Copper Pad Interconnect Stack for Oxidation-Resistant Reliability
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Solution Overview
Problem
Existing semiconductor devices face challenges in forming reliable electrical interconnects, particularly with thick copper pads, due to issues such as particulate contamination, copper oxide formation, and deformation under high temperature stress, which can lead to shorting and device failure.
Innovation Solution
The method involves forming a barrier layer of tantalum or tantalum nitride, followed by a copper seed layer, electroplating copper, and applying a polyimide layer to cover and protect the copper pads, along with additional layers like nickel, gold, or palladium to enhance adhesion and reduce copper oxide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick copper pads are used for electrical interconnects, then electrical conductivity is improved, but susceptibility to particulate contamination and copper oxide formation increases
Solution Approach 1:
A barrier layer of tantalum or tantalum nitride is introduced as an intermediary between the copper pad and the external environment. This barrier layer prevents direct contact between copper and contaminants/oxidizing agents, thereby eliminating copper oxide formation and particulate contamination issues while preserving the electrical conductivity benefits of thick copper pads.
Solution Approach 2:
The patent creates a composite interconnect structure consisting of multiple layers: copper pad (for conductivity), barrier layer (for protection), and polyimide coating (for additional protection and mechanical strength). This composite structure combines the advantages of each material while mitigating their individual weaknesses, particularly protecting the copper from oxidation and contamination.
2Reliability
If thick copper pads are used, then current carrying capacity is improved, but mechanical deformation under high temperature stress increases
Solution Approach 1:
The patent forms a composite interconnect structure with copper pad, barrier layer, and polyimide coating. The polyimide layer has high thermal stability and low coefficient of thermal expansion, which counteracts the thermal stress on the copper pad during high temperature processing, preventing mechanical deformation while preserving current carrying capacity.
Solution Approach 2:
The patent changes the physical and chemical parameters of the copper pad by introducing the barrier layer and polyimide coating. These layers modify the thermal and mechanical properties of the overall interconnect structure, reducing thermal expansion and improving resistance to deformation under high temperature stress.
3Reliability
If multiple protective layers are added to copper pads, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The barrier layer of tantalum or tantalum nitride is formed preliminary to the copper pad formation, and the polyimide coating is applied subsequently. This preliminary and sequential action approach allows each layer to be optimized independently while simplifying the overall manufacturing process by establishing a clear fabrication sequence.
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 reliability of copper interconnects by preventing contamination, reducing copper oxide formation, and improving mechanical strength, thereby ensuring stable electrical connections and reducing failure rates under high temperature and stress conditions.
Implementation Method 1
forming a first copper layer by electroplating into each opening of the plurality of openings
Implementation Method 2
forming a barrier layer including tantalum over a metallization layer included in a semiconductor substrate
Implementation Method 3
patterning a layer of polyimide over the first copper layer to expose a copper pad and form a dielectric layer for a copper gate pad
Data Source
AI summary
Implementations of a semiconductor device may include an interconnect that may include a tantalum layer directly coupled with a first copper layer a titanium tungsten layer directly coupled with the first copper layer; a second copper layer coupled directly with the titanium tungsten layer; and a metal layer directly coupled to the second copper layer. The device may include a gate that may include a tantalum layer directly coupled with a first copper layer; a polyimide layer directly coupled over the first copper layer; a titanium tungsten layer directly coupled over the polyimide layer; a second copper layer coupled directly with the titanium tungsten layer; and a metal layer directly coupled to the second copper layer.