Experimental Investigation On Cleaning Of Sapphire Substrate By Carbon Dioxide Snow Jet Spray Cleaning

Surface cleanliness of sapphire substrates is one of the important factors affecting the performance of semiconductor light emitting diodes(LED).The existing cleaning technology for sapphire substrates uses cleaning agents to multiple passes,which causes many problems such as cumbersome process and environmental pollution caused by chemical cleaning agent.This paper explores the use of carbon dioxide snow jet spray cleaning technology to clean the sapphire substrate.Three-dimensional video microscope and built-in energy dispersive spectrometer desktop scanning electron microscopy were used to analyze the residue of sapphire substrates.The results showed that the residue mainly consisted of polishing base fluid and diamond abrasive.By calculating the adsorption force between polishing base fluid and sapphire substrate and the force of the diamond abrasive adhered to sapphire substrate,the feasibility of cleaning the different types of pollutants by carbon dioxide snow jet spray cleaning technology was analyzed,and an experimental device for carbon dioxide snow jet spray cleaning was designed and manufactured.Through the numerical simulation,the gas flow field inside the straight-type and Venturi nozzles in the experimental device of carbon dioxide snow jet spray cleaning and the flow field distribution of their sprays in the air were studied.The Venturi nozzle structure was selected by comparison,and the influence of geometrical structure of Venturi nozzle on cleaning efficiency was further studied by simulation.The simulation results were verified to be reliable through high-speed camera.The orthogonal experimental method was used to develop the experimental scheme.The effects of the spraying distance,cleaning time and spraying angle on the cleaning effect were studied.The optimum process parameter combinations were that the spraying distance was 35 millimeters,the cleaning time was 45 seconds,the spraying angle was 45 degrees.The surface cleanliness of sapphire substrates before and after cleaning was compared by contact angle measurement and X-ray photoelectron spectroscopy(XPS),and the cleaning effect of carbon dioxide snow jet spray cleaning was verified.The influence of carbon dioxide snow jet spray cleaning on the surface quality of sapphire substrates was analyzed by detecting the surface damage of sapphire substrates before and after cleaning.The application range of carbon dioxide snow jet spray cleaning technology was also studied.The results show that carbon dioxide snow jet spray cleaning can effectively remove organic residues of sapphire substrates without damage and has wide applicability.