Airborne molecular contamination poses a serious problem for advanced wafer fabrication as the devices are continually scaled down. The amount of this contamination may be only a few monolayers, which are extremely difficult to detect by the commonly used analytical techniques, such as FTIR. ToF-SIMS has extremely high surface sensitivity for the analysis of trace contaminants on wafer surfaces. The high mass resolution of ToF-SIMS is also a powerful tool for the identification of the contaminants. In the current study, ToF-SIMS is used to monitor the build-up of airborne amine contamination on Black Diamond1 surfaces. It has been found that cleaning of the Black Diamond surfaces using wet chemicals can lead to photoresist poisoning. Thermal desorption-GC-MS analysis revealed that wet cleaning would result in the accumulation of hydrocarbons on the Black Diamond surfaces. ToF-SIMS shows that amines can build up gradually on the Black Diamond surfaces after wet cleaning, probably via airborne molecular contamination. For the Black Diamond wafers which did not go through the wet cleaning process, there was no significant increase of amines on the wafer surfaces. The amount of amines on the Black Diamond surfaces depends on the chemicals used in the cleaning processes and the wafer storage conditions. The level of amine contamination can be significantly reduced after the samples are heated up to 300°C for a few minutes in inert atmosphere.

For conventional photoemission microscopy the silicon is thinned to a few tens of micrometres for backside imaging since silicon is opaque in the visble part of the spectrum. However, at wavelengths greater than approximately 1050 nm, most silicon is effectively transparent. Hence, the use of an infrared photoemission microscope (IRPEM) operating at wavelengths of 1100 to 2500 nm, usually eliminates the need for thinning, except where the silicon is heavily doped. However, the plastic encapsulation of packaged devices must be removed and the die surface polished. A polishing system has been evaluated and optimised for this purpose. Surface roughness (Ra) of 1 nm or better was obtained. Representative applications are shown and discussed.