Cobalt-Capped Copper Interconnects for Low Galvanic Corrosion
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Solution Overview
Problem
Galvanic corrosion in semiconductor device interconnects causes voids and pits, leading to increased resistance, electromigration defects, and reduced device reliability, exacerbated by exposure to strong acids and bases during manufacturing.
Innovation Solution
Implementing a cobalt cap layer with a modified top surface and a charge neutralization process to reduce galvanic corrosion, along with a liner layer to slow copper diffusion, and using etch stop layers to enhance interconnect integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper interconnects are used in semiconductor devices, then electrical conductivity is improved, but galvanic corrosion and electromigration defects increase
Solution Approach 1:
A cobalt cap layer is introduced as an intermediary protective layer between the copper interconnect and the environment. This cobalt layer acts as a barrier that prevents direct exposure of copper to corrosive chemicals during manufacturing, thereby eliminating galvanic corrosion while maintaining copper's electrical conductivity
Solution Approach 2:
The interconnect structure is designed as a composite system combining copper (for electrical conductivity) with a cobalt cap layer (for corrosion protection). This composite structure leverages the complementary properties of both materials to achieve both high conductivity and corrosion resistance
2Productivity
If charge buildup occurs on wafer during manufacturing, then manufacturing process continues, but voids and pits form in conductive material
Solution Approach 1:
The cobalt cap layer is applied in advance before the copper interconnect is exposed to manufacturing chemicals. This preliminary protective action prevents charge buildup-related damage before it can occur, eliminating voids and pits without requiring process interruptions
Solution Approach 2:
The cobalt cap layer serves as a cushioning barrier that absorbs and protects the copper interconnect from the harmful effects of charge buildup during manufacturing. This beforehand protection prevents the formation of voids and pits while allowing continuous manufacturing
3Ease of manufacture
If strong acids and bases are used during manufacturing, then cleaning and etching effectiveness is improved, but galvanic corrosion and pitting worsen
Solution Approach 1:
The cobalt cap layer acts as an intermediary protective barrier between the copper interconnect and strong acids/bases used in manufacturing. This barrier allows effective cleaning and etching processes to occur while preventing direct contact between corrosive chemicals and the copper, thereby eliminating pitting
Solution Approach 2:
The cobalt cap layer provides self-service protection by inherently resisting corrosion from strong acids and bases. This protective function occurs automatically without requiring additional process steps, allowing aggressive cleaning chemicals to be used effectively while the cobalt layer autonomously prevents pitting of the underlying copper
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
Significantly reduces the frequency of electromigration defects and galvanic corrosion, enhancing semiconductor device reliability and lifespan by up to 100 times compared to devices without cobalt layers.
Implementation Method 1
Galvanic corrosion causes voids and pits in conductive material of semiconductor device interconnects
Implementation Method 2
Galvanic corrosion is caused by charge buildup on a wafer during a semiconductor device manufacturing process
Implementation Method 3
a liner layer to slow copper diffusion
Data Source
AI summary
A method of making a semiconductor device includes forming a cap layer comprising a first metal over a substrate. The method further includes modifying the cap layer to form an organometallic film. Modifying the cap layer includes adding ammonia to a top surface of the cap layer; reacting a portion of the ammonia with methyl radicals; and removing hydrogen from the ammonia and methyl groups of the methyl radicals to form the organometallic film.