Self-Forming Manganese Silicate Barrier for BEOL Interconnects
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Solution Overview
Problem
As feature sizes in integrated circuits shrink, the reduced spacing between interconnect structures in BEOL (Back-End-Of-Line) structures increases the risk of dielectric breakdown, necessitating improved methods for forming high-density, reliable interconnects.
Innovation Solution
A method involving the formation of manganese copper alloy seed layers in trenches within a dielectric layer, followed by annealing to create a self-forming manganese silicate barrier, which increases the separation between vias and neighboring metal lines, and the use of a non-planar via structure with a lower portion in contact with copper regions and an upper portion with the manganese silicate liner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are shrunk to achieve higher circuit densities, then the number of devices and interconnect structures can be increased, but the reduced spacing between interconnect structures creates the potential for dielectric breakdown
Solution Approach 1:
A manganese-containing seed layer is deposited in advance during the copper fill process, which then forms a manganese silicate barrier layer at the copper-dielectric interface through subsequent annealing. This preliminary barrier formation prevents dielectric breakdown before it can occur during device operation.
Solution Approach 2:
A manganese silicate barrier layer is introduced as an intermediary between the copper interconnect and the dielectric material. This intermediate layer physically separates the copper from the dielectric, preventing direct interaction that could lead to breakdown while maintaining the reduced spacing needed for high density.
2Area of stationary object
If the spacing between interconnect structures is reduced to increase density, then more interconnects can be packed into the same area, but the electric field between adjacent structures increases creating breakdown risk
Solution Approach 1:
The manganese silicate barrier layer serves as a dielectric intermediary between adjacent copper interconnect structures, providing additional electrical isolation that reduces the harmful electric field effects even when structures are closely spaced.
Solution Approach 2:
The barrier layer changes the electrical parameters at the copper-dielectric interface by introducing a material with different dielectric properties, thereby modifying the electric field distribution and reducing peak field strengths between adjacent interconnects.
3Device complexity
If a conventional planar via structure is used, then the fabrication process is simpler, but the via bottom surface creates direct contact between copper and dielectric increasing breakdown risk
Solution Approach 1:
The manganese-containing seed layer is deposited beforehand in the trench before copper filling, positioning the barrier-forming material at the trench bottom and sidewalls. Subsequent annealing activates this material to form the protective barrier layer at critical interfaces.
Solution Approach 2:
The copper fill process itself serves a dual purpose: it provides the interconnect conductor and simultaneously enables barrier layer formation through the pre-deposited manganese-containing seed layer that reacts during annealing to create the protective interface layer.
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 enhances the effective distance between vias and metal lines, reducing the electric field and the likelihood of time-dependent dielectric breakdown, allowing for reduced dimensions while maintaining voltage levels and improving product yield.
Implementation Method 1
annealing the plurality of M(x) copper regions to form a manganese silicate liner between the first dielectric layer and the M(x) copper regions
Data Source
AI summary
Embodiments of the present invention provide increased distance between vias and neighboring metal lines in a back end of line (BEOL) structure. A copper alloy seed layer is deposited in trenches that are formed in a dielectric layer. The trenches are then filled with copper. An anneal is then performed to create a self-forming barrier using a seed layer constituent, such as manganese, as the manganese is drawn to the dielectric layer during the anneal. The self-forming barrier is disposed on a shoulder region of the dielectric layer, increasing the effective distance between the via and its neighboring metal lines.