In situ monitoring and universal modelling of sacrificial PSG etching using hydrofluoric acid

A video system has been designed to monitor in situ and accurately the etching of sacrificial phosphosilicate-glass (PSG) microchannels using hydrofluoric acid (HF). An universal model, which predicts accurately the etching length vs. time over a wide range of HF concentration (3-49 wt.%), has been identified. In addition to diffusion, this model is based on a first-and-second order chemical reaction mechanism. It is found that the PSG microchannel etching rate in HF is sensitive to channel thickness but not width. Finally, bubble formation and movement inside the etched microchannels are observed. Most of the generated bubbles are mobile and can enhance the etching rate