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the cleaning mechanisms are not independent of each other, e.g. adsorbed moisture may influence the field enhancement pattern. Compared to DLC the state of modeling the SLC process is at a rather initial stage . Two groups [28, 65] have suggested models to describe it. Yet these models rely on far-reaching assumptions in the description of the processes of laser induced bubble nucleation and growth as well as on the assumption of the temperature of the superheated water layer as growth medium. As our experiments on the last aspect show, it is impossible to transfer the results gained on rough metal films [50, 55, 56] to the water film/silicon system. Furthermore, it is not clear neither qualitatively no r quantitatively how the explosive evaporation differs between bulk water (as in our investigations) and water films (as in SLC) or even small water menisc i as they can be found in ambient environment DLC. Therefore, a good deal of future research on the dynamics of laser induced bubble nucleation and th e explosive evaporation in all these systems is necessary to accurately describe SLC. 6. SUMMARY In thi s paper we have described our state of knowledge on the cleaning mechanisms responsible for particle removal in laser cleaning. Beside s the well-known thermal expansion of the substrate and the explosive evaporation of a water film we identified local substrate ablation a s another cleaning mechanism. Additionally we have shown the significant impact of the explosive evaporation of atmospheric moisture adsorbed at the particles for DLC. Local substrate ablation caused by field enhancement in the particles' near field not only causes particle remova l in DLC, but inevitably also causes substrate damage. Furthermore a damage-free DLC process was not possible with the laser parameters we used in our experiments. Steam laser cleaning, o n the contrary, proved to be superior to the DLC process due to its higher efficiency, universal cleaning threshold and its capability to remove much smaller particles. These findings argue for the application of SLC in wafer cleaning and underline the need for further research on the physics of both DLC and SLC as only this knowledge will ensure a successful implementation of the technique in future industrial applications. Acknowledgements We thank Prof. B. Luk'yanchuk (DSI, Singapore) and Dr. Nikita Arnold (Johannes-Kepler-University, Linz, Austria) for useful discussions. The authors would also like to thank Dr. Bernd-Uwe Runge, Christof Bartels, Johannes Graf, Florian Lang, and Michael Olapinski (all of University of Konstanz) for constructive discussions of the findings of our experiments. Financial support by the EU TMR project "Laser Cleaning" (No. ERBFMRXCT98 0188) and the Konstanz Center for Modern
DOI link for the cleaning mechanisms are not independent of each other, e.g. adsorbed moisture may influence the field enhancement pattern. Compared to DLC the state of modeling the SLC process is at a rather initial stage . Two groups [28, 65] have suggested models to describe it. Yet these models rely on far-reaching assumptions in the description of the processes of laser induced bubble nucleation and growth as well as on the assumption of the temperature of the superheated water layer as growth medium. As our experiments on the last aspect show, it is impossible to transfer the results gained on rough metal films [50, 55, 56] to the water film/silicon system. Furthermore, it is not clear neither qualitatively no r quantitatively how the explosive evaporation differs between bulk water (as in our investigations) and water films (as in SLC) or even small water menisc i as they can be found in ambient environment DLC. Therefore, a good deal of future research on the dynamics of laser induced bubble nucleation and th e explosive evaporation in all these systems is necessary to accurately describe SLC. 6. SUMMARY In thi s paper we have described our state of knowledge on the cleaning mechanisms responsible for particle removal in laser cleaning. Beside s the well-known thermal expansion of the substrate and the explosive evaporation of a water film we identified local substrate ablation a s another cleaning mechanism. Additionally we have shown the significant impact of the explosive evaporation of atmospheric moisture adsorbed at the particles for DLC. Local substrate ablation caused by field enhancement in the particles' near field not only causes particle remova l in DLC, but inevitably also causes substrate damage. Furthermore a damage-free DLC process was not possible with the laser parameters we used in our experiments. Steam laser cleaning, o n the contrary, proved to be superior to the DLC process due to its higher efficiency, universal cleaning threshold and its capability to remove much smaller particles. These findings argue for the application of SLC in wafer cleaning and underline the need for further research on the physics of both DLC and SLC as only this knowledge will ensure a successful implementation of the technique in future industrial applications. Acknowledgements We thank Prof. B. Luk'yanchuk (DSI, Singapore) and Dr. Nikita Arnold (Johannes-Kepler-University, Linz, Austria) for useful discussions. The authors would also like to thank Dr. Bernd-Uwe Runge, Christof Bartels, Johannes Graf, Florian Lang, and Michael Olapinski (all of University of Konstanz) for constructive discussions of the findings of our experiments. Financial support by the EU TMR project "Laser Cleaning" (No. ERBFMRXCT98 0188) and the Konstanz Center for Modern
the cleaning mechanisms are not independent of each other, e.g. adsorbed moisture may influence the field enhancement pattern. Compared to DLC the state of modeling the SLC process is at a rather initial stage . Two groups [28, 65] have suggested models to describe it. Yet these models rely on far-reaching assumptions in the description of the processes of laser induced bubble nucleation and growth as well as on the assumption of the temperature of the superheated water layer as growth medium. As our experiments on the last aspect show, it is impossible to transfer the results gained on rough metal films [50, 55, 56] to the water film/silicon system. Furthermore, it is not clear neither qualitatively no r quantitatively how the explosive evaporation differs between bulk water (as in our investigations) and water films (as in SLC) or even small water menisc i as they can be found in ambient environment DLC. Therefore, a good deal of future research on the dynamics of laser induced bubble nucleation and th e explosive evaporation in all these systems is necessary to accurately describe SLC. 6. SUMMARY In thi s paper we have described our state of knowledge on the cleaning mechanisms responsible for particle removal in laser cleaning. Beside s the well-known thermal expansion of the substrate and the explosive evaporation of a water film we identified local substrate ablation a s another cleaning mechanism. Additionally we have shown the significant impact of the explosive evaporation of atmospheric moisture adsorbed at the particles for DLC. Local substrate ablation caused by field enhancement in the particles' near field not only causes particle remova l in DLC, but inevitably also causes substrate damage. Furthermore a damage-free DLC process was not possible with the laser parameters we used in our experiments. Steam laser cleaning, o n the contrary, proved to be superior to the DLC process due to its higher efficiency, universal cleaning threshold and its capability to remove much smaller particles. These findings argue for the application of SLC in wafer cleaning and underline the need for further research on the physics of both DLC and SLC as only this knowledge will ensure a successful implementation of the technique in future industrial applications. Acknowledgements We thank Prof. B. Luk'yanchuk (DSI, Singapore) and Dr. Nikita Arnold (Johannes-Kepler-University, Linz, Austria) for useful discussions. The authors would also like to thank Dr. Bernd-Uwe Runge, Christof Bartels, Johannes Graf, Florian Lang, and Michael Olapinski (all of University of Konstanz) for constructive discussions of the findings of our experiments. Financial support by the EU TMR project "Laser Cleaning" (No. ERBFMRXCT98 0188) and the Konstanz Center for Modern
ABSTRACT