A novel laser-assisted particle removal (LAPR) technique capable of removing micron scale particles from semiconductor substrates is presented. In our preliminary experiments the contaminated substrates were dosed with water which preferentially adsorbs in the capillary spaces under and around the particles and were subsequently irradiated with transverse, electric, atomspheric CO2 laser pulses. At the CO2 laser wavelength the beam energy is mainly absorbed in the water and not the substrate. The subsequent explosive evaporation of the adsorbed water molecules produces forces many orders of magnitude larger than the adhesion forces between the particle and the substrate which propel the particles off the substrate surface. LAPR is inherently clean and can easily be incorporated into current or planned wafer processing systems.

Laser "direct writing" (LDW) or maskless pattern deposition has been extensively studied for more than a decade. 1,2 LDW is potentially attractive in semiconductor device customization, repair, prototyping, and packaging applications. [3][4][5] Copper is an important metallization material in microelectronic circuits 6,7 and multichip module interconnections, 8,9 largely because of its low electrical resistivity. A major limitation of LDW technologies for device metallization applications using laser chemical vapor deposition (LCVD) techniques has been the lack of Cu precursors with sufficiently high vapor pressure. The most common precursors used for the large area CVD of copper are copper(II) and ligand-stabilized copper(I) ␤-diketonate compounds. 10 While the vapor pressures of these precursors are, in general, sufficient for conventional CVD (deposition rates greater than or equal to a micrometer per hour), they are too low to allow the fast deposition rates (mm/s) required for LCVD applications. Advanced technologies making direct use of liquidphase delivery of precursors to the reaction zone have been developed. Solid-phase precursors can be dissolved into selected solvents such as 2-propanol or ethanol to provide highly controllable flow rates to the reaction zone. 11 Liquid precursors can be dissolved in solvents, 12 made into a paste layer, 13 or used as neat compounds. 14,15 The mechanism of deposition using liquid precursors has been proposed to be either a photochemical 16,17 or thermal decomposition reaction involving one or more precursors. 18,19 Laser-enhanced electroplating 20,21 and electroless plating 22 were first reported by von Gutfeld et al. They reported local plating enhancement rates as high as ϳ10 3 utilizing highly localized heating caused by the absorption of a focused laser beam at the substrate. Self-induced repair (SIR) of microelectronic circuits using joule heating induced local electrodeposition demonstrated by Chen is analogous to laser enhanced electroless plating. 23 The electrochemical conditions necessary for an electroless plating process to take place are (i) the reducing potential of the reductant must be less than that of the reducing potential of the metal and (ii) the metal must have enough catalytic activity for the anodic oxidation to take place at a reasonable rate. In a laser-enhanced electroless plating (LEEP) process the laser-induced temperature rise in the substrate enhances the local chemical reaction, causing the redox reaction to take place and metal to be deposited. The reducing agent needs to be chosen such that reduction takes place at an elevated temperature but not at ambient so that spatially selective laser deposition can take place. The redox potentials of selected reducing agents are listed in Table I. ExperimentalThe experimental setup is shown in Fig. 1. An Ar ion laser delivering a linearly polarized transmission electron microscopy (TEM 00 ) beam was used as the driving energy source. The laser was operated at a single wavelength of 514.5 nm whi...

The reflection of a planar ion-acoustic soliton from an insulated or a biased metallic planar wall is studied. Numerical solutions of the cold-ion fluid equations, the Boltzmann distribution for electrons, and Poisson’s equation show that the incident soliton is partially reflected and partially absorbed by the wall. The reflection is larger for wider solitons and for a more negatively biased wall. The numerical results are in reasonable agreement with the recent experiment of Nishida [Phys. Fluids 27, 2176 (1984)].

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Laser assisted particle removal (LAPR) is an innovative laser cleaning technique which can remove various particles from solid surfaces via laser induced explosive evaporation of a chosen energy transfer medium, e.g., water. An Ar+ ion continuous-wave laser (488 nm) was used to study the CO2 laser pumped explosive evaporation of water adsorbed on a Si substrate. The probe laser beam was parallel to the sample surface at different displacements and interacted with the ejected material upon pulsed CO2 laser irradiation in analogy with the time resolved laser beam deflection experiments on laser induced vaporization of copper by Guo et al. [Opt. Commun. 77, 381 (1990)]. Using CO2 laser energies which are much greater than the LAPR thresholds, we observed the generation and propagation of a shock wave at supersonic speeds followed by a water vapor/aerosol/particle cloud at a much slower speed. From the evolution of the shock wave, the total conversion efficiency of the incident laser beam into the shock wave has been determined using a self-similar approximation.