Takashi Mashiko - Academia.edu (original) (raw)

Papers by Takashi Mashiko

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2003

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2016

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2017

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2004

Meeting Abstracts of the Physical Society of Japan, 2018

Abstract: Several versions of the “flexible chainlike walker ” (FCW) model are proposed and inves... more Abstract: Several versions of the “flexible chainlike walker ” (FCW) model are proposed and investigated by numerical simulations on a square lattice. It is shown that the “original ” FCWs aggregate spontaneously and irreversibly, where no adherence is assumed, triggered by “mutual locking”. This is in complete contrast to established aggregation models which necessarily require adherence, and exemplifies the significance of the deformability of self-driven objects. The behaviors of the “smart ” FCWs, which have higher ability of moving, are similar to those of the original FCWs. This suggests that the spontaneous, irreversible aggregation is a robust feature peculiar to a many-body system of deformable self-driven objects. On the other hand, the “double-headed ” FCWs do not undergo the mutual locking and the resultant irreversible aggregation, unlike the original and the smart FCWs. This indicates that “bidirectionality ” prevents deformable self-driven objects from aggregating.

The Proceedings of the Symposium on Environmental Engineering, 2013

Solid State Phenomena, 2012

We performed two experiments on resist-coated wafers. In the measurement of the resist-wafer adhe... more We performed two experiments on resist-coated wafers. In the measurement of the resist-wafer adhesivity, we confirmed that it is significantly increased by an HMDS layer in between. In the resist-removal experiment using steam-water mixed spray, we found that the area of resist removal is limited within the area of spray application if HMDS is used, otherwise the former can be larger than the latter. These results suggest that the resist removal from a wafer surface by steam-water mixed spray is essentially a peel-off process.

Solid State Phenomena, 2012

We have been developing an innovative ultra-low environmental load cleaning technique by the use ... more We have been developing an innovative ultra-low environmental load cleaning technique by the use of steam-water mixed spray. We showed that this technique is quite effective in both cleaning and photo-resist stripping. We also found that the physical force associated with steam-water mixed spray is greater than that with air-water mixed spray; hence we proposed that the condensation plays an important role in this cleaning technique. In order to discuss further this mechanism, we perform the order estimation of physical processes in dynamics of liquid droplet moving in vapor flow impacting on a solid interface in this study. Results show that droplet impact velocity can be reduced while the droplet approaches to the solid surface. However, the vapor in the gap can condensate to either the liquid droplet or the solid surface with the velocity whose order of magnitude cannot be negligible compared to the impact velocity; hence the amount of vapor that should be pushed out from gap can...

ECS Transactions, 2009

Performance of photoresist stripping using steam-water mixed spray is quantitatively investigated... more Performance of photoresist stripping using steam-water mixed spray is quantitatively investigated with water flow rate as the operating parameter. The most striking and the most important finding is that air-water mixed spray turns out hardly effective. This result shows the peculiar superiority of the proposed technique. As we found that the prominently excessive long time of spraying of steam-water mixture on metal surface results in surface abrasion, this result strongly suggests that both the resist strippping and metal surface abrasion are dominated by essentially the same mechanism. We speculate that our proposing technique is categorized in the physical force cleaning. We discuss the role of the water flow rate in this cleaning technique and the validity of the assumption of physical force cleaning.

ECS Transactions, 2009

A novel ultra low environmental load removal technique of post-dry etch residue is developed, by ... more A novel ultra low environmental load removal technique of post-dry etch residue is developed, by applying physical force cleaning technique using high-speed steam-water mixture spray. It is found that the removal rate of the proposed technique depends on the dry-etch processes, and that the steam-water mixture spray almost completely removes the post-dry etch residue from some kinds of dry etched wafers without help of any chemicals. It is also found that the proposed technique requires very dilute concentration of inorganic solution, if necessary, to remove post-dry etch residue completely from other kinds of wafers and that removal process using amine compound with isopropyl alcohol is unnecessary. By contrast, air-water mixture spray could not remove the dry-etch residue at all even with some chemicals. Therefore it is understood that steam atmosphere significantly contributes the proposed technique. The characteristic feature and efficiency of the proposed technique are discussed.

Physica A: Statistical Mechanics and its Applications, 2009

A two-dimensional square lattice system, on which flexible, chainlike, selfdriven objects move ra... more A two-dimensional square lattice system, on which flexible, chainlike, selfdriven objects move randomly but are drifted to a same direction, causing a unidirectional net flow, is investigated by numerical simulations. It is shown that the objects exhibit a freezing transition from a smoothly flowing state to a completely jammed state, in which the objects get immobile and cannot move anymore. Comparison with the flow of rigid objects shows that this complete jamming (hardening) results from the flexibility (softening) of each self-driven object. This is the first report of the freezing transition of a free transport system (without obstacles) where the net flow is not multidirectional (as in the case of opposing flows or crossing flows) but unidirectional.

