Memory functions of nanocrystalline cadmium selenide embedded ZrHfO high-k dielectric stack

Abstract

Metal-oxide-semiconductor capacitors made of the nanocrystalline cadmium selenide nc-CdSe embedded Zr-doped HfO2 high-k stack on the p-type silicon wafer have been fabricated and studied for their charge trapping, detrapping, and retention characteristics. Both holes and electrons can be trapped to the nanocrystal-embedded dielectric stack depending on the polarity of the applied gate voltage. With the same magnitude of applied gate voltage, the sample can trap more holes than electrons. A small amount of holes are loosely trapped at the nc-CdSe/high-k interface and the remaining holes are strongly trapped to the bulk nanocrystalline CdSe site. Charges trapped to the nanocrystals caused the Coulomb blockade effect in the leakage current vs. voltage curve, which is not observed in the control sample. The addition of the nanocrystals to the dielectric film changed the defect density and the physical thickness, which are reflected on the leakage current and the breakdown voltage. More than half of the originally trapped holes can be retained in the embedded nanocrystals for more than 10 yr. The nanocrystalline CdSe embedded high-k stack is a useful gate dielectric for this nonvolatile memory device.

Light Emission Enhancement by Embedding Nanocrystalline Cadmium Selenide in Amorphous ZrHfO High-k Dielectric Thin Film Deposited on Silicon Wafer

“…According to the high resolution transmission electron spectroscopy (HRTEM) and the X-ray photoelectron spectroscopy (XPS) analyses, the final sample contained an amorphous bulk ZrHfO film and an amorphous Hf-silicate (HfSiO x ) interface layer in contact with the Si substrate. 16 Also, CdSe nanocrystals with the lattice fringe space of 0.22 nm corresponding to the (110) structure were formed in the ZrHfO film. 16 The sample's current density-voltage (J-V) curves were measured with the Agilent 4155C semiconductor parameter analyzer.…”

“…16 Also, CdSe nanocrystals with the lattice fringe space of 0.22 nm corresponding to the (110) structure were formed in the ZrHfO film. 16 The sample's current density-voltage (J-V) curves were measured with the Agilent 4155C semiconductor parameter analyzer. For the light emission experiment, the ITO electrode was stressed with a gate voltage (V g ).…”

“…1 is contributed by the thermal excitation of an individual conductive path formed from the dielectric breakdown process. [11][12][13][14][15][16] The number of bright dots in the nc-CdSe embedded sample is larger than that in the control sample. Also, the brightness of the former appears to be higher than that of the latter.…”

“…11 Separately, authors have demonstrated the nonvolatile memory characteristics of the nanocrystalline CdSe (nc-CdSe) embedded high-k film. 16 In this paper, the light emitting characteristics as well as the corresponding electrical and material properties of the * Electrochemical Society Fellow.…”

“…It was made by the breakdown of an amorphous Zr-doped HfO 2 (ZrHfO), HfO x , or WO 3 high-k dielectric thin film on a silicon wafer. [11][12][13][14][15][16] The warm white light was emitted from the device based on the principle of thermal excitation of the nano-sized conductive paths in the dielectric film, which is the blackbody emission similar to that of an incandescent light bulb. The intensity and wavelength range of the emitted light were enhanced by inclusion of a nanocrystalline ZnO (nc-ZnO) layer in the high-k film.…”