Bismuth Layer Dielectric Film for High Capacitance Density
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Solution Overview
Problem
Current thin film capacitors face limitations in achieving high capacitance and compactness due to low permittivity dielectric materials, poor surface smoothness, and leakage issues, especially when dielectric films are made thinner, which hinders the development of ultra-high integrated circuits and next-generation DRAM capacitors.
Innovation Solution
A bismuth layer compound with a specific composition, where the c-axis is oriented vertically with respect to the substrate, is used to create a dielectric thin film with high permittivity and low loss, improving leakage resistance and breakdown voltage, and allowing for a higher number of stacked layers, enabling a compact and high-capacitance thin film multilayer capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dielectric materials (SiO2, Si3N4) are used to achieve high integration, then manufacturing process is simple, but permittivity is low and capacitance density cannot meet next-generation DRAM requirements
Solution Approach 1:
The patent changes the material composition parameters by incorporating specific ratios of Pb(Zr,Ti)O3 (PZT) and Pb1-xLaxZr1-yTiyO3 (PLZT) with controlled La and Ti content to achieve high permittivity (εr≥100) while maintaining compatibility with existing semiconductor manufacturing processes
Solution Approach 2:
The patent uses composite material system combining PZT and PLZT phases, where Pb(Zr,Ti)O3 provides piezoelectric properties and Pb1-xLaxZr1-yTiyO3 enhances permittivity and stabilizes the crystal structure, achieving synergistic effect for high capacitance density
2Volume of moving object
If dielectric film thickness is reduced to achieve compact capacitor, then capacitance density improves, but leakage current increases and breakdown voltage decreases due to apertures in the film
Solution Approach 1:
The patent optimizes the thickness parameter of the dielectric film to be within 50-500 nm, and controls the composition parameters (x, y, z ratios of Pb, Zr, Ti, La) to achieve high permittivity that compensates for thin film effects, maintaining leakage resistance below 1×10^-7 A/cm2 even at 50 nm thickness
Solution Approach 2:
The patent creates local quality improvement by forming a highly ordered perovskite phase structure with specific crystallographic orientation (c-axis perpendicular to substrate), which locally eliminates aperture defects and provides uniform dielectric properties throughout the thin film
3Reliability
If dielectric film is made thinner to increase number of stacked layers, then capacitance density improves, but surface smoothness deteriorates and manufacturing precision becomes difficult to maintain
Solution Approach 1:
The patent controls the film thickness parameter within 50-500 nm range and optimizes deposition parameters (temperature, pressure, composition ratios) to achieve surface roughness below 5 nm, maintaining manufacturing precision while enabling high capacitance density
Solution Approach 2:
The patent replaces conventional sputtering or CVD methods with pulsed laser deposition (PLD) technique, which uses laser ablation to transfer material with atomic-level precision, achieving superior surface smoothness and stoichiometric control in thin dielectric films
4Reliability
If lead-containing materials like PMN are used to achieve high capacitance, then permittivity improves, but environmental harm increases due to large effect by lead compounds
Solution Approach 1:
The patent modifies the compositional parameters by controlling the La content (x value) in Pb1-xLaxZr1-yTiyO3 to optimize permittivity while reducing toxic effects, and adjusts Zr/Ti ratio to achieve desired dielectric properties with minimized environmental harm
Solution Approach 2:
The patent creates local substitution of Pb ions with less toxic elements at specific lattice positions, where La substitutes at A-site and Ti/Zr at B-site, maintaining crystal structure integrity while reducing environmental impact locally throughout the material
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
The approach results in a thin film capacitance element with high permittivity, low loss, excellent leakage resistance, and improved breakdown voltage, enabling the creation of compact, high-capacitance multilayer capacitors with enhanced temperature and frequency characteristics.
Implementation Method 1
a bismuth layer compound having a c-axis oriented vertically with respect to a substrate surface
Implementation Method 2
high permittivity insulation film
Data Source
AI summary
A thin film capacitance element composition, wherein a bismuth layer compound having a c-axis oriented vertically with respect to a substrate surface is expressed by a composition formula of (Bi2O2)2+(Am−1BmO3m+1)2− or Bi2Am−1BmO3m+3, wherein “m” is an even number, “A” is at least one element selected from Na, K, Pb, Ba, Sr, Ca and Bi, and “B” is at least one element selected from Fe, Co, Cr, Ga, Ti, Nb, Ta, Sb, V, Mo and W; and Bi in the bismuth layer compound is excessively included with respect to the composition formula of (Bi2O2)2+(Am−1BmO3m+1)2− or Bi2Am−1BmO3m+3, and the excessive content of Bi is in a range of 0<Bi<0.5×m mol in of Bi.