TABLE OF CONTENTS Rajiv Kohli and Kash L. Mittal
Contaminants on surfaces are of fundamental interest in a wide variety of industries due to their proclivity for causing the failure of critical components. These contaminants can be small particles, thin films, molecular species, ionic species, or microbiological species. Particulate contamination most often is present in the form of dust, for example, lint from clothing and lens tissue, or fine airborne particles. Tiny particles of abrasive or other machining debris also can become embedded in a surface during polishing or other processing operations. On the other hand, film contamination can originate from a variety of sources, including airborne pollutants (water vapor, organic materials, and cleanroom construction materials), outgassing of plastic containers holding finished components, residues from protective strip coatings, dried liquid residue following an improper cleaning operation, and fingerprints left during handling.
In the form of contaminants, small particles can have a major impact on the performance of precision and other products. For example, the presence of impurities such as boron and phosphorous in the parts per billion range can result in the irrecoverable loss of an entire production lot of semiconductor wafers. In a hard disk drive, a particle of dimensions similar to the nominal flying height trapped between the head and the disk can lead to catastrophic failure of the drive. Similarly, the presence of low levels of hydrocarbon contaminants in the components for oxygen service can cause catastrophic damage to spacecraft due to autoignition.
Film contaminant...
