Metal-Ferroelectric-Semiconductor Characteristics of BaMgF 4 Films on p-Silicon
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METAL-FERROELECTRIC-SEMICONDUCTOR
CHARACTERISTICS OF BaMgF 4
FILMS
ON p-SILICON T.S.
KALKUR,
J.R.
KAMMERDINER*** Microelectronics and
Computer
KULKARNI *,R.Y.
KWOR,
University
of
Springs, CO 80933 * Presently with National Semiconductors, **
Department
of
Physics,
University
LEVINSON**
Department
Research Laboratories,
Engineering,
L.
and
L.
of Electrical
Colorado
at
Colorado
Santa Clara, CA. of
Colorado
at
Colorado
Springs, CO 80933 *** Ramtron Corporation, Colorado Springs. ABSTRACT Capacitance-voltage characterstics of BaMgF 4 film deposited in an ion-assisted deposition system shows hysteresis and the direction of hysteresis corresponds to ferroelectric polarization. Electrical characterization of the films shows that these films can be used to implement non-destructive read-out non-volatile ferroelectric memories. These films were found to dissolve in water and other aqueous solutions. In order to overcome this problem, a suitable capping layer like zirconium oxide and in The shift amorphous silicon was deposited on BMF films. due to the threshold voltage did not change significantly in threshold voltage incorporation of the capping layer. The shift was found to be temperature dependent and this might be due to ionic conduction in fluorides.
INTRODUCTION Recently, there has been tremendous interest in the use of for Bismuth Titanate like PZT and materials ferroelectric radiation hardened non-volatile memory applications ( 1-3). There are two approaches to implement non-volatile memories using ferroelectric materials. In one approach, which is commonly used for materials like PZT, the ferroelectric memory element is a simple metal-ferroelectric-metal capacitor. The memory read out in these capacitors is destructive because whenever the information is read, it has to be written so as to preserve the memory (1). undergo fatigue as the read-write This makes the memory element the ferroelectric another approach, In cycles are increased. incorporated as a gate insulator of the metalmaterial is insulator-semiconductor field effect transistor(MISFET) (4). This results in non-distructive read out of the information so that the metalThe element can be minimised. of memory fatigue of ferroecelectric characteristics ferroelectric-semiconductor materials like PZT and Bismuth Titanate have been studied (5-7). Mat. Res. Soc. Symp. Proc. Vol. 230., 1992 Materials Research Society
316
Because of the interdiffusion of these ferroelectric materials with silicon, it was not possible to integrate them directly on silicon. The hysteresis observed in the capacitance-voltage characteristics of these devices was predominantly due to the injection of carriers at the interface rather than due to the Recently, field effect caused by ferroelectric behaviour. fluoride based ferroelectrics have attracted the attention of many investigators for the implementation of non-destructive read out ferroelectric MISFETs (8-10). In this paper, we are presenting the results of the characteristics of BMF fluoride MIS
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