Airgap Formation Using Multi-Layer Spacer With Intervening Etch Barrier
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Solution Overview
Problem
Current semiconductor etch processes face challenges in maintaining selectivity across multiple materials, leading to issues with parasitic capacitance and device performance as device sizes shrink, particularly in forming airgaps without exposing source/drain materials to etchants, which can degrade their quality.
Innovation Solution
The implementation of a multi-layer spacer structure that includes a first material and a second material, with an intervening layer to prevent exposure of source/drain materials to etchants during airgap formation, allowing for the use of less selective etchants and maintaining the integrity of the source/drain materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective etching is used to form airgaps, then airgap formation precision is improved, but source/drain materials are exposed to etchants which degrades their quality
Solution Approach 1:
The patent introduces an intervening layer as a mediator between the sacrificial material and the source/drain materials. This intervening layer allows the etchant to selectively remove the sacrificial material to form airgaps while preventing the etchant from exposing or degrading the source/drain materials, thus resolving the contradiction between airgap formation precision and source/drain material quality
Solution Approach 2:
The spacer structure is segmented into multiple layers: a first spacer layer containing sacrificial material, an intervening layer, and a second spacer layer. This segmentation allows differential etching where the sacrificial material is removed to form airgaps while the intervening layer protects the source/drain materials from etchant exposure
2Productivity
If device sizes are shrunk, then device performance is improved, but selectivity maintenance becomes more difficult leading to increased parasitic capacitance
Solution Approach 1:
The patent applies local quality by creating an intervening layer with specific material properties in the critical region between the sacrificial material and source/drain structures. This localized material placement provides the necessary selectivity and protection precisely where needed, enabling reliable airgap formation in scaled devices without compromising source/drain material integrity
3Reliability
If wet etching is used, then selectivity between materials is improved, but penetration into constrained trenches is insufficient
Solution Approach 1:
The spacer structure is divided into segments with different etch selectivities. The sacrificial material layer is designed to be selectively removable by wet etchants while the intervening layer and other spacer layers provide structural integrity and protection, enabling both high selectivity and adequate penetration in constrained geometries
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 the formation of consistent airgaps that reduce parasitic capacitance without detrimental effects on source/drain materials, improving device performance by maintaining material selectivity and reducing etching impacts.
Implementation Method 1
Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface
Data Source
AI summary
Processing methods may be performed to form an airgap spacer on a semiconductor substrate. The methods may include forming a spacer structure including a first material and a second material different from the first material. The methods may include forming a source/drain structure. The source/drain structure may be offset from the second material of the spacer structure by at least one other material. The methods may also include etching the second material from the spacer structure to form the airgap. The source/drain structure may be unexposed to etchant materials during the etching.