Barbara Hasler

Investigations on the damage caused by ion etching of SiO2 layers at low energy and high dose

Abstract The radiation damage caused by argon ion bombardment during ion etching of thermally grown SiO 2 films at an energy below 1 keV and a dose of about 10 18 cm −2 has been studied by evaluating MOS C-V curves, FET characteristics, as well as Rutherford ion backscattering spectra. The bombarded samples revealed that ion beam etching in this energy range causes a damaged layer of 5–10 nm thickness at the single crystal silicon surface. Moreover, traces of metal atoms are found in the damaged layer together with argon atoms (≈ 10 21 cm −3 ).

ROS: an extremely high density mask ROM technology based on vertical transistor cells

A novel mask-ROM technology enabling a twofold packing density compared to conventional, planar ROM layout relying on the same design rules is presented. The key of the new technology is a cell concept based on a vertical MOS transistor in a trench, and a doubling of the bitline pitch by use of the trench bottom as additional bitline. The features of the ROS-technology are demonstrated by means of a 1 Mbit demonstrator memory. Since vertical transistors are manufacturable far below channel lengths of 100 nm, the technology is very promising for mass storage and thus for the replacement of conventional mass storage devices by semiconductor-memories.