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Contamination on devices such as semiconductors and disk drive components poses a serious risk for reduced yield and reliability. In many industries there is a general attitude that some loss is acceptable, resulting in billions of dollars of lost revenue every year. The authors contend that this loss is not inevitable, but rather can be reduced or eliminated through careful but basic contamination and static control policies and procedures.
The physics of electrostatically driven micro-contamination becomes more important as feature size shrinks and "killer" particle size shrinks with it. Proper material selection, airflow control, tool qualification, particle control, and static charge reduction through ionization will reduce and even eliminate defect density and yield loss due to contamination induced defects.
Contamination issues in hi-tech manufacturing
Micro-contamination in high technology manufacturing can be a significant source of yield and reliability loss. For instance, a particle on the surface of a wafer being exposed during a photolithography operation will create a shadow that prints in the subsequent step. If that particle is larger than half of the feature size of the process (Critical Dimension -- CD), the die with the particle on its surface will likely be non-functioning. In photolithography one particle destroys one component, but in other steps perhaps one particle can destroy a component roughly 25 percent of the time. The state-of-the-art for semiconductor manufacturing today is 14 nm CD. That means that a 7.2 nm particle can kill a die. Compare this to the size of a typical germ (several thousands of nm) or compare it to the size of a virus (several tens of nm) and it becomes clear that the consequences of micro-contamination can be devastating to the profitability of a semiconductor fab. Likewise, similar micro-contamination issues in the hard disk drive industry where particles as small as several tenths of a micron can lodge between the head and magnetic disk, or in many other high technology manufacturing operations, can be devastating.
The total number of particles landing on a surface in manufacturing can limit the yield and, hence, the profitability of the process. Virtually every semiconductor fab in the world checks each process step frequently in order to validate that the process is working correctly.
Early in the initial qualification of...