Fin Profile Modulation for GAAFET Uniformity
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Solution Overview
Problem
Tapered fin profiles in semiconductor devices, such as FinFETs and GAAFETs, reduce flexibility for subsequent patterning, leading to reduced device performance and worse outcomes for narrower fins, as they compromise the uniformity and independence of fin shape from size and separation distance.
Innovation Solution
A method for fabricating fins with substantially uniform profiles by burying the wider fin base under the substrate surface, preserving the height of the fin top and improving uniformity through the use of flowable chemical vapor deposition (FCVD) processes, chemical mechanical planarization (CMP), and annealing to densify and strengthen the insulating material, allowing for the adjustment of fin profiles to achieve uniform widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fins are formed using conventional etching processes, then fin structures are created, but the fin profiles become tapered with non-uniform widths
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure with the desired uniform cross-sectional shape before creating the fins. The mandrel is deposited and patterned to define the target fin profile, then used as a template for subsequent conformal deposition and etching processes. This preliminary structuring ensures that the final fins inherit the uniform geometry from the mandrel, resolving the tapering issue caused by conventional direct etching methods.
Solution Approach 2:
The mandrel structure serves as an intermediary element that mediates between the deposition process and the final fin structure. By conformally depositing material around the mandrel and then transferring its shape through etching, the mandrel acts as a template that ensures uniform fin profiles. This intermediary approach allows the fins to achieve the desired uniform width that cannot be obtained through conventional etching alone.
2Ease of manufacture
If fin width varies with separation distance, then manufacturing is simplified, but device performance and control over current flow deteriorate
Solution Approach 1:
The mandrel-based approach provides a universal solution that works for fins with any separation distance. The same conformal deposition and etching process sequence produces uniform fin profiles regardless of the spacing between fins, eliminating the need to adjust manufacturing parameters based on fin density. This universal process simultaneously achieves ease of manufacture and consistent device performance across different fin geometries.
Solution Approach 2:
The patent changes the fundamental parameter of fin width uniformity from variable (dependent on separation distance) to constant (independent of separation distance). By using conformal deposition thickness control and mandrel-based patterning, the fin width becomes a controlled parameter determined by deposition thickness rather than by spacing between fins, enabling consistent electrical characteristics across different device densities.
3Device complexity
If tapered fin profiles are accepted, then manufacturing complexity is reduced, but subsequent patterning flexibility and device performance are compromised
Solution Approach 1:
The mandrel structure is formed in advance with the exact cross-sectional geometry needed for the final fins. This preliminary action of creating a precise template allows subsequent patterning steps to work with uniform fin profiles, providing maximum flexibility for gate and contact patterning. The uniform fins enable better control during later lithography and etching steps, improving adaptability without significantly increasing overall process 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
The method enhances the uniformity of fin profiles, improving device performance by maintaining the height of the fin top while ensuring uniform widths, independent of fin size and separation distance, thereby improving control over current flow and reducing current leakage.
Implementation Method 1
annealing to densify and strengthen the insulating material
Implementation Method 2
flowable chemical vapor deposition (FCVD) processes
Data Source
AI summary
Fins for use in gate all-around field effect transistors (GAAFETs) can be manufactured to have substantially uniform profiles, so the shapes of the fins are independent of size and pitch. Fin profile optimization from a tapered profile to a substantially uniform profile can be achieved via fin height control modulation using additional physical shaping operations to reduce pattern loading. These improvements in the fin profile can be accomplished by stacking and refilling a flowable chemical vapor deposition (FCVD) film multiple times and by using composition tuning during the FCVD process to further modulate fin profiles.