Laser cleaning of silicon surface with deposition of different liquid films

Laser cleaning can efficiently remove tiny particles from a silicon surface on which a liquid film has been previously deposited when the laser fluence is large enough. The cleaning force is due to the high pressure of stress wave generated through the rapid growth of vapor bubbles inside the superheated liquid. The behaviors of this type of laser cleaning are theoretically described with deposition of two kinds of liquid film: acetone and ethanol. The cleaning threshold of laser fluence is different for these two kinds of liquids for some differences in their thermodynamic properties. For removal of alumina particles with a size of 1 mu m, the lower cleaning threshold of laser fluence is obtained with deposition of acetone because of its lower boiling point and volume heat capacity. The theoretical result also indicates that the cleaning force with deposition of ethanol increases more quickly along with laser fluence than with acetone. This phenomenon is much useful for removal of smaller particles and can lead to high cleaning efficiency. (C) 1999 published by Elsevier Science B.V. All rights reserved.