Study On Sapphire Ultrasonic Chemical Mechanical Polishing Process And Material Removal Mechanism

As an important semiconductor material,sapphire wafers are used in the manufacture of advanced optoelectronic products.With the rapid development of information technology,related products are iterating rapidly,and the application of sapphire wafers requires higher and higher surface quality.Sapphire wafers are typical hard and brittle materials.The traditional chemical mechanical polishing process has been difficult to meet the requirements for sapphire’s processing efficiency and surface quality after polishing.It is necessary to develop new composite polishing technologies to achieve high-efficiency and high-quality processing of sapphire wafers.Studies have shown that ultrasonic processing can achieve high-efficiency and high-quality processing of hard and brittle materials such as silicon and silicon carbide.In view of the shortcomings of chemical mechanical polishing of sapphire wafers,combined with the characteristics of ultrasonic processing,a sapphire ultrasonic chemical mechanical polishing process(UV-CMP)was proposed.A ultrasonic mechanical polishing system for sapphire wafer was designed,and a corresponding polishing device was developed.This device can be used for both traditional chemical mechanical polishing process and ultrasonic-assisted polishing.On the basis of this equipment,the polishing effects of sapphire wafers under the two processes were compared.The results show that the introduction of ultrasound can improve the material removal rate and surface quality of sapphire polishing.Three kinds of polishing pads,including polyester fiber,damping cloth,slotted damping cloth,and three polishing slurries of silica,alumina and cerium oxide were used to polish sapphire under UV-CMP.Polishing results showed that the damping cloth pad and silica slurry were the best.Under UV-CMP,the polishing effects of silica slurries with different particle diameters and different p H values on sapphire wafers were compared.The results showed that the silica slurry with particle diameter of 100 nm and p H value of 10 was the best.The polishing process parameters were optimized through orthogonal experiments.The results showed that the polishing pressure was the greatest influence factor on the material removal rate,followed by the rotating speed.The rotating speeds of the polishing head and pad were the main elements of the polished surface quality.Finally,the best polishing parameters were found.The effects of ultrasound on the mechanical removal and chemical corrosion of sapphire UV-CMP were explored respectively.The reasons for the excellent performance of sapphire UV-CMP were explained.On this basis,a material removal model of sapphire UV-CMP was established.