Quantifying Sputter Yield Scaling under Argon Gas Cluster Bombardment
Argon cluster sputter yields scale nonlinearly with energy per atom, where low energy partitioning suppresses matrix damage during depth profiling.
Sputter Yield Scaling
Rate Proportion
Mathematical estimation of the rate at which target atoms are ejected from a substrate per incident primary ion determines the speed of depth profiling measurements on electronic materials. This numerical adjustment, known as sputter yield scaling, accounts for differences in erosion rates among the varied layers of a printed circuit board assembly. It adjusts the raw sputtering time to produce an accurate depth scale for multi-layered structures like nickel-gold pad finishes.
The application of this scaling factor prevents the distortion of interface thicknesses during surface analysis.
Energy Factor
The calculation of these scaling factors depends on the primary ion energy, the angle of incidence, and the atomic masses of both the ion and the target material. In multi-layer electronic boards, sputtering through a polymer coating and then through a copper trace involves very different sputtering rates. Sputter yield scaling uses reference values from pure elemental standards to convert the experimental ion dose into a true physical depth.
Without this scaling, the apparent thickness of thin metal coatings on the board would be severely miscalculated.
Depth Profiling
Accurate representation of the barrier layer thickness requires this scaling approach to evaluate board reliability. The method ensures that the nickel barrier thickness in gold-plated pads is measured correctly during quality checks.