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Project Designs

Identify the question to be answered.
Generate subquestions based on preliminary evaluation using the techniques at hand.
Determine which analytical methods will be useful for answering each subquestion.
Evaluate the trade-offs among the various techniques for analysis.
Determine whether the selected methods of analysis are available within the time and cost budgets available for the study.
Cross correlate the data obtained at each step with previous results to determine need for additional study using new methods or additional samples.
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Example: Wire Bond Corrosion
Conference Proceedings, ASM 4th Electronic Materials and Processing Congress, Montreal, Canada, 1991, pp 99-106.

When they are improperly removed from the surface of a microelectronic device, cleaning solution residues can cause dramatic failure modes. In one such example, a microelectronic circuit was found to suffer corrosion of its bond pads after installation in a DIP package. The corrosion was visible in scanning electron microscope images of the device (see below).

The wire bonds which attach the microelectronic device to the package on one failed specimen were found to be surrounded by a layer of some unknown foreign material. This was found by analysis using Auger electron spectroscopy and energy-dispersive x-ray spectroscopy to be an organic material rich in chlorine. Since several chlorine-bearing solutions are used in the manufacture of the device, it was of interest to determine which of these might be associated with the residue detected on the failing devices.

To study the material, an extraction was performed on devices which exhibited the contamination after mechanical removal of the bottom side and edge material using abrasives. This was done to avoid any sources of contamination not associated with the residue observed around the wire bonds. Next, examples of each material used in processing which were known to contain chlorine were obtained. The extracted residue from the problem microelectronic device and the various processing materials were dried onto float zone silicon plates to provide samples for FTIR analysis. A comparison of the various solution residues and the contamination resulted in a close resemblance between the contaminant and one of the final stage cleaning solutions (applied just prior to DIP package installation of the device). Replacement of the cleaning solution with a residue-free alternate eliminated the problem.

SEM Micrograph

FTIR Spectrum of Residue

Analysis:
SEM/EDS/AES: Cl Observed on Corroded Aluminum Bond Pads
FTIR: Identified Cl-bearing Organic Residue from Cleaning Solution

Conclusion:
Infrequent Replacement of Cleaning Solution Resulted in Residue and Corrosion

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