Diagonal FinFET SRAM Layout for Variability Control
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Solution Overview
Problem
Conventional finFET designs with orthogonal layouts face limitations in variability, particularly in SRAM cell manufacturing as transistors shrink, leading to challenges in achieving optimal performance and reducing power consumption.
Innovation Solution
A novel design layout where silicon fins are diagonally skewed relative to the gates, allowing for increased effective channel length and width, enabling longer gate lengths and improved variability, suitable for high-density SRAM cells in advanced technology nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If orthogonal layout is used for finFET SRAM cell, then manufacturing process is simple, but variability in effective channel width and length increases
Solution Approach 1:
The patent applies asymmetry by rotating the fin structure relative to the gate at a specific angle (e.g., 30 degrees) instead of using the conventional orthogonal (90-degree) alignment. This asymmetric orientation allows the effective channel width (Weff) and length (Leff) to be decoupled from the strict geometric constraints of orthogonal layouts, providing better control over variability while maintaining manufacturing feasibility through standard photolithography processes.
2Quantity of substance
If transistor size is reduced to increase density, then power consumption decreases, but variability in effective channel dimensions increases
Solution Approach 1:
The patent changes the geometric parameters of the fin structure by introducing a rotation angle parameter (θ) between the fin and gate. By optimizing this angle parameter, the effective channel dimensions (Weff and Leff) can be independently tuned even as the overall transistor size is reduced for higher density. This parameter adjustment allows maintaining precise control over channel dimensions while scaling down transistor footprint for reduced power consumption and increased density.
3Reliability
If gate length is increased to improve variability control, then short channel effects are reduced, but device area increases
Solution Approach 1:
The patent utilizes dimensional transformation by rotating the fin structure at an angle relative to the gate, which effectively changes the projection geometry. This angular transformation allows the effective channel length to be extended in one dimensional projection while maintaining a compact overall device footprint in the planar area. The rotated fin configuration enables longer Leff for better SCE control without proportionally increasing the SRAM cell area, as the extended channel length is achieved through angular orientation rather than linear extension.
Data Source
AI summary
A method of forming a finFET SRAM and related device, are provided. Embodiments include forming a plurality of silicon fins in a substrate; and forming a gate over each of the fins, wherein all of the fins are diagonally skewed in a single direction relative to the gates, and all of the gates extend in a single direction relative to the respective fins.