Access Line Bending Reduction in Semiconductor Memory Devices
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Solution Overview
Problem
In semiconductor memory device fabrication, the increasing aspect ratios of trenches lead to access line bending, which decreases the performance of memory devices and becomes more challenging to prevent at critical dimensions less than or equal to 150 Å, causing damage to memory arrays.
Innovation Solution
The use of a dielectric nitride material, such as titanium nitride (TiN) or titanium silicon nitride (TiSiN), as scaffolding within the trenches, combined with a low resistivity metal material like ruthenium (Ru) or cobalt (Co), to support the access lines and reduce bending during semiconductor structure formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If trenches with high aspect ratios are used to form access lines, then memory device density is improved, but access line bending increases
Solution Approach 1:
A dielectric material is deposited into the trench before the access line metal is formed. This preliminary deposition of dielectric material provides structural support that prevents the access line from bending during subsequent processing steps, resolving the contradiction between achieving high density through narrow trenches and maintaining access line straightness
2Area of moving object
If the width of trenches is reduced to increase density, then memory device density is improved, but access line bending becomes more difficult to prevent
Solution Approach 1:
The dielectric material is deposited into the narrow trench before the access line is formed, providing preliminary structural support that prevents bending even in extremely narrow trenches (widths of 50 Å or less), enabling high density while maintaining manufacturing precision
Solution Approach 2:
The dielectric material acts as an intermediary substance between the trench walls and the access line metal, providing mechanical support and preventing direct contact that would cause bending in narrow trenches
3Reliability
If more metal material is used to fill trenches, then access line conductivity is improved, but manufacturing cost increases
Solution Approach 1:
The dielectric material serves as an intermediary that fills portions of the trench, allowing the access line metal to be formed only in necessary regions. This reduces the total quantity of expensive metal material required while maintaining adequate conductivity through optimized metal placement
Data Source
AI summary
An example apparatus includes a first source/drain region and a second source/drain region formed in a substrate. The first source/drain region and the second source/drain region are separated by the channel. The example apparatus further includes a gate separated from the channel by a dielectric material and an access line formed in a high aspect ratio trench connected to the gate. The access line includes a first titanium nitride (TiN) material formed in the trench, a metal material formed over the first TiN material, and a second TiN material formed over the metal material. The example apparatus further includes a sense line coupled to the first source/drain region and a storage node coupled to the second source/drain region.