Aluminum Pad Fabrication Without Fluorine-Induced Crystal Defects
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Solution Overview
Problem
The existing methods for manufacturing aluminum pads in semiconductor chips are prone to crystal defects caused by fluorine elements, leading to wire bonding failures and increased costs due to high scrapping rates.
Innovation Solution
A method involving a SiN-OX-SiN-OX four-layer passivation structure is used, where the passivation layer is selectively removed in via areas, and an aluminum pad layer process is performed without the need for a cover etching process or fluorine introduction, thereby avoiding crystal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluorine-containing polymers are used to remove TiN in the conventional APL process, then TiN removal is achieved, but fluorine residue occurs and causes Al pad crystal formation
Solution Approach 1:
The patent extracts and removes the harmful fluorine-containing polymer from the process entirely. Instead of using fluorine-based chemistry for TiN removal, the invention employs a fluorine-free alternative method that achieves TiN removal without introducing fluorine residues that would subsequently react with aluminum to form crystals.
Solution Approach 2:
The patent converts the harmful effect of fluorine (which causes Al pad crystal) into a beneficial outcome by completely eliminating fluorine from the process. The solution transforms the problem of fluorine residue into an opportunity to develop a fundamentally different, fluorine-free TiN removal approach using alternative chemistry that does not compromise aluminum pad integrity.
2Ease of manufacture
If aluminum is exposed to air after passivation layer etching, then pad window opening is achieved, but electrochemical reactions with water vapor and fluorine form crystal defects
Solution Approach 1:
The patent applies preliminary anti-action by preventing the introduction of fluorine elements into the system before the aluminum pad is exposed to air. By eliminating fluorine-containing processes entirely, the invention preemptively blocks the source of fluorine that would otherwise react with aluminum and water vapor to form crystal defects during subsequent air exposure.
Solution Approach 2:
The patent creates a fluorine-free environment (an inert environment with respect to aluminum reactivity) by eliminating all fluorine-containing chemicals and processes. This fluorine-free atmosphere prevents electrochemical reactions between aluminum, water vapor, and fluorine that would otherwise form harmful crystal defects on the pad surface.
3Reliability
If cover etching process is used to remove TiN, then initial protection is provided, but additional process steps and fluorine introduction are required
Solution Approach 1:
The patent extracts and eliminates the cover etching process step entirely from the manufacturing sequence. By removing this intermediate protection and removal step, the invention simplifies the overall process flow while maintaining aluminum pad integrity through the fluorine-free approach described above.
Solution Approach 2:
The patent merges or eliminates the separate cover etching step by integrating the TiN removal into a simplified, fluorine-free process that combines protection and removal functions more efficiently, reducing the total number of discrete process steps required.
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 effectively prevents the formation of crystal defects on aluminum pads, ensuring reliable wire bonding, reducing scrapping costs, and maintaining a stable and cost-effective manufacturing process.
Implementation Method 1
depositing a passivation layer on the top metal layer
Implementation Method 2
the aluminum pad is exposed to air and is prone to electrochemical reactions with water vapor and fluorine in the environment
Data Source
AI summary
This application discloses a method for manufacturing an aluminum pad of a semiconductor chip, an upper surface of a semiconductor substrate is a top metal layer which has been grown, a passivation layer with a SiN-OX-SiN-OX four-layer structure from bottom to top is deposited on the top metal layer, the passivation layer in a via area is removed and the passivation layer outside the via area is reserved, an aluminum pad layer process is performed, remove aluminum in areas not requiring aluminum and reserve aluminum in the via area to complete the fabrication of the aluminum pad. This application can not only solve the side effect of aluminum pad crystal from the source on the premise of ensuring the functionality of the aluminum pad, but also save one mask and one photo layer, the cost is low, and the process is stable.