Effect of Particle Size Distribution, pH, and Na⁺ Concentration on the Chemical Mechanical Polishing of Sapphire and 4H-SiC (0001)

Abstract

As two typical representatives of super-hard materials, the processing of sapphire and silicon carbide has always been a hot spot. Chemical mechanical polishing technology is the only way to achieve global planarization, and it has also become one of the most important processes for precision machining of these materials. We have studied the relationship between the removal rate and surface roughness of sapphire and 4H-SiC (0001) and the size distribution and pH of the alumina slurry. More importantly, we explored the negative effect of Na+ on the removal rate of an alumina-based sapphire polishing slurry, and the more negative effect of Na+ on the removal rate of an alumina-based silicon carbide polishing slurry and the surface state of SiC(0001). Finally, the polishing mechanism of sapphire with alumina used as a brasive is given.

Nanomaterials and Equipment for Chemical–Mechanical Polishing of Single-Crystal Sapphire Wafers

“…The formation trend of the hydration reaction layer also changes with pH value. It is well known that nitric acid (HNO 3 ), potassium hydroxide (KOH), sodium hydroxide (NaOH), and strontium hydroxide (Sr(OH) 2 ) are often used as inorganic alkaline pH regulators [77,[110][111][112][113]. The FA/O chelating agent, aminopropanol (AMP) and sodium metasilicate (SMSN) are organic base pH regulators [114,115].…”

“…Table 5 summarizes the effect of a pH regulator on the polishing efficiency of sapphire [110][111][112][113][114]. For instance, Yin et al used Sr(OH) 2 to adjust the pH value of the polishing solution [113].…”

Recent Advances in Chemical Mechanical Polishing Technologies of Silicon Carbide

“…In practice, the abrasive particle size also has a considerable effect on MRR and surface roughness. In 2022, Wang et al 19 studied the impact of different alumina abrasive particle size distribution D50 on 4H-SiC (0001) MRR and surface roughness. The pH adjustment that was applied to regulate the pH value to 9.20 in the test is KOH, and the oxidant was 3 wt% KMnO 4 .…”

“…From Figure 2, it can be seen that the surface roughness increased as the particle size D50 increased from 0.1 μm to 2 μm can be obtained. 19 Similarly, in 2022, Zhao et al 20 studied the MRR variation in Mn-based polishing slurry abrasive size with three different abrasive sizes of 0.4 μm, 1 μm and 3 μm. As the polishing abrasive size became larger, the mechanical removal ability was improved.…”

“…At the moment, most of the CMP of SiC is carried out in alkaline environments. 19,25,26 Numerous researchers have explored the impact of different pH values on the effect of SiC in the CMP process.…”