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Chemical solution deposition has been used to fabricate continuous ultrathin lead lanthanum zirconate titanate (PLZT) films as thin as 20 nm. Further, multilayer capacitor structures with as many as 10 dielectric layers have been fabricated from these ultrathin PLZT films by alternating spin-coated dielectric layers with sputtered platinum electrodes. Integrating a photolithographically defined wet etch step to the fabrication process enabled the production of functional multilayer stacks with capacitance values exceeding 600 nF. Such ultrathin multilayer capacitors offer tremendous advantages for further miniaturization of integrated passive components.

I. INTRODUCTION

As shown in Eq. (1), the capacitance of a simple parallel plate structure (Cp) varies linearly with dielectric constant, K, and active electrode area, A, but inversely with dielectric thickness, t, Cp =

KA⑀0 , t

(1)

where ⑀0 represents the permittivity of free space (8.854 × 10−12 F/m). Present capacitor technologies maximize two of the variable parameters at the expense of the third. For example, both wound polymer and electrolytic capacitors achieve very large effective areas with thin dielectric layers, but use dielectric materials with K values between 3 and 30; similarly, thin films of ∼200 to 500 nm are routinely fabricated from ferroelectric materials having K values >1000, but the effective areas of these capacitors are typically limited to hundreds of square micrometers. By demonstrating multilayer capacitor structures with ultrathin dielectric layers based on high-K ferroelectric materials, this work represents a fabrication scheme that capitalizes on advances in all three basic capacitor parameters. Multilayer structures have been the hallmark of the ceramic capacitor industry for more than two decades, and the layer thicknesses that are achievable using tapecasting techniques continue to shrink.1 Eventually, the use of powder-based approaches to produce capacitors with thinner and thinner layers will no longer be feasible. Chemical solution deposition (CSD) has recently been shown effective for the fabrication of ultrathin singlea)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0010 176 http://journals.cambridge.org

layer capacitors, having active layers of high-dielectric constant (K) materials as thin as 50 nm.2 While there have been a few reports on the fabrication of multilayer capacitors using chemical vapor deposition,3–6 the literature available on the fabrication of multilayer ceramic capacitors by solution deposition is more limited.7,8 Capacitors based on ferroelectric thin films—whether deposited from the vapor phase or from solution—are generally limited in their active areas because of relatively poor yields traditionally achieved with large active electrode areas. However, using recently reported advances in solution deposition,2 we have been able to fabricate capacitors in multilayer structures that have active electrode dimensions nearly five orders of magnitude greater