Self-Aligned Trench Isolation for DRAM Density
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Solution Overview
Problem
Current DRAM fabrication technologies face challenges in achieving higher device density and integration due to limitations in transistor miniaturization and isolation structure design, which hinder further miniaturization and performance enhancement.
Innovation Solution
A self-aligned trench isolation structure is implemented in the dynamic random access memory unit, with a substrate featuring pillar-shaped active bodies and trenched gates, where the self-aligned trench isolation structure is formed in the bottom portion of the trench, allowing for increased electrical insulation and defined width, enabling higher device density without being limited by lithography process tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional isolation structures are used in DRAM fabrication, then manufacturing process is simpler, but device density cannot be increased further
Solution Approach 1:
The patent transitions from planar isolation structures to three-dimensional self-aligned trench isolation structures. The isolation structure extends vertically into the substrate with self-aligned sidewalls, utilizing the vertical dimension to achieve higher device density without proportionally increasing lateral footprint or process complexity
Solution Approach 2:
The self-aligned trench isolation structure forms its own boundaries through the etching process, where the trench sidewalls are defined by the substrate surface topology rather than requiring separate alignment steps. This self-alignment mechanism eliminates the need for additional photolithography alignment processes, maintaining manufacturing simplicity while achieving higher density
2Quantity of substance
If transistor size is reduced to increase density, then device integration increases, but manufacturing precision requirements exceed current lithography capabilities
Solution Approach 1:
The self-aligned trench isolation structure uses the substrate surface and previously formed features as self-defined boundaries for trench formation. The etching process automatically aligns the trench to the active region edges without requiring external alignment marks or additional photolithography steps, thereby achieving high precision beyond current lithography limits
Solution Approach 2:
The isolation structure is formed preliminarily during the early stages of device fabrication, establishing precise geometric boundaries before subsequent processing steps. This preliminary self-aligned structure serves as a template that guides subsequent trench gate and contact formation, ensuring consistent alignment throughout the fabrication sequence
Data Source
AI summary
A dynamic random access memory unit includes a substrate having a trench disposed therein, a self-aligned trench isolation structure formed in the bottom portion of the trench, and a first trenched gate formed in the bottom portion of the trench and above the self-aligned trench isolation structure. The substrate includes at least one pillar-shaped active body having a drain region, a body region atop the drain region, and a source region atop the body region. The first trenched gate includes a first spacer formed on the side-wall in the bottom portion of the trench to selectively cover and surround the portion of the side-wall in the trench that comprises the drain region, such for defining the width of the self-aligned trench isolation structure.