Integrated Circuit Resistor With Deep Buried Layer
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Solution Overview
Problem
Integrated circuit resistors formed in conductive films surrounded by amorphous materials exhibit high noise and variability due to material mismatch between crystalline and amorphous or polycrystalline regions, leading to inconsistent performance and noise issues.
Innovation Solution
The integration of a deep buried layer of crystalline material with access wells of the same conductivity type, isolated by a region of opposite conductivity, reduces low-frequency noise by avoiding contact between crystalline and amorphous materials, ensuring crystal lattice continuity and improved linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is formed in a film surrounded by insulating regions made of amorphous material, then the resistor can be integrated into the circuit, but the noise is high and varies greatly from one resistor to another
Solution Approach 1:
The patent applies homogeneity by ensuring that the deep buried layer and the region of opposite conductivity both exhibit crystal lattice continuity, eliminating material mismatch between adjacent regions. This homogeneous crystalline structure throughout the resistor path prevents noise generation at interfaces and ensures consistent electrical properties across all resistors in the circuit.
Solution Approach 2:
The patent extracts the problematic amorphous insulating material from contact with the deep buried layer by introducing a region of opposite conductivity that acts as an intermediary. This removes the source of noise and variability by preventing direct contact between the crystalline deep buried layer and amorphous materials.
2Quantity of substance
If the deep buried layer is heavily doped, then the resistance is reduced, but the linearity deteriorates
Solution Approach 1:
The patent applies local quality by creating different doping concentrations in different regions: the deep buried layer is lightly doped to maintain linearity, while the region of opposite conductivity is also lightly doped to enhance depletion on its side. This localized differentiation of doping levels optimizes both resistance and linearity performance in their respective regions.
Solution Approach 2:
The patent changes the doping parameter from heavy to light doping in the deep buried layer, and further optimizes by implementing asymmetric light doping where the region of opposite conductivity has slightly higher doping than the deep buried layer. This parameter optimization achieves the desired balance between resistance and linearity.
3Quantity of substance
If the region of opposite conductivity is heavily doped, then the depletion is reduced on that side, but the linearity of the resistor deteriorates
Solution Approach 1:
The patent applies local quality by implementing asymmetric light doping where the region of opposite conductivity has a slightly higher doping concentration than the deep buried layer. This localized differentiation creates the desired depletion distribution with greater depletion on the region of opposite conductivity side, optimizing linearity while maintaining adequate resistance.
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 configuration significantly reduces low-frequency noise by over 1000 times, enhances reproducibility, and maintains high resistance, allowing for well-matched resistors with improved linearity and reduced fabrication dispersions.
Implementation Method 1
The material of the deep buried layer and the material of the region of opposite conductivity exhibit crystal lattice continuity. The low-frequency noise is greatly reduced.
Data Source
AI summary
An integrated circuit includes a substrate and a resistor. The resistor is formed from at least two access wells of a first conductivity type and a deep buried layer electrically connecting the wells. The deep buried layer is at least partly covered by a region of opposite conductivity.