Meaning
A mass spectrometry method uses a pulsed ion beam to knock fragments from a surface to determine its chemical identity with high precision. Relying on tof-sims allows for the detection of trace contaminants at concentrations as low as parts per million. The tool measures the duration each fragment takes to reach a sensor after being ejected.
Use of this method is typically reserved for troubleshooting interface failures between chip layers.
Ion Bombardment
Primary beams of heavy atoms strike the sample to dislodge a cloud of target ions. Inside a tof-sims chamber, these secondary particles are accelerated into a long flight tube. The surface is gradually worn away during the process to enable depth profiling.
Mass Separation
Separation of heavy and light molecules occurs naturally as the particles travel the length of the vacuum. Results from tof-sims appear as a sequence of arrival times that indicate specific atomic weights. Software converts these timings into a detailed inventory of the elements present.
Contamination Profiling
Analysts use the data to see where unwanted residue has settled between manufacturing steps. Successful application of tof-sims identifies the exact source of a salt or oil smudge on the silicon wafer. Correcting the upstream rinse cycles often follows the visual discovery of these clusters in the flight time data.
