3D Memory Word Line Contacts Without Stair-Step Defects
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in forming stair-like structures during the manufacturing process, which can lead to inefficiencies and potential defects in the contact regions, affecting the reliability and performance of the devices.
Innovation Solution
The formation of a three-dimensional memory device involves creating an alternating stack of insulating and conductive layers, with memory openings and contact via assemblies that include a contact via structure and an insulating spacer, and through a series of etching and deposition processes to create a stairless word line contact structure, ensuring smooth transitions and reliable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional contact via structures are formed through the alternating stack, then electrical connections to word lines are established, but stepped surfaces (stair-like structures) are created that lead to manufacturing defects and reduced reliability
Solution Approach 1:
The patent applies preliminary action by forming insulating spacers around the contact via structures before completing the contact formation process. This preliminary spacer formation prevents the formation of stepped surfaces during subsequent manufacturing steps, eliminating the root cause of manufacturing defects while maintaining reliable electrical connections to the word lines.
Solution Approach 2:
The insulating spacer acts as an intermediary element between the contact via structure and the surrounding alternating stack. This intermediary structure prevents direct contact between conductive layers at different levels, eliminating the formation of harmful stepped surfaces while maintaining the necessary electrical connectivity through the contact via structures.
2Reliability
If contact via structures extend through multiple electrically conductive layers, then electrical connectivity is improved, but the formation of stepped surfaces increases manufacturing complexity and defect risk
Solution Approach 1:
The insulating spacers are formed in advance around the contact via structures that extend through multiple electrically conductive layers. This preliminary action maintains the necessary electrical connectivity while preventing the formation of complex stepped surfaces, thereby reducing manufacturing complexity and defect risk without compromising connectivity.
Solution Approach 2:
The insulating spacers serve as intermediary structures that manage the interaction between contact via structures extending through multiple conductive layers. These spacers simplify the overall structure by preventing the formation of stepped surfaces, thereby reducing device complexity while maintaining the required electrical connectivity through the contact vias.
3Ease of manufacture
If stair-like structures are formed during manufacturing, then contact regions are created, but manufacturing defects increase and device performance decreases
Solution Approach 1:
The insulating spacers act as intermediary structures that enable contact region formation without creating harmful stair-like structures. By introducing these spacers, the manufacturing process can proceed more easily while simultaneously improving the quality of the contact structures, as the spacers prevent the formation of stepped surfaces that lead to defects.
Solution Approach 2:
The patent applies the taking out principle by removing the harmful stepped surfaces from the contact region structure through the use of insulating spacers. This extraction of the problematic feature (stepped surfaces) allows for easier manufacturing while maintaining high contact structure quality, as the spacers prevent the formation of defects during the contact formation process.
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
This method results in a stairless word line contact structure that enhances the reliability and performance of three-dimensional memory devices by eliminating stepped surfaces, improving electrical connectivity and reducing manufacturing defects.
Implementation Method 1
forming an insulating spacer at a peripheral portion of each of the via cavities by conformally depositing an insulating material
Implementation Method 2
performing an anisotropic etch process that etches the insulating material
Implementation Method 3
isotropically recessing proximal portions of the electrically conductive layers around each of the via cavities
Data Source
AI summary
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers, memory openings located in a memory array region and vertically extending through the alternating stack, memory opening fill structures located in the memory openings, and laterally-isolated contact via assemblies located in a contact region that is located adjacent to the memory array region. Each of the laterally-isolated contact via assemblies includes a contact via structure contacting a top surface of a respective one of the electrically conductive layers and a dielectric spacer laterally surrounding the contact via structure. Each contact via structure other than a contact via structure contacting a topmost one of the electrically conductive layers extends through and is laterally surrounded by each electrically conductive layer that overlies the respective electrically conductive layer.