Self-Aligned Contact Hard Mask Structure to Prevent Gate Shorting
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Solution Overview
Problem
Conductive features in semiconductor devices can become shorted due to misalignment during etching processes, leading to unintended exposure and connection with adjacent features.
Innovation Solution
A self-alignment scheme is employed using multiple mask layers to protect conductive features during contact opening etching, utilizing hard mask layers with different etch selectivities to prevent damage and ensure precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single mask layer is used during contact opening etching, then the manufacturing process is simpler, but misalignment occurs causing conductive features to be exposed and shorted
Solution Approach 1:
The patent divides the single mask layer into multiple segmented mask layers (first mask layer and second mask layer) with different etch selectivities. The first mask layer has higher etch selectivity than the second mask layer, allowing the etching process to selectively remove the first mask layer while preserving the second mask layer, thereby achieving precise alignment and preventing conductive feature exposure.
Solution Approach 2:
The patent applies different etch selectivity properties to different mask layers. The first mask layer is designed with locally optimized high etch selectivity to be selectively removed during etching, while the second mask layer maintains lower etch selectivity to remain intact and protect adjacent conductive features, creating localized functional differences within the mask structure.
2Productivity
If etching is performed without protective mask layers, then the etching process is faster and simpler, but adjacent conductive features become exposed and connected causing shorting
Solution Approach 1:
The patent applies the second mask layer in advance over the adjacent conductive features before performing the etching process. This preliminary protective action ensures that even if the etching process extends beyond the intended contact opening area, the second mask layer prevents exposure and electrical connection of adjacent conductive features, maintaining reliability while allowing efficient etching.
Solution Approach 2:
The second mask layer serves as an intermediary protective element between the etching process and the adjacent conductive features. It mediates the interaction by absorbing potential etching damage and preventing direct contact between the etchant and the conductive features, thereby maintaining electrical isolation without requiring excessive etching control.
3Manufacturing precision
If multiple mask layers with different etch selectivities are used, then alignment precision and protection are improved, but the device structure becomes more complex
Solution Approach 1:
The patent segments the mask structure into two functional layers with distinct etch selectivity characteristics. This segmentation allows each layer to perform its specific function (selective removal and protection) without requiring additional complex structures, achieving precise alignment through functional division rather than structural complexity.
Solution Approach 2:
The patent changes the etch selectivity parameter between the two mask layers rather than changing the physical structure or material composition significantly. By adjusting the etch selectivity parameter, the patent achieves differentiated functionality with minimal structural complexity, allowing precise control of the etching process while maintaining a relatively simple overall device structure.
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
Prevents unintended exposure and shorting of conductive features, enhancing the integration density and reducing current leakage in semiconductor devices.
Implementation Method 1
the second hard mask having a second etch selectivity greater than the first etch selectivity
Data Source
AI summary
A method includes using a second hard mask layer over a gate stack to protect the gate electrode during etching a self-aligned contact. The second hard mask is formed over a first hard mask layer, where the first hard mask layer has a lower etch selectivity than the second hard mask layer.