Electroless Plating Pretreatment for Nodule Reduction
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Solution Overview
Problem
Electroless plating in semiconductor device formation often results in surface defects such as nodules due to insufficient surface cleaning and unstable deposition solutions, particularly when depositing Co or Ni on patterned Cu surfaces with dielectric surfaces in between, leading to contamination and particle formation.
Innovation Solution
A method involving pretreatment of the dielectric surface with an alkaline solution of pH 8 or higher containing a complexing agent to form a negatively charged metal complex, followed by an acidic solution to dissolve metal oxide residue, ensuring effective removal of metal residue before electroless deposition of Co or Ni on Cu patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the dielectric surface is not pretreated, then the process is simple and fast, but metal residue remains causing nodule formation and surface defects
Solution Approach 1:
The patent applies preliminary action by performing a two-step pretreatment process before electroless plating: first treating with alkaline solution containing complexing agent to remove organic residues, then treating with acidic solution to remove metal oxide residues. This preliminary cleaning prevents nodule formation during subsequent plating, ensuring high surface quality while maintaining process efficiency.
Solution Approach 2:
The pretreatment process is segmented into two distinct steps: (1) alkaline treatment with complexing agent at controlled pH and temperature, and (2) acidic treatment to dissolve metal oxides. Each step targets specific types of residues, allowing thorough cleaning without excessive complexity by dividing the overall cleaning function into specialized sub-processes.
2Manufacturing precision
If strong cleaning methods are used to remove all metal residue, then surface quality improves, but the deposition solution becomes unstable and nodules form
Solution Approach 1:
The patent carefully controls chemical parameters throughout the process: maintaining alkaline solution pH between 8-12, treating at temperatures of 20-80°C for 1-30 minutes, and using mild acidic solutions. These controlled parameter changes enable effective residue removal while preventing deposition solution contamination and maintaining solution stability, avoiding nodule formation.
Solution Approach 2:
The complexing agent acts as an intermediary substance that binds to metal residues during alkaline treatment, forming soluble complexes that can be removed without aggressive cleaning. This intermediary mechanism allows gentle yet effective residue removal that doesn't destabilize the subsequent deposition solution.
3Manufacturing precision
If alkaline solution with complexing agent is used, then metal residue is removed effectively, but metal oxide residue remains requiring additional treatment
Solution Approach 1:
The cleaning process is segmented into two specialized steps: alkaline treatment with complexing agent targets organic and metallic residues, while a subsequent acidic treatment step specifically addresses metal oxide residues. This segmentation allows each step to be optimized for its specific function, achieving thorough cleaning without requiring excessively complex single-step processes.
Solution Approach 2:
The two-step pretreatment process maintains continuous useful action by seamlessly transitioning from alkaline to acidic treatment without interrupting the overall cleaning objective. Each step builds upon the previous step's results, with the acidic treatment completing the residue removal initiated by the alkaline step, ensuring complete surface preparation for plating.
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 significantly reduces or eliminates nodule formation, enhancing the quality of electroless deposition by ensuring thorough residue removal and minimizing defects on semiconductor wafers.
Implementation Method 1
the complexing agent forms a negatively charged metal complex with the metal residue
Implementation Method 2
the acidic solution dissolves metal oxide residue
Implementation Method 3
Metal is electrolessly deposited on the plurality of metal patterns
Data Source
AI summary
A method for providing electroless deposition of a metal layer on a plurality of metal patterns, wherein a dielectric surface is between some of the plurality of metal patterns and metal residue is on the dielectric surface is provided. The dielectric surface is pretreated with an alkaline solution with a pH of at least 8 comprising at least one complexing agent, wherein the complexing agent forms a metal complex with the metal residue and wherein some metal oxide residue remains. The dielectric surface is pretreated with an acidic solution, wherein the acidic solution dissolves metal oxide residue. Metal is electrolessly deposited on the plurality of metal patterns.