Method of removing material on solid bodies with degradation of the time and/or spatial coherence of the laser beam

摘要

The method of material removal on solid body by laser ablation, comprises reducing spatially and/or temporally coherence of a laser radiation used for the material removal, and/or directly striking on the solid body. The step of reducing the coherence of the laser radiation is reduced by: a transmission of the laser radiation through a medium scattering the laser radiation; reflection of the laser radiation at the medium scattering the laser radiation; and/or relative movement of a source of the laser radiation and the solid body during an ablation process. The method of material removal on solid body by laser ablation, comprises reducing spatially and/or temporally coherence of a laser radiation used for the material removal, and/or directly striking on the solid body. The step of reducing the coherence of the laser radiation is reduced by: a transmission of the laser radiation through a medium scattering the laser radiation; reflection of the laser radiation at the medium scattering the laser radiation; and/or relative movement of a source of the laser radiation and the solid body during an ablation process. The scattering medium consists of particles scattering the laser radiation or particle-containing systems such as in form of the laser radiation scattering powders or dispersions, emulsions and/or solutions of the particles, and/or the reflecting medium consists of plates scattering the laser radiation. The particle is silicon dioxide or titanium dioxide-particles and/or its mixtures, and/or has an average particle diameter that lies between 0.5- and 1-fold of a wavelength of the applied laser light. Before the laser ablation, the particle is applied as the powder or dispersion on the surface of the solid body to be processed. The dispersion is applied or sprayed by spin coating and/or dip-coating. The solid body has a regular structured surface such as a pyramidal structure. The structure has a periodicity of 5-15 mu m. The solid body is a semiconductor such as a silicon wafer, and a solar cell having an anti-reflective coating. The material removal is performed on a side comprising the anti-reflection coating of the solar cell. The laser abalation has a pulse length of 400 fs and 100 ns, the wavelength of 193-1064 nm, and/or an intensity of 1-100 kJ/m 2>. Two lasers are used with different wavelengths starting from a first phase of wave after a period of 50-fold. The laser source consists of carbon dioxide laser, helium-neon laser, excimer laser, dye laser, diode laser, fiber laser and/or solid state laser. After the material removal, a partially filling cavity originated at the material removal is performed with an electrically conductive material.