MFIS and MFS structures using SrBi 2 Ta 2 O 9 thin films for the FRAM applications
- PDF / 1,749,478 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 73 Downloads / 156 Views
T2.3.1/U7.3.1
MFIS and MFS structures using SrBi2Ta2O9 thin films for the FRAM applications P.Victor, S.Bhattacharyya,1 S.Saha2 and S.B.Krupanidhi Materials Research Center, Indian Institute of Science, Bangalore 560012, India 1 Max-Planck-Institut fur Mikrostrukturphysik, Halle, Germany 2 Materials Science Division, Argonne National Laboratory, Argonne, IL-60439, USA ABSTRACT Recently there is an increasing demand and extensive research on high density memories, in particular to the ferroelectric random access memory composed of 1T/1C (1 transistor/1 capacitor) or 2T/2C. FRAM's exhibit fast random acess in read/write mode, non - volatility and low power for good performance. An integration of the ferroelectric on Si is the key importance and in this regard, there had been various models proposed like MFS, MFIS, MFMIS structure etc., Choosing the proper insulator is very essential for the better performance of the device and to exhibit excellent electrical characteristics. ZrTiO4 is a potential candidate because of its excellent thermal stability and lattice match on the Si substrate. SrBi2Ta2O9 and ZrTiO4 thin films were prepared on p - type Si substrate by pulsed excimer laser ablation technique. Optimization of both ZT and SBT thin films in MFS and MFIS structure had been done based on the annealing, oxygen partial pressures and substrate temperatures to have proper texture of the thin films. The dc leakage current, P - E hysteresis, capacitance - voltage and conductance - voltage measurement were carried out. The effect of the frequency dependence on MFIS structure was observed in the C – V curve. It displays a transition of C - V curve from high frequency to low frequency curve on subjection to varied frequencies. Density of interface states has been calculated using Terman and high - low frequency C - V curve. The effect of memory window in the C - V hysteresis were analysed in terms of film thickness and annealing temperatures. DC conduction mechanism were analysed in terms of poole - frenkel, Schottky and space charge limited conduction separately on MFS, MIS structure. INTRODUCTION Ferroelectric field effect transistor (FeFET) type memories exhibit its excellent features as nonvolatility and nondestructive readout with promising applications in the field of low-power and low-voltage portable electronic devices.[1,2,3] The MFSFET type of memory utilizes the remanent polarization of the ferroelectric thin films to control the surface conductivity on the Silicon substrate. Most of the perovskite ferroelectric thin films are not thermally stable on the Si substrate;[4] for instance the Sr, Pb , etc. diffuses into the Si, eventually leading to the degradation of the device.[5,6] Hence the MFS configuration was extended to the MFIS structure, on introducing a higher dielectric constant and thermally stable insulator in between the ferroelectric and the Silicon to act as a diffusion barrier. The research on SiO2, Si3N4, Al2O3, CeO2, ZrO2 and ZrTiO4 are investigated extensively as a diffusion barrier. [7] The prop
Data Loading...
