Copper Interconnect Mn Barrier Layer for Low-RC Reliability
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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 difficulties in selective deposition of metal caps on copper interconnects.
Innovation Solution
A method involving the formation of a copper interconnect structure with a capping layer, oxidation of residual material, and outdiffusion of Mn to create a barrier layer (MnO or MnSiO) that protects the capping layer during etching, ensuring selective removal of residual material and preventing electron flow paths and leakage.
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 manganese-containing capping layer is introduced as an intermediary material between the copper interconnect and the dielectric. This layer serves multiple functions: it acts as a diffusion barrier, enables selective etching of residual material, and protects the underlying structures. The capping layer composition is carefully controlled to achieve these functions without requiring complex integration processes for low-k dielectrics.
2Loss of energy
If the dielectric cap material is minimized to reduce capacitance, then RC delay is reduced, but the etching stop layer function is compromised
Solution Approach 1:
The manganese-containing capping layer serves as a new intermediary that performs the etching stop function more effectively than traditional dielectric cap materials. During selective etching processes, this layer remains intact while allowing residual material to be removed, providing reliable etching stop functionality without requiring thick dielectric caps.
Solution Approach 2:
The invention changes the material composition parameters of the capping layer by incorporating manganese at specific concentrations (0.1-10 atomic percent). This compositional modification enables the layer to exhibit both etching stop properties and selective etchability, resolving the contradiction between minimizing cap thickness and maintaining etching stop function.
3Reliability
If metal cap deposition is performed on copper interconnects, then electromigration resistance is improved, but selective deposition becomes difficult
Solution Approach 1:
The manganese-containing capping layer is formed in-situ during the copper interconnect formation process, eliminating the need for separate selective metal cap deposition steps. The layer self-organizes to provide electromigration protection while maintaining compatibility with standard fabrication processes, avoiding the complexities of selective deposition.
4Reliability
If residual material is removed from dielectric surface, then leakage paths are eliminated, but the capping layer may be damaged
Solution Approach 1:
The manganese-containing capping layer acts as a protective intermediary that enables selective removal of residual material. During the selective etching process, the capping layer remains intact due to its etching stop properties, while residual material is selectively removed. This protects the underlying copper interconnect from damage while eliminating leakage paths.
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 reduces RC delay and enhances reliability by eliminating leakage issues and improving electromigration resistance in copper nano-interconnects, while maintaining low resistance and preventing time-dependent dielectric breakdown.
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.