High Density Charge Storage Memory with Scanning Probe Microscopy

We demonstrate an ultrahigh density erasable charge storage memory with a scanning probe microscope in an oxide-nitride-oxide-silicon (ONOS) system of semiconductor nonvolatile memory media. It is found that by applying a voltage pulse between the tip and the silicon substrate, charge carriers can be made to be recorded and erased in the ONOS media. It is also found that the locally trapped charges cause local changes of the surface potential. The locally trapped charges ( recorded bits) can be read efficiently by detecting the change of the surface potential, without contacting the ONOS media, with the scanning Maxwell-stress microscope (SMM). A pattern of a 4 ×3 array of recorded bits could be successfully fabricated. The size of the smallest recorded bit is about 100 nm in diameter. This value corresponds to about 63 Gb/in2 in recording density. Furthermore, it is found that the recorded bits can be read at up to a frequency range as high as 10 MHz with heterodyne detected SMM.