An Image Analysis Technique for Assessing Particle Size and Agglomeration Tendency of Slurries
- PDF / 322,018 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 82 Downloads / 144 Views
An Image Analysis Technique For Assessing Particle Size And Agglomeration Tendency Of Slurries Susan R. Machinski1,2, Kathleen A. Richardson1,2, and Aristide Dogariu2 Department of Chemistry School of Optics, CREOL University of Central Florida, 4000 Central Florida Boulevard Orlando, FL 32816 1 2
ABSTRACT Understanding the time-dependent behavior and size of particulate systems, specifically, particles in abrasive slurries, is a key part of chemical mechanical polishing (CMP). Microscopy and image analysis enables both qualitative and quantitative analysis of particle interaction behavior in diluted samples of such particulate suspensions. A technique using microscopy and image analysis has been developed specific to the analysis of suspensions of, micron size or larger, abrasive particle slurry systems. This technique has been applied to aluminum oxide (Al2O3) slurries and measurements of particle size and stability have been obtained with good accuracy and precision. INTRODUCTION A wide variety of particulate materials have been used as the mechanical abrasive chosen to grind (coarse removal) or polish (fine) solid surfaces. These include Al2O3, SiO2, SiC, and Si3N4. An important issue in understanding the chemical and mechanical processes in optical glass polishing systems is the nature of the abrasive slurries. The nature of the crystalline particle (single versus polycrystalline), particle size, and concentration of the abrasive in the slurry, as well as the stability of the system, all have a direct impact on the polishing mechanism and eventually on the resulting quality of the finished workpiece [1]. Currently, the abrasive slurries used in semiconductor wafer processing are used once, and not recycled in the process. By understanding the particle sizing and the stability of the dispersed solid-liquid system, such as those used in the CMP industry, optimal end use shelf-life for the abrasive slurries may be determined. Thus, the analysis of particle sizes in the slurries over a period of time can provide a relationship between the abrasive slurry particle and the point of its resultant degradation in the polishing process. Abrasive slurry particles tend to form aggregates which then may agglomerate into large clusters. Base-stabilized (BS) and acid-stabilized (AS) Al2O3 slurry systems remain dispersed over short working times but, have been reported to agglomerate over time [1]. Large abrasive clusters can lead to scratching, surface defects, and if not completely removed following polishing, surface contamination. It is this agglomeration behavior that must be controlled. Understanding the agglomeration process is further complicated by the interaction of particles with the aqueous slurry solution. There is believed to be a direct correlation between micro scratching and the presence of larger particles [2]. Most particle sizing algorithms are calculated by the spherical equivalence principle [3]. However, if the shape of the particle is non-spherical, different sizes will be measured by different methods
Data Loading...