Development of a Nano-Material Doping Characterisation Tool by a Novel Combination of Secondary-Ion mass Spectrometry and Resistivity Measurement (SIMSAR)

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Principal Investigator: Prof Patrick McNally

Co-Investigator: Dr Nick Bennett

Funding: Science Foundation Ireland / Enterprise Ireland

Secondary-ion mass spectrometry (SIMS) is an established technique for measuring doping profiles in semiconductors. The method benefits from high sensitivity, wide dynamic range and good depth resolution.

These advantages have made it a staple technique for the semiconductor industry for measuring the one-dimensional depth-profile of ion-implanted dopants – such as arsenic – in silicon.

One limitation of the SIMS technique is that while it identifies the total concentration of an element as a function of depth, it is unable to distinguish between those atoms that act as donors or acceptors from those that do not, i.e. it cannot distinguish so-called ‘active’ dopants from ‘inactive’ dopants. Several techniques exist for chemical dopant profiling and numerous for electrical profiling. Crucially however, there is no technique which can measure both electrical and chemical profiles in parallel.

In this study a method was found that allowed measurement of the electrically active dopant profile in unison with the chemical profile. The method was not without complications, however potential problems were identified, explained and corrected for. The measurement principle was tested and could feasibly be incorporated in a commercial SIMS tool for use in semiconductor manufacturing metrology.