Ir-Ti Alloy Bottom Electrode for Ferroelectric Memory
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Solution Overview
Problem
The challenge in manufacturing high-density ferroelectric random access memory (FRAM) with smaller cell sizes is the insufficient space for forming layers in the trench, leading to poor film quality, increased leakage current, and higher power consumption, as well as the high cost and rough surface of conventional Ir bottom electrodes.
Innovation Solution
A ferroelectric capacitor structure with a bottom electrode comprising an alloy of Ir and Ti (or Ru and Ti), which reduces the number of layers, enhances adhesion, and acts as an oxidation barrier, allowing for higher density memory cells with improved film quality and reduced material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional Ir bottom electrode with multiple layers (Ti adhesion layer, Ir bottom electrode, PTO seed layer) is used, then adhesion to trench sidewalls is achieved, but the number of layers increases and material cost increases
Solution Approach 1:
The patent combines the adhesion layer and bottom electrode into a single alloy layer. The Ir-Ti alloy layer simultaneously provides adhesion to the trench sidewalls and functions as the bottom electrode, eliminating the need for separate Ti adhesion layer and Ir bottom electrode layers.
Solution Approach 2:
The Ir-Ti alloy layer performs multiple functions: it provides adhesion to the trench sidewalls, serves as the bottom electrode, and prevents oxygen diffusion. This multi-functional layer replaces the conventional multi-layer structure, reducing overall device complexity.
2Ease of manufacture
If conventional Ir bottom electrode with multiple layers (Ti adhesion layer, Ir bottom electrode, PTO seed layer) is used, then adhesion to trench sidewalls is achieved, but material cost increases
Solution Approach 1:
The patent combines the adhesion layer and bottom electrode into a single alloy layer. The Ir-Ti alloy layer simultaneously provides adhesion to the trench sidewalls and functions as the bottom electrode, eliminating the need for separate Ti adhesion layer and Ir bottom electrode layers.
Solution Approach 2:
The patent uses an Ir-Ti alloy composite material that combines the advantages of both Ir (high conductivity, oxidation resistance) and Ti (low cost, good adhesion). This composite material reduces material cost while maintaining adhesion performance.
3Productivity
If PZT ferroelectric layer is formed at small thickness to fit in smaller trench, then device density increases, but leakage current increases and film quality deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the bottom electrode by using an Ir-Ti alloy instead of pure Ir. This parameter change improves the interface quality with the PZT ferroelectric layer, reducing leakage current and enabling better film quality even at reduced thicknesses for higher density devices.
4Productivity
If PZT ferroelectric layer is formed at small thickness to fit in smaller trench, then device density increases, but film quality deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the bottom electrode by using an Ir-Ti alloy instead of pure Ir. This parameter change improves the interface quality with the PZT ferroelectric layer, reducing leakage current and enabling better film quality even at reduced thicknesses for higher density devices.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the fabrication of high-density FRAM with reduced leakage current, improved retention of stored information, and lower material costs by using an Ir-Ti alloy as the bottom electrode, which provides better adhesion, smoother surfaces, and stable ferroelectric properties.
Implementation Method 1
The Ti adhesion layer 105 is conventionally used because the Ir bottom electrode 102 would not otherwise adhere well to the sidewalls of the trench 111
Implementation Method 2
A TiAlN oxidation barrier 103 is disposed within a trench 111
Implementation Method 3
The ferroelectric layer is made of a ferroelectric material that exhibits spontaneous electric polarization that can be maintained in the absence of power and that can be reversed in direction by the application of an appropriate electric field
Implementation Method 4
forming a first electrode comprising a compound, the compound including a first metallic element and a second metallic element
Data Source
AI summary
A ferroelectric capacitor comprises a first electrode comprising an alloy containing a first element and a second element of the periodic table of the elements, the first element being selected from the group consisting of Ir and Ru. A ferroelectric layer is disposed on the first electrode, wherein the ferroelectric layer comprises a ferroelectric material containing the second element. A second electrode is disposed on the ferroelectric layer. The ferroelectric capacitor can be provided as part of a memory cell of a ferroelectric memory.