EEPROM Cell with HB (One Half Barrier Height) Oxide for VLSI

EEPROM for VLSI requires the scaling of programming voltage as well as device size. In order to write and erase the cell by lower voltage, the thickness of tunnel oxide should be decreased, while it is strictly limited by malfunction of storage due to direct tunneling mechanism. One way to resolve this contradiction is to lower the barrier height of' tunnel oxide, keeping the thickness. Therefore, several kinds of injectors, which is rather thick oxide with moderate barrier height such as oxide grown on poly-Si and Si-rich sio2 or silicon nitride, have been proposed and investigated. Since, all of them, however, use CVD method, they have certain problems of controllability and reliability to form a very thin layer.