Composite Copper Wire Interconnects for Thermal Stability
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Solution Overview
Problem
Thick damascene copper wires exhibit significant surface roughness and grain morphology issues due to lack of constraint, leading to diminished cap adhesion and potential delamination of nitride/oxide films during thermal processing, resulting in undesirable via opens.
Innovation Solution
A composite copper wire structure is formed within a substrate, comprising a liner layer, a thick first copper layer, a copper grain growth barrier layer, and a thinner second copper layer, where the second layer's thickness is less than the first, inhibiting surface roughness and improving adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thick copper wire (3 microns or thicker) is used for interconnect, then current carrying capacity is improved, but surface roughness and grain morphology deteriorate
Solution Approach 1:
The thick copper wire is segmented into multiple layers: a first copper layer (3 microns or thicker) for current carrying capacity, and a second copper layer (0.5-2 microns) for surface smoothness. This segmentation allows each layer to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the copper wire structure are assigned different qualities: the bulk (first copper layer) provides high current carrying capacity while the surface (second copper layer) provides smooth morphology. This local differentiation resolves the contradiction between thickness and surface quality.
2Quantity of substance
If thick copper wire is used for interconnect, then conductivity is improved, but cap adhesion deteriorates
Solution Approach 1:
The copper interconnect is divided into functional segments: the first copper layer provides conductivity while the second copper layer provides a smooth surface for cap adhesion. This segmentation allows both requirements to be satisfied without compromise.
Solution Approach 2:
The interconnect structure uses a composite copper wire comprising multiple copper layers with different thicknesses. This composite structure combines the high conductivity of thick copper with the good adhesion properties of thin copper surfaces.
3Quantity of substance
If thick copper wire is used for interconnect, then electrical performance is improved, but thermal processing stability deteriorates
Solution Approach 1:
The copper structure is segmented into a thick first layer for electrical performance and a thin second layer for thermal stability. During thermal processing, the thin second layer remains stable while the thick first layer maintains electrical conductivity.
Solution Approach 2:
The thickness parameter of the copper layers is optimized: the first layer is thick (≥3 microns) for electrical performance while the second layer is thin (0.5-2 microns) for thermal stability. This parameter differentiation resolves the contradiction between electrical and thermal requirements.
Data Source
AI summary
Various embodiments include interconnect structures and methods of forming such structures. The interconnect structures can include a composite copper wire which includes at least two distinct copper sections. The uppermost copper section can have a thickness of approximately 1 micrometer or less, which inhibits surface roughening in that uppermost section, and helps to enhance cap adhesion with overlying layers.