Abstract

Since the introduction of copper metalization into mainstream semiconductor processes, new backend debug and failure analysis techniques are needed to deal with the different reaction rate and milling behavior of copper. Focused Ion Beam (FIB) systems have long been a major tool in debug and analysis of semiconductor chips. With the introduction of copper, many of the current FIB chemistries and techniques will need to be modified in order to accommodate this process. The metal etch gases currently in most FIB systems either have no effect on copper or have detrimental effects. Chlorine, iodine and bromine all will etch copper spontaneously and will undercut exposed copper lines. [1,2] The ion channeling properties of copper are also significantly greater than aluminum, which makes large area metal removal very difficult due to differential milling rates. Depending on the crystallographic grain orientation, straight sputter of copper could have up to 3 times differential milling rates. Various other FIB function will also need to be examined with regard to copper. This paper will discuss the differences in dealing with copper instead of aluminum chips. It will also offer a few application techniques and new system enhancements in dealing with copper and discuss some limitation of the current system hardware. [1]

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