GAA SRAM Cell Channel Width Tuning for Density and Noise Margin
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Solution Overview
Problem
The electronics industry faces challenges in creating integrated circuits (ICs) that balance high-density and high-speed memory requirements while maintaining low power consumption and complexity, particularly in advanced process nodes, where existing memory cell designs struggle to optimize both performance and efficiency.
Innovation Solution
The use of gate-all-around (GAA) transistors with varying channel widths and beta ratios in SRAM cells, combined with write-assist circuits for high-density memory and wider channels for high-speed memory, allows for efficient noise margin improvement and reduced power consumption, enabling both high-density and high-speed memory implementations in the same IC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional memory cell designs are used to achieve high-density memory, then memory density is improved, but read/write performance and noise margin deteriorate
Solution Approach 1:
The patent applies local quality by implementing different channel widths for different transistor types within the same memory cell. Specifically, pull-down transistors have a first channel width while pass-gate transistors have a second channel width that is 0.5 to 2.0 times the first channel width. This localized differentiation optimizes each transistor's function: wider pass-gate transistors improve read/write performance and noise margin, while controlled pull-down transistor width maintains density. This resolves the contradiction by allowing high density overall while locally enhancing performance-critical transistors.
2Quantity of substance
If memory cell dimensions are reduced to increase density, then manufacturing complexity increases
Solution Approach 1:
The patent employs parameter changes by systematically varying channel width as a key parameter to achieve density improvement without proportionally increasing manufacturing complexity. Instead of uniformly scaling all dimensions, the invention selectively adjusts channel width parameters for different transistor types. The pull-down transistors maintain a baseline channel width while pass-gate transistors use scaled widths within a controlled range (0.5 to 2.0 times the baseline). This parameter differentiation allows density optimization through vertical stacking and selective width modulation rather than comprehensive miniaturization, thereby managing manufacturing complexity.
3Reliability
If pull-down transistor channel width is increased to improve noise margin, then pass-gate transistor performance deteriorates
Solution Approach 1:
The patent applies asymmetry by deliberately creating unequal channel widths between pull-down and pass-gate transistors, breaking the conventional symmetry where all transistors have identical or similar dimensions. The pull-down transistors use a first channel width optimized for noise margin control, while pass-gate transistors use a second channel width (0.5 to 2.0 times the first) optimized for read/write performance. This asymmetric design allows each transistor type to be independently optimized for its specific function, resolving the contradiction between noise margin and pass-gate performance that would exist under symmetric design constraints.
Data Source
AI summary
A semiconductor structure includes a substrate and first and second SRAM cells. The first SRAM cell includes first and second pull-up transistors, first and second pull-down transistors, and first and second pass-gate transistors. The first and the second pass-gate transistors have a first channel width. The first and the second pull-down transistors have a second channel width. A ratio of the second channel width to the first channel width is in a range of 1.05 to 1.5. The second SRAM cell includes third and fourth pull-up transistors, third and fourth pull-down transistors, and third and fourth pass-gate transistors. The third and the fourth pass-gate transistors have a third channel width. The third and the fourth pull-down transistors have a fourth channel width. The third and the fourth channel widths are substantially same. The fourth channel width is larger than the second channel width. The transistors are GAA transistors.