Floating Body DRAM Structure for Charge Storage
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Solution Overview
Problem
Conventional DRAM devices face challenges in miniaturization due to the large size of capacitors, and existing capacitorless DRAM structures require further reduction in size or innovative manufacturing methods.
Innovation Solution
A memory structure with a floating body and trench-type gate structure is developed, where multiple floating bodies and source/drain regions are formed on a substrate with isolation structures, allowing for a compact design and easy fabrication, utilizing dopants and semiconductor material layers to create junctions and charge storage regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional capacitor is used in DRAM, then charge storage capacity is sufficient, but device size becomes large
Solution Approach 1:
The patent transitions from a planar capacitor structure to a three-dimensional floating body structure extending vertically from the substrate surface. The floating body rises above the substrate plane, utilizing the vertical dimension to increase charge storage volume without proportionally increasing the horizontal footprint, thereby achieving higher charge capacity in a compact area.
Solution Approach 2:
The floating body is formed within and extends from the substrate, with source and drain regions nested within the floating body structure. The gate structure is positioned adjacent to and alongside the floating body, creating a nested configuration where multiple functional elements occupy overlapping spatial volumes, maximizing space utilization.
2Area of stationary object
If capacitorless DRAM with floating body is used, then device size is reduced, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is divided into distinct sequential stages: substrate preparation with isolation structures, formation of source/drain regions, creation of the floating body through doping, trench formation for the gate, and final gate structure fabrication. Each stage produces a discrete structural element that is subsequently integrated, breaking down the complex manufacturing into manageable, standardized steps.
3Quantity of substance
If floating body extends vertically, then charge storage capacity increases, but manufacturing precision requirements increase
Solution Approach 1:
Isolation structures are formed on the substrate before the floating body is created. These pre-formed isolation structures define the boundaries and provide reference planes that guide subsequent floating body formation processes, ensuring consistent vertical extension and positioning without requiring high-precision direct patterning of the floating body itself.
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 proposed memory structure achieves a smaller size and easier manufacturing process, enabling efficient charge storage with potential differences between word and bit lines, storing sufficient charges (2-5 fF) without increasing the horizontal area, facilitating miniaturization in electronic devices.
Implementation Method 1
A first type dopant is incorporated into the substrate in the active area to form a first source/drain region. A second type dopant is incorporated into the substrate above the first source/drain region to form a first floating body.
Data Source
AI summary
A memory structure having a floating body is provided, which includes a substrate including an active area and an isolation structure surrounding the active area, a first source/drain region in the substrate in the active area, a first floating body in the substrate above the first source/drain region, a second floating body on the first floating body, a second source/drain region on the second floating body, and a trench-type gate structure in the substrate and beside the first floating body. A method of fabricating a memory structure having a floating body is also provided.