Japanese Journal of Applied Physics, 2012

We performed experiments to elucidate the physical action of a steam-water mixture jet, which we ... more We performed experiments to elucidate the physical action of a steam-water mixture jet, which we have proposed as a promising, environmentally friendly tool for cleaning surfaces. Photoresist-coated silicon wafers were adopted as the target and the jet performance of resist removal was evaluated, with several parameters being varied. We found that the resist-removal performance improves as the thickness or the mechanical strength of the resist film decreases, resist-wafer adhesivity decreases, or jet duration increases. The results imply that the essential part of the resist removal by the jet is a physical process including peel-off, in contrast to the established techniques such as the batch cleaning method utilizing chemical reactions. The results also indicate that the physical impact of the jet can be controlled, which will be a significant advantage in applying the jet as a cleaning technique.

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2011

Applying the numerical program for the bubble migration in space, we performed a numerical simula... more Applying the numerical program for the bubble migration in space, we performed a numerical simulation of the bubble behavior with the thermocapillary flow in an open cylindrical container under microgravity conditions. In the present study, 45o sector of the container were modeled. We assumed Marangoni forces on the bubble surfaces were negligible small and calculated a single bubble behavior in 3 dimensional thermocapillary flow in order to make clear the interaction between the thermocapillary flow and the bubble behavior. The following results were obtained by these results; (1) steady state results calculated by the present program agreed well with the results by the previous investigations, (2) the single bubble flowed largely along the streamline of the thermocapillary flow and the moving bubble did not largely change the temperature field, and (3) the repulsive forces were produced by the bubble motion and the magnitudes became larger as the bubble approached to the hot region.

ABSTRACT An experimental study of thermocapillary convection in the half-zone liquid bridge of lo... more ABSTRACT An experimental study of thermocapillary convection in the half-zone liquid bridge of low Prandtl number fluid was performed to observe the transition behavior from steady to oscillatory flows. In thermocapillary convection, one of the still open problems is the observation of onset of oscillatory flow in low Prandtl number fluids. Numerical simulations predicted that there would be two transition points which were a first and second critical Marangoni number (Mac1 and Mac2). However, an experimental verification has not been performed previously because of its difficulties. A molten tin was used as test fluid and a liquid bridge configuration was employed. The temperature distribution at the interface between the liquid bridge and the cold disk was measured by using several fine thermocouples. It could be experimentally detected that the axisymmetric steady flow changes to three-dimensional steady one with increasing the temperature difference. At higher temperature difference, onset of oscillatory flow was also observed. Experimental results concerning the critical Marangoni numbers agreed very well with numerical simulation.

Bulletin of the American Physical Society, 2007

We report numerical simulations of the mixed flows of two groups of deformable self-driven object... more We report numerical simulations of the mixed flows of two groups of deformable self-driven objects. The objects belonging to the group A (B) have drift coefficient D = D A ( D B ), where a positive (negative) value of D denotes the rightward (leftward) driving force. For co-current flows ( D A , D B > 0 ), the result is rather intuitive: the net flow of one group ( Q A ) increases if the driving force of the other group is stronger than its own driving force ( i.e. , D B > D A ), and decreases otherwise ( D B D A ). For countercurrent flows ( D B 0 D A ), however, the result appears paradoxical: the net flow of one group ( Q A ) can increase with the driving force of the other group ( | D B | ), and the net flow with a stronger countercurrent can be larger than the net flow with a weaker co-current. This phenomenon is observed only for deformable objects and results from the entanglement of objects, which in turn is caused by their deformability.

To investigate the effect of phase transitions of the fluid on thermal convection, we are conduct... more To investigate the effect of phase transitions of the fluid on thermal convection, we are conducting experiments of thermal convection of the mixture of a thermosensitive gel and water. The gel absorbs water and swells below a certain critical temperature, while it discharges water and contracts above the critical temperature. The swelling ratio, as well as the critical temperature, can be controlled, which enables us to investigate the effect of phase transition in a series of experiments, where the critical temperature is set between the top and bottom boundary temperatures and the swelling ratio is systematically changed. In flow visualization, we have observed temporally stable and spatially fixed low-velocity regions which are surrounded by distinct high-velocity regions. Such a phenomenon is not observed in thermal convection of a single-phase fluid like water or air, and peculiar to the phase-changing fluid. Also, we have measured the rheological properties of the fluid and f...

