ION-BEAM NITRIDATION OF A SI(111) SURFACE - EFFECTS OF ION REACTIVITY AND THERMAL-TREATMENT

Abstract

Ion beam nitridation of Si has been investigated in a low energy ion-surface collision chamber. Silicon nitride layer was generated on a Si(111) surface by N+ ion beam reaction and post-annealing, and the resulting surface was examined in situ by Auger electron spectroscopy (AES), ultraviolet photoemission spectroscopy (UPS), and low energy electron diffraction (LEED). Initial reaction of N+ ions with a Si at room temperature produces surface nitrides of various chemical states. Ion beam reaction to a saturation results in a nitride layer which mostly contains the sp(2) nitrides of D-3h symmetry. The sp(2) nitrides are randomly oriented at room temperature. Annealing of the reacted surface above 900 degrees C changes the LEED pattern from a featureless diffuse background directly to the well-defined ''quadruplet'' pattern, indicating crystallization of the disordered sp(2) nitrides into small domains. The ''8 x 8'' LEED phase, which is an intermediate phase of thermal nitridation, is not produced in ion beam reaction. The detailed nature of the nitride layer is discussed based on spectroscopic features.