel für das Entzundern hitzebeständiger Stähle. Zunderungsversuche an ferritischen und austenitischen hitzebeständigen Stählen bei freiem Luftzutritt oder im Luftstrom mit getrockneter oder befeuchteter Luft zur Überprüfung der Festlegungen im Stahl-Eisen-Werkstoffblatt 470-60. Statistische Auswertung der Ergebnisse zur Feststellung der Versuchsstreuung.