Laser Technology has wide application in industry as well as in scientific research. Semiconductor industry also interested to use laser for cleaning contaminant. However, until today, no laser has been deployed to take over the traditional method due to lack of intension on it. As a first step to embark into industrial solution, initiative has been carried out to do fundamental experiment. Optimization has been established to find out the best position for cleaning without associated with damage. A Q-switched Nd:YAG laser was focused to create breakdown in the air. This is an indicator for plasma formation and shock wave generation as the main mechanisms of damage. Pure aluminium was used as a substrate and mounted on précised a 3D linear translational stage.  The defocused distance was varied in the range of 0-25 mm. The damage image was recorded and analysed via the aid of ImageJ software. Small and deep dense deformation was observed as the target located at the focal point. As the defocused distance move further away, the damage tend to be eliminated and its depth approaching the same level as original.