Spring 2011 Newsletter
We Are Now Part of EAG!
Chemir recently became part of Evans Analytical Group (EAG). EAG is world-renowned for its expertise in surface analysis and materials characterization; microelectronics “release to production” services and electronics failure analysis. We are very excited to be able to apply the existing broad range of analytical expertise within EAG to our client’s investigations. EAG’s existing focus on surface analysis and materials characterization techniques will help Chemir’s scientists to better identify unknowns and contaminants and to better address complex problems.
A number of the new techniques available to Chemir through EAG allow us to examine both the surface of a product and also its layer structure. This can help determine if a contaminant is present on the surface only or if it has penetrated into the sample. The new suite of surface analysis tools can also help confirm results from measurements performed within Chemir, or provide additional evidence to improve understanding during a project.
EAG was originally formed in 1978 in the San Francisco Bay Area as Charles Evans & Associates. Initially focusing on semiconductor materials analysis, it has expanded greatly over the years, both geographically and in the industries served. It is privately held and is headquartered in Sunnyvale, CA, with labs in 10 states (AZ, CA, MA, MI, MN, MO, NC, NJ, NY and TX) and 4 countries (USA, France, Taiwan and China), and sales offices in the UK, Japan, South Korea and Singapore. EAG’s approach has always been to provide our customers with the highest quality measurements as quickly as possible, with direct access to the scientists doing the measurements. Measurements available from EAG are typically focused on the compositional analysis of solid materials and surfaces. In most cases electrons, ions, X-rays or photons are used to stimulate a sample and the resulting emitted species (also electrons, ions, X-rays or photons) are then measured. EAG instruments range from 40 feet in length (e.g. Rutherford Backscattering Spectroscopy) and 10 feet tall (e.g. TEM) to tabletop in size (e.g. Raman microscopy).
EAG has a wide array of analytical techniques available (more than 30 at the last count!) so initially we would like to describe three that we think have particular relevance to Chemir customers: XPS (X-ray Photoelectron Spectroscopy), TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) and XRF (X-ray Fluorescence).
XPS (X-ray Photoelectron Spectroscopy)
XPS, also commonly known as ESCA (Electron Spectroscopy for Chemical Analysis) is one of the standard tools used to investigate surfaces. Data is obtained by bombarding the sample with X-rays and measuring the energy of photoelectrons which are emitted. XPS provides a quantitative survey of the elements present on the extreme surface of a sample (~ the top 100Å) with detection limits in the sub % range. A further benefit is that it can also determine the oxidation states of these elements so you can determine how they are connected to each other. The surface sensitivity makes XPS an ideal tool to investigate surface functionalization and the effects of plasma treatment on surfaces. It is also an excellent tool to investigate stains and discolorations. XPS is available from EAG’s labs in CA, MN and NJ.
Example: In a glue adhesion investigation, this XPS survey spectra shows that no silicone was detected in the sample, ruling out silicone contamination. A higher O concentration was found on the good carton.
High resolution XPS spectra shows that the bad carton polyethylene was not corona treated.
TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry)
TOF-SIMS is an extremely surface sensitive method used to investigate elemental and molecular species on surfaces. Data is obtained by bombarding the sample with a beam of primary ions (usually gallium or gold) and then measuring the secondary ions which are emitted. The mass of these ions is determined by measuring how long they take to travel a known distance (i.e. their ‘time-of-flight’). The information depth of the measurement is very low (~10-30Å) and the detection limit is in the part per million range. In most cases TOF-SIMS is carried out in a mode where sample are compared (e.g. old/new, or good/bad) and relative differences between them determined. TOF-SIMS is an excellent choice for investigating potential contaminants such as lubricants, surfactants, plasticizers, antioxidants and other additives. It can also provide data about low levels of elemental species on surfaces. Ion images obtained using TOF-SIMS can show the lateral location of species with an image resolution of less than 1µm. TOF-SIMS is available from EAG’s labs in CA, MN and NJ.
Here is an example of using TOF-SIMS for identifying contaminant droplets on a hard disk.
Another example of the TOF-SIMS method is investigating a residue on a flat panel TFT.
XRF (X-ray Fluorescence)
In contrast to the techniques discussed above, XRF is a bulk materials analysis technique rather than an extreme surface measurement. It works by bombarding the sample with high energy X-rays and measuring the intensity of any emitted X-ray fluorescent photons. In this way, XRF provides information regarding the elemental content of materials. It is an excellent way to determine the identity of alloys and metals and also is very good at determining the metallic content of polymers (e.g. as additives or contaminants). XRF can be used efficiently as a rapid screening technique to determine the presence or absence of specific elements. Due to the differences in material density and X-ray energies, the information depth can vary from a few µm to mm or more. The detection limit is also element dependent, but can be as low as 100 part per million (by weight). XRF is available from EAG’s lab in Sunnyvale.
Examples of XRF spectra for Au/Ni plating on copper and alloy composition:
