Precision Grinding Slurry "Nanopure(TM)"

CMP slurry may be used after dilution according to the manufacturer's recommendations. Since the recommended conditions and expressions vary depending on the manufacturer and product specifications, it is necessary to start using it only after fully understanding these aspects. ■ Is the dilution by weight ratio or volume ratio? The manufacturer provides recommendations for dilution ratios, but the ratio may change depending on whether it is by weight or by volume, so caution is required. Example) When diluting Slurry A (specific gravity 1.38) with pure water: 1) Weight 3 times dilution: Adjust 10 kg of slurry with 20 kg of pure water. 2) Volume 3 times dilution: Adjust 10 L (=13.8 kg) of slurry with 20 L of pure water. ■ Dilution procedure CMP slurries are designed to maximize their characteristics, and there are products available in packaging forms such as two-component or three-component systems. The manufacturer may recommend dilution procedures for reasons such as ensuring the stability of the slurry. Example) When diluting a two-component slurry (Component A and Component B) with pure water: 1) Dilute Component A with pure water. 2) Add Component B to the mixture from step 1. Since various cases can be considered depending on the manufacturer and product specifications, it is recommended to contact the manufacturer for more details.

This time, I will explain about abrasives, one of the materials used in CMP slurries. ■ Types of Slurry Abrasives Currently, the materials used as abrasives for slurries include the following: 1) Silica (SiO2) 2) Ceria (CeO2) 3) Alumina (Al2O3) Most of the abrasives mentioned above are inorganic, but at the research level, composite abrasives of inorganic and organic materials are also being developed. ■ Overview and Characteristics of Abrasives 1) Silica Abrasives - Colloidal Silica: Synthesized by precipitation methods or sol-gel methods. The shapes can be spherical or irregular. - Fumed Silica: Synthesized through gas-phase reactions in flames. The processing efficiency is often higher than that of colloidal silica. 2) Ceria Abrasives - The abrasives themselves have chemical activity, which generally results in higher processing efficiency for SiO2. - They have high sedimentation properties and low washability. 3) Alumina Abrasives - They have a strong mechanical polishing effect. Due to their larger particle size and Mohs hardness, they exhibit high processing efficiency. - They have even higher sedimentation properties but are inferior in defect performance, such as scratching. The selection of abrasives is a very key factor in slurry design. We select abrasives based on the intended applications and targets of our customers.

I will explain the components of CMP slurry. Currently, many slurries used in the CMP process have the following composition: 1) Abrasives: They enhance processing efficiency through mechanical action. Some also exhibit chemical action. 2) Chemicals and additives: They enhance processing efficiency through chemical action and provide special functions or performance. They have various functions such as surface modification of the workpiece, prevention of re-adhesion of impurities, and improvement of cleaning properties. 3) Dispersion medium: It evenly disperses the abrasive components and mediates mechanical and chemical actions. Currently, almost pure water is used. It serves roles such as cooling, transporting abrasives, discharging residues, and lubrication. We optimally select abrasives and additives according to each application, ensuring the stability of the slurry itself and maximizing performance up to the customer. Next time, I will explain "abrasives," one of the components.

Silicon wafers are an important material that serves as the supporting substrate for semiconductor integrated circuits such as ICs and LSIs. There is a polishing process in the manufacturing process. In this process, scratches and impurities formed on the wafer surface up to the previous step are removed, and the wafer is processed into a high-flatness wafer without distortion. Once finished in this process, the wafer achieves a completely distortion-free mirror-like surface. For more details, please refer to our corporate website via the URL link below. ■ Silicon Wafer Polishing Case Study Before CMP, the wafer is in the state where the rough polishing as "As Lapped" has been completed, with a surface roughness of Ra=1.57nm. Through multi-step CMP processing, the surface roughness is reduced to Ra=0.22nm. - Achieving nano-level surface roughness and mirror finish - Reduction of surface defects such as scratches and particles - Improved yield