3D Memory Pillar Stop Layer Protects Against Etching Damage
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Solution Overview
Problem
Three-dimensional memory devices with a vertical channel structure face challenges in process window and reliability due to etching damage during contact opening formation, which affects the charge storage and channel layers.
Innovation Solution
A memory device with a stacked structure, including a pillar and a first stop layer that covers the stacked structure and a portion of the pillar, along with a contact plug that penetrates through the stop layer to connect with the memory cells, enhancing the process window and reliability by protecting the charge storage and channel layers from etching damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact opening is formed in a vertical channel memory device, then electrical connection to memory cells is achieved, but etching damage occurs to the charge storage layer and channel layer
Solution Approach 1:
A stop layer is introduced as an intermediary protective layer between the contact opening etch process and the vulnerable charge storage layer/channel layer. This stop layer acts as a mediator that absorbs the harmful etching effects, preventing direct damage to the memory functional layers while still allowing electrical connection to be established through the contact plug.
Solution Approach 2:
The stop layer is formed in advance before the contact opening etch process. This preliminary protective layer is deposited over the stacked structure including the charge storage layer and channel layer, creating a protective barrier prior to the harmful etching operation, thereby preventing etching damage before it can occur.
2Manufacturing precision
If the contact opening is precisely aligned with the pillar, then manufacturing precision is improved, but the process window is reduced
Solution Approach 1:
The stop layer serves as a tolerant intermediary layer that decouples the precise alignment requirement. Since the stop layer is formed over the entire stacked structure, the contact opening can be formed with relaxed alignment tolerances while still achieving proper electrical connection through the contact plug to the pillar, thereby expanding the process window.
Solution Approach 2:
The introduction of the stop layer changes the structural parameters of the contact formation process. By adding this intermediate layer, the etch selectivity and depth control parameters are modified, allowing for a larger process window in terms of alignment tolerance and etch depth control while maintaining manufacturing precision.
Data Source
AI summary
Provided is a memory device, including a stacked structure, a pillar, a first stop layer, and a contact plug. The stacked structure includes a plurality of conductive layers. The pillar penetrates the plurality of series-connected memory cells. The plurality of series-connected memory cells are located in a layout pattern of pillar locations at cross-points between the pillar and the conductive layers. The first stop layer covers the stacked structure and a portion of a top surface of the pillar. The contact plug passes through the first stop layer, extending into the pillar, and is electrically connected to the plurality of series-connected memory cells. The contact is landed on the contact plug, and is electrically connected to a portion of the pillar through the contact plug.