Copper-Silver Alloy Interconnection Stress Migration Resistance
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Solution Overview
Problem
Semiconductor devices face challenges with electromigration and stress migration in copper interconnections, particularly due to grain boundary mass transfer and internal stress, which lead to connection defects and reduced device reliability, especially when exposed to heat during manufacturing processes.
Innovation Solution
A semiconductor device with a metal region comprising a copper-silver alloy having a silver content exceeding 1 wt% and a recrystallization temperature of 200° C. or higher, along with a maximum hysteresis error of 150 MPa or less, is developed to prevent stress migration and ensure reliability. The process involves forming a silver-containing metal region by contacting a semiconductor substrate with a silver-containing liquid and heating it, allowing silver to diffuse and form a homogeneous copper-silver alloy, which can be consistently manufactured using a damascene process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver content is increased to reduce electromigration, then electromigration resistance is improved, but the metal may form compounds with Cu leading to rupture or crack
Solution Approach 1:
The patent precisely controls the silver content parameter within the range of 0.1 wt% to less than the maximum solid solution limit, optimizing the balance between electromigration resistance and interconnection integrity. This parameter optimization prevents compound formation while maximizing EM resistance.
Solution Approach 2:
The patent uses a copper-silver alloy composite material that combines the advantages of both metals. The alloy structure allows silver to provide electromigration resistance while copper maintains the interconnection's structural integrity and conductivity.
2Use of energy by moving object
If copper interconnection is used to reduce resistance, then electrical resistance is improved, but stress migration occurs leading to void formation and connection defects
Solution Approach 1:
The copper-silver alloy combines copper's low electrical resistance with silver's stress migration resistance. The alloyed structure modifies the material properties to simultaneously achieve low resistance and high resistance to stress migration-induced void formation.
Solution Approach 2:
By adjusting the silver content parameter in the copper alloy, the patent optimizes the balance between electrical resistance and stress migration resistance. The specific silver concentration range achieves both low resistance and high reliability under thermal stress.
3Reliability
If silver content is increased above solid solution limit to improve stress migration resistance, then stress migration resistance is improved, but compound formation causes rupture or crack
Solution Approach 1:
The patent strictly controls the silver content parameter to remain below the maximum solid solution limit, ensuring the alloy maintains homogeneous solid solution structure without intermetallic compound formation. This parameter control preserves both stress migration resistance and compositional stability.
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 prevents stress migration and enhances the reliability of semiconductor devices by reducing irreversible losses and maintaining device stability under heat history conditions, ensuring consistent formation of a copper-silver alloy with improved adhesiveness and resistance properties.
Implementation Method 1
contacting a semiconductor substrate or a film formed thereon with a silver-containing solution to precipitate silver; forming a metal region on the precipitated silver; and heating the metal region
Data Source
AI summary
A semiconductor device of improved stress-migration resistance and reliability includes an insulating film having formed therein a lower interconnection consisting of a barrier metal film and a copper-silver alloy film, on which is then formed an interlayer insulating film. In the interlayer insulating film is formed an upper interconnection consisting of a barrier metal film and a copper-silver alloy film. The lower and the upper interconnections are made of a copper-silver alloy which contains silver in an amount more than a solid solution limit of silver to copper.