Semiconductor Electrode Adhesion via Dilute Acid Cleaning
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Solution Overview
Problem
The adhesion between the gold-containing metal layer and its base metal layer in semiconductor devices is weak, leading to a lower bonding yield rate due to the presence of a natural oxide film on the nickel-containing metal layer, which results in poor bonding when a bonding wire is connected to the electrode pad.
Innovation Solution
A first cleaning treatment with diluted hydrochloric acid having a concentration of less than 1% by weight is performed on the nickel-containing metal layer to remove the natural oxide film, improving the adhesion between the nickel and palladium layers, and subsequently enhancing the adhesion of the gold-containing metal layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gold-containing metal layer is applied to the electrode pad surface to improve oxidation resistance and stability, then reliability is improved, but adhesion force between the gold layer and base metal layer becomes weak
Solution Approach 1:
A cleaning treatment with diluted hydrochloric acid is performed on the nickel-containing metal layer before forming the gold-containing metal layer. This preliminary action removes the natural oxide film that would otherwise form on the nickel layer surface, ensuring optimal adhesion conditions are established before gold deposition, thereby resolving the contradiction between achieving high reliability through gold plating and maintaining strong adhesion to the base metal layer.
2Reliability
If a natural oxide film forms on the nickel-containing metal layer, then oxidation protection is provided, but adhesion between nickel and palladium layers deteriorates
Solution Approach 1:
The cleaning treatment with diluted hydrochloric acid is performed at a specific timing - after the nickel-containing metal layer is formed but before the gold-containing metal layer is deposited. This timing ensures that any natural oxide film that has formed on the nickel layer is removed, creating a fresh, highly adhesive surface for subsequent palladium and gold layer deposition, thus preventing adhesion deterioration while maintaining the protective function of the metal stack.
Solution Approach 2:
The concentration of hydrochloric acid is specifically controlled to be 0.01% by weight or more and less than 1% by weight. This parameter optimization ensures effective removal of the natural oxide film without causing excessive etching or damage to the underlying nickel layer, thereby maintaining both oxidation protection and adhesion strength.
3Strength
If diluted hydrochloric acid with concentration of 0.01% by weight or more and less than 1% by weight is used for cleaning, then adhesion is improved, but cleaning effectiveness must be optimized
Solution Approach 1:
The concentration of diluted hydrochloric acid is precisely controlled within the range of 0.01% by weight or more and less than 1% by weight. This parameter optimization balances two competing requirements: sufficient cleaning effectiveness to remove the natural oxide film and gentle enough action to avoid excessive etching or damage to the nickel-containing metal layer, thereby achieving both improved adhesion and controlled cleaning effectiveness.
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 method improves the adhesion of the gold-containing metal layer, resulting in a semiconductor device with a high bonding yield and a metal stacked structure, effectively addressing the issue of film peeling and poor bonding.
Implementation Method 1
performing a first cleaning treatment on the nickel layer with diluted hydrochloric acid having a concentration of less than 1% by weight
Data Source
AI summary
A method for manufacturing a semiconductor device includes forming a first metal layer above a substrate of a semiconductor chip, forming a nickel layer on the first metal layer, performing a first cleaning treatment on the nickel layer with diluted hydrochloric acid having a concentration of less than 1% by weight, forming a gold layer on the nickel layer, and connecting a bonding wire to a surface of the gold layer.