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Tsukuba, Japan

Yamada H.,Tohoku University | Nozawa M.,Tohoku University | Kinoshita M.,NEC Corp | Ohashi K.,MIRAI Selete | Ohashi K.,NEC Corp
Optics Express | Year: 2011

We present a vertical-coupling optical interface with a grating coupler for transmitting and receiving optical signals between single-mode optical fibers and microphotonic waveguides with a view to realize on-chip optical interconnection. The optical interface consisting of a simple grating structure with a reflective mirror and an optical power combiner exhibits high optical coupling efficiency and wide tolerance range for the misalignment of optical fibers. The optical interface exhibits high coupling efficiency even if the optical input is almost vertical to the chip surface. © 2011 Optical Society of America. Source

Mogami T.,MIRAI Selete
Extended Abstracts of the 11th International Workshop on Junction Technology, IWJT 2011 | Year: 2011

CMOS scaling has been a basic power of LSI development for higher performance, higher packing density and lower cost. For device scaling-down, size miniaturization has been one of the important issues to fabricate fine devices. Furthermore, normal device operation, including reliability, has been another issue. There have been any breakthroughs [1] to lead device scaling-down as shown in Fig. 1. For >100nm regime, simple scaling technologies have been developed. For <100nm regime, oster technologies with scaling-down have been created, In advanced CMOS development for 50nm regime, the variation of device characteristics is one of the Source

Hiraiwa A.,Waseda University | Nishida A.,MIRAI Selete | Nishida A.,Renesas Electronics Corporation
Journal of Micro/Nanolithography, MEMS, and MOEMS | Year: 2011

We formerly developed the "assembly method" for analyzing the line-edge and line-width roughness (LER/LWR) that has a long-range correlation beyond the conventional analysis limit, as reported in a previous work. In that method, we repeatedly assembled virtual long lines by gathering line segments, which were arbitrarily disposed on actual long lines and by randomly changing their combination and order, permitting the assembled lines to share the same line segments. Then, we obtained the power spectral density (PSD) of the LER/LWR of the assembled lines considering the lines as seamless. We also derived an analytic formula of the assembled-line PSDs for use in the PSD fitting method. This formula agreed very well with experimental PSDs. In this report, we propose guidelines for suppressing the statistical-noise effect on the assembly method for the purpose of accurately analyzing the long-range-correlated LER/LWR. The guidelines will greatly help shed light on the long-range correlation, which causes the variability even in large devices but has long been veiled due to the lack of metrology. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). Source

Hiraiwa A.,MIRAI Selete | Hiraiwa A.,Renesas Electronics Corporation | Nishida A.,MIRAI Selete
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2010

Accurate characterization of line-edge roughness (LER) and line-width roughness (LWR) is essential to cope with the growing challenge of device variability in large-scale integrations. The accuracy is affected markedly by statistical noise, which is caused by the finiteness of a number of samples. The statistical noise produces random oscillatory fluctuations of autocorrelation function (ACF) of LER/LWR. These fluctuations are obstacles to estimating LWR statistics by comparing experimental and theoretical ACFs. Using the Monte Carlo (MC) method to prepare pseudoexperimental ACFs (MC-ACFs), the authors found that an error of the estimates is minimized in the case when a ratio of a fitting-window size to a correlation length is 0.3 or smaller, being less affected by the statistical noise. under a fixed sampling interval is determined by the total number Nall of width data used to obtain the MC-ACF. This comes from the fact that the MC-ACF is obtained after averaging approximately for Nall times. The authors also investigated the case when LWR consisted of two components that had different correlation lengths. They confirmed that of both components increase with a decrease in their occupancies in the entire LWR. This, together with a large correlation length, makes it difficult to accurately characterize the longer-correlation component, which is mostly minor (small occupancy) in actual cases. This difficulty is also an obstacle to estimating the shorter-correlation component, because the statistics of the former are mostly the prerequisites for analyzing the latter. These facts make a stark contrast to a power-spectral-density (PSD) fitting method, where at least the shorter-correlation component is estimated with almost the same accuracy as in the case of a single component. Based on these results, the authors propose to investigate PSDs, rather than ACFs, in the case of multicomponent LWR. © 2010 American Vacuum Society. Source

Hiraiwa A.,MIRAI Selete | Hiraiwa A.,Renesas Electronics Corporation | Nishida A.,MIRAI Selete
Journal of Micro/Nanolithography, MEMS, and MOEMS | Year: 2010

The accuracy of estimated line-edge-roughness and line-widthroughness (LER and LWR) statistics is mostly determined by the noise inherent in experimental power spectral densities (PSDs). One type of noise is statistical noise, a kind of jagged structure, that is caused by the finiteness of a number NL of line segments used in analyses. To keep the estimation error below 5%, the ratio of sampling interval to correlation length should be 0.3 or smaller, and NL needs to be larger than 100 under the condition that the length of line segments is 2000 nm or larger, in compliance with the Semiconductor Equipment and Materials International standard. Another noise type is scanning-electron-microscope image noise. It causes edge-detection errors and induces an additional variation in LER/LWR. This variation raises the minima of PSDs and accordingly enhances the errors. The factor of the error enhancement is suppressed below 1.5 by controlling the ratio of image-noise-induced LER/LWR variance to the true variance below 0.6. This is achieved by averaging image pixels perpendicularly to fine lines, and is free from any appreciable drawbacks. The experimental results agree well with analytical approximations to Monte-Carlo results that are separately obtained. This leads us to obtain more general guidelines for accurate analyses by using the analytical formulas. © 2010 Society of Photo-Optical Instrumentation Engineers. Source

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