Developmental Research for Manipulation of Submicron Particles by Laser Beam

为了防止半导体晶片被悬浮在空气中的颗粒污染，屏障由波长为488 nm的扫描激光束、438 nm的可见光和300 nm的紫外光在水平面内组成。本文从理论和实验上分析了激光束中小颗粒的行为以及激光束中光子、小颗粒和小颗粒周围气体分子之间相互作用所引起的现象，并对操纵和消除悬浮在空气中的颗粒进行了发展性的科学研究。其结果是得到了一些前人研究中没有得到的有效结果。(1)在激光束聚焦点附近捕获直径为1 μ m ~ 20 μ m的聚苯乙烯乳胶粒子或对粒子进行三维操纵的实验结果明确表明， ...更多信息 可以安全地捕获或操纵粒子。结果表明，阻挡层扫描直接激光束在入射光束的前进方向上可以消除直径为1 ~ 20 μ m的聚苯乙烯颗粒，为此，强烈需要保持激光束的高斯强度分布稳定。(2)可以清楚地看出，悬浮在空气中的亚微米颗粒突破了强度为1 w、波长为488 nm的屏障扫描激光束。因此，从理论和实验上研究了共振吸收的效果，以提高辐射压力消除颗粒的效果。作为结果，共振吸收的效果取决于复折射率的变化，颗粒尺寸和入射激光束的波长已经澄清，如在一个例子中所示的共振吸收的效果显着变化，从几微米的点的颗粒直径的差异。(3)利用粒子在高斯光强分布的激光束中的Mie散射理论，编制了计算粒子在行进方向和垂直于光束方向上的辐射压强的程序软件。从而建立了激光束中任意位置粒子所受辐射压力的模拟方法。(4)观察到了粒子随入射激光束前进方向突然向后飞的异常现象。为了弄清产生这种现象的原因，定量测量了粒子在入射光束前进和逆前进方向上的飞行速度以及粒子被捕获的力的大小。其原因被解释为取决于电泳或共振吸收后的发射。激光操纵粒子的实验研究在真空室中继续进行。少

Protecting the wafer of semiconductor from contamination by the particles suspended in the air, the barrier was composed of the scanning laser beam with wave length 488 nm, 438 nm visible light and 300 nm ultra-violet light in the horizontal plane. The analysis of the behavior of small particles in the laser beam and of phenomena caused by the interaction between photons, small particle and molecules of gas surrounding the small particle in the laser, and the developmental scientific research on the manipulation and the elimination of particles suspended in the air, were examined theoretically and experimentally. The consequence is that some effectual results, have not gotten in the former researches are obtained as follows.(1) It has been definitely shown by the results of experiments making-attempts trapping Particles from 1 um to 20 um in diameter consisting of polystyrene latex in the vicinity of focussing point of laser beam or manipulating particles three-dimensinonally that the' … More particles could be trapped or manipulated safely. It is clarified that polystyrene particles from 1 um to 20 um in diameter could be eliminated for the progressive direction of incident beam by the barrier scanning direct laser beam, for that purpose, it was strongly needed to preserve Gaussian intensity distribution of the laser beam steadily.(2) It is clarified that the submicron particles suspended in the air break through the barrier scanning laser beam having intensity of 1 w and wave length of 488 nm. Therefore, the effect of the resonance absorption was examined theoretically and experimentally, to improve the effect of radiation pressure eliminating particles. As the results, the effect of the resonance absorption depending on the variation of complex index number of refraction, particle size and wave length of incident laser beam has been clarified as shown in an example which the effect of resonance absorption remarkably changes from the difference of particle diameter in the point of several microns.(3) By using Mie scattering theory for the particle in the laser beam having Gaussian intensity distribution, a program software has been made to calculate the radiation pressure acting to the particle for the direction of the progression and the perpendicular to the beam. Hence, the simulation method has been built up for the radiation pressure acting to the particle at the arbitrary position in the laser beam.(4) An extraordinary phenomena which particles suddenly fly backward for the progressive direction of the incident laser beam was observed. To clear up the cause of the phenomena, the velocities of particles flying to the progressive and anti-progressive direction of incident beam, and the magnitude of the force trapping particles were measured quantitatively. The cause was conjectured as depending on the photophoresis or the emission after resonance absorption. Glarifying the cause, the experimental research on the manipulation of particles by laser beam has been continued in the vacuum chamber. Less