The influence of several material and processing parameters on the dielectric strength of thermally grown SiO,, films on silicon has been assessed. This was accomplished by statistically analyzing the breakdown characteristics of a large number of MOS capacitor structures, which had been fabricated in various ways. Although the results of this investigation are only qualitative, they clearly demonstrate that the effective breakdown strength of these films is strongly dependent on: SiO2 purity, structural perfection and thickness; the presence of a passivating phosphosilicate glass layer; the presence and reactivity of the metal electrode; and, the duration of the postmetallization heat treatment. The morphology of certain micron-size defects which develop in the MOS structure during annealing is described in some detail, since these faults are apparently responsible for oxide shorting in some instances.Since the oxide layer under the gate electrode in MOSFET's is subjected to very large electric fields (up to 2 MV-cm-1), its dielectric strength has an important bearing on the reliability of these devices. Although interest in electrical breakdown phenomena in such films has increased in recent years, along with the rapid development of MOSFET technology, the effect of various process and material variables on the effective dielectric strength of thermally grown SiO~ films has not yet been well characterized. This ~-s due to the extreme sensitivity of this property to changes in oxide composition and structure, which are, in turn, quite dependent on device fabrication procedures. An additional uncertainty is introduced by the dependence of the breakdown characteristics on the particular testing technique employed.The dielectric strength of thermally grown SiO2 has been reported by Deal (1) to increase with the density of the insulating film, going from 4.8 to 5.5 MV-cm -1 as the density was raised from 2.04 to 2.22 g-cm -3. Breakdown strength values of 4 to 6 MV-cm -1 for 2000A thick SiO2 films on silicon were found by Ainger (2), who also observed that lower values were encountered on oxide films grown on more heavily doped, p-type silicon. A more thorough investigation of breakdown phenomena in A1-SiO2-Si structures has been made by Klein (3,4), who found that a succession of breakdown events could be initiated at low fields (< 2 MV-cm -1) when the applied voltage was slowly increased. These events produced visible spark discharges which created individual macroscopic holes in the capacitor, due to localized evaporation of oxide and metal. Such events were labeled "single-hole" or "self-healing" because the test capacitor was still operational after they occurred. When the applied field reached the 5 to 9 MV-cm -1 range, the dielectric failure was accompanied by arcing or by propagation of single-hole events to adjacent sites. This resulted in permanent destruction of the capacitor. Consequently, Klein's data indicate that the effective breakdown strength of SiO2 films does not have a well-defined value but incr...

This study describes a fabrication method of microsized AgNW patterns based on poly dimethylsiloxane (PDMS) substrate using a poly(p-xylylene) (parylene) stencil technique. Various patterns of AgNW conductive sheets were created on the wafer scale area in the forms of straight and serpentine lines, texts, and symbols, which dimensions ranged from a few tens of micrometers to hundreds of micrometers. We demonstrated the electrical performance of straight line and serpentine line patterned AgNW electrodes when subjected to mechanical strains. The gauge factor and stretchability ranged from 0.5 to 55.2 at 2% uniaxial strain and from 4.7 to 55.7%, respectively, depending on the shapes and structures of the AgNW electrodes. Using the developed AgNW patterning technique, we fabricated strain sensors to detect small body signals epidermally such as hand motion, eye blink and heart rate. Also, tactile sensors were fabricated and exhibited the sensitivity of 3.91 MPa(-1) in the pressure range lower than 50 kPa, and 0.28 MPa(-1) in the pressure range greater than 50 kPa up to 1.3 MPa. From these results, we concluded that the proposed technique enables the fabrication of reliable AgNW patterns on wafer-scale PDMS substrate and the potential applications for various flexible electronic devices.

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The present paper examines the theoretical aspects of the triangular voltage sweep (TVS) technique and describes the development of a unified quasiequilibrium approach wherein various polarization processes in an MOS capacitor structure subjected to the changing applied field are evaluated in terms of their contributions to the externally observed current. It is shown that a self-consistent experimental and analytical approach must be used when the TVS technique is applied to mobile charge studies in MOS structures.

Cracks commonly appear in metal patterns when fabricated on native poly(dimethylsiloxane) (PDMS) substrate using general micro-electro-mechanical systems (MEMS) fabrication processes such as lift-off and metal etching. This paper introduces simple, reliable and reproducible fabrication methods to realize crack-free metal patterns on PDMS using intermediate-parylene-deposited PDMS substrate and parylene-filled PDMS substrate. The fabrication parameters of crack-free metal patterning were optimized resulting in reliable and reproducible fabrication outputs. The adhesion of metals on these surface-modified PDMS substrates was evaluated by ASTM tape tests in wet and dry conditions. X-ray photoelectron spectroscopy (XPS) was used to characterize the element composition on the surface of parylene-filled PDMS. The surfaces of native PDMS, parylene-deposited PDMS and parylene-filled PDMS were investigated using scanning electron microscopy (SEM) and XPS for analysis of crack generation during the metal patterning processes. The mechanical properties, such as stress and strain, of native and surface-modified PDMS substrates were measured by standard tension tests. Based on these results, it was concluded that the proposed methods successfully generated reliable crack-free metal patterns based on PDMS substrate using general MEMS technologies, which can be used for various applications such as biomedical devices and flexible electronics.