Solder Bump Oxide Removal via Carboxylic Acid Reduction Reflow
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Solution Overview
Problem
In semiconductor device manufacturing, the oxide films on solder bumps interfere with electrical connections between bump electrodes, causing resistance increases and potential connection failures due to wet spreading and short circuits, which existing methods fail to adequately address.
Innovation Solution
A reduction reflow process is employed using a carboxylic acid gas to remove oxide films from solder bumps within a controlled temperature and pressure environment, ensuring the oxide films are removed before melting, while maintaining a stable carboxylic acid gas concentration to prevent void defects and ensure proper solder bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide films on solder bumps are not removed, then the manufacturing process is simpler, but electrical connection reliability deteriorates due to resistance increases and potential connection failures
Solution Approach 1:
The patent applies preliminary action by removing oxide films from solder bumps before the bonding process. The method involves heating the solder bump to a temperature where the oxide film becomes removable, then applying a reducing atmosphere or reducing agent to eliminate the oxide film prior to bonding, ensuring reliable electrical connection without compromising the bonding process
Solution Approach 2:
The patent employs parameter changes by controlling temperature and atmospheric conditions during oxide film removal. The solder bump is heated to a specific temperature range that enables oxide film removal while maintaining solder integrity, and reducing atmosphere parameters are adjusted to achieve effective oxide elimination without causing adverse effects
2Reliability
If reducing gas concentration is increased to remove oxide films, then oxide film removal effectiveness improves, but void defects increase due to excessive gas presence during melting
Solution Approach 1:
The patent applies periodic action by implementing a multi-stage heating and reducing process. The process cycles through different temperature zones and reducing atmosphere concentrations: first heating to remove surface oxide, then maintaining a reducing atmosphere during melting to prevent new oxide formation, and finally controlling the atmosphere to minimize void formation. This periodic control of temperature and gas concentration achieves effective oxide removal while preventing void defects
Solution Approach 2:
The patent employs dynamics by dynamically adjusting the reducing gas concentration and heating rate during the process. The reducing atmosphere is introduced gradually and adjusted in real-time based on the heating stage, ensuring optimal oxide removal effectiveness while preventing excessive gas entrapment that would cause voids. The process adapts gas flow rates and concentrations to match the thermal state of the solder
3Strength
If temperature is increased to melt solder for bonding, then bonding strength improves, but oxide films reform on solder bump surfaces
Solution Approach 1:
The patent applies inert atmosphere by maintaining a reducing or inert gas environment throughout the heating and bonding process. After oxide film removal, the solder is melted and bonded while surrounded by a controlled reducing atmosphere that prevents oxygen exposure and oxide film reformation, ensuring both strong bonding and oxide-free interfaces
Solution Approach 2:
The patent employs continuity of useful action by maintaining the reducing atmosphere continuously from the oxide removal stage through the melting and bonding stages. The reducing environment is not interrupted or reduced during the critical bonding phