Electrical properties of integrated capacitors made of BST and BCTZ material for impedance adaptation applications

Abstract

Tunable materials, which exhibit in same time, a non-linear variation of their dielectric permittivity (ɛr) under an external electric field and low dielectric losses, are widely used in electronics for tunable applications. Single capacitors and a network of capacitors and resistors have been manufactured for an exhaustive electric characterization of three paraelectric materials. The first one is a Ba0.55Sr0.45TiO3 (BST) thin film prepared by RF sputtering technique. The second one is a film of Ba0.7Sr0.3TiO3 doped with Cu0.5%Mn1% prepared by using sol-gel processing technique. The third one is a Ba0.94Ca0.06Ti0.84Zr0.16O3 (BCTZ) thin film prepared by sol-gel technique. The first electrical parameter extracted is the breakdown voltage of the capacitors to define the maximum electric field applicable for the following characterizations. These three films have a high relative permittivity, up to 680 for the BST sputtered, 870 for the BST sol-gel, and 570 for the BCTZ sol-gel. They are also characterized by a very high dielectric tunability with 6.7:1 for the BST sputtered, 9.3:1 for the BST sol-gel and 7.6:1 for the BCTZ sol-gel. The quality factor of these paraelectric films is measured at 150 for the BST sputtered, 140 for the BST sol-gel, and 45 for the BCTZ sol-gel. These very high electrical properties are obtained with no compromise on the capacitor lifetime. In conclusion, these three paraelectric films could be used and the choice of either films is driven by which parameters would be the most important in the targeted tunable application.

The influence of the PZT buffer layer on electrophysical properties of MDM structures with the BST film

“…It becomes possible to control the level of dielectric nonlinearity and temperature properties of the film, as well as the figure of merit of the ferroelectric heterostructure based on BST, due to the variation in Ba/Sr concentration ratio, that specifies the temperature of the phase transition from ferroelectric to paraelectric phase and thus the operating temperature range. For example, the use of ferroelectric films of the compositions Ba 0.67 Sr 0.33 TiO 3 [10] and Ba 0.55 Sr 0.45 TiO 3 [11] in periodic multilayer structures opens up the possibility of creating capacitors with the prospect of their practical application in modern microelectronics. The study [12] shows that due to the variation of Ba 0.2 Sr 0.8 TiO 3 sublayer thickness and/or the amplitude of one period of the external bipolar field action it is possible to create various electrophysical states of the structure, and this can serve as basis for creating a memory cell, in particular, a multilevel one.…”