Sol-gel Polishing Research Articles

Preparation and application of sol-gel polishing tool with carbon fibers as skeleton

Preparation and application of sol-gel polishing tool with carbon fibers as skeleton

Preparation and application of sol-gel polishing tool with carbon fibres as skeleton

Preparation and application of sol-gel polishing tool with carbon fibres as skeleton

Study on Polishing of Polycrystalline AlN Using Sol–Gel Polishing Tool

Polycrystalline aluminum nitride has extensive application prospects in substrate materials, insulating layer materials, and packaging materials. Polycrystalline aluminum nitride is sintered from powder. The traditional mechanical polishing method is easy to cause aluminum nitride grains to fall off to form pits. In this paper, to improve the polishing effect, based on the hydration of polycrystalline aluminum nitride, a sol-gel (SG) polishing tool was proposed to polish polycrystalline aluminum nitride. The polishing process was divided into rough polishing and fine polishing. The diamond particle size of the SG tool used for rough polishing was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40\mathbf {\mathrm {\mu }}\text{m}$ </tex-math></inline-formula> . The diamond particle size of the SG tool used for fine polishing was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\mathbf {\mathrm {\mu }}\text{m}$ </tex-math></inline-formula> . Moreover, the polycrystalline AlN was processed with or without deionized water. The results showed that in the rough polishing stage, the material removal rate (MRR) of the polishing method without deionized water was four times higher than that of the polishing method with deionized water. However, in the fine polishing stage, the MRR of the polishing method with deionized water was slightly higher than that of the polishing method without deionized water. The results showed that mechanical removal is the primary material removal method in the rough polishing stage. In the fine polishing stage, hydration can improve the polishing effect of polycrystalline aluminum nitride.

Mechanical chemical polishing of large-size single-crystal diamond substrates with a sol-gel polishing tool

To process large-size single-crystal diamond (SCD) substrates efficiently, we proposed a method that utilises mechanical action to induce a chemical reaction for SCD polishing. In this study, a novel semi-fixed abrasive polishing tool suitable for high-speed polishing was fabricated using the sol-gel technique. A single-diamond abrasive and a mixed abrasive of diamond and CuO were selected for the SCD (100) plane polishing. After polishing for 2.5 h, the surface roughness of the SCD was reduced from approximately Ra 80 nm to approximately Ra 9 nm. The material removal rate (MRR) was measured quantitatively, and it was found that the mixed abrasive polishing performance was superior. In addition, the amorphous carbon content on SCD surface/subsurface after mixed abrasive polishing was significantly lower than single-diamond abrasive diamond abrasive. These results indicate that the scratching of the SCD surface by diamond abrasives induced the transformation of the carbon into amorphous carbon, which could then react with CuO powder. The wear debris morphology indicates that the surface material of the SCD was peeled off with a slice shape during single-diamond abrasive polishing, while it was removed with a slag-shape by the chemical reaction and slightly crushed during the mixed abrasive polishing. The material removal process for the mixed abrasive polishing was CDia→MechanicalCAmo→CuOCu+CO, which is a mechanical chemical polishing process. Experiments confirmed that the synergistic effects of the mechanical action and chemical reaction could increase the MRR and produce a smoother surface and less damage to the subsurface of the SCD, which provides inspiration for the processing of large-size SCD substrates.

Preparation and Application of Sol-Gel Polishing Pad for Polishing CVD Single Crystal Diamond at High Speed

A new polishing pad based on the sol-gel (SG) technique is fabricated and can polish the single crystal diamond (SCD) substrate at high speed. In this work, the base material, fillers, and coating height of the polishing pad are selected. Pressed polymer fiber is used as the base material, talcum powder is chosen as filler, and the coating height of the gel formulation system on the surface of the base material is between 20 and 40 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>. The surface morphology of SCD substrate was observed with a 3D optical surface profiler. The surface roughness decreased from 78.024 nm to 6.126 nm in 2 h and the material removal rate of the SCD (100) was about 135 nm/h. The Raman spectroscopy result shows that there was phase transformation on the surface of the SCD substrate after polishing. The material removal mechanism was proposed based on the result. During the scratch of the diamond abrasive, the diamond on the surface of the SCD substrate was transformed into amorphous carbon. Then the amorphous carbon was removed mechanically. The new gel polishing pad can polish the SCD substrate with high efficiency.

