Research on R-Plane Sapphire Substrate CMP Removal Rate Based on a New-Type Alkaline Slurry

Abstract

Chemical mechanical polishing (CMP) is widely used as one of the most effective methods to achieve atomic-scale smooth surface. In order to investigate the mechanism of sapphire (α-Al 2 O 3 ) substrate CMP, the X-ray photo-emission spectroscopy (XPS) was applied to analyze the chemical state of elements. From XPS analysis it was demonstrated that AlO(OH) whose hardness was lower than α-Al 2 O 3 , existed only in c-plane sapphire after c-and r-plane polishing, so it's difficult to get high removal rate for r-plane CMP. But GaN epitaxial film grown on the r-plane sapphire substrate is semi-polar, and the luminous efficiency of the thin film is significantly improved. In order to improve r-plane sapphire substrate processing efficiency and accuracy, effects of pH regulator, KNO 3 concentration and surfactant concentration on r-plane sapphire CMP were studied. Higher removal rate of r-plane was obtained when KNO 3 concentration was 0.1 wt%, which was attributed to the particle size increase and new chemical reaction. But the removal rate decreased slightly due to the broadening of particle size distribution scope at higher ionic strengths. Anionic surfactant could improve removal rate and surface quality due to its good dispersion and stability to prevent nano-SiO 2 sol agglomeration. For r-plane sapphire, removal rate and surface roughness Sq can reach 1.43 um/h and 0.173 nm respectively, which provides guiding significance for the development of industrial sapphire ultra precise processing.

Effect of Alkali Metal Ion on Chemical Mechanical Polishing of LiTaO3

“…Under alkaline conditions, hydroxyl groups were dissociated to form surface functional groups with negative charges. They are existed compound of SiOK 23 as shown in Eq. 3:…”

“…Figure 9 shows the particle size and zeta potential of silica particles when different potassium salts are added to the slurry. The concentration of the K + in the slurry is 0.14 M. By comparing the effects of four potassium salts on the particle size of silica, it can be seen that in the slurry added with KCl, the average particle size of silica is relatively large and the absolute value of zeta potential is relatively low, which increases the mechanical effect 23 of abrasive on LiTaO 3 wafer, so that LiTaO 3 wafer has a higher MRR.…”

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

“…In addition, surfactants have an important impact on material removal rates and abrasive particle contamination of the polished surface during wafer polishing. [21][22][23] Park et al [24][25][26][27] investigated the effect of anionic surfactants such as polyacrylic acid (PAA), sodium dodecyl sulfate (SDS), dodecyl benzene sulfonate (DBSA), dodecyl phosphate (DP), and sodium lauroyl sarcosinate (SLS) on the polishing of Si 3 N 4 films and found that these anionic surfactants could be selectively adsorbed on the surface of Si 3 N 4 film through electrostatic action to form a dense adlayer. This adlayer prevented abrasive particles from approaching the film surface, thereby inhibiting the material removal rate of the Si 3 N 4 film.…”

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

“…Sapphire has outstanding physical, chemical and optical characteristics so that it has been widely used in semiconductor devices, LEDs, solid-state lasers, infrared windows and precision optics. 1,2 In particular, sapphire can be applied as the substrate material for epitaxial growth of GaN, integrated circuits and other devices. [3][4][5][6] As a substrate material, the sapphire surface quality is greatly affecting the performance and reliability of semiconductor devices.…”