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2003

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2016

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2017

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2004

Meeting Abstracts of the Physical Society of Japan, 2018

Abstract: Several versions of the “flexible chainlike walker ” (FCW) model are proposed and inves... more Abstract: Several versions of the “flexible chainlike walker ” (FCW) model are proposed and investigated by numerical simulations on a square lattice. It is shown that the “original ” FCWs aggregate spontaneously and irreversibly, where no adherence is assumed, triggered by “mutual locking”. This is in complete contrast to established aggregation models which necessarily require adherence, and exemplifies the significance of the deformability of self-driven objects. The behaviors of the “smart ” FCWs, which have higher ability of moving, are similar to those of the original FCWs. This suggests that the spontaneous, irreversible aggregation is a robust feature peculiar to a many-body system of deformable self-driven objects. On the other hand, the “double-headed ” FCWs do not undergo the mutual locking and the resultant irreversible aggregation, unlike the original and the smart FCWs. This indicates that “bidirectionality ” prevents deformable self-driven objects from aggregating.

The Proceedings of the Symposium on Environmental Engineering, 2013

Solid State Phenomena, 2012

We performed two experiments on resist-coated wafers. In the measurement of the resist-wafer adhe... more We performed two experiments on resist-coated wafers. In the measurement of the resist-wafer adhesivity, we confirmed that it is significantly increased by an HMDS layer in between. In the resist-removal experiment using steam-water mixed spray, we found that the area of resist removal is limited within the area of spray application if HMDS is used, otherwise the former can be larger than the latter. These results suggest that the resist removal from a wafer surface by steam-water mixed spray is essentially a peel-off process.

Solid State Phenomena, 2012

We have been developing an innovative ultra-low environmental load cleaning technique by the use ... more We have been developing an innovative ultra-low environmental load cleaning technique by the use of steam-water mixed spray. We showed that this technique is quite effective in both cleaning and photo-resist stripping. We also found that the physical force associated with steam-water mixed spray is greater than that with air-water mixed spray; hence we proposed that the condensation plays an important role in this cleaning technique. In order to discuss further this mechanism, we perform the order estimation of physical processes in dynamics of liquid droplet moving in vapor flow impacting on a solid interface in this study. Results show that droplet impact velocity can be reduced while the droplet approaches to the solid surface. However, the vapor in the gap can condensate to either the liquid droplet or the solid surface with the velocity whose order of magnitude cannot be negligible compared to the impact velocity; hence the amount of vapor that should be pushed out from gap can...

ECS Transactions, 2009

Performance of photoresist stripping using steam-water mixed spray is quantitatively investigated... more Performance of photoresist stripping using steam-water mixed spray is quantitatively investigated with water flow rate as the operating parameter. The most striking and the most important finding is that air-water mixed spray turns out hardly effective. This result shows the peculiar superiority of the proposed technique. As we found that the prominently excessive long time of spraying of steam-water mixture on metal surface results in surface abrasion, this result strongly suggests that both the resist strippping and metal surface abrasion are dominated by essentially the same mechanism. We speculate that our proposing technique is categorized in the physical force cleaning. We discuss the role of the water flow rate in this cleaning technique and the validity of the assumption of physical force cleaning.

ECS Transactions, 2009

A novel ultra low environmental load removal technique of post-dry etch residue is developed, by ... more A novel ultra low environmental load removal technique of post-dry etch residue is developed, by applying physical force cleaning technique using high-speed steam-water mixture spray. It is found that the removal rate of the proposed technique depends on the dry-etch processes, and that the steam-water mixture spray almost completely removes the post-dry etch residue from some kinds of dry etched wafers without help of any chemicals. It is also found that the proposed technique requires very dilute concentration of inorganic solution, if necessary, to remove post-dry etch residue completely from other kinds of wafers and that removal process using amine compound with isopropyl alcohol is unnecessary. By contrast, air-water mixture spray could not remove the dry-etch residue at all even with some chemicals. Therefore it is understood that steam atmosphere significantly contributes the proposed technique. The characteristic feature and efficiency of the proposed technique are discussed.

Physica A: Statistical Mechanics and its Applications, 2009

A two-dimensional square lattice system, on which flexible, chainlike, selfdriven objects move ra... more A two-dimensional square lattice system, on which flexible, chainlike, selfdriven objects move randomly but are drifted to a same direction, causing a unidirectional net flow, is investigated by numerical simulations. It is shown that the objects exhibit a freezing transition from a smoothly flowing state to a completely jammed state, in which the objects get immobile and cannot move anymore. Comparison with the flow of rigid objects shows that this complete jamming (hardening) results from the flexibility (softening) of each self-driven object. This is the first report of the freezing transition of a free transport system (without obstacles) where the net flow is not multidirectional (as in the case of opposing flows or crossing flows) but unidirectional.

