Advanced functional materials: using local field modulation to extend the refresh time of semi floating gate memory by 535%

wallpapers Nicaragua News 2020-08-05

IC industry plays an important role in the development of modern information society. As one of the essential core technologies in this field storage technology is facing unprecedented challenges in the era of big data. However the existing memory is difficult to achieve high speed large capacity non-volatile at the same time. How to develop low-power ultra-high speed non-volatile memory based on new principles new materials new structures to break through the limitations of "storage wall" has become a key scientific problem. Recently a quasi nonvolatile half floating gate memory based on van der Waals heterojunction is reported. Its write speed data retention ability fill the gap between the volatile nonvolatile memories create the third kind of memory technology. The introduction of PN junction brings about ultra fast write speed but it also causes a problem that is due to the existence of charge leakage the data refresh time (10s) is not long enough which is obviously not enough to reduce the power consumption caused by frequent refresh. Therefore it is still a challenge to extend the refresh time reduce the power consumption while maintaining the ultra fast write speed.

In order to solve this problem

has made research by Zhou Peng research group of Fudan University Liu Qi research group of Institute of microelectronics of Chinese Academy of Sciences. It uses the polarization of ferroelectric gate medium hfzro4 to introduce a local nonvolatile electric field which can continuously control the charge leakage rate of PN junction. Therefore it greatly prolongs the refresh time of semi floating gate memory (more than 535%) solves the problem of previous semi floating gate memory Memory data retention time is relatively short.

take into account that the electrical properties of two-dimensional materials are easily modulated by external conditions so they can reduce the charge leakage of PN junction under certain external conditions. Spontaneous polarization exists in ferroelectric materials the polarization state can be changed by external electric field. It is worth noting that the polarization electric field is non-volatile which has a great advantage in solving the problem of PN junction leakage. The research team uses ferroelectric materials to control two-dimensional materials uses ferroelectric hfzro4 to replace the Al2O3 gate dielectric in the semi floating gate memory to control the channel current prolong the data retention time. Under the grid voltage pulse a polarized electric field is formed in hfzro4 more holes are trapped in the floating gate which has a stronger modulation effect on the channel current. In addition the local field formed by ferroelectric hfzro4 polarization is non-volatile that is it will not disappear after the gate voltage pulse is removed which is equivalent to applying a continuous write voltage to the gate electrons can be reinjected into the channel leaving holes in the capture layer. Therefore the current leakage is reduced by continuous data writing in the local electric field which is the key factor to prolong the refresh time. The design of introducing local field into the semi floating gate structure realizes the combination of ultra fast writing speed significantly enhanced data retention ability which provides a new idea for the development of ultra fast nonvolatile memory technology.


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