FinFET Backside Recess Control for Scalable Drive Current
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Solution Overview
Problem
The scalability of tri-gate transistors is limited by the integer number of fins under the controlling gate, leading to larger transistors and increased power consumption, necessitating a semiconductor structure and manufacturing process that enhances scalability.
Innovation Solution
The method involves forming FinFET devices with multiple active channel heights by using backside reveal and etching processes, with etch-stop layers to control precise etching and achieve varying fin heights, allowing for better control over current flow and reducing unnecessary transistor size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of fins is increased to improve drive capability, then transistor performance is improved, but transistor size and power consumption increase
Solution Approach 1:
The patent applies local quality by creating fins with different active channel heights within the same transistor structure. Some fins have taller active channels while others have shorter active channels, allowing different regions of the transistor to contribute differently to current flow. This enables fine-grained control of drive capability without proportionally increasing the overall transistor footprint, as shorter fins provide drive current with less area contribution.
2Power
If the number of fins is increased to improve drive capability, then transistor performance is improved, but power consumption increases
Solution Approach 1:
The patent creates a heterogeneous fin structure where fins with shorter active channel heights contribute to drive capability while consuming less power compared to uniformly tall fins. The shorter active channels reduce the current path length and associated power consumption while still providing sufficient drive current when combined with the taller fins, achieving an optimized power-performance balance.
3Ease of manufacture
If uniform fin heights are used, then manufacturing is simplified, but current flow control is limited
Solution Approach 1:
The patent segments the fin structure into multiple height levels by introducing intermediate etch stop layers at different depths. The etch process is divided into multiple stages, with each stage removing material down to a specific etch stop layer. This segmentation enables precise control of active channel heights for different fins while using standardized manufacturing processes, balancing fabrication complexity with current flow control versatility.
Solution Approach 2:
The patent introduces etch stop layers as intermediary structures that mediate between the uniform fin formation process and the desired varied active channel heights. These etch stop layers serve as intermediate references during the multi-stage etch process, enabling precise termination of etching at different depths for different fins. The etch stop layers are later removed, having served their purpose as process intermediaries.
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 enables improved control over current flow and reduces power consumption by allowing for the formation of transistors with varying active channel heights, enhancing the scalability and performance of tri-gate transistors.
Implementation Method 1
etch-stop layers to control precise etching and achieve varying fin heights
Data Source
AI summary
Embodiments of the present invention are directed to formation of fins with different active channel heights in a tri-gate or a Fin-FET device. In an embodiment, at least two fins are formed on a front side of the substrate. A gate structure extends over a top surface and a pair of sidewalls of at least a portion of the fins. In an embodiment, the substrate is thinned to expose the bottom surface of the fins. Next, backside etching may be performed on each fin to form active channel regions. The fins may be recessed to different depths, forming active channel regions with differing heights.