Establishing an accurate depth-scale calibration in the top few nanometers of an ultrashallow implant profile

A method to accurately determine the sputter yield of the matrix from the earliest stages of a sputter profile is described. Using the technique of medium-energy ion-scattering spectroscopy, this method provides data that enable a depth scale to be established from subnanometer depths onward. It may be adapted to samples containing a thin amorphous surface layer (e.g., a preamorphized shallow implant) or to crystalline surfaces containing a heavy-element marker layer. In this Brief Report we have used this method to interpret the near-surface profile using erosion-rate data obtained from a 1-keV boron implant into a germanium preamorphized silicon (001) surface.