Stepped Bit Line Structure to Reduce Memory Parasitic Capacitance
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in optimizing the structure of bit lines and contacts to enhance electrical performance and reduce parasitic capacitance, which affects the overall efficiency and reliability of data storage.
Innovation Solution
The semiconductor memory device is designed with a bit line structure that includes a first portion vertically overlapped with the source/drain region and a second portion vertically overlapped with the insulating layer, where the lowermost level of the first portion is lower than the second portion, and a contact structure that maintains a larger width for the first portion to reduce etching impacts and increase spacing between adjacent bit lines, thereby minimizing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bit line structure is designed with a first portion vertically overlapped with the source/drain region and a second portion vertically overlapped with the insulating layer, then parasitic capacitance is reduced, but manufacturing complexity increases
Solution Approach 1:
The bit line is divided into two distinct portions: a first portion vertically overlapped with the source/drain region and a second portion vertically overlapped with the insulating layer. This segmentation allows each portion to serve different functional purposes, reducing parasitic capacitance while maintaining electrical performance.
Solution Approach 2:
The bit line structure transitions from a conventional planar configuration to a three-dimensional structure with vertical overlap differences. The first portion extends lower than the second portion, creating a stepped configuration that reduces capacitance between the bit line and source/drain regions while maintaining connectivity.
2Ease of manufacture
If the first portion of the bit line has a larger width, then etching impacts are reduced, but device area increases
Solution Approach 1:
The bit line structure implements local quality variations where the first portion has a larger width for etching resistance and the second portion has a smaller width for area efficiency. This localized differentiation optimizes both manufacturing ease and space utilization by assigning different dimensional characteristics to different functional regions.
Data Source
AI summary
A semiconductor memory device including a substrate including an active pattern that includes a first source/drain region and a second source/drain region; an insulating layer on the substrate; a line structure on the insulating layer and extending in a first direction to cross the active pattern, the line structure penetrating the insulating layer on the first source/drain region and including a bit line electrically connected to the first source/drain region; and a contact spaced apart from the line structure and electrically connected to the second source/drain region, wherein the bit line includes a first portion vertically overlapped with the first source/drain region; and a second portion vertically overlapped with the insulating layer, and wherein a lowermost level of a top surface of the first portion of the bit line is at a level lower than a lowermost level of a top surface of the second portion of the bit line.