Femtosecond Laser Stealth Dicing Of Silicon Carbide

Owing to the development of electric vehicle industry and the demand for high power devices,the traditional silicon wafer based devices have been unable to meet people’s demand for high power and low energy consumption.The silicon carbide（Si C）as the representative of the third generation semiconductor device substrate material,has the advantages of chemical stability,high hardness,heat resistance and high thermal conductivity,but expensive.At present,the processing method of Si C wafer is dominated by the diamond wire-saw cutting,which needs to go through the cutting,grinding,polishing and other processes.The entire processing process is complex and the material loss can reach to 46%,which increases the cost of silicon carbide wafer.More important,this processing process is usually carried out in a liquid environment,the grinding and polishing process needs to use chemical reagents,generating serious environmental pollution.Femtosecond laser has the advantages of high machining accuracy,small heat effect,which has been widely applied to the basic research and practical application.Femtosecond laser has high peak power,it can generate multiphoton effects on the transparent material clean ablation,thus can realize stealth dicing.In this paper,we investigate the interaction between femtosecond laser and silicon carbide and propose a femtosecond laser stealth dicing method of silicon carbide wafer.In order to achieve the purpose of wafer dicing,a femtosecond laser is focused on the surface of Si C wafer,and the silicon carbide wafer is machined by adjusting the machining speed and laser peak power.The dependence of machining speed,laser peak power and the notch is established,and the best parameters are obtained.Furthermnore,through the analysis and characterization of the Raman signal inside the notch,the mechanism of femtosecond laser and silicon carbide interaction was verified.We demonstrated that femtosecond laser uses the multi-photon absorption effect to decomposition single crystal silicon carbide into amorphous carbon and amorphous silicon,in result achieving stealth dicing effect,which effectively reducing the thermal effect in machining.The method of femtosecond laser stealth dicing on silicon carbide can effectively reduce the production cost,improve the efficiency and quality of dicing,and has a wide application prospect in hard and brittle crystal cutting.