LIBS Analysis of Microprocessor Chips
Goal:
Assess the feasibility of using LIBS system to characterize elements in microprocessor coating and core
Introduction:
It may be necessary in certain applications to determine the elemental composition of chip components, including the core metals and coating plastics. In this experiment, LIBS was used to assess whether gold and silver were present in the core of chips, and whether the core could be distinguished from the plastic coating in resulting spectra. It was found that silver was present in the core, while gold was present only in protruding wires from certain chips. It was also found that the coating could be distinguished based on elements present in the core but not in the coating.
Hardware Used:
LIBS 2000+ broadband, high resolution spectrometer
200 mJ Nd:YAG Big Sky laser
LIBS-SC sampling chamber with imaging module
Acquisition Parameters:
3 scans/average
Laser level 8
Q switch delay: -2.5 microseconds
Experimental Conditions:
All samples were placed individually on double sided tape within the sampling chamber to prevent movement from laser ablation. The plastic sheath was assessed on all samples, while two samples with protruding filaments were assessed for metal content by creating a hole in the plastic sheath with the laser through which the metal core could be ablated.
Measurement Mode:
LIBS
Results:
Using the elemental analysis tool in OOILIBS, All samples of coating were shown to contain silicon to varying degree by the presence of corresponding peaks at 251.61, 288.15, and 252.81nm. Elemental analysis also revealed that the coating of sample 2 contained high counts of magnesium as well as silicon. High peak values and strong correlation to elemental peaks in sample 4 suggested a strong presence of hydrogen and carbon, while sample 5 also suggested carbon in high presence. However, none of the coatings displayed any detectable amounts of silver. When the coating on sample 3 was degraded down to the core via repetitive laser strikes, a strong presence of silver was detected, both in the number of peak correlations and high signal counts. Once the core had been reached, sodium peaks no longer appeared. In addition, lasing of wires protruding from sample 4 showed noticeable presence of gold via close correlation to peaks. In all coating samples, sodium and potassium were also detected, however this is likely attributable to contamination from handling.
Conclusions:
It was shown that LIBS compounded with the elemental analysis function in OOILIBS is a capable tool for distinguishing between elemental components of the core and coating of computer chips. By correlating peak intensity counts and the number of elemental peaks present in each spectrum, it was possible to distinguish the major elements within each chip coating of samples 1-7, and the core of sample 3. Further ablation of sample 3 showed that the presence of silver distinguishes core material from coating, and ablation of sample 4 on protruding wires showed that metal components present on the chip or in the core of the chip can be differentiated using LIBS.
Tags: computer chips, elemental composition, ICs
