Vertical Memory Gate Electrode Pad Curvature for Stair Structure Alignment
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Solution Overview
Problem
Existing methods for manufacturing vertical memory devices face challenges in forming reliable stair structures for gate electrodes, leading to potential electrical shorts between different levels.
Innovation Solution
A vertical memory device design featuring gate electrodes with pads having specific convex and concave edge curvatures, arranged in a staircase shape, to prevent electrical shorts by ensuring precise contact between contact plugs and gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching methods with photoresist patterns are used to form stair structures, then the manufacturing process can be completed, but electrical shorts may occur between gate electrodes at different levels due to imprecise contact plug formation
Solution Approach 1:
The pad structures at the ends of gate electrodes are designed with convex and concave curved surfaces instead of flat surfaces. The convex surface of a pad at one level fits into the concave surface of a pad at the next level, creating a mechanically interlocked staircase structure. This curvature design ensures precise positioning of contact plugs and prevents electrical shorts between adjacent gate electrode levels.
2Quantity of substance
If gate electrodes are stacked closely to increase memory density, then storage capacity improves, but the risk of electrical shorts between levels increases
Solution Approach 1:
The pad structures exhibit asymmetric geometry with convex surfaces on one gate electrode level fitting into concave surfaces on the adjacent level. This asymmetric design creates a unique geometric interlock that prevents lateral displacement and ensures proper alignment, thereby maintaining electrical isolation even when gate electrodes are densely stacked to increase memory capacity.
3Manufacturing precision
If the stair structure is formed with straight edges, then manufacturing is simpler, but contact plugs cannot be precisely positioned to avoid shorts
Solution Approach 1:
Instead of using straight edges for the stair structure, convex and concave curved surfaces are formed at the pad regions. These curved surfaces provide self-aligning features that guide contact plug formation and ensure precise positioning. The curvature can be achieved through standard photolithography and etching processes, balancing manufacturing feasibility with positioning precision.
Data Source
AI summary
A vertical memory device includes a substrate including a first region including a cell array formed thereon and a second region surrounding the first region, the second region including a stair structure formed thereon, gate electrodes stacked on the substrate to be spaced apart from each other in a first direction vertical to an upper surface of the substrate, each of the gate electrodes extending in a second direction parallel to the upper surface of the substrate and including a pad at an end portion thereof in the second direction, a channel extending through the gate electrodes in the first direction on the first region of the substrate, and contact plugs formed on the second region, the contact plugs extending in the first direction to contact the pads of the gate electrodes respectively. A first pad of the pads, in a plan view, may have a convex edge portion that is convex in a direction away from the first region of the substrate, and a second pad disposed on the first pad, in a plan view, may have a concave edge portion that is concave in a direction toward the first region of the substrate.