Types of Laser Cleaning Technology

Laser Dry Cleaning: Dry laser cleaning involves directly irradiating the workpiece with a pulsed laser, causing the substrate or surface contaminants to absorb energy, increasing their temperature, and generating thermal expansion or substrate thermal vibration, thereby separating the two. This method is roughly divided into two scenarios: one is that the surface contaminants absorb the laser and expand; the other is that the substrate absorbs the laser and generates thermal vibrations.  

Laser Wet Cleaning: Before irradiating the workpiece to be cleaned with a pulsed laser, a liquid film is pre-coated on the surface. Under the action of the laser, the liquid film's temperature rapidly rises and vaporizes. The instantaneous vaporization generates a shock wave that acts on the contaminant particles, causing them to detach from the substrate. This method requires that the substrate and the liquid film do not react, thus limiting the range of applicable materials.  

Laser Plasma Shock Wave Cleaning: Laser plasma shock wave cleaning involves the breakdown of the air medium during laser irradiation to generate a spherical plasma shock wave. The shock wave acts on the surface of the substrate to be cleaned and releases energy to remove contaminants. The laser does not act on the substrate, thus causing no damage to it. Laser plasma shock wave cleaning technology can now clean particulate contaminants with particle sizes of tens of nanometers and has no restrictions on laser wavelength.  

Plasma is generated only when the energy density is above a certain threshold, which depends on the contamination layer or oxide layer being removed. This threshold effect is very important for effective cleaning while ensuring the safety of the substrate material. There is also a second threshold for the appearance of plasma. If the energy density exceeds this threshold, the substrate material will be damaged. To achieve effective cleaning while ensuring the safety of the substrate material, laser parameters must be adjusted according to the situation so that the energy density of the light pulse is strictly between the two thresholds.  

The initial purpose of the above three types of laser cleaning technology was to clean tiny particles on the surface of semiconductor wafers. It can be said that laser cleaning technology emerged with the development of semiconductor technology. However, laser cleaning technology has been continuously applied to other fields, such as tire mold cleaning, aircraft skin paint removal, and cultural relic surface restoration.