L-Shaped Stepped Word Line Layout for 3D NAND Contact Isolation
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Solution Overview
Problem
Three-dimensional NAND memory technology faces increasing integration difficulties, particularly in the word line connection process, where a high selection ratio is required to prevent short circuits as the number of layers increases, and current etching technologies fail to meet these requirements.
Innovation Solution
An L-shaped stepped word line structure is introduced, featuring L-shaped word line units with a stepped stacked layer structure, where the surface metal layer is longer than the internal metal layer, allowing for a connection hole to be positioned safely without causing short circuits, even at low etching selection ratios, by ensuring an insulating layer is present below the metal layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of layers in three-dimensional memory is increased to improve storage capacity, then the integration density is improved, but the etching selection ratio requirement increases making the word line connection process more difficult
Solution Approach 1:
The patent transitions from a planar word line structure to a three-dimensional stepped structure with surface and internal metal layers at different heights. This dimensional change allows the connection hole to be positioned on the surface metal layer while the insulating layer remains at the bottom, providing short circuit prevention without requiring high etching selection ratio
Solution Approach 2:
The word line terminal is segmented into multiple stacked layers including surface metal layers and internal metal layers separated by insulating layers. This segmentation creates a stepped structure where each layer serves a specific function: surface layers for connection and internal layers for structural support, with insulating layers preventing short circuits
2Ease of manufacture
If conventional etching technology is used to maintain simple manufacturing process, then the ease of manufacture is improved, but the probability of word line short circuit increases
Solution Approach 1:
The patent incorporates insulating layers between the surface metal layer and the substrate before the connection hole etching process. This beforehand cushioning ensures that even if the etching process is not highly selective, the insulating layer remains at the bottom to prevent short circuits between the word line and substrate
Solution Approach 2:
The insulating layer acts as an intermediary element between the surface metal layer and the underlying structures. It provides electrical isolation and physical separation, ensuring reliable word line connection without requiring precise etching control
Data Source
AI summary
Provided is an L-shaped stepped word line structure including: L-shaped word line units, each including a long side extending in a second direction and arranged adjacent to a gate line slit, and a short side extending in a first direction. A word line terminal included in the short side is formed in a stepped stacked layer structure including stacked layer pairs formed of an insulating material, a region close to the gate line slit in a stacked layer of each stacked layer pair serves as a replacement metal region including a short side region surface/internal metal layer respectively located on a surface/in an interior. In a first direction, a length of the short side region surface metal layer is greater than that of the short side region internal metal layer, and the word line terminal corresponds to the short side region surface metal layer.