Bismuth-zinc-niobate embedded capacitors grown at room temperature for printed circuit board applications

Abstract

We fabricated metal-insulator-metal (MIM) thin film capacitors with Bi1.5Zn1.0Nb1.5O7 (BZN) dielectric films. The BZN films were deposited at room temperatures by pulsed laser deposition and annealed below 200°C which is compatible with the used polymer-based substrates. The dielectric constant of BZN films increases from 2 to 70, when they are annealed at 150°C, but still in amorphous phase. We found that a considerable portion of Bi metallic phase still remains in the as-deposited film. They turn into oxides upon annealing at >120°C, causing the dramatic change of the dielectric properties. Amorphous BZN thin films exhibit superior dielectric characteristics, capacitance density of 150nF∕cm2, and leakage current less than 1μA∕cm2 at 5V. The MIM capacitors using amorphous BZN thin films will be a promising candidate for the PCB-embedded capacitors.

Structural and dielectric properties of Bi2Zn2/3Nb4/3O7 thin films prepared by pulsed laser deposition at low temperature for embedded capacitor applications

“…The high energy particle collisions during deposition in PLD process probably produce the small grains (typically in a nanometer scale) and highly disordered amorphous phase in the films, which have also been identified by the analysis of TEM in the Bi-based pyrochlore films fabricated at low temperature [3]. In general, amorphous paraelectric (such as Ta 2 O 5 , Al 2 O 3 and SiO 2 ) thin films fabricated at low temperature usually exhibit low dielectric constants (<25) [2]. However, in the Bi-based thin films, such as Bi 1.5 Zn 1.0 Nb 1.5 O 7 , Bi 2 Zn 2/3 Nb 4/3 O 7, Bi 2 Mg 2/3 Nb 4/3 O 7, if some nanosized crystallites are present in thin films, these films exhibit high dielectric constants [2][3][4]12].…”

“…However, ferroelectric thin films deposited at or near room temperature exhibit very low dielectric constants and high dielectric losses [5,6]. Moreover, the conventional paraelectric oxides such as SiO 2 (∼3.9), Ta 2 O 5 (∼25) and Al 2 O 3 (∼9) can be fabricated at low temperature but they have very low dielectric constants [1][2][3]. Bi 2 Zn 2/3 Nb 4/3 O 7 is one of the candidate materials, which is feasible for PCB applications.…”

“…In integrated circuit packages, the polymer substrates cannot sustain the temperature of more than 200 • C, which limits the thermal process of capacitor materials [2]. Ferroelectric thin films have been investigated for such applications [2,3,5,6]. But ferroelectric materials with high dielectric constants can only be obtained for the crystallite phase, which usually requires a high temperature (>550 • C).…”

“…Embedding thin-film capacitors with high permittivity dielectrics into printed circuit boards (PCBs) is one of the methods to approach these goals [2][3][4]. In integrated circuit packages, the polymer substrates cannot sustain the temperature of more than 200 • C, which limits the thermal process of capacitor materials [2].…”

Effect of Ag on the sintering and dielectric properties behavior of Bi1.5ZnNb1.5O7 ceramics

“…Cubic bismuth zinc niobate (Bi 1.5 ZnNb 1.5 O 7 ) pyrochlore ceramics exhibit high permittivity ∼170, relatively low dielectric loss ∼10 −4 , compositionally adjustable temperature coefficients of capacitance (TCC), and the lower firing temperature ∼1000 • C. These properties make this compound a potential candidate for integrated microwave resonators and decoupling capacitors [1][2][3][4][5][6][7]. However, for microwave application of electronic equipment, further enhancing the permittivity and reducing the dielectric loss are still the topics of research.…”