Japanese Journal of Applied Physics, 2012

We performed experiments to elucidate the physical action of a steam-water mixture jet, which we ... more We performed experiments to elucidate the physical action of a steam-water mixture jet, which we have proposed as a promising, environmentally friendly tool for cleaning surfaces. Photoresist-coated silicon wafers were adopted as the target and the jet performance of resist removal was evaluated, with several parameters being varied. We found that the resist-removal performance improves as the thickness or the mechanical strength of the resist film decreases, resist-wafer adhesivity decreases, or jet duration increases. The results imply that the essential part of the resist removal by the jet is a physical process including peel-off, in contrast to the established techniques such as the batch cleaning method utilizing chemical reactions. The results also indicate that the physical impact of the jet can be controlled, which will be a significant advantage in applying the jet as a cleaning technique.

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2011

Applying the numerical program for the bubble migration in space, we performed a numerical simula... more Applying the numerical program for the bubble migration in space, we performed a numerical simulation of the bubble behavior with the thermocapillary flow in an open cylindrical container under microgravity conditions. In the present study, 45o sector of the container were modeled. We assumed Marangoni forces on the bubble surfaces were negligible small and calculated a single bubble behavior in 3 dimensional thermocapillary flow in order to make clear the interaction between the thermocapillary flow and the bubble behavior. The following results were obtained by these results; (1) steady state results calculated by the present program agreed well with the results by the previous investigations, (2) the single bubble flowed largely along the streamline of the thermocapillary flow and the moving bubble did not largely change the temperature field, and (3) the repulsive forces were produced by the bubble motion and the magnitudes became larger as the bubble approached to the hot region.

ABSTRACT An experimental study of thermocapillary convection in the half-zone liquid bridge of lo... more ABSTRACT An experimental study of thermocapillary convection in the half-zone liquid bridge of low Prandtl number fluid was performed to observe the transition behavior from steady to oscillatory flows. In thermocapillary convection, one of the still open problems is the observation of onset of oscillatory flow in low Prandtl number fluids. Numerical simulations predicted that there would be two transition points which were a first and second critical Marangoni number (Mac1 and Mac2). However, an experimental verification has not been performed previously because of its difficulties. A molten tin was used as test fluid and a liquid bridge configuration was employed. The temperature distribution at the interface between the liquid bridge and the cold disk was measured by using several fine thermocouples. It could be experimentally detected that the axisymmetric steady flow changes to three-dimensional steady one with increasing the temperature difference. At higher temperature difference, onset of oscillatory flow was also observed. Experimental results concerning the critical Marangoni numbers agreed very well with numerical simulation.

Bulletin of the American Physical Society, 2007

We report numerical simulations of the mixed flows of two groups of deformable self-driven object... more We report numerical simulations of the mixed flows of two groups of deformable self-driven objects. The objects belonging to the group A (B) have drift coefficient D = D A ( D B ), where a positive (negative) value of D denotes the rightward (leftward) driving force. For co-current flows ( D A , D B > 0 ), the result is rather intuitive: the net flow of one group ( Q A ) increases if the driving force of the other group is stronger than its own driving force ( i.e. , D B > D A ), and decreases otherwise ( D B D A ). For countercurrent flows ( D B 0 D A ), however, the result appears paradoxical: the net flow of one group ( Q A ) can increase with the driving force of the other group ( | D B | ), and the net flow with a stronger countercurrent can be larger than the net flow with a weaker co-current. This phenomenon is observed only for deformable objects and results from the entanglement of objects, which in turn is caused by their deformability.

To investigate the effect of phase transitions of the fluid on thermal convection, we are conduct... more To investigate the effect of phase transitions of the fluid on thermal convection, we are conducting experiments of thermal convection of the mixture of a thermosensitive gel and water. The gel absorbs water and swells below a certain critical temperature, while it discharges water and contracts above the critical temperature. The swelling ratio, as well as the critical temperature, can be controlled, which enables us to investigate the effect of phase transition in a series of experiments, where the critical temperature is set between the top and bottom boundary temperatures and the swelling ratio is systematically changed. In flow visualization, we have observed temporally stable and spatially fixed low-velocity regions which are surrounded by distinct high-velocity regions. Such a phenomenon is not observed in thermal convection of a single-phase fluid like water or air, and peculiar to the phase-changing fluid. Also, we have measured the rheological properties of the fluid and f...