The stress dependence of the room-temperature cathodoluminescence spectrum of N-doped cubic silicon carbide has been evaluated in a field-emission-gun scanning electron microscope, using the electron beam as an excitation source for luminescence emission. The electron-stimulated spectrum was dominated by only one broad band centered at about 544nm, with a broad shoulder centered at a slightly lower energy level (≈572nm). The cathodoluminescence spectrum, which was attributed to the four-particle N-bound excitonic transition, arose from substitutional N in the cubic silicon carbide lattice. Using experimentally measured probe response functions and energy shift magnitude collected near the tip of a Vickers indentation microcrack, it was possible to retrieve the actual magnitude of the piezospectroscopic coefficient [i.e., the slope of a linear plot of spectral band shift versus the trace of the stress tensor: Π=0.61±0.02nm∕GPa] of the N-bound exciton (cumulative) band of cubic silicon carbide.
The cathodoluminescence (CL) spectrum arising from diamagnetic point defects of silicon oxynitride lattice was analyzed to extract quantitative information on local stress fields stored on the surface of a silicon nitride polycrystal. A calibration procedure was preliminarily made to obtain a relationship between CL spectral shift and applied stress, according to the piezo-spectroscopic effect. In this calibration procedure, we used the uniaxial stress field developed in a rectangular bar loaded in a four-point flexural jig. Stress dependence was clearly detected for the most intense spectral band of a doublet arising from diamagnetic ([triple bond]Si-Si[triple bond]) defects, which was located at around 340 nm. The shallow nature of the electron probe enabled the characterization of surface stress fields with sub-micrometer-order spatial resolution. As applications of the PS technique, the CL emission from [triple bond]Si-Si[triple bond] defects was used as a stress probe for visualizing the residual stress fields stored at grain-boundary regions and at the tip of a surface crack propagated in polycrystalline silicon nitride.
In recent years, further improvement in planarization at Tungsten (W) Chemical Mechanical Planarization (CMP) is becoming increasingly important at advanced technology nodes.A combination of hydrogen peroxide and metal catalyst has mainly been used as the W slurry components. On the other hand, these components which take on the character of high etching for Tungsten film is unfitted for advanced planarization. This study sought alternative oxidant source for W slurry with lower etching effect which could replace the combination of hydrogen peroxide and metal catalyst. Etching rate of Tungsten film and oxidation potential of each oxidant were checked in the first screening test. And then, slurries were prepared with using different oxidizers. Finally, W removal rate and recess performance on patterned wafer were evaluated. As the result, it was confirmed that the slurry with iodic oxidant showed etch free and much better planarization performance totally than that of the hydrogen peroxide. The iodic oxidant could be a first choice for W slurry from now on.
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