A guideline for evaluating LER and total procedure to estimate effects of measured LER on device performance were proposed. Spatial-frequency distributions of LER in various resist materials were investigated and general characteristics of spatial-frequency distribution of LER were obtained. Measurement parameters for accurate LER measurement can be calculated according to the guideline. Measured line-width distribution was used to predicting degradation and variation in MOS transistor performance using the two-dimensional device simulation. Effect of long-period component of LER was clarified as well as short-period component.
Reproducible memory switching has been observed in metal/ Langmuir–Blodgett (LB) film/metal sandwich structures: LB films consist of organic molecules such as dyes having a number of conjugated bonds. The device switches from a nonconducting off state to a conducting on state via an intermediate state, and it switches directly from the on to the off state within less than 10 ns upon the application of a voltage. Both off-state and on-state resistances of the device depend linearly on the number of monolayers, the conduction being predominantly through the LB films.
The influence of line-edge roughness (LER) on transistor performance was investigated experimentally and the preciously proposed guideline for CD and LER measurements was examined.First, regarding the transistor-performance measurements, a shift of roll-off curves caused by LER within a gate pattern was observed. Moreover, the effect of transistor-width fluctuation originating from long-period LER was found to cause a variation in transistor performance. Second, regarding LER and CD metrology, the previously reported guideline was validated by using KrF and ArF resist-pattern samples. It was found that both CD and LER should be evaluated with the 2-µm-long inspection area. Based on this guideline, a comprehensive approach for evaluating LER and CD for transistor fabrication process is presented. The authors consider that this procedure can provide useful information for the 65-nm-node technology and beyond.
The linewidth measurement ability of the Model-Based Library (MBL) matching technique is evaluated by a simulation study, and an improvement in the technique is proposed. In this study, a focused electron beam model is introduced in the MONSEL Monte Carlo simulator to estimate the effects of the electron incident angle distribution on linewidth measurements. By using the focused electron beam model, the images that will be obtained by an actual critical-dimension scanning electron microscope (CD-SEM) were simulated. Measurements were carried out on the images which would be taken with the SEM focus conditions in a range maintained by the auto-focus system. As a result of measurements of simulated images with various sample geometries, it was confirmed that the current MBL matching with a simple Gaussian electron beam model could cause a measurement error of more than 3 nm for the linewidth and 2º for the sidewall angle. Since the incident angle distribution distorts the effective beam shape and image profile at the edge of a pattern, conventional MBL matching with a simple Gaussian beam model cannot give a proper measurement of sample geometry for the image profile formed by the focused electron beam, and this results in measurement errors. To eliminate these measurement errors, another library produced by the focused electron beam model, is employed for the MBL matching. The new library consists of simulated profiles at only the best focus, and it enables the MBL to use a better model and to achieve accurate measurements without increased computational costs. By using the new library, measurement errors are reduced to 0.6nm for the linewidth and to 0.2º for the sidewall angle.Keywords: CD-SEM, model-based library, focused electron beam model, electron incident angle, measurement error
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