Stress and Plastic Flow in Silicon During Amorphization by Ion-Bombardment

Abstract

ABSTRACTThe in-plane stress in silicon wafers during amorphization by ion-bombardment was determined from wafer curvature measurements using an in-situ laser scanning technique. Measurements were made during room temperature bombardment with 2 MeV Ne, Si, Ar, Kr, and Xe ions. In all experiments, compressive stress was built-up in the bombarded region as a function of the fluence, until a maximum was reached at the dose required to form amorphous silicon. During further amorphization by bombardment, the stress decreased and eventually stabilized. If ion bombardment was interrupted during amorphization, a stress increase was observed over a period of several minutes; when the beam was turned on again, the stress returned immediately to the value measured before interruption. Step height measurements were performed on implanted wafers to determine the out-of-plane strain, and RBS was used to determine the damage profiles. A model is proposed that describes the behavior in terms of the expansion of crystalline silicon by the creation of defects and the flow of amorphous silicon under the ion beam.