(A) study on novel functional memory with ferroelectric material

Abstract

We develop a semi-empirical model of ferroelectric(FE) capacitor for SPICE macro implementation. The model explains the static and dynamic characteristics of ferroelectric capacitor very well. Proposed model takes account of arbitrary polarization state switching and successfully describes the followings with 5 paprameters ($V_c$, $V_o$, $P_s$, $C_o$, τ) which have definite physical meanings. These include 1) hysteresis of charge vs. Voltage (Q-V) and capacitance vs. Voltage (C-V) relationships 2) characteristic time dependent polarization reversal(switching) current. Simple parameter extraction procedure makes this model very promising for ferroelectric based electronic circuit design, as well as for ferroelectric material characterization. To simulate FE capacitor as a circuit element, we carry out an critical review on behavioral modeling approaches. SPICE macro implementation procedure based on the proposed semi-empirical model is described and the results are demonstrated by several examples. Sawyer-Tower circuit simulation shows the superiority of proposed macro model to conventional one. A Metal-Ferroelectric-Metal-Insulatior-Semiconductor (MFMIS) Transistior is simulated by using the macro model of FE capacitor, which shows the usefulness of our model in new functional FE based circuit design. The cell area optimization problem concerned with 1T-1C FeRAM structure is also addressed. An analog memory using ferroelectric(FE) capacitor is proposed, which utilizes the pulse amplitude programming characteristic of FE polarization. A new sense amplifier in the programming circuit is implemented to control the FE polarizations. Experimental implementation confirms the proposed idea and shows 21-level(4-bit) storage per cell in the program voltage range 0.3 V~1.3 V with ±25 mV resolution. We propose a 1T Type FeRAM array structure using selective channel inhibit operation. W/L erase operation is employed to erase cell data along a selected Word Line. We use c...