Non-Uniform Metal Mask for High Aspect Ratio Etch Profiles
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Solution Overview
Problem
High aspect ratio etching processes in semiconductor manufacturing face challenges such as tapered features, increased device failure, limited device density, and performance issues due to non-uniform passivation and etching characteristics, particularly with tungsten passivation leading to defects like CD increase, notching, and profile twisting.
Innovation Solution
A non-uniform metal or metalloid containing mask is used, comprising layers with varying metal or metalloid content, allowing for controlled etching and redeposition of sputtered metal or metalloid on sidewalls as a passivation layer, balancing etching and sidewall protection across different etch depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten passivation is used during high aspect ratio etching, then sidewall protection is improved, but non-uniform passivation causes profile twisting, kink, and ion sided bowing
Solution Approach 1:
The patent applies local quality by creating a non-uniform mask structure where the top portion has different properties than the bottom portion. Specifically, the mask has a first thickness at the top and a second thickness at the bottom, with the top being thicker to provide enhanced protection where needed while allowing controlled etching elsewhere. This spatial variation in mask properties enables uniform sidewall protection without the profile distortion caused by uniform tungsten passivation.
Solution Approach 2:
The patent changes physical parameters of the mask structure, specifically the thickness distribution and material composition. The mask transitions from a uniform structure to a non-uniform structure with varying thickness (first thickness at top, second thickness at bottom) and different material properties (carbon-based with optional metal/metalloid doping). This parameter variation allows the mask to provide appropriate protection levels at different heights, preventing profile twisting and kink while maintaining sidewall integrity.
2Productivity
If high etch rate is achieved, then productivity is improved, but tapered features with wider top than bottom increase device failure and limit device density
Solution Approach 1:
The patent uses local quality by implementing a mask with spatially varying properties - a first thickness at the top portion and a second thickness at the bottom portion. The top portion has greater thickness to provide enhanced protection that compensates for the tapered etch profile, while the bottom portion allows faster etching. This local differentiation enables high overall etch rates while maintaining vertical sidewalls and preventing excessive tapering that would compromise device performance.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the mask with a non-uniform thickness profile before etching begins. The mask is designed with a first thickness at the top and second thickness at the bottom to anticipate and compensate for the tapered etch profile that will develop during high-rate etching. This pre-planned mask structure prevents profile distortion before it occurs, enabling both high productivity and precise profile control.
3Ease of manufacture
If uniform mask is used, then manufacturing simplicity is improved, but non-uniform passivation leads to increased defects such as CD increase and notching
Solution Approach 1:
The patent implements local quality by creating a mask with non-uniform properties - specifically, a first thickness at the top and a second thickness at the bottom, with optional variations in material composition. This controlled non-uniformity is designed to compensate for the non-uniform passivation behavior during etching, providing enhanced protection at the top where passivation is weaker and preventing defects like notching and CD increase. The approach maintains reasonable manufacturing simplicity while dramatically improving defect control.
4Length of moving object
If deeper etching is performed to increase device depth, then device performance is improved, but tapered features and defects increase device failure
Solution Approach 1:
The patent applies local quality by designing a mask with depth-dependent properties - a first thickness at the top portion and a second thickness at the bottom portion. This non-uniform mask structure provides enhanced protection at the top where the etch profile is most vulnerable to tapering, while allowing efficient etching deeper into the substrate. The result is the ability to achieve greater feature depths with uniform vertical sidewalls and minimal defects, thereby improving device performance without increasing failure rates.
Solution Approach 2:
The patent uses preliminary action by pre-configuring the mask with a non-uniform thickness profile before deep etching begins. The mask is designed with greater thickness at the top (first thickness) and reduced thickness at the bottom (second thickness) to anticipate the challenges of deep etching, including profile tapering and defect formation. This pre-planned structure enables successful deep etching with maintained profile uniformity and reduced device failure.
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 precise control of feature profiles, reduces defect formation, and enhances etch rate, facilitating deeper and more uniform etching of semiconductor structures, thereby improving device performance and reducing manufacturing costs.
Implementation Method 1
the etching sputters metal or metalloid in the non-uniform metal or metalloid containing mask and the sputtered metal or metalloid physically redeposits on sidewalls of features etched in the stack as a sputtered metal or metalloid containing passivation layer
Data Source
AI summary
A method for etching features in a stack is provided. A non-uniform metal or metalloid containing mask is formed over the stack. The stack is etched through the non-uniform metal or metalloid containing mask, wherein the etching sputters metal or metalloid in the non-uniform metal or metalloid containing mask and the sputtered metal or metalloid physically redeposits on sidewalls of features etched in the stack as a sputtered metal or metalloid containing passivation layer.