TY - JOUR
T1 - Elimination of blind zone in nanoparticle removal on silicon wafers using a double-beam laser shockwave cleaning process
AU - Zhang, Shuowen
AU - Yan, Qingyu
AU - Lin, Jian
AU - Zhang, Qunli
AU - Lu, Yongfeng
AU - Yao, Jianhua
AU - Fan, Lisha
N1 - Funding Information:
This work was financially supported by the 111 Project from Overseas Expertise Introduction Center for Discipline Innovation (No. D16004) and National Key R&D Program of China (2017YFB1103600).
PY - 2021/2/15
Y1 - 2021/2/15
N2 - Laser shockwave cleaning (LSC) has been gaining increasing attention due to its advantages in decontaminating various micron- and nano-scale contaminated particles on silicon (Si) wafer surfaces. However, the particles in a blind zone right under the laser-induced plasma, the origin of the shockwave, cannot be removed efficiently, thereby impeding the conventional LSC process in industrial wafer cleaning applications. Here, we demonstrate a simple but intriguing method of eliminating the blind zone in nanoparticle removal on Si wafers by employing a double-beam laser shockwave cleaning process (DLSC). The size of the uncleaned blind zone in DLSC is reduced by 98% compared to the traditional single-beam LSC (SLSC) process with a laser pulse energy of 150 mJ and a gap distance between the laser focus and the wafer of 1 mm. The time-resolved, laser-induced plasma evolution reveals that the steady single-laser-beam-induced plasma splits into multiple plasma kernels distributed around the focus point due to the disruption from the second laser beam. The formation of multiple plasma kernels makes it possible to expose the particles in the blind zone to the cleaning-effective zone of the shockwave from a nearby passing plasma. The angle between the two laser beams plays a critical role in eliminating the blind zone. The comparison of the particle removal force between DLSC and SLSC suggests that the horizontal drag force from a nearby passing plasma acts on the particles in the blind zone and facilitates their removal.
AB - Laser shockwave cleaning (LSC) has been gaining increasing attention due to its advantages in decontaminating various micron- and nano-scale contaminated particles on silicon (Si) wafer surfaces. However, the particles in a blind zone right under the laser-induced plasma, the origin of the shockwave, cannot be removed efficiently, thereby impeding the conventional LSC process in industrial wafer cleaning applications. Here, we demonstrate a simple but intriguing method of eliminating the blind zone in nanoparticle removal on Si wafers by employing a double-beam laser shockwave cleaning process (DLSC). The size of the uncleaned blind zone in DLSC is reduced by 98% compared to the traditional single-beam LSC (SLSC) process with a laser pulse energy of 150 mJ and a gap distance between the laser focus and the wafer of 1 mm. The time-resolved, laser-induced plasma evolution reveals that the steady single-laser-beam-induced plasma splits into multiple plasma kernels distributed around the focus point due to the disruption from the second laser beam. The formation of multiple plasma kernels makes it possible to expose the particles in the blind zone to the cleaning-effective zone of the shockwave from a nearby passing plasma. The angle between the two laser beams plays a critical role in eliminating the blind zone. The comparison of the particle removal force between DLSC and SLSC suggests that the horizontal drag force from a nearby passing plasma acts on the particles in the blind zone and facilitates their removal.
KW - Double-beam
KW - Laser shockwave cleaning
KW - Nanoparticle removal
KW - Plasma evolution
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U2 - 10.1016/j.apsusc.2020.148057
DO - 10.1016/j.apsusc.2020.148057
M3 - Article
AN - SCOPUS:85093658296
VL - 539
JO - Applied Surface Science
JF - Applied Surface Science
SN - 0169-4332
M1 - 148057
ER -