Non-volatile memory is slower than DRAM (Dynamic Random Access Memory) but faster than HDD (Hard Disk Drive). In addition, compared to volatile memory, the non-volatile memory can retain stored information without power, and consume only low power. These characteristics show its popularity of flash memory built in portable devices. Currently the non-volatile memory applies the polysilicon and SONOS structure as floating gate, however, the new technologies of nanocrystal non-volatile memory are processed at high temperature. The manufacturing cost is rather high, so the process at lower temperature is very necessary. In this work, mixed zinc and silica amorphous layers are applied as floating gate to construct nano thin film non-volatile memory devices. The process does not need high temperature to form crystalline, and the defects in zinc oxide can be applied for charge storage. Supercritical carbon dioxide (SCCO2) treatment has been studied for the passivation of dielectric and reducing the activation energy. Using this low-temperature SCCD process ZnO nanocrystal can be formed, and the feasibility of fabricating nanocrystal NVMs device with low temperature SCCO2 is possible. The nonvolatile memory devices with Zn nano thin film embedded in MIS structure are performed. From C-V measurement, it is found that defects in SiO2 are repaired after 500¢J annealing. Because of the thermal diffusion, the storage layer SiO2/Zn-SiO2/SiO2 in device cannot be observed and the memory window disappears when the annealing temperature is higher than 700¢J. Therefore, the annealing process should be performed between 500¢J - 700¢J in making memory device. From DLTS analysis, a species with energy level of 0.6 eV is found in the as deposited Zn-SiO2 layer. After annealing in Ar, a new energy level 0.47 eV is found, and which shifts to energy level 0.85 eV after annealing in O2. In comparison to XPS results, traps of Zn-SiO2 exist before annealing, and after annealing in Ar, Zn-SiO2 transforms into Zn-O-Si. Traps of ZnO-SiO2 have been found after annealing in O2, which increases the memory effect with a 2 Volt memory window, so that more charges can be stored in the deep level traps of ZnO-SiO2 in the storage layer.

Non-volatile memory can keep the data without supplying power, and it is suitable for portable electronic products due to the advantage of low power consumption. In current industrial production, high-temperature and long-time process are necessary for the fabrication of non-volatile memory, which are heavy loadings on production capacity and lots cost. Therefore, decreasing the temperature of the process is a trend. Recently using the oxidation treatment of supercritical carbon dioxide fluid can efficiently decrease the temperature of the process. In this thesis, the mixture layer of Zn, Sn, and SiO2 is applied to reduce the temperature of process, and to employ the defects of ZnO and SnO2 as floating gate for electron storage to fabricate the nonvolatile memory device. Zn and Sn are applied due to the low temperature melting points. To ensure the layer of cosputtering with Zn and Sn to be able to successfully fabricate as nano material device, the process of traditional rapid temperature annealing treatment was applied for first step. The co-sputtered Zn-Sn-SiO2 thin film was deposited on the tunneling oxide layer, and then the thin film was treated with varied annealing temperature to precipitate ZnO and SnO2 nanocrystals. After that, the C-V measurement is applied to analyze the change of the electrical and material properties. Using a positive bias, the electrons are injected into the oxide layer, by the threshold voltage the offset is occurred, which is defined as the memory window of the memory effect, and the property of nonvolatile memory will be applied. In addition, no matter the charge is injected from the gate oxide or tunnel oxide, the defects position of DLTS¡¦s peak is with the same property. The supercritical carbon dioxide fluid technology has been performed to study the memory effect. The capability of electron injection, storages and the defect, in the storage layer were studied by the C-V measurement and DLTS. The experiment confirmed that the Zn-Sn alloy has the memory property after it been treated by the supercritical carbon dioxide fluid technology. It has shown that Zn can promote to the storage capability ability due to the formation of deep level defects of SnO2 from the DLTS spectra. A new species is found at 0.93 eV with low activation energy and high capability of electron storage. The defect formation mechanism of Zn, ZnO, Zn-O-Si, Sn, and SnO are analyzed by found by the XPS and DLTS. The device fabrication using Zn-Si alloy and supercritical carbon dioxide fluid technology has the potential to reduce the process temperature and to improve the memory property of nonvolatile memory device.

No description available.