| Abstract [eng] |
Micromachining is widely used in the fields of medicine, mechanics, optics, electronics, and other industries. The use of femtosecond laser irradiation in micromachining enables the processing of dielectric materials such as glass through nonlinear processes (multiphoton absorption, tunnel ionization, etc.). This process is characterized by a small heat-affected zone and high precision, as the material is affected at the focal point of the laser beam. The glass regions affected by laser radiation exhibit increased etching rates compared to the rest of the material. The ratio of etching rates between modified and unmodified regions is referred to as selectivity. Fused silica glass is popular due to its high achievable chemical etching selectivity, allowing for the efficient fabrication of various geometries for applications such as microfluidic devices. Glasses with additional modifiers (e.g., B2O3, Al2O3, etc.) are cheaper and, in the case of borosilicate glass, compatible with the thermal expansion coefficient of silicon, making it suitable for MEMS applications. However, they do not exhibit the same high chemical etching selectivity as fused silica glass, posing a challenge for the fabrication of more complex structures in these glasses. The aim of this study is to investigate the influence of laser fabrication parameters and wet etching condition on etching selectivity of various glasses. The main conclusions of the study are as follows: 1. Glass with more modifiers did not exhibit as significant chemical etching selectivity as borosilicate glass. Increased aluminum content in the glass and the formation of insoluble salts in potassium hydroxide solution reduce the overall etching rate. 2. Higher etching temperatures increase the chemical reaction rate and diffusion, leading to increased etching rates for both borosilicate glass and glass with more modifiers. However, etching becomes less selective. 3. Additional agitation during etching in 80℃ potassium hydroxide solution had a positive effect on glass with more modifiers. The increased etching rate can be attributed to the fact that etching at this temperature is diffusion-limited, and agitation improves the diffusion of the solution into the etched channel, preventing the rapid formation of insoluble aluminum salts on the surface. |