Sol–gel polishing technology for extremely hard semiconductor substrates

Sol–gel polishing technology for extremely hard semiconductor substrates

Low-Destructive Processing of Single Crystal Aluminum Nitride Based on Sol-Gel Polishing Tool

Aluminum nitride (AlN) is a semiconductor material with the wide band gap. The requirement of the substrate for the semiconductor device is no surface damage. In this paper, based on the principle of the hydration reaction of aluminum nitride, the single crystal aluminum nitride was polished under dry conditions and wet conditions using a sol-gel (SG) tool. The abrasive used in the SG polishing tool was diamond with a particle size of $5~{\mu }\text{m}$ . Surface morphology of single crystal aluminum nitride was observed by scanning electron microscopy (SEM). Surface damage to the polished single crystal aluminum nitride was detected by 3D optical surface profiler, and the wear debris were analyzed by high resolution transmission electron microscopy (TEM). The product of the hydration reaction remaining on the aluminum nitride surface after polishing was studied by X-ray photoelectron spectroscopy. The results demonstrate that the removal rate of single crystal aluminum nitride by wet polishing is higher than that of dry polishing. The final roughness Sa of workpiece by dry polishing is 1.8–2.2 nm, and the final roughness Sa of workpiece by wet polishing is 1.1–1.2 nm. In addition, wear debris of workpiece by two polishing methods are amorphous.

Fabrication of a sol–gel polishing tool for green manufacturing of the seal stone

A newly developed sol–gel polishing tool consisted of gel balls is fabricated for green manufacturing of the seal stone, the processing performance and degradability of the sol–gel polishing tool are evaluated in this paper. Different forming and drying ways have been conducted to achieve small size gel balls. The processing performance of the sol–gel polishing tool is investigated by the surface roughness Ra and surface morphology of seal stone. The degradability of the sol–gel polishing tool is analyzed through the surface morphology and Fourier transform infrared spectra of gel balls in different environments. Results show that a sol–gel polishing tool consisted of gel balls with a sphere size of 3 mm2 or less is successfully mass prepared using the chosen method. A glossy and smooth seal stone surface can be obtained after processing by the sol–gel polishing tools. And the gel balls can be disposed in the recovery tank with water and bacteria for degradation to avoid environmental pollution and recover abrasive particles. Therefore, the application of sol–gel polishing tools in the field of seal stone precision machining would advance further development of seal stone craft and bring great economic and social benefits.

Study on the enhancement of sol–gel properties by binary compounding technology for dry polishing hard and brittle materials

The newly developed sol–gel (SG) polishing pad based on the sodium alginate (AGS) binary compound system can be used for dry polishing hard and brittle materials to obtain high-quality surfaces. Based on the flexible SG polishing technology, a suitable biopolymer material is selected, and a binary compounding technology is used to prepare an AGS binary compound gel system, thereby optimizing the water-holding and mechanical properties of the gel. Through dry polishing experiments of a hard and brittle SiC material, the advantages of the SG polishing pad based on the sodium alginate-xanthan gum (AX) binary compound system under dry polishing conditions are obvious. The durability of the SG polishing pad is significantly improved compared with that of the AGS single system, which effectively solves the problem of pollution caused by the polishing waste liquid produced during the wet polishing process. At the same time, a high material removal rate will effectively shorten the processing time of hard and brittle materials, improve production efficiency. These results will lay the foundation for the industrialization of dry polishing with SG polishing pads.

Precision Polishing of Single Crystal Diamond (111) Substrates Using a Sol-Gel (SG) Polishing Pad

In recent years, the application prospect of single crystal diamond (SCD) in the field of electronics is remarkable, and material processing technologies are the basis for the application of semiconductor materials. In this paper, a novel polishing method for SCD substrates was developed utilizing a sol-gel (SG) polishing pad, which is a semi-fixed abrasive polishing tool fabricated by SG technique. The surface morphology of SCD substrates was observed with a 3-D optical profiler and scanning electron microscopy (SEM). The results showed that the surface roughness was 1.32 nm Ra and the material removal rate of SCD (111) was about 120 nm/h. The polished diamond surfaces and wear debris were investigated using Raman spectroscopy and transmission electron microscopy (TEM), respectively. The results showed the removal mechanism of SCD using an SG polishing pad was mainly dominated by the mechanical removal and phase transformation, including the mechanical cleavage, amorphization, and graphitization.

