To eliminate the deep scratches on the 4H-SiC wafer surface in the grinding process, a PVA/PF composite sol-gel diamond wheel was proposed. Diamond and fillers are sheared and dispersed in the polyvinyl alcohol-phenolic resin composite sol glue, repeatedly frozen at a low temperature of −20°C to gel, then 180°C sintering to obtain the diamond wheel. Study shows that the molecular chain of polyvinyl alcohol-phenolic resin is physically cross-linked to form gel under low-temperature conditions. Tested by mechanical property testing machines, microhardness tester, and SEM. The results show that micromorphology is more uniform, the strength of the sol-gel diamond wheel is higher, the hardness uniformity is better than that of the hot pressing diamond wheel. Grinding experiments of 4H-SiC wafer were carried out with the prepared sol-gel diamond wheel. The influence of grinding speed, feed rate, and grinding depth on the surface roughness was investigated. The results showed that by using the sol-gel diamond wheel, the surface quality of 4H-SiC wafer with an average surface roughness Ra 6.42 nm was obtained under grinding wheel speed 7000 r/min, grinding feed rate 6 µm/min, and grinding depth 15 µm, the surface quality was better than that of using hot pressing diamond wheel.

As a critical link of efficient and high-quality semiconductor substrate chemical mechanical polishing process, this paper focuses on the effects of the changes of the atmosphere to be processed on the CMP property of Si substrate. The experiment results showed that O2 existing in the processing atmosphere played an active role in facilitating material removal, and when the partial pressure of O2 in the processing atmosphere increased to 500kPa, the Si MRR of CMP reached 905nm/min. The Si material surface dissolutions in different atmospheres were analyzed respectively using SEM, EDS and light interference microscope. It was found that when O2 was sufficient, an extremely thin and tight oxide film was formed on the Si substrate surface, which prevented the furtherance of oxidation reaction, and compared with the Si-Si bonds, the Si-O bonds generated during this process were more inclined to undergo hydrolysis reaction; on the other hand, the O2 atmosphere caused the polishing pad, polishing particles and Si substrate to contact closely, increasing the mechanical friction and thus significantly improving the MRR. Based on the results of experiment and analysis, the Mechanisms of Si substrate polishing in high-pressure O2 atmosphere were summarized and a material removal model was built.

The broad applications of sapphire substrates in many fields warrants an urgent demand for a highly efficient and high precision polishing method for the sapphire substrates. The authors proposed a novel sapphire substrate polishing method that is based on the dielectrophoresis (DEP) effect. The principle of dielectrophoresis polishing (DEPP) is described. A non-uniform electric field was added in the polishing area to drive abrasives moving in the direction towards the plate by the DEP force. The amount of abrasives that participates in the polishing action increases as the distribution of polishing slurry on sapphire surface changes, leading towards the improvement of sapphire polishing both in quality and efficiency. Comparative experiments between DEPP and traditional chemical mechanical polishing (CMP) were carried out. It was found that the maximum increase of sapphire MRR for DEPP is 71%, reaching 13 mg/h, and the minimum increase was 9.5%, reaching 4.6 mg/h. The surface roughness of the sapphire substrate decreases faster and more uniform with DEPP. The final surface roughness of the sapphire substrate after DEPP was Ra 0.87 nm and the flatness was 0.3078 waves (RMS value), which is better than 0.6863 waves (RMS value) of sapphire substrate with traditional CMP polishing.

To solve the problem of phase agglomeration and microstructure inconsistency in the conventional powder pressing method of ultrafine diamond abrasive tool, a fabrication method of ultrafine diamond abrasive tool based on gel forming was proposed. The gel experiments of polyvinyl alcohol (PVA) and phenolic resin (PF) were carried out, and the basic physicochemical properties of the gel were tested by SEM, IR and TGA. The mechanical properties of gel forming and hot pressing forming abrasive tools were Compared. The polishing experiments of the gel abrasive tool and the hot-pressing abrasive tool were carried out. The results showed that when the PF/PVA ratio was between 5:1 and 10:1, the porous network gel structure was formed. The IR and TGA analysis indicated that the molecular crosslinking of PF and PVA occurred after gel. Compared with hot pressing abrasive samples, the abrasive distributions of gel abrasive samples were more uniform. The supersmooth surface of the SiC flat mirror with surface roughness Ra below 3 nm was obtained by the gel abrasive tool, which was better than by hot pressing abrasive tool. The surface flatness value PV 0.213 μm could be obtained by using the gel abrasive tool with low PVA content.

Silicon wafer with high surface quality is widely used as substrate materials in the fields of micromachines and microelectronics, so a high-efficiency and high-quality polishing method is urgently needed to meet its large demand. In this paper, a dielectrophoresis polishing (DEPP) method was proposed, which applied a non-uniform electric field to the polishing area to slow down the throw-out effect of centrifugal force, thereby achieving high-efficiency and high-quality polishing of silicon wafers. The principle of DEPP was described. Orthogonal experiments on important polishing process parameters were carried out. Contrast polishing experiments of silicon wafer were conducted. The orthogonal experimental results showed that the influence ratio of electric field intensity and rotation speed on material removal rate (MRR) and surface roughness was more than 80%. The optimal combination of process parameters was electric field intensity 450 V/mm, rotation speed 90 rpm, abrasive concentration 30 wt%, size of abrasive particle 80 nm. Contrast polishing experiments indicated that the MRR and material removal uniformity of DEPP were significantly better than traditional chemical mechanical polishing (CMP). Compared with the traditional CMP, the MRR of DEPP was increased by 17.6%, and the final surface roughness of silicon wafer reached Ra 0.31 nm. DEPP can achieve high-efficiency and high-quality processing of silicon wafer.