Invited Paper AS+SS-WeA1
ASSD 30th Anniversary Speaker: Characterization of Sub-surface Interfaces using SIMS, TEM, and FIB or: How Much will it Cost me to Fix that Interface?

Wednesday, October 21, 2015, 2:20 pm, Room 212D

Characterization of interfaces between layers or between layer and substrate has always been of interest. Interface issues include visible problems, such as delamination or corrosion, and contamination that can affect product quality, such as electrical properties in semiconductors. The information desired includes the physical quality of the interface and identification and quantification of contaminants. This presentation summarizes multiple approaches to interface analysis, particularly with use of SIMS, FIB, and TEM.

Common approaches for analysis of a buried interface involve a depth profile or cross section. Depth profiling by SIMS is often used because of good sensitivity and depth resolution. Matrix, dopant and contaminant species in the structure can be characterized with a single SIMS depth profile. Quantification of contamination at an interface is highly desired but can be difficult to obtain. Once an element has been identified as a contaminant, quantification at interfaces may be possible with ion implantation. Significant improvements have been made with the species used for depth profiling. C₆₀ and argon cluster beams are used to depth profile organic materials. These high mass ion beams provide better sensitivity for high mass species and do not affect the chemical composition, so it is possible to obtain interfacial chemistry.

The FIB has revolutionized sample preparation and lift-out methods can routinely prepare cross section specimens for TEM analysis. A sample polished to provide an edge can rapidly be trimmed with FIB to provide a surface 50 to 100µm in height that is suitable for high resolution analysis. Optimization of beam conditions such as dwell and overlap can increase removal rate by several times. Plasma ion sources dramatically increase material removal rates and make possible the study of 100µm deep interfaces which will cover most layers of interest. Plating coatings are commonly less than 5µm thick and paint coatings 100 to 150µm.