Study on the surface quality of marble tiles polished with Sol-Gel derived pads

Sol–gel (SG) pads are used to polish different types of marble tiles and obtain high-gloss, low roughness, and scratch-free surfaces. The main features of such tools are semiconsolidated abrasives and flexible substrates. Through experiments with three types of polishing methods and two different types of tools used to polish marble tiles, the polishing mechanism of SG pads was confirmed. An abrasive yield phenomenon was observed for the semiconsolidated abrasive polishing tool with a flexible matrix, which resulted in a mirrored marble surface with high gloss, and the polishing steps were simplified. For SG polishing pads, a larger abrasive can be used to obtain high-gloss marble surfaces compared to the fine abrasives used in traditional resin polishing tools. Therefore, the agglomeration problem associated with fine particle size abrasives is avoided. In addition, after SG pad polishing, the surface of the marble tiles exhibited hydrophobic properties, and the oleophobic properties were simultaneously improved.

Study on high efficient sapphire wafer processing by coupling SG-mechanical polishing and GLA-CMP

Abstract A novel surface finish process sequence has been developed with a sequential process employing sol-gel (SG) semi-fixed abrasive polishing tool and gas-liquid assisted chemical mechanical polishing (GLA-CMP) instead of general copper-resin lap or plate (CP) and chemical mechanical polishing (CMP) to enhance the surface finishing efficiency for sapphire wafer. The surface and subsurface quality of sapphire wafer after the SG and GLA-CMP process have been compared with those by CP and CMP, respectively. Results show that the SG polishing can offer a better surface quality in terms of both surface roughness and sub-surface damage for the next fine polishing step. Based on the contact mechanics models, yielding effects of the SG polishing pad are found to be effective to scratch mitigation. This trend is consistent with experimental results. Furthermore, oxygen is applied as catalyst to improve the removal material rate (MRR) of sapphire by GLA-CMP. It is found that oxygen concentration can improve MRR of sapphire polishing. Among four combinations of CP, SG, CMP, and GLA-CMP, the machining by coupling SG and GLA-CMP shows the maximum MRR approximately as high as 77.6 nm/min, more than 10.23% larger than that of CP-machined wafer and traditional CMP. Ultra-smooth wafer surface with damage-free can be achieved by this new process sequence and the sapphire wafer with qualified surface can be obtained within 50 min by GLA-CMP, which is 90 min shorter than the original 140 min polished by the conventional CMP method. Compared to the conventional surface finish process sequence, the proposed sequence shows superior processing efficiency and quality for sapphire wafers.

Surface damage of single-crystal diamond (100) processed based on a sol-gel polishing tool

A semi-fixed abrasive polishing tool fabricated by sol-gel (SG) technique used diamond abrasives for mechanical polishing (MP), diamond and SiC abrasives for mechanical chemical polishing (MCP), and diamond abrasives and chemical reagent of KNO3 for chemical mechanical polishing (CMP). Then, the surface damage of 100-oriented single-crystal diamond (SCD) was investigated by comparing three different polishing methods. The surface quality of SCD specimen was observed with an optical profiler and scanning electron microscopy, and subsurface damage was detected by transmission electron microscopy (TEM) after processing. Moreover, products and wear debris of diamond after MCP were investigated using Raman spectroscopy and high-resolution TEM. The results show that surface damage is reduced in SCD polished by the SG polishing pad. Subsurface damage with the nanoscale ranges from 2.0 nm to 3.3 nm. No significant difference in subsurface damage was observed between the hard and soft directions when the SG polishing pad was used. In addition, the polishing rate of MCP was 25.5 nm/min, which was higher than that of other approaches owing to the combination of mechanical force and chemical reaction. Subsurface damage in the soft direction induced by MCP includes amorphization, dislocation, and lattice distortion, which is 3.3 nm deeper than that in the hard direction with thickness of 2.3 nm.

Removal mechanism of 4H- and 6H-SiC substrates (0001 and 0001¯) in mechanical planarization machining

This article describes the mechanical planarization machining of SiC substrates involving the Si face (0001) and C face ([Formula: see text]) of N-type (doping nitrogen) 4H-SiC, N-type 6H-SiC, and V-type (doping vanadium) 6H-SiC with a sol–gel polishing pad. The polishing results indicate that the C face, which has a surface roughness of less than 2 nm, is smoother than the Si face (&gt;10 nm), and the material removal rate of the C face is higher than that of the Si face. The removal mechanism of SiC substrates was investigated with regard to the wear debris and subsurface structure through transmission electron microscopy, and instrumented nanomechanical tests were performed to further reveal the removal mechanism by nanoindentation and nanoscratching. The analysis results demonstrate that the difference in the material removal rates of the Si face and C face depends on the material removal scale together with the mechanical properties of SiC substrates. The processing of SiC substrates is dominated by the mechanical removal of SiC material during mechanical planarization machining.

