Study On The Key Factors Of Single Event Effect In Ferroelectric Memory

In the space missions,semiconductor memories play an important role in the access and storage of information.With the rapid development of space technology,the demand of related industries for high-performance memories is increasing.Besides,aerospace electronics will face the threat from many kinds of radiation effects,among which the single event effect(SEE)is one main effect to cause the failure of memory devices.Therefore,it is necessary to conduct single event effect experiments of the alternative devices in order to take essential radiation hardening methods.Ferroelectric random access memory(FRAM)is a new kind of nonvolatile memory which has many advantages such as high read/write durability,high write speed and ultra-low power consumption.In addition,ferroelectric thin film features a good anti-radiation performance,which,as a result,presents a good prospect of space application for ferroelectric memory.Aiming at the single event effect of ferroelectric memory,many institutes abroad have carried out a large number of spaceborne and ground simulation experiments.On the contrary,few related research are reported in domestic institutes.In this dissertation,experimental study is conducted on the single event effect sensitive region spotting and single event effect sensitivity variation under different operating frequencies,temperatures and radiation environments.The main content in this dissertation include:1.Single event latch-up(SEL)threshold energies and cross section curves of the function blocks in ferroelectric memory are obtained using the pulsed laser single event effect facility.Testing results show that the SEL sensitivity of the function blocks in the same device differs a lot.Meanwhile,data upsets caused by SEL under static and dynamic operating modes are analysed and it is found that the upset cross section under dynamic mode is larger than that under static mode.2.A positioning method for pulsed laser backside testing experiment is proposed,by which we can get the backside position of the testing area in the front of the device without the help of the infrared imaging system and construct the mapping from sensitive nodes in backside testing experiment to the device layout.Further,the backside testing method is used to study the impact of operating frequency on the single event upset(SEU)sensitivity of ferroelectric memory.Analysis shows that the active time of chip enable signal has a direct relationship with the increase of SEU sensitivity.Besides,the SEU cross sections under different duty cycles of chip enable signal are studied to verify the conclusion.3.SEU and SEL experiments of ferroelectric memory under different temperatures are conducted.The relationship between temperature and SEU sensitivity of memory cells and periphery circuits are depicted separately.Analysis shows that the impact of temperature on the upsets caused by periphery circuits is obvious when the energy is near the threshold,and the impact on the upset of the memory cells is attributed to the change of remanent polarization and coercive field of the ferroelectric capacitor.The relationship between temperature and the SEL threshold energies and SEL cross sections of function blocks are depicted,too.Analysis indicates that the increase of the well sheet resistance with elevated temperature is the main cause of the decrease of SEL threshold energy and the increase of SEL cross section before it is saturated.The increase of the saturated SEL cross section is mainly because that the diffusion charges outside the well boundary increase the total charge collect,so the SEL sensitive volume is expanded.4.SEU sensitivity of ferroelectric memory under different accumulated radiation doses is studied using 60 Co source?209Bi ions and pulsed laser.It is found that the SEU cross section of the device under test shows different variation trends with the change of dose and test pattern.The results indicate that ionizing radiation-induced degradation in the periphery circuits is very faint.The variation of SEU sensitivity is mainly attributed to the radiation-induced fatigue-like and imprint-like phenomenon of the ferroelectric capacitor.