2009 Volume 44 Issue 3 Pages 170-173
In flash memory, both the “1” and “0” states are stored by changing the threshold voltage (Vth) of the transistor, where the Vth shifts are induced by stored charges. The metal-SiO2-SiN-SiO2-semiconductors (MONOS) memory stores charges in the SiN film of the gate SiO2-SiN-SiO2 (ONO) film. By using a scanning nonlinear dielectric microscopy (SNDM), we have succeeded in the identification of the charges (electrons and holes) concentrated areas in the ONO gate film in high-resolution. We also demonstrated that the SNDM has high performance and resolution for observing the charge distribution after program-erase operations cycling. Thus, it is expected that SNDM will be an effective method for observing the charges in the semiconductor devices. Finally, in downsized MONOS flash memory; we succeeded in visualizing the charge distribution by detecting a second-order nonlinear dielectric constant by using SNDM.