Semiconductor Air Gap Formation via Cap Layer Protection
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Solution Overview
Problem
Existing methods for forming air gaps in semiconductor devices are prone to misalignment issues, leading to damaged interconnections and failures such as air gaps and connecting holes becoming continuous, which compromises the reliability and performance of the semiconductor device.
Innovation Solution
A method involving the formation of a cap layer on the surfaces of lower interconnections before creating interconnection-to-interconnection gaps, ensuring the connection portion is formed adjacent to non-air gap areas, thereby preventing misalignment-induced damage and ensuring reliable air gap formation between interconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air gaps are formed between interconnections by removing insulating film, then signal delay is reduced and capacitance decreases, but misalignment occurs leading to damaged interconnections and reliability deterioration
Solution Approach 1:
A cap layer is formed on the lower interconnections before the air gap formation process. This preliminary protective action ensures that even if misalignment occurs during etching, the interconnections are already protected and cannot be damaged by the etching process.
Solution Approach 2:
The cap layer acts as a cushioning protective layer that prevents direct contact between the etching process and the lower interconnections. This beforehand protection measures against potential misalignment issues by providing a buffer zone that absorbs the impact of positioning errors.
2Reliability
If air gaps are formed between interconnections, then capacitance between interconnections is reduced, but connecting holes may become continuous with air gaps causing device failure
Solution Approach 1:
The cap layer is formed in advance on the lower interconnections before air gap formation. This preliminary protective measure ensures that even if connecting holes become misaligned and continuous with air gaps, the lower interconnections remain protected and functional.
Solution Approach 2:
The cap layer serves as an intermediary protective element between the etching process and the lower interconnections. It mediates the potential harmful effect of misalignment by providing a protective barrier that prevents direct damage to the interconnections.
3Ease of manufacture
If conventional materials are used for interlayer insulating films, then manufacturing cost is reduced, but signal delay between interconnections increases
Solution Approach 1:
The insulating film structure is segmented into two parts: the first insulating film (conventional material) and the second insulating film (low dielectric constant material). This segmentation allows the lower interconnections to be surrounded by low-k material for reduced capacitance, while using conventional materials for the bulk structure to maintain cost-effectiveness.
Solution Approach 2:
The low dielectric constant material is locally applied only in the regions where air gaps are formed between lower interconnections, rather than using it throughout the entire interlayer structure. This local application reduces signal delay where needed while maintaining cost efficiency overall.
Data Source
AI summary
A method for fabricating a semiconductor device includes the steps of: forming a plurality of lower interconnections at intervals in a first insulating film; removing a portion of the first insulating film located between the lower interconnections, thereby forming an interconnection-to-interconnection gap; forming a second insulating film over the first insulating film in which the lower interconnections and the interconnection-to-interconnection gap are formed such that an air gap is formed out of the interconnection-to-interconnection gap; and forming, in the second insulating film, a connection portion connected to one of the lower interconnections and an upper interconnection connected to the connection portion. The connection portion is formed to be connected to one of the lower interconnections not adjacent to the air gap.