Ion beam synthesis based formation of Si-and Ge-rich thermally grown silicon dioxide layers for memory applications

Ion beam synthesis (IBS) is a versatile instrument to circumvent obstacles dictated by the thermal equilibrium. The basic steps to perform ion beam synthesis include ion beam irradiation with stoichiometric doses into a target kept at a certain temperature followed by another dedicated annealing step. On the other hand the actual EEPROM´s basing on floating gate transistors are driven to their limits of performance. An advanced very promising approach to circumvent these problems bases on the concept of Si-and Ge-nanoclusters embedded into silicon dioxide layers using IBS.
We have performed room temperature implantation of high fluences (3..9x1015 cm-2) of silicon and germanium into silicon dioxide layers with a thickness in the range 20-30 nm. This was followed by an annealing step at 950°C for 30 sec using Rapid Thermal Annealing (RTP). The microstructure and the electrical properties were investigated using a variety of methods. It will be shown that this type of processing leads to the formation of nanoclusters and the formation of trapping centres within the silicon dioxide layers. First device tests look promising.