Buried Word Line DRAM Layout for Misalignment Margin
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Solution Overview
Problem
As DRAM components shrink, misalignment during the formation of buried word lines can cause short circuits and junction leakage due to reduced process margins during manufacturing.
Innovation Solution
A method involving the formation of a first hard mask on the sidewalls of openings before forming isolation trenches, which protects active regions from damage during subsequent etching processes, ensuring correct alignment and preventing short circuits by maintaining a process margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If component size is shrunk to increase integration, then high integration is achieved, but process margin becomes smaller and misalignment causes short circuits
Solution Approach 1:
The first hard mask is formed on the sidewalls of openings before the isolation trenches are etched. This preliminary protective layer is deposited conformally to protect the active regions from potential misalignment damage during subsequent etching processes, allowing high integration without sacrificing process margin
Solution Approach 2:
The first hard mask acts as an intermediary protective layer between the active regions and the etching process. This intermediate layer prevents direct contact between the etchant and the active region sidewalls, eliminating the harmful effect of misalignment-induced damage while maintaining the benefits of component shrinkage
2Ease of manufacture
If misalignment occurs during buried word line trench formation, then manufacturing simplicity is maintained, but short circuit between buried word line and active region occurs
Solution Approach 1:
The first hard mask is deposited beforehand on the sidewalls of the openings that will become active regions. This cushioning layer is in place before the buried word line trench etching begins, providing a protective buffer that absorbs the impact of potential misalignment and prevents the etchant from damaging the active region, thereby preventing short circuits and junction leakage
Solution Approach 2:
The first hard mask provides preliminary anti-action against the harmful etching process. By being deposited before the trench formation, it preemptively counteracts the potential harmful effect of misalignment, creating a protective barrier that neutralizes the risk of short circuits between the buried word line and active region
Data Source
AI summary
Provided is a DRAM including: a substrate, a plurality of chop structures, and a plurality of buried word lines. The plurality of chop structures are located in the substrate. Each of the plurality of chop structures comprises a first portion and a second portion. The first portion is located above the second portion, and a width of the second portion is less than a width of the first portion. The plurality of buried word lines, located at bottoms of a plurality of buried word line trenches. The plurality of buried word line trenches passes through the first portion of the plurality of chop structures and the substrate.