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Itani T.,Semiconductor Leading Edge Technologies
Journal of Photopolymer Science and Technology | Year: 2011

The Selete research and development program was started to prepare extreme ultraviolet (EUV) lithography for the manufacturing of semiconductor devices. In the past five years, Selete has evaluated more than 1000 EUV resists from resist suppliers using the small field exposure tool (SFET) which is linked in-line to a coater/developer track system under chemically controlled environments. From the results obtained, the lithographic performance of various Selete standard resists (SSRs) and optimization of related processes has been reported. Based on these, advancement in resist materials was observed to be of steady progress in terms of resolution limit, sensitivity and line width roughness (LWR). LWR reduction and pattern collapse prevention were also achieved through the application of various alternative processes. One such alternative process is the application of the aqueous solution of tetrabutylammonium hydroxide (TBAH) instead of the conventional tetramethylammonium hydroxide developer. TBAH was found to be most effective in the suppression of resist film swelling which causes pattern collapse. Alternative rinse solutions evaluated and utilized have also allowed improvements in LWR reduction and pattern collapse. Meanwhile, EUV resist outgassing, which is also a concern for the effective application of EUV lithography, was quantified and analyzed. Analysis results have shown that protecting group and photo-acid generator components of EUV resists are the main source of such outgassing during exposure. Moreover, for fundamental research, a new approach using high speed atomic force microscopy in the in situ analysis of resists during the dissolution and rinse processes is presented. The results obtained with this method supported a number of previous assumptions about resist dissolution and rinse mechanisms which presented potential pointers for use in next-generation lithographic applications. © 2011 CPST.


Hiraiwa A.,Semiconductor Leading Edge Technologies | Nishida A.,Semiconductor Leading Edge Technologies | Nishida A.,Renesas Electronics Corporation | Mogami T.,Semiconductor Leading Edge Technologies
IEEE Transactions on Electron Devices | Year: 2011

The authors propose a model of line-edge and line-width roughness (LER and LWR) of actual device patterns, which received some smoothing steps, for accurate estimation of device variability. The model assumes that LER/LWR has originally an exponential autocorrelation function (ACF) and is smoothed using another exponential function. The power spectrum of this ACF almost completely fits the experimental one of polycrystalline silicon lines, which were formed using plasma etching. The authors investigate the effect of LER/LWR on the current factor of metal-oxide-semiconductor field-effect-transistors, comparing this to conventional models. The Gaussian ACF, which is widely used in device simulations, calculates the variation in the current factor with considerable accuracy as long as accurate LER/LWR statistics are used. However, it alone cannot provide the statistics. The exponential ACF underestimates the variation by a nonnegligible amount. From these results, the authors propose to use the aforementioned smoothed exponential ACF in the device simulations. They also alert to the possibility that a little-known long-range correlation exists universally in the LER/LWR even of the present-day devices and is causing an unexpectedly large mismatching between wide-channel devices. © 2011 IEEE.


Tsunomura T.,Semiconductor Leading Edge Technologies | Nishida A.,Semiconductor Leading Edge Technologies | Hiramoto T.,Semiconductor Leading Edge Technologies | Hiramoto T.,University of Tokyo
IEEE Transactions on Electron Devices | Year: 2011

The mechanism behind the threshold voltage VT variability difference between n- and p-type field-effect transistors (NFETs and PFETs, respectively) is investigated from the viewpoint of the channel dopant profile. First, the effect of the depth profile is investigated by comparing the V T variability among FETs with various depth channel profiles. It is clarified that the VT variability of NFETs is larger than that of PFETs with similar depth profiles. The effect of the lateral channel profile is also examined. As one of the causes of the modulation of the lateral channel profile, the effect of halo implantation is evaluated. It is confirmed that VT variability is enhanced with halo implantation. However, the VT variability of NFETs is still larger than that of PFETs even without halo implantation. Without halo implantation, the reverse short-channel effect appears in NFETs but not in PFETs. From this result, we find that lateral channel profile nonuniformity appears in NFETs even without halo implantation because of the transient-enhanced diffusion (TED) of the channel dopant of boron in NFETs. Since arsenic or phosphorus, which shows no TED characteristic, is used as the channel dopant in PFETs, lateral channel profile nonuniformity does not appear in PFETs without halo implantation. Channel profile nonuniformity, which is caused by boron TED, is thought to be the origin of the VT variability difference between NFETs and PFETs. © 2006 IEEE.


Itani T.,Semiconductor Leading Edge Technologies | Santillan J.J.,Semiconductor Leading Edge Technologies
Journal of Photopolymer Science and Technology | Year: 2010

The characterization of the photoresist dissolution process after exposure has been continuously investigated in search for possible clues in the development of optimal photoresist materials and processes suit the requirements for next generation lithography. In this paper, an in-situ analysis of the photoresist's dissolution behavior is performed utilizing high-speed atomic force microscopy. Here, the physical changes in the surface of the exposed extreme ultraviolet (EUV) photoresist film is observed in real-time before, during and after the development process. This new information on the actual pattern formation of photoresists provides clues on how to better understand its mechanism and in effect further improve its performance. In this work, a comparison of the dissolution characteristics in terms of EUV photoresist platform (acryl-based polymer and fullerene-based molecular resist) in tetramethylammonium hydroxide (TMAH) developer was performed. Moreover, using the same polymer resist, the dissolution characteristic difference between the TMAH and tetrabutylammonium hydroxide (TBAH) developers was analyzed. © 2010 CPST.


Itani T.,Semiconductor Leading Edge Technologies | Santillan J.J.,Semiconductor Leading Edge Technologies
Applied Physics Express | Year: 2010

Recent work on extreme ultraviolet (EUV) resists has shown the application of alternative resist processes as a possible solution to achieve lithographic performance targets. In this study, the potential of tetrabutylammonium hydroxide (TBAH) as a possible alternative to the currently used tetramethylammonium hydroxide developer solution was investigated. A significant improvement in lithographic performance was achieved using the TBAH developer. However, this developer solution has a relatively high freezing temperature, particularly at high concentrations. We report that the addition of glycerin to the TBAH developer lowered the freezing temperature without adversely affecting lithographic performance. © 2010 The Japan Society of Applied Physics.

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