Semiconductor Memory Device Parasitic Coupling Capacitance Reduction
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Solution Overview
Problem
As semiconductor technology miniaturizes, parasitic coupling capacitance between word lines increases, leading to operation defects and data loss due to the close proximity of signal lines, which is exacerbated by the reduction in critical dimension and increased integration in semiconductor memory devices.
Innovation Solution
The implementation of an interleaved arrangement of sub word line driving units connected to different main word lines, along with a decoding unit to generate and manage word line driving signals, effectively reduces parasitic coupling capacitance by ensuring neighboring sub word lines are controlled by distinct main word line signals, preventing unwanted voltage increases and data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the critical dimension is reduced to increase integration capacity, then the number of net dies per wafer increases, but the parasitic coupling capacitance between word lines increases
Solution Approach 1:
The word line driving circuit is segmented into multiple independent driving units (first sub word line driving unit and second sub word line driving unit), each controlling different word lines. This segmentation allows neighboring word lines to be driven by separate units with different main word line signals, reducing coupling capacitance effects while maintaining high integration density
Solution Approach 2:
Different main word line signals are applied to different regions (first and second regions) of the memory array. The first main word line signal is applied to the first region while the second main word line signal is applied to the second region, creating local differentiation that reduces parasitic coupling effects in densely packed word lines
2Productivity
If the interval between signal lines is reduced to increase integration, then the capacity increases, but the capacitance between conductive materials increases
Solution Approach 1:
The driving circuit is divided into separate first and second sub word line driving units that are spatially separated and control different word lines. This segmentation allows the circuit to maintain small intervals between signal lines for high integration while reducing capacitive coupling through the separation of driving units
Solution Approach 2:
Different main word line signals act as intermediaries that isolate the effects of adjacent word lines. By applying different main word line signals to neighboring regions, the circuit prevents direct capacitive coupling effects from causing simultaneous activation, thereby allowing reduced spacing between lines
3Productivity
If sub word lines are arranged in narrow space to increase density, then the integration level increases, but coupling capacitance causes word lines to be inactivated
Solution Approach 1:
The narrow space between sub word lines is managed by segmenting the driving function into separate first and second sub word line driving units. Each unit independently controls its respective word line, preventing the coupling capacitance in narrow spaces from causing unintended activation while maintaining high density
Solution Approach 2:
Different main word line signals are applied to different local regions (first and second regions) containing the sub word lines. This local differentiation ensures that even though sub word lines are densely packed, the coupling capacitance does not cause simultaneous or incorrect activation, maintaining reliability in high-density regions
Data Source
AI summary
A semiconductor memory device includes a main word line shared by a plurality of mats. Each of the mats includes a plurality of sub word lines. A decoding unit is configured to decode a row address bit and output a word line driving signal. A plurality of sub word line driving units are each configured to activate one of the sub word lines according to the word line driving signal. In the semiconductor memory device each neighboring sub word line driving units is connected to a different main word line to remove parasitic coupling capacitance.