Koichiro Ichikawa

Basic Characteristics of a Simultaneous Double-Side CMP Machine, Housed in a Sealed, Pressure-Resistant Container

We designed and manufactured a prototype of a unique CMP machine, which can perform double-side CMP simultaneously in a sealed and pressure container as regarding effective action of the processing atmosphere around workpieces as important. Polishing experiments with single crystal silicon (Si) wafers (100) are performed by charging the container with various gases. As a result, the removal rates increased by up to 25% under high pressure oxygen gas atmosphere.

Effect of Pad Surface Asperity on Removal Rate in Chemical Mechanical Polishing

In a chemical mechanical polishing (CMP) process, the removal rate is affected by the actual contact conditions between the wafer and the polishing pad. The polishing pad is one of the most important consumable materials: when the wafer is polished, the pad surface asperity changes. Further, the polishing pad surface asperity has a substantial influence on the actual contact conditions. Therefore, measurement and quantitative evaluation methods for the pad surface asperity have been proposed by various research institutes. We have developed a novel measurement and quantitative evaluation method for polishing pad surface asperity based on contact image analysis using an image rotation prism. We have proposed four effective evaluation parameters: the number of contact points, the contact ratio, the maximum value of the minimum spacing of the contact points, and the half-width of the peak of the spatial Fast Fourier transform (FFT) result of a contact image. This paper discusses the change in the polishing pad surface asperity measured by the proposed evaluation parameters in serial batch polishing tests. In particular, this research focused on the relationships between the proposed evaluation parameters and the removal rate, which change with an increase in the number of serial batch polishing tests. As a result, linear correlations were found between the evaluation parameters and the removal rate.