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Method for interlayer interfacial adhesion in ferroelectric polymer memory devices

IP.com Disclosure Number: IPCOM000127907D
Publication Date: 2005-Sep-14
Document File: 5 page(s) / 84K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for interlayer interfacial adhesion in ferroelectric polymer memory devices. Benefits include improved functionality, improved performance, improved reliability, and improved ease of implementation.

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Method for interlayer interfacial adhesion in ferroelectric polymer memory devices

Disclosed is a method for interlayer interfacial adhesion in ferroelectric polymer memory devices. Benefits include improved functionality, improved performance, improved reliability, and improved ease of implementation.

Background

              Conventionally, polymer memory devices can have adhesion failures at interlayer and interfacial junctions. Examples include ferroelectric film interfaces to metals, silicon oxide layers, and/or organic interlayer dielectric (ILD) or passivation materials. Unsuccessful approaches to resolve this problem include chemical modification of the metal, oxide, or organic surfaces, using various materials, such as silane adhesion promoters/coupling agents. The disadvantages of these approaches include:

•             Modification of the interface chemistry can impart deleterious changes to the ferroelectric properties.

•             Coupling agent can undergo adverse side reactions with increased temperature or in reaction to ambient moisture, oxygen, and/or light. These uncontrollable chemical reactions can lead to diffusion through the ferroelectric film.

•             Aqueous solution of some coupling agents are subject to prehydrolysis and self-condensation. The result can adversely affect the silane-layer thickness, orientation, and molecular organization in its bonding to the hydroxylated substrate surface. This type of self-condensation can lead to the formation of sizeable defects, which can reduce the yield of polymer memory devices per wafer.

•             Layers of different natures, such as metals, organics, and silicon oxides, require different adhesion promoters that can cause adverse chemical reactions with different promoters on various interfaces.

      Due to the high dissociation energy for C–F bonds (345 kJ) and the high electronegativity of fluorine atoms, the surface of fluoropolymers are typically considered to be inert and exhibit low interfacial adhesion with typical materials used for semiconductor device fabrication. 

      One conventional solution includes adhesion between untreated (not-activated) surfaces of polymer on metal, metal on low-temperature silicon oxide, and low-temperature silicon oxide on metal. The required success criterion, the value of the adhesion energy (Gc), for integration is a Gc value above 5 J/m2. The results of a 4-point bending test (J/m2) indicate all interfaces show poor adhesion energy with Gc values below 4 J/m2. The polymer-metal interface has the lowest adhesion energy, below 2.5 J/m2 (see Figure 1).

      Typical traces of a 4-point bend test indicate a plateau in the load-displacement curve that corresponds to a steady state of crack growth at the weak interface (see Figure 2).

      The Gc value is calculated (J/m2) using the plateau load, sample width, and sample thickness, according to equation 1, which includes the following values (see Figures 3...