Study On The Application Of Graphene Film In Ferroelectric Memory

As a semiconductor memory,ferroelectric memory has the advantages of non-volatility,low power consumption,fast reading and writing speed and strong radiation resistance.It has been widely used in intelligent instruments,automotive electronics,edge computing,aerospace and other fields.Graphene is a new kind of two-dimensional material formed by carbon atoms arranged closely in honeycomb hexagonal lattice.It has very large mechanical strength,excellent thermal properties,high transmittance and good conductivity,and is widely used in the field of electronic devices.This paper intends to study the feasibility of using graphene film as electrode material for ferroelectric memory.The main work of this paper is as follows:Firstly,PZT ferroelectric thin films were prepared by sol-gel method,and ferroelectric capacitors with different area and thickness were prepared by using this medium.The capacitance of the sample was measured by multimeter and the hysteresis loop was measured by Sawyer-Tower method.According to the measured hysteresis loop,the symmetrically modified hysteresis loop and its fitting parameters are obtained.Secondly,the fitting parameters of hysteresis loop are applied to the simulation and design of 2T-2C ferroelectric storage unit.A 2T-2C ferroelectric storage unit is fabricated by using CMOS transistor and ferroelectric capacitor,which can read and write correctly.From the simulation and read-write test results of 2T-2C ferroelectric storage unit,it can be seen that:(1)the better the ferroelectricity of ferroelectric capacitor(the greater its residual polarization intensity),the larger the line voltage difference of ferroelectric storage unit;(2)parasitic capacitance and ferroelectric capacitance must match to ensure that the storage unit has the largest line voltage difference;if the size of ferroelectric capacitance in storage unit is changed,then The parasitic capacitance should also be changed to match the two.Then,on the basis of SRAM system circuit,a ferroelectric memory with capacity of8 Bit is designed and manufactured,which mainly includes decoder circuit,driver circuit,latch circuit,sensitive amplifier circuit and read-write control circuit.The read-write test of the ferroelectric memory shows that when the speed of the read-write test is about 3.3×10~5Bit/s,the ferroelectric memory can realize the correct addressing of the unit and the correct reading and writing of the data.Finally,the transfer,patterning and electrode extraction of single-layer graphene films prepared by CVD were studied.The results were used to fabricate ferroelectric capacitors with graphene film as the upper electrode,platinum electrode as the lower electrode and PZT as the dielectric layer.The ferroelectric capacitor with graphene upper electrode was replaced by the original ferroelectric capacitor in 2T-2C ferroelectric storage cell.The ferroelectric storage cell with graphene upper electrode was obtained.The results of reading and writing tests show that graphene as the electrode material of ferroelectric memory is feasible,but it will reduce the reading and writing speed of ferroelectric memory.