Copper Interconnect Capping Layer with Mn Outdiffusion Barrier
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Solution Overview
Problem
Microelectronic devices face challenges in reducing interconnect resistive-capacitive (RC) delay and increasing reliability due to electromigration (EM) and time-dependent dielectric breakdown (TDDB) as device dimensions shrink, particularly with the limited integration of low-k dielectrics and issues with selective metal cap deposition.
Innovation Solution
A copper interconnect structure is formed with a capping layer and a barrier layer, such as MnO or MnSiO, which is outdiffused to protect the interconnect structure during the removal of residual material, reducing electron flow paths and leakage issues, and enhancing reliability by preventing oxidation of the capping layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low-k dielectric materials are used to reduce capacitance, then RC delay is reduced, but integration in fine dimensions becomes difficult
Solution Approach 1:
A capping layer is introduced as an intermediary between the copper interconnect and the dielectric material. This capping layer enables the use of low-k dielectrics by providing a protective interface that prevents copper oxidation and facilitates controlled material deposition, thereby resolving the integration difficulty while maintaining the low capacitance benefit
Solution Approach 2:
The invention uses composite material structures including copper interconnects with protective capping layers (such as manganese oxide or silicon nitride) combined with low-k dielectric materials. This composite approach allows the system to achieve both low RC delay through low-k materials and manufacturability through the protective copper-capping layer interface
2Loss of energy
If the dielectric cap material is minimized to reduce capacitance, then RC delay is reduced, but the material cannot function as an etching stop layer
Solution Approach 1:
The protective function is segmented from the dielectric cap material and assigned to a separate capping layer. This allows the dielectric cap to be minimized for low capacitance while the dedicated capping layer (with materials having appropriate etch selectivity) provides the etching stop function during via etching processes
Solution Approach 2:
The capping layer acts as an intermediary that provides etching stop functionality, allowing the dielectric cap material to be minimized without compromising the etching process. The capping layer has controlled thickness and material properties that enable it to serve as the primary etch barrier
3Reliability
If selective metal cap deposition is performed, then protection is provided, but residual material forms on dielectric surface causing leakage
Solution Approach 1:
The residual material that would normally cause leakage is converted into a beneficial oxide layer through controlled oxidation. The capping layer material (such as manganese or silicon) oxidizes to form a protective barrier that eliminates electron flow paths and prevents leakage, transforming the harmful residual material into a protective feature
Solution Approach 2:
Controlled oxidation processes are applied to convert residual capping layer material into stable oxide forms. This oxidation eliminates conductive pathways that would cause leakage while maintaining the protective function of the capping layer 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
The solution effectively reduces RC delay and improves reliability by eliminating electron flow paths and TDDB issues, ensuring high EM reliability in copper nano-interconnect devices.
Implementation Method 1
forming a barrier layer on the capping layer by outdiffusing a material from the copper based interconnect structure to a surface of the capping layer
Implementation Method 2
oxidizing the capping layer and the residual material by exposing the capping layer and residual material to air
Data Source
AI summary
Low capacitance and high reliability interconnect structures and methods of manufacture are disclosed. The method includes forming a copper based interconnect structure in an opening of a dielectric material. The method further includes forming a capping layer on the copper based interconnect structure. The method further includes oxidizing the capping layer and any residual material formed on a surface of the dielectric material. The method further includes forming a barrier layer on the capping layer by outdiffusing a material from the copper based interconnect structure to a surface of the capping layer. The method further includes removing the residual material, while the barrier layer on the surface of the capping layer protects the capping layer.