FinFET Fin Removal via Two-Step Anisotropic and Isotropic Etching
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Solution Overview
Problem
Existing methods for removing selected fins in FinFET semiconductor devices face challenges such as non-uniform fin sizes due to etch loading effects in the 'fin-cut-first' approach and limited margin for error in the 'fin-cut-last' approach, which can lead to damage to adjacent fins, especially as trench depth increases.
Innovation Solution
A two-step etching process involving an anisotropic etching process followed by an isotropic etching process to define fin cavities, ensuring accurate removal of fins while protecting adjacent structures with insulating material, allowing for smaller critical dimensions and reduced risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single anisotropic etching process is used to remove fins, then the etching process is simple and fast, but the fin cavity shape is not optimized and complete fin removal cannot be ensured
Solution Approach 1:
The etching process is divided into two distinct steps: first an anisotropic etching process to create an initial fin cavity with vertical sidewalls, then an isotropic etching process to complete the fin removal and optimize the cavity shape. This segmentation allows each etching step to be optimized for its specific function, ensuring complete fin removal while maintaining process control
Solution Approach 2:
The invention changes the etching parameters between steps by transitioning from an anisotropic etch (directional, vertical profile) to an isotropic etch (omnidirectional, rounded profile). This parameter change enables the process to first create a controlled initial cavity and then complete the removal with optimized shape, achieving both completeness and shape optimization
2Manufacturing precision
If the mask opening size is reduced to achieve smaller critical dimensions, then the precision of fin selection improves, but the margin for error decreases and adjacent fins may be damaged
Solution Approach 1:
The initial anisotropic etching step creates a cushioning layer of insulating material around the fin cavity before the final isotropic etching completes the removal. This cushioning provides a safety margin that protects adjacent fins during the etching process, allowing smaller mask openings to be used for precise fin selection without increasing the risk of damage to neighboring structures
3Reliability
If deeper trenches are formed to accommodate isolation material, then the isolation effectiveness improves, but the risk of fin damage during etching increases
Solution Approach 1:
The etching process is segmented into two steps where the first anisotropic etch creates the initial deep cavity with controlled vertical profile, minimizing lateral etching that could damage adjacent fins. The second isotropic etch then completes the cavity formation with a rounded profile that further protects surrounding structures. This segmentation allows deep trenches to be formed effectively while reducing the harmful lateral etching effects
Solution Approach 2:
By changing from anisotropic to isotropic etching parameters between steps, the process achieves deep trench formation with optimized safety margins. The isotropic etch's omnidirectional nature ensures complete removal while its self-limiting characteristic provides inherent protection against over-etching and damage to adjacent fins, enabling deeper isolation trenches with reduced risk
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 method ensures precise and uniform fin removal with reduced risk of damaging adjacent fins, improving the accuracy and reliability of the fin-cutting process, especially for deeper trenches, and allows for smaller critical dimensions in the fin removal mask.
Implementation Method 1
performing a first anisotropic etching process to remove at least a portion of one of the plurality of fins and thereby define an initial fin cavity
Implementation Method 2
performing a second isotropic etching process to define a final fin cavity
Data Source
AI summary
One illustrative method disclosed herein includes, among other things, forming a plurality of trenches in a semiconductor substrate to thereby define a plurality of fins in the substrate, forming a layer of insulating material in the trenches, performing an etching process sequence to remove at least a portion of one of the plurality of fins and thereby define a fin cavity, wherein the etching process sequence includes performing a first anisotropic etching process and, after performing the first anisotropic etching process, performing a second isotropic etching process. In this embodiment, the method concludes with the step of forming additional insulating material in the fin cavity.