Separation of silicon carbide and silicon powders in kerf loss slurry of loose abrasive sawing by means of phase transfer separation method with mixed cationic-anionic surfactant collectors addition

Abstract

Kerf loss slurry generated from the slicing process of silicon wafer by using loose abrasive sawing method contains silicon carbide (SiC) and silicon (Si) powders. This study attempted to separate SiC and Si powders in kerf loss slurry through phase transfer separation method with mixed cationic-anionic surfactant collectors addition. Isooctane and water were employed as the two phases. Dodecylamine acetate (DAA) and sodium oleate (NaOL) was used as the cationic and anionic surfactant collector, respectively. The effects of single surfactant collector addition (DAA/NaOL) and mixed cationic-anionic surfactant collectors addition (DAA + NaOL) on the transfer of individual SiC and Si powders from the water phase to the isooctane phase, as well as on the separation of SiC and Si powders in kerf loss slurry, were investigated and compared.The results indicated that DAA could improve the transfer of both SiC and Si powders to the isooctane phase, and the improvement for SiC powder was higher than for Si powder. In contrast, NaOL could only improve the transfer of SiC powder to the isooctane phase, and the improvement for SiC powder was less than DAA did. Compared to single DAA/NaOL addition, mixed DAA + NaOL addition could improve the separation of SiC and Si powders in kerf loss slurry at lower surfactant collector dosages. In addition, the dosage of NaOL in mixed DAA + NaOL addition had more significant effect on improving their mutual separation than that of DAA did. The optimal separation results were obtained with mixed surfactant collectors addition of 0.01 kg/ton DAA and 0.05 kg/ton NaOL at pH 5. The purity and recovery of SiC powder recovered from the isooctane phase was 90.0% and 92.0%, respectively, and those of Si powder recovered from the water phase was 89.5% and 87.0%, respectively. The total dosage of surfactant collectors was 40% reduced.