Phase Transformation of Monocrystalline Silicon Induced by Polishing With Diamond Abrasives

A newly developed semi-fixed flexible polishing tool called sol-gel (SG) polishing pads can satisfy the polishing demand of silicon wafers with scratch-free and nano-roughness surface. However, an obvious damage layer emerges on the surface of monocrystalline silicon wafer after polished by SG polishing pads with diamond abrasives. In this paper, combined characterizations consist of grazing incidence X-ray diffraction, Raman spectroscopy (RS), focused ion beam-scanning electron microscopy (FIB-SEM), transmission electron microscopy (TEM), and SEM were used to observe the damage layer together with the polishing residue. The results indicated that the surface monocrystalline silicon transformed to α-Si and nano-Si. Analysis on the polishing processes under the same experimental parameters with different tools and abrasives revealed that the material removing scale about 100-300 nm may account for the generation of damage layer.

The effects of abrasive yielding on the polishing of SiC wafers using a semi-fixed flexible pad

A newly developed sol-gel (SG) polishing pad can satisfy the processing demands of SiC wafers by providing scratch-free polished surfaces with nano-roughness. The main characteristic of this polishing tool is the semi-fixed abrasive together with the flexible matrix. In this article, contrastive experiments involving polishing of SiC wafers with three different types of tools were conducted to confirm the machining mechanism of the SG polishing pad. The results indicate that the abrasives in the pad exhibit yielding effects during the polishing process, contributing to the achievement of a mirror-like wafer surface. In addition, larger abrasives can be chosen for the SG polishing pad to obtain relatively high wafer surface quality instead of smaller ones, thereby avoiding the agglomeration problem of ultrafine abrasives.

The Research of Reactivity between Nano-abrasives and Sapphire during Polishing Process

Reactivity between nano-sized abrasives and sapphire wafer has been studied by interfacial solid state reaction during polishing process, and the abrasive with the highest reactivity has been selected from magnesium oxide, silicon dioxide and ferric oxide. Using the Sol-Gel polishing films, sapphire wafers were polished in the form of wet and dry mechanical chemical polishing respectively. The Raman spectra and Grazing incidence X-ray diffraction records show that aluminum silicate with the composition mullite was formed on the polished wafer surface, and silicon dioxide has the highest reactivity than other oxide abrasives under the same conditions during polishing the sapphire substrates.

Research on Performance of Fixed Abrasive Tools of Polishing 6H-SiC Wafers

6H-SiC single crystal substrates are considered to be suitable for thin film growth of semi-conductive GaN with wide energy bandgaps, because the lattice mismatch between 6H-SiC and GaN is quite small compared with sapphire substrates. However, the process of SiC wafer prior to epitaxial growth is quite difficult due to its high hardness and chemical stability. The chemical mechanical polishing (CMP) is typically performed in semiconductor device planarization, but the polishing slurry is not environmental friendly and the polishing efficiency is very low. In this paper, polishing experiments were conducted on 6H-SiC wafers using a flexible fixed abrasive film fabricated by sol-gel technique. Other three fixed abrasive tools bought from the different companies were also chosen in these experiments. Abrasive wear resistance on the different tools was observed with the increase of polishing time. Studies were also made on the surface micrographs and roughness of the 6H-SiC wafers polished by the four different tools in order to evaluate the tool performance. The results indicated that poor wear resistance of abrasive were showed in tool C and D, less abrasive worn out in the sol-gel polishing film and tool B. The surface quality of 6H-SiC wafer polished by the sol-gel polishing film was much better than the other three tools, and it attained the lowest surface roughness Ra=0.003 μm. Keywords: Sol-Gel polishing film; Fixed abrasive tools; 6H-SiC wafers

Surface Characterization of Silicon Wafers Polished by Three Different Methods

The surface roughness and surface morphology of silicon wafers polished by three different polishing methods were analyzed in this paper. A polishing pad was prepared by means of sol-gel technology as semi-fixed abrasive tool. An electroplated polishing pad was chosen as fixed abrasive tool. And a polishing cloth was chosen as free abrasive tool. The results showed that the surface of silicon wafer polished by the sol-gel polishing pad was superior to the other two. It was easy to get mirror effect with few scratches while the free abrasive and fixed abrasive got lots of scratches on 23silicon wafers. The surface roughness of silicon wafer polished by the sol-gel polishing pad reached 1.41nm measured by atomic force microscope (AFM).