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.
Thermal Spike
Localized Melt
Intense energy deposition within a tiny volume of a target material by a high-energy primary ion generates a transient region of extremely high localized temperature. This localized phenomenon is termed a thermal spike, and it causes the transient melting and reorganization of the surrounding atomic lattice in the target. It occurs during ion sputtering of semiconductor or circuit board materials when heavy ions transfer their kinetic energy to the lattice over a very short timescale.
The localized temperature can exceed several thousand kelvins for a few picoseconds before dissipating.
Surface Restructuring
Atomic rearrangements driven by these high-temperature events can cause extensive damage to the target substrate, such as the destruction of molecular structures in polymer coatings. In this phase of the collision, the thermal spike induces chemical reactions, phase transitions, or extensive atomic mixing that alters the original sample surface. This atomic mixing makes it difficult to obtain high-resolution depth profiles of organic layers on circuit board assemblies.
The temperature rise causes the breakdown of the polymer chain, leaving a carbon-rich layer that does not represent the original chemical composition of the board.
Damage Prevention
Prevention of these localized high-temperature zones is achieved by using gas cluster ions instead of single heavy ions. This reduces the energy deposited per atom and prevents molecular degradation during board inspection.