Effect of ion energy and dose on the positioning of 2D-arrays of Si nanocrystals ion beam synthesised in thin SiO2 layers

Silicon nanocrystals (ncs) buried in a thin oxide can be used as charge storage elements and be integrated in standard CMOS technology to fabricate new non-volatile memory devices. In this work, we report on a systematic study of the effect of varying the beam energy (0.65-2 keV) and the dose (10(15)-10(16) cm(-2)) on the positioning of 2D-arrays of ncs within 10 nm thick oxide after annealing at 950 and 1050 degreesC. For this, different Transmission Electron Microscopy (TEM) methods have been used including High Resolution Electron Microscopy (HREM) for imaging isolated ncs and Fresnel contrast imaging of populations of ncs. Our results show that the 'injection distance' can be precisely tuned in the 5-8 nm range by varying the beam energy. Moreover, very large swelling of the SiO2 layer has been observed when increasing the implanted dose which could be the result of a partial oxidation of the Si ties layer and/or of the SiO2/Si interface. (C) 2003 Elsevier Science B.V. All rights reserved.