Particle Issue

As the semiconductor industry move towards ever shrinking it gate size to smaller spacing, the technology hence becomes more sensitive towards defect contaminating the wafer surface. In the dielectric deposition area, any location that is been affected with particulate will eventually lead to yield losses which eventually translates to the loss in the company revenue due to the customer return or wafer compensation.

Particle contamination has been one of the biggest challenge that any CVD engineer will ever face. To make matters worst the problem of particle contamination is normally a random event. Many factors can actually lead to the generation of this particulate contamination. From the equipment perspective, any degraded oring or parts lifetime normally are the two most common factors contributing to the particle generation inside the chambers. Although a certain lifetime has been set, there is more often that not that there will be some erratic behavior on one of the parts that is not able to reach its lifetime cycle. Other common factors might be due to the misalignment of parts causing two separate bodies that is been separated by a small distance scratches each others and hence generating those particles.

In the aspect of a process induced defects certain studies has shown that some of the factors that is likely to induce unwanted particulates are the regions of the gas flow. This studies indicates that if there is only a small gas been flowed then its likely to generate a localized entrapment area where the particulate will eventually agglomerate. Therefore a certain threshold of minimum flow is required in order for the process to be able to stay away from this process regions. Another factors that can contribute to particles generation are the temperature itself, certain study conducted reveals that the lower temperature of the wafers the more likely that the particulate will be attracted towards the wafer itself, hence running a process with lower temperature will create a process that is vulnerable towards particulate generation.

Moving forwards, there are a substantial amount of research been conducted to study the behavior of the particles in CVD chambers. Nonetheless it remains a very hotly debated subject since process to its equipment pose a different condition and region which guarantees a good and stable particle performance. As for myself, learning to develop a new particle-free process has always been a dream that I have, but so far the only way I can see through this development is by running many wafers to determine its failure rate since defectivity is something more of the probability problem rather than an empirical problem. Its rather a tossing of a coin problem rather than digital problem with a determined on and off switch.