BEOL Mobile Metal Oxidation Prevention via Inert Cavity
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Solution Overview
Problem
Metallic devices in the BEOL of integrated circuits face oxidation issues when exposed to air, leading to degradation of ohmic contacts and formation of additional dielectrics, which can prevent electrical connections and alter capacitive values.
Innovation Solution
The use of etched vias with additional orifices overlapping mobile metal pieces, filled with conductive materials resistant to insulating compound formation, such as titanium or tungsten, to prevent oxidation and maintain ohmic contacts and capacitive values, while being compatible with CMOS technologies and minimizing volume costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal pieces are exposed to air in the cavity, then the device can be manufactured with simple structure, but the metal pieces become oxidized leading to degradation of ohmic contact quality
Solution Approach 1:
An inert atmosphere (nitrogen or argon) is introduced into the cavity to act as an intermediary between the metal pieces and air, preventing oxidation while maintaining manufacturing simplicity. The cavity is sealed and filled with inert gas to create a protective environment for the metal pieces throughout operation.
Solution Approach 2:
The cavity containing the metal pieces is filled with an inert atmosphere (nitrogen or argon) to eliminate oxygen contact. This creates a chemically inert environment that prevents oxidation of the metal surfaces, thereby maintaining ohmic contact quality without complicating the manufacturing process.
2Reliability
If additional protective measures are taken to prevent oxidation, then ohmic contact quality is maintained, but device complexity increases
Solution Approach 1:
The cavity structure serves multiple functions: it provides mechanical support for the metal pieces, defines the operational space, and when filled with inert atmosphere, prevents oxidation. This multi-functionality maintains reliability without adding separate protective structures, thereby avoiding increased device complexity.
Solution Approach 2:
The inert atmosphere in the cavity provides self-service protection against oxidation throughout the device lifetime. Once the cavity is sealed and filled with inert gas during manufacturing, the protection is automatic and continuous without requiring additional active components or complex control mechanisms.
3Reliability
If the cavity is sealed to prevent oxidation, then metal piece oxidation is prevented, but manufacturing process complexity increases
Solution Approach 1:
The cavity is sealed and filled with inert atmosphere during the manufacturing process before the device is put into operation. This preliminary action ensures that the metal pieces are protected from oxidation throughout their service life. The sealing and gas filling are performed as standard manufacturing steps, integrating protection into the existing process without requiring complex post-manufacturing operations.
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 effectively prevents the degradation of ohmic contacts and formation of additional dielectrics, ensuring reliable electrical connections and capacitive performance, even at elevated temperatures, with reduced extra volume costs.
Implementation Method 1
The use of etched vias with additional orifices overlapping mobile metal pieces
Implementation Method 2
filled with conductive materials resistant to insulating compound formation, such as titanium or tungsten, to prevent oxidation
Implementation Method 3
maintain ohmic contacts and capacitive values, ensuring reliable electrical connections
Implementation Method 4
maintain ohmic contacts and capacitive values
Data Source
AI summary
In order, for example, to improve the ohmic contact between two metal pieces located at a metallization level, these two metal pieces are equipped with two offset vias located at the metallization level and at least partially at the via level immediately above. Each offset via comprises, for example, a nonoxidizable or substantially nonoxidizable compound, such as a barrier layer of Ti/TiN.