FinFET Fin Tip Gate Oxide Thickness Variation
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Solution Overview
Problem
FinFET cells with variable active fins face gate oxide breakdown due to sharp angled fin tips, which are created when using a single cut mask for manufacturing, leading to electrical field effects and potential device failure.
Innovation Solution
A method involving forming a thicker first area and a thinner second area of the gate oxide layer, with the thicker area covering the fin tip and the thinner area covering the remaining fins, using a single corner rounding cut mask to reduce electrical field stress and prevent breakdown, while maintaining efficient manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single cut mask is used to form variable number of fins, then manufacturing time and expense are reduced, but gate oxide breakdown occurs at the fin tip due to sharp angled end
Solution Approach 1:
The patent applies local quality by forming a thicker gate oxide layer specifically at the fin tip region where the sharp angled end creates electrical field concentration. This localized thickening (first area) compared to the standard gate oxide thickness in other regions (second area) directly addresses the reliability issue at the critical fin tip location while maintaining the manufacturing efficiency of using a single cut mask for variable fin formation.
2Reliability
If a thicker gate oxide layer is formed at the fin tip, then gate oxide breakdown is reduced, but manufacturing complexity increases due to multiple oxide formation steps
Solution Approach 1:
The gate oxide layer is segmented into two distinct areas with different thicknesses: a first area above the fin tip with greater thickness (30-70 Å) and a second area above the remaining fins with standard thickness (10-15 Å). This segmentation allows the structure to withstand electrical field stress at the critical fin tip location while maintaining optimal gate control in other regions, effectively managing the trade-off between reliability and device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces gate oxide breakdown at the fin tip, enhancing the reliability of the FinFET device by mitigating the vertical electrical field effects and allowing for cost-effective manufacturing with a single mask, thus improving the performance and longevity of the device.
Implementation Method 1
Because of electrical field effects at the fin tip, the fin tip may cause a breakdown in the gate oxide of a corresponding gate
Data Source
AI summary
Methods for forming a variable fin FinFET cell wherein a plurality of fins is formed above a substrate, a portion of a fin is removed, forming a fin tip, a first area of a gate oxide layer is formed above the fin tip, and a second area of the gate oxide layer is formed above at least a remaining portion of the plurality of fins, wherein the first area is thicker than the second area.