3D Memory Cell Layout With Staggered Bit Lines for Faster Reads
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Solution Overview
Problem
Conventional stacked type semiconductor memory devices face limitations in increasing integration and performance due to the complexity of miniaturizing memory units and bit lines, which hinders efficient data access and read speed.
Innovation Solution
The semiconductor memory device employs a staggered arrangement of memory units with bit lines connected in a unique pitch configuration, allowing for simultaneous access to twice the number of bit lines, thereby enhancing read speed without increasing circuit area, and incorporates a U-shaped semiconductor layer as a channel body to facilitate efficient data storage and retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If memory units are arranged in a conventional grid pattern with bit lines connected in traditional configuration, then circuit area is minimized, but read speed is limited and page length is constrained
Solution Approach 1:
The patent transitions from a conventional two-dimensional grid arrangement to a three-dimensional stacked configuration where memory units are arranged vertically across multiple layers. Bit lines are connected to memory units in different layers at different pitch positions, creating a multi-dimensional connection topology that enables simultaneous access to multiple bit lines without increasing planar circuit area, thereby improving read speed while managing complexity through vertical integration
Solution Approach 2:
The patent implements a nested structure where multiple bit lines are connected to memory units across different layers in a hierarchical manner. The staggered pitch arrangement allows bit lines from different layers to be interleaved and connected through shared contact structures, creating a nested connection pattern that multiplies access capability without proportionally increasing the number of physical bit line traces
2Loss of energy
If circuit area is kept constant, then integration is optimized, but parasitic capacitance and power consumption increase with traditional configurations
Solution Approach 1:
By arranging memory units in multiple stacked layers and connecting bit lines at different pitch positions across layers, the patent reduces parasitic capacitance between adjacent bit lines by increasing their spatial separation in the vertical dimension. This three-dimensional arrangement allows efficient data access across multiple memory units while maintaining constant planar circuit area and reducing power consumption through minimized capacitive coupling
Solution Approach 2:
The patent employs asymmetric pitch arrangements where bit lines connected to memory units in different layers are offset from each other by different amounts. This asymmetric staggering pattern optimizes the spatial distribution of bit lines to minimize parasitic capacitance while maximizing simultaneous access capability, thereby reducing power consumption without compromising data access efficiency
3Manufacturing precision
If memory units are miniaturized to increase integration, then device density improves, but manufacturing complexity and difficulty of miniaturization increase
Solution Approach 1:
The patent divides the memory device into multiple stacked layers, each containing memory units connected to bit lines at different pitch positions. This segmentation allows each layer to be manufactured with standardized processes while the overall device achieves high integration through vertical stacking. The modular layer structure simplifies manufacturing precision requirements compared to attempting to miniaturize a single monolithic structure
Solution Approach 2:
The patent creates a universal manufacturing approach where identical memory unit structures are repeated across multiple layers with consistent fabrication processes. The staggered bit line connection pattern serves multiple functions: enabling simultaneous access to multiple bit lines, reducing parasitic capacitance, and maintaining design consistency across layers. This multi-functionality reduces manufacturing complexity by eliminating the need for specialized processes for each layer
Data Source
AI summary
According to an embodiment, a semiconductor memory device comprises: a semiconductor substrate; a memory cell array configured having a plurality of memory units, each of the memory units including a plurality of memory cells connected in series, the plurality of memory cells being stacked, the plurality of memory units involving a first memory unit and a second memory unit; and a plurality of bit lines connected to ends of each of the memory units in the memory cell array. The first memory unit and the second memory unit are arranged in a staggered manner by the first memory unit being displaced in a row direction with respect to the second memory unit by an amount less than an arrangement pitch in a row direction of the first memory unit or the second memory unit.