Temperature Effect on Memory Functions of the nc-CdSe Embedded ZrHfO High-k MOS Device

Abstract

The temperature effect on the memory characteristics of the MOS capacitor containing the nanocrystalline CdSe embedded ZrHfO high-k gate dielectric has been investigated. At the high temperature, the Coulomb blockade phenomenon is suppressed and the leakage current is increased due to the relative high conductivity of the dielectric film. At the same time, the density of interface states is high and the memory window is small. When the temperature is increased, the hole trapping capacity is enhanced because of the improve the supply of holes from the Si. However, the electron trapping capacity is reduced because of the easy transfer of electrons through the high-k stack. The frequency dispersion phenomenon is enhanced at the high temperature. The temperature has strong influence on the carrier generation, transport, and trapping at the interface and the bulk film.

Temperature Effects on Charge Storage and Transfer of Nanocrystalline CdSe Embedded Zr-Doped HfO2MOS Memory Device

“…The shift in the backward sweep direction is larger than that in the forward sweep direction, which results in a small reduction of both V FB and Q. This phenomenon can be explained by the competitive trapping and retention of holes and electrons in the highk stack, 22 which will be discussed in detail later. Separately, the inset of Fig.…”

“…22,24 On the other hand, under the +6 V to −6 V sweep condition, the magnitude of the positive V FB shift decreases from 0.49 V at 20…”

“…15 At the high temperature, electrons can obtain more energy to transfer through the high-k stack without being retained by the nc-CdSe related trapping sites. 22 Moreover, the electron concentration in the n-type CdSe increases with the increase of temperature, which can inhibit the trap of electrons 25,26 The above principle can be used to explain the result of Fig. 1, i.e., the decrease of V FB with the increase of temperature.…”

“…22 When the sample is swept from the opposite direction, i.e., from +6 V to −6 V, the C-V curve shifts toward the positive V g direction due to the trap of electrons. 22 The amount of charges trapped in the V g sweep can be quantified by comparing the V FB of the nc-CdSe embedded sample with that of the "fresh" sample. For example, under the −6 V to +6 V sweep condition, the magnitude of the negative V FB shift increases with the increase of temperature, i.e., from 0.49 V at 20…”

“…15,20 At the high temperature, more holes can gain enough thermal energy to be detrapped from the high-k stack and, therefore, the jump of J is small. 18,22 For the nc-CdSe embedded sample, a second jump of J, i.e., at point B, is observed at 20…”