Effect of Potassium Persulfate as an Additive On Chemical Mechanical Polishing Performance on C-, A- and R-Plane Sapphire

Abstract

Sapphire with different crystal planes is widely used in light-emitting diode (LED), silicon on sapphire (SOS) IC chips, hybrid microelectronic applications, and other high-tech fields. Chemical mechanical polishing (CMP) technology is widely applied to obtain super-smooth and non-damaged wafer surface on the sapphire wafer. Due to its higher hardness and brittleness, sapphire CMP processing is difficult because of its lower processing efficiency. In this paper, in order to improve the CMP performance of different plane sapphire, K2S2O8 was used as an additive in the slurry. On the basics of chemical thermodynamic theory, HSC(enthalpy (H), entropy(S), heat capacity (C)) chemistry software was used to judge whether the chemical reactions can occur spontaneously. According to the experiment results, a higher material removal rate (MRR) was obtained with the slurry containing 0.2 wt% K2S2O8 and the surface roughness Sq of different plane sapphire substrates were all less than 0.3 nm. At the same time, the reaction mechanism and process of K2S2O8 was revealed. X-ray photoelectron spectroscopy (XPS) analysis showed that there were new chemical reactions between the sapphire wafer and K2S2O8 sol and the reaction products included aluminum sulfate (Al2(SO4)3) and potassium sulfate (K2SO4), which increased the chemical effect during the polishing process and resulted in the increasing of MRR.

Effect of ZnO-SiO2 Composite Abrasive on Sapphire Polishing Performance and Mechanism Analysis

“…XPS measured results of sapphire soaked.-The XPS results of the soaked sapphire shows that the peak at the binding energy of 73.08 eV, 73.86 eV and 74.35 eV are consistent with Al 2p of Al 2 O 3 /Al, 31 Al(OH) 3 14 and AlOOH 33 respectively from Fig. 9a.…”

“…The results showed that three kind of potassium salts were effective in increasing the MRR of sapphire substrate. [12][13][14] Xu et al reported a catalyst (Fe-Nx/C) and found pyrrole nitrogen can weaken the Al-O bond via the bonding between oxygen and nitrogen or the adjacent carbon atom to promote the chemical reaction. 15 Zhao et al reported adding chelating agent in slurry can enhance the MRR of c-plane sapphire.…”

Effects of Surfactants on the Chemical Mechanical Polishing Performance of a-Plane Sapphire Substrates

“…Lei and Dai et al [9][10][11] prepared composite abrasive particles to improve the material removal rates and the polished surface quality during the CMP process of sapphire. Zhang and Xu et al [12][13][14][15][16][17] added different additives such as coordination agents, catalysts, and ionic strength agents to the polishing solution to promote the polishing effect of sapphire. Yan et al [18][19][20] found that the material removal rates of the sapphire substrate were greatly affected by the pH value of the polishing solution, and the material removal rate reached the maximum in a neutral environment.…”

Effects of Different Dispersants on Chemical Reaction and Material Removal in Ultrasonic Assisted Chemical Mechanical Polishing of Sapphire

“…The results showed that adding 0.2 wt% K 2 S 2 O 8 could improve the removal rate and reduce the roughness. 18 It was due to the addition of K 2 S 2 O 8 enhancing the chemical action in polishing. Niu et al added PH reagents, chelating agents and oxidants to enhance the chemical action in sapphire CMP and improve the polishing efficiency.…”