Effects of mixed ultrafine colloidal silica particles on chemical mechanical polishing of sapphire

Sapphire is widely used in solid lasers, semiconductor chip substrates, light emitting diodes substrates and other high-tech fields for its excellent mechanical and optical properties. At the same time, the chemical mechanical polishing(CMP) performance and quality need to be improved for different crystal plane sapphire substrate. In this paper, in order to improve the removal rate NaCl was used as an additive in sapphire slurry. From the CMP experiment results of a- and c-plane sapphire, it was found that higher material removal rate (MRR) and lower surface roughness (Sq) were obtained by adding NaCl with the concentration of 0.2wt% in sapphire slurry. In order to reveal the action mechanism of NaCl, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) measure methods were used. From the SEM measure results it can be seen that there were microscopic corrosion pits on substrate surface, which indicates that chemical reaction took place between NaCl and substrate material. From XPS measure results it was verified that sodium tetrachloroaluminate (NaAlCl4) was formed during CMP. However, during the experiment, it was found there was a very small amount of silica sol crystalline particles after NaCl was added to the slurry. After analyzing the formation mechanism of crystalline particles, KCl was selected to replace NaCl. The same polishing effect was obtained and there were no crystalline particles found in the slurry tank. From the results it is found chloride ions played an important role in improving the removal rate and surface roughness of sapphire substrate.

mentioning

confidence: 99%

Effect of Chloride Ions on the Chemical Mechanical Planarization Efficiency of Sapphire Substrate

Cui

Niu

Zhou

et al. 2019

“…Firstly the large specific surface area of small particles relative to larger particle sizes leads to a reaction between the particles and the SiO 2 film at a very low activation energy. 18 During the polishing process, the colloidal silica acts not only as a mechanical grinder but also as a catalyst for activating the SiO 2 surface, thus accelerating the kinetics of the chemical reaction and increasing the RRs. Under these conditions, chemical catalysis predominates, which leads to higher RRs.…”

Section: Resultsmentioning

confidence: 99%

Effect of Particle Size and pH Value of Slurry on Chemical Mechanical Polishing of SiO₂ Film

Xu¹,

Wang²,

Xu³

et al. 2022

This study investigated the effects of particle size and pH of SiO2-based slurry on chemical mechanical polishing for SiO2 film. It was found that the removal rates and surface roughness of the material was highly dependent on the particle size and pH. As the particle size varied, the main polishing mechanism provided the activation energy to mechanical erasure. In addition, pH affected the particle size and Zeta potential, which had an important effect on the strength of the mechanical and chemical action of the chemical mechanical polishing. The change in mechanical action greatly influenced the removal rate. According to the experimental results, the best polishing of SiO2 film was achieved with 40 nm particle size SiO2 abrasives when the pH was 4.

“…When the abrasive particle size was 10 nm, the removal rate of silicon wafers was higher, which may be due to the large specific surface area of small particles that enabled the reaction between the particles and the silicon wafer at very low activation energy. 12 In the polishing process, SiO 2 abrasive did not just play the role of mechanical grinder, but it also acted as a catalyst to activate the surface of Si(as shown in Eqs. 2-4), and thus accelerated the kinetics of the chemical reaction, which resulted in an improvement in the removal rate.…”

Section: Methodsmentioning

confidence: 99%

Effect of Abrasive Particle Size Distribution on Removal Rate of Silicon Wafers

Wang

Zhao

Xie

et al. 2020

The effects of silica abrasives of five different particle sizes (10 nm, 40 nm, 60 nm, 80 nm and 100 nm) on the removal rate of silicon wafers were studied. The experiments were performed under two conditions, by taking the abrasive particles of uniform size and of two different sizes. The mixture of abrasive particles of two sizes increased the removal rate of the silicon wafer, and this improvement was more apparent when 10 nm particles were mixed with any other particle size. According to the stability of the slurry, the size pair of 10 nm and 60 nm presented the optimal result for the particle size mixing of abrasives. The physical model of the abrasive distribution between the silicon wafer and the polishing pad was established. The mechanism of the effect of mixed abrasive on the increase of silicon wafer removal rate was presented. Further, the contact area between the abrasive and silicon wafer was calculated by MATLAB. Based on this, the removal rate of the silicon wafer by the abrasive with mixed-sized particles was predicted with an error value of less than 10%.