Al-Cu Metallization Ashing to Suppress Copper Dendrites
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Solution Overview
Problem
Copper precipitates in aluminum-copper alloy lines of integrated circuits can form conductive bridges, leading to malfunctions and potential device failure, especially during storage before further processing.
Innovation Solution
Implementing a plasma ashing process with a nitrogen-to-oxygen gas flow ratio of at least 15% during the removal of photoresist layers to passivate grain boundaries in the aluminum-copper sidewalls, thereby preventing or slowing the formation of copper dendrites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is added to aluminum to reduce electromigration effects, then electromigration resistance is improved, but copper precipitates may form causing conductive bridges
Solution Approach 1:
The patent changes the chemical composition parameters of the aluminum alloy by specifying copper content within 2-4 wt% and adding silicon content of 0.5-2 wt%, which modifies the metallurgical properties to reduce copper precipitate formation while maintaining electromigration resistance
Solution Approach 2:
The patent creates a multi-element composite material system (Al-Cu-Si) where silicon acts as a third element that modifies the interaction between aluminum and copper, preventing copper precipitation while maintaining the beneficial electromigration resistance of the Al-Cu alloy
2Productivity
If plasma ashing is used to remove photoresist, then photoresist removal efficiency is improved, but copper dendrite formation may occur
Solution Approach 1:
The patent changes the plasma process parameters by controlling oxygen flow rate at 50-200 sccm and nitrogen flow rate at 50-200 sccm during ashing, which modifies the plasma chemistry to remove photoresist while suppressing copper dendrite formation through controlled oxidation conditions
Solution Approach 2:
The patent implements a continuous plasma ashing process that maintains controlled oxygen and nitrogen flow rates throughout the photoresist removal process, ensuring continuous protection against copper dendrite formation while achieving complete photoresist removal
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 formation of copper precipitates and dendrites, enhancing the reliability and integrity of integrated circuits by maintaining the integrity of the metal lines.
Implementation Method 1
ashing the patterned photoresist layer in a plasma provided in a process chamber sourced with a gas flow having an N2—O2 flow ratio of at least 15%
Implementation Method 2
passivate grain boundaries in the aluminum-copper sidewalls, thereby preventing or slowing the formation of copper dendrites
Data Source
AI summary
Described examples include a method for forming an integrated circuit, the method including depositing a metal layer including aluminum and copper over a semiconductor substrate and forming a patterned photoresist layer over the metal layer. The method also including etching the metal layer to produce a patterned metal layer and ashing the patterned photoresist layer in a plasma provided in a process chamber sourced with a gas flow having an N2/O2 ratio of at least 15%.