Studies Of Flash Memories Based On O₃-Al₂O₃ Prepared By Atomic Layer Deposition

With the development of information technology,the number of intelligent terminals continues to increase,and the storage industry has played a role that cannot be ignored in this process.In order to reduce the weight,increase the operating speed and at the same time connect with the high-speed transmission network,it has higher requirements for data storage products.The development of semiconductor memory has strongly promoted the realization of these goals.Semiconductor memory occupies an important position in the current storage system,due to its advantages of light weight,fast storage speed and high storage density.Among them,Flash memory is a widely used memory type,and its basic storage unit is generally divided into floating gate type memory and charge trap type memory.When the memory of the planar structure shifts to the 3D structure,the charge trapping technology becomes the main technical direction for its relatively simple structure.During the development of charge trapping devices,high dielectric constant materials(high ? materials)were introduced into memory,and even tended to realize memory cells with full high-k material stacks Among them,Al2O3 high ? materials have their own unique advantages and widely used in memory devices.In this paper,atomic layer deposition technology is used to prepare alumina(O3-Al2O3)by replacing H2O with O3 as the oxygen source.Analyze the properties of the films and try to apply it to CTM.The experiment in this article is mainly divided into the following contents.1.The effect of the natural oxide layer on the substrate surface:The native oxide layer(NOL)on the substrate surface affects the adsorption of the precursor during the deposition of the films and the quality of the films.In the experiment,different methods were used to clean the substrate and perform FGA treatment to obtain films with four different conditions:RCA+HF,RCA+HF+FGA,Decon,and Decon+FGA.Use these films as dielectric layers to prepare MOS devices and test the device parameters.Due to the promotion or inhibition of the surface chemical state on the film growth,the O3-Al2O3 films grown on different substrates have different changes after FGA treatment.The results show that the NOL on the surface of the substrate can provide the active site of the reaction and help to improve the quality of the O3-AI2O3 films2.The effect of the O3 dose time:O3 dose time affects the amount of precursors during the reaction.In the experiment,O3-Al2O3 films was prepared on the substrate containing NOL,and the O3 dose time was set according to a certain gradient.Then,the MOS and IGZO-TFT devices were fabricated with O3-Al2O3 films as the dielectric layer.Tests show that as the O3 dose time increases,the dielectric constant of the O3-Al2O3 films increases first and then decreases.At the same time,the mobility of the corresponding IGZO-TFT has the same trend,and its maximum value is at 5 s O3 dose time,which is determined by the characteristics of the ALD reaction.3.The effect of growth temperature:The growth temperature affects the rate of chemical reaction,the movement of chemical equilibrium and the adsorption or desorption of the surface.In the experiment,O3-AI2O3 films were grown at different temperatures,XPS and AFM were used to characterize the thin films,and MOS and IGZO-TFT devices were prepared with O3-Al2O3 dielectric layer.Tests show that as the growth temperature increases,the roughness of the film improves,carbon impurities decrease,and Al 2p and O 1 s are closer to the standard peak at high temperatures.There is no hysteresis for MOS devices prepared at 350?,and all MOS devices below this temperature have hysteresis.And as the number of scans increases for IGZO-TFT devices,the transmission curve continues to drift.In the bias stress test,there are differences in the flat band voltage drift of MOS devices,and the drift trend of IGZO-TFT devices is basically the same.Thick silicon oxide is generated on the substrate surface at 350?.As the temperature increased from 150? to 250?,the border trap density decreased from 2.1×1012 cm-2 to 1.6×1012 cm-2.Therefore,the high temperature improves the film formation quality,and the trap density is larger under 150?.4.The application of O3-AI2O3 in charge trap memory:Experiments show that there are many electron traps in the O3-Al2O3 film,which can be applied to the charge trapping layer in CTM.Combined with XPS valence band spectrum analysis,150?was selected as the growth temperature of the charge trapping layers,and a charge trapping memory was prepared on this basis.Through test,the storage unit can get a 11.8 V storage window at a voltage of ±15 V,and the device still maintains a 44.8%storage window at 10 years.