MISTD Memory Cell Layout for Low-Power Charge Retention
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Solution Overview
Problem
The semiconductor industry faces challenges in forming reliable semiconductor devices at increasingly smaller sizes due to the complexity and difficulty of fabrication processes as feature sizes decrease, affecting production efficiency and cost.
Innovation Solution
The implementation of a metal-insulator-semiconductor tunnel diode (MISTD) structure with a specific configuration of transistors, diodes, and electrodes, including a metal-insulator-semiconductor tunnel diode structure with an inner circular electrode and an outer ring electrode, which utilizes a thin insulator layer to enable efficient memory operations and improve retention time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are decreased to increase functional density, then production efficiency and cost are improved, but fabrication process complexity and difficulty increase
Solution Approach 1:
The memory device is divided into distinct functional regions including a first region with a first transistor and first capacitor, and a second region with a second transistor and second capacitor. This segmentation allows each region to be optimized independently while maintaining overall device functionality, thereby managing fabrication complexity at smaller feature sizes.
Solution Approach 2:
The patent introduces a vertical dimension by stacking capacitors and transistors in three-dimensional arrangements. The first and second capacitors are positioned at different vertical levels with corresponding bit lines extending to different heights, enabling increased functional density without proportionally increasing planar fabrication complexity.
2Area of stationary object
If feature sizes are decreased to increase functional density, then chip area utilization is improved, but manufacturing reliability deteriorates
Solution Approach 1:
Different regions of the memory device are designed with locally optimized characteristics. The first region contains a first transistor with specific doping concentrations and channel dimensions, while the second region contains a second transistor with different parameters. This local quality approach allows each region to be tailored for optimal performance and reliability within the constrained chip area.
Solution Approach 2:
The patent employs composite material structures including stacked dielectric layers with different permittivities, doped semiconductor regions with varying conductivity types, and metal interconnects with different cross-sectional areas. These composite structures enable reliable operation at reduced feature sizes by distributing electrical stress and improving device robustness.
3Productivity
If functional density is increased by reducing feature sizes, then the number of interconnected devices per chip area increases, but fabrication process difficulty increases
Solution Approach 1:
The memory device implements a nested structure where capacitors are positioned within or adjacent to transistor regions, and bit lines are stacked at different vertical levels. The first bit line and second bit line are arranged in a nested configuration with different heights, allowing multiple interconnections to occupy overlapping spatial volumes, thereby increasing functional density without proportionally increasing fabrication steps.
Solution Approach 2:
The patent incorporates adjustable device parameters such as variable doping concentrations,可调 channel widths, and flexible dielectric thicknesses that can be optimized during fabrication. This dynamic design approach allows the device to maintain high functional density while accommodating variations in manufacturing processes and material properties.
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 allows for reliable memory operations with low power consumption and extended retention time, overcoming the challenges of smaller feature sizes by leveraging Schottky barrier modulation and deep depletion effects.
Implementation Method 1
leveraging Schottky barrier modulation and deep depletion effects
Implementation Method 2
metal-insulator-semiconductor tunnel diode structure with an inner circular electrode and an outer ring electrode, which utilizes a thin insulator layer to enable efficient memory operations
Implementation Method 3
leveraging Schottky barrier modulation and deep depletion effects
Data Source
AI summary
A method includes forming a first dielectric layer over the substrate and covering first, second, third, fourth, fifth and sixth protrusion regions; forming first, second, and third gate conductors over the first, fourth, and fifth protrusion regions, respectively; performing a first implantation process to form a second source region and a second drain region in the fourth protrusion region; performing a second implantation process to form a first source region and a first drain region in the first protrusion region, and to form a third source region and a third drain region in the fifth protrusion region; forming a metal layer over the third protrusion region; patterning the metal layer to form an inner circular electrode and an outer ring electrode encircling the inner circular electrode; forming a word line; and forming a bit line.