Ferroelectric parallel-plate capacitors with copper electrodes for high-frequency applications

Abstract

Sr 1−x TiO 3 / Cu parallel-plate structure have been fabricated using a layer transfer method. The use of a Cu bottom electrode results in a giant electrode Q-factor ϫ capacitor area product of Q elec A = 3.79ϫ 10 5 m 2 at 1 GHz. The dielectric constant at room temperature is 420 and the tunability amounts to 73% near a breakdown voltage of 35 V. The major advantages of the layer transfer method include low electrode losses, the freedom to select an auxiliary substrate and seed layer for ferroelectric film growth irrespective of their high-frequency properties, and the possibility to utilize a large variety of device substrates as they no longer act as template for film growth.

Growth and high frequency characterization of Mn doped sol-gel PbxSr1−xTiO3 for frequency agile applications

“…For this particular test structure, the platinum bottom electrode having a thickness of only 100 nm dominates the total resistance of the electrodes and would be the main factor limiting the Q of a potential PST varactor. However, a way to overcome this which has been recently demonstrated 25 is to transfer bond the fabricated device onto a separate substrate which would enable the bottom electrode to be thickened up. The total inductance, L EL = L TE + L BE , can be approximately extracted from the measured selfresonance of the MIM capacitor's phase and was found to be approximately 0.02 nH.…”

Influence of Substrate Bias on the Structural and Dielectric Properties of Magnetron-Sputtered BaxSr1-xTiO3Thin Films

“…High quality polycrystalline BST capacitors have been grown by magnetron sputtering 5,6 , chemical vapor deposition 7,8 , sol gel 4,9 , pulsed laser deposition 10,11 and other methods and the dependence of the dielectric properties on deposition temperature, growth rate, process pressure, composition, and film thickness has been reported 5,6,8,12,13 . The properties of BST thin films are usually inferior to their bulk analogs due to grain size effects, charged defects, the formation of interface layers, and the build-up of lattice strain.…”

“…As an alternative, a layer transfer method for the fabrication of parallel-plate capacitors was recently demonstrated allowing the use of highly conductive electrodes of Ag and Cu. 4 Besides the choice of bottom electrode material, the deposition method and growth parameters also greatly influence the microstructure and dielectric properties of BST films.…”

Transfer of Functional Ceramic Thin Films Using a Thermal Release Process

“…Transfer of PZT thin films can allow integration of such films on substrates that are incompatible with the requirements of film deposition. However, transfer of functional ceramic thin films has long been hampered by the difficulty of detaching the film from the growth substrate 13, 14. Here, we describe a transfer process for PZT films grown on Ti/Pt coated Si wafers, where the films are solder bonded onto a target substrate and lifted off in one step, using separation of the PZT–Pt interface by thermal stress.…”

“…Therefore, the transfer of these films onto target substrates is important to enable them to be used in integrated structures that are not compatible with these materials or process steps, such as organic substrates. Several techniques have been reported for transfer of PZT films to make devices, involving wet etching,17 dry etching,18 mechanical grinding and etching,13 or laser induced forward transfer (LIFT) 14. Wet etching can be used to pattern PZT films, but is not practical for the etching of some metal seed layers, such as Pt, which is normally removed by dry etching.…”