Improving Imaging in the Semiconductor Industry via SEM Cleaning

Nanotechnology is progressing with giant strides and the semiconductor industry is moving towards smaller and smaller components. This has inspired the need for higher resolution and magnification. Scanning electron microscopes or SEMs are extensively used for observing surface features at magnifications of the range of 200,000x. One of the main reasons why resolution and magnification in SEM imaging cannot be considerably increased is due to hydrogen contamination in the SEM vacuum chamber. When contamination gets settled on the analyte surface, polymerization takes place due to interaction with the electron beam and a non-conductive layer is formed that when imaged will look like black rectangle and not allow reliable measurements.

SEM Cleaning Equipment – The GV10x DS AsherTM

The ibss Group introduced the GV10x Downstream (DS) AsherTM 2009, which is employed by the semiconductor industry for removal of hydrocarbon contamination from CD-SEMs and Review SEMs. Since these SEMs are engineered for the study of large semiconductor wafers, their vacuum chamber size is much more than that of standard SEMs. Hence the industry required a more effective technique for hydrocarbon cleaning and this was fulfilled in the GV10x DS Asher.

The equipment has an innovative patented design and is capable of operating at pressures lesser than other commercially available contamination removal systems. Hydrocarbons can thus be removed uniformly and effectively from large chambers. Along with cleaning the large chambers of CD-SEMs and Review SEMs, ibss reports that it is also possible to effectively clean standard SEMs. Since this equipment is highly efficient, the downtime for the system is considerably reduced. The cleaning cycle of the GV10x involves the time taken by the user to prepare the SEM for cleaning, cleaning of the SEM and allowing the SEM to return to its normal operation mode. This cleaning cycle is substantially reduced as the GV10x operates at pressures safe for turbo molecular pump operation.

Case Study

Gerald Neumann at Infineon in Munich, Germany used the GV10x to remove carbon from his SEM, which he uses for studying semiconductor components. In case the GV10x is not used, just 1 minute of scanning at 200,000x magnification will cause hydrocarbon contamination that will completely block the surface being examined.

After cleaning for just 10 minutes it was observed that scans of 1-2 minutes at 200,000x magnification can be done without any contamination effects seen. According to Mr Neumann the GV10x has very quick and effective cleaning. Cleaning can be done with active turbo molecular pumps, and it starts without venting the chamber.

SEM Images taken at 200,000x magnification with scan time = 1 minute. The left image was taken before GV10x cleaning and the right image (different section of sample) was taken after a 5 minute clean.

Figure 1. SEM Images taken at 200,000x magnification with scan time = 1 minute. The left image was taken before GV10x cleaning and the right image (different section of sample) was taken after a 5 minute clean. (Courtesy Infineon Technologies)

Pierre Hovington also used the GV10x in Hydro Québec in Canada where he examines particles using the SEM. He observed that if samples were examined for a longer period the image contrast on his SEM reduced. Also in cases of high magnification examination, the tell-tale dark areas, indicative of hydrocarbons, will be seen on the sample. After cleaning the SEM with the GV 10x, the contrast loss was no longer seen. Also the dark area on the sample was removed. The ibss GV10x DS plasma cleaning system was very effective at cleaning hydrocarbon contamination in the scanning electron microscope. It will be very essential for in-situ analyses and the system can be used at relatively high vacuum, allowing decontamination in situ samples without cooling/reheating of the objective aperture.

EM images taken during 2 hour examination before (left) and after (right) a 30 minute GV10x cleaning.

Figure 2. EM images taken during 2 hour examination before (left) and after (right) a 30 minute GV10x cleaning. (Courtesy Hydro- Québec)

Conclusion

The ibss Group has introduced a new and more efficient method of removing hydrocarbon contamination from SEMs and other analytical systems with the GV10x. The case studies prove that the GV10 x is a highly effective tool for SEM cleaning and will enable to obtain improved resolution and magnification of the SEM

This information has been sourced, reviewed and adapted from materials provided by IBSS Group

For more information on this source, please visit IBSS Group.

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