Hydrogen-Water Vapor Plasma for Copper Via Pre-Plating
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Solution Overview
Problem
Conventional plasma processing methods for semiconductor substrates fail to effectively prevent oxidation of copper films, achieve high-speed ashing of photoresist residues, and hydrophilize the via inner surface, which are crucial for micro-bump formation and pre-processing in semiconductor and lead frame connections.
Innovation Solution
A plasma processing method using a source gas composed of hydrogen and water vapor, generated by a water electrolysis apparatus, is applied to convert the gas into plasma for processing semiconductor and lead frame substrates, ensuring a water vapor content of at least 3.3% saturation pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen plasma processing is performed in a specific chamber to prevent oxidation of copper film, then oxidation prevention effect is improved, but photoresist residue ashing effect and via surface hydrophilization effect are insufficient
Solution Approach 1:
The invention changes the chemical composition parameters of the plasma processing gas from pure hydrogen to a mixed gas containing hydrogen and oxygen (specifically 1-50% oxygen by volume). This parameter change enables the plasma to simultaneously achieve oxidation prevention, photoresist ashing, and surface hydrophilization without requiring multiple separate processing steps.
Solution Approach 2:
The mixed gas plasma processing method performs multiple functions in a single processing step: it prevents oxidation of copper film, ashes photoresist residues, and hydrophilizes the via inner surface. This multi-functionality resolves the contradiction by eliminating the need to choose between oxidation prevention and ashing speed, as both effects are achieved simultaneously.
2Reliability
If conventional plasma processing is used to achieve copper film oxidation prevention, then oxidation reduction effect is improved, but via inner surface hydrophilization and plating solution penetration are insufficient
Solution Approach 1:
By adding oxygen to the hydrogen plasma processing gas, the invention creates a mixed gas plasma that generates hydroxyl radicals and other reactive species capable of hydrophilizing the via inner surface. This parameter change maintains the oxidation prevention effect while simultaneously improving surface wettability for plating solution penetration.
Solution Approach 2:
The invention uses a composite gas mixture of hydrogen and oxygen to create plasma with combined properties: hydrogen provides oxidation prevention through reducing atmosphere, while oxygen provides surface hydrophilization through oxidation and hydroxyl group formation. This composite approach resolves the contradiction between oxidation prevention and plating solution entry ease.
3Reliability
If multiple separate plasma processing steps are performed to achieve oxidation prevention, ashing, and hydrophilization, then comprehensive processing effect is improved, but processing time and complexity increase
Solution Approach 1:
The invention merges three separate plasma processing functions (oxidation prevention, photoresist ashing, and surface hydrophilization) into a single processing step using mixed gas plasma. This consolidation maintains comprehensive processing effects while significantly reducing processing time and process complexity.
Solution Approach 2:
The mixed gas plasma processing method achieves multi-functionality in a single step, simultaneously preventing oxidation, ashing photoresist residues, and hydrophilizing surfaces. This resolves the time loss contradiction by eliminating the need for multiple sequential processing steps while maintaining all required processing effects.
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 method effectively reduces copper oxide, achieves high-speed ashing of photoresist residues, and hydrophilizes the surface, facilitating plating solution entry, while also preventing oxidation of metal portions in semiconductor and lead frame connections.
Implementation Method 1
a water electrolysis apparatus to be connected to the processing chamber, the water electrolysis apparatus being a supply source of a source gas consisting of hydrogen and water vapor
Implementation Method 2
a plasma generation section configured to convert the source gas introduced into the processing chamber into plasma
Data Source
AI summary
Provided is a plasma processing method capable of providing, in plasma processing of an electronic device substrate in which a semiconductor substrate having a copper film on a surface is etched using a photoresist and plating processing is performed, effects of (1) chemical reduction of the copper film, (2) high-speed ashing of the photoresist, and (3) hydrophilization of an inner surface of a via. The plasma processing method for plating processing of an electronic device substrate according to the present invention includes: a) a step of disposing the electronic device substrate such as a semiconductor substrate, a lead frame, or the like in a processing chamber; b) a step of supplying a source gas consisting of hydrogen and water vapor to the processing chamber, the source gas being obtained from a water electrolysis apparatus; and c) a step of subjecting the electronic device substrate to plasma processing by converting the source gas in the processing chamber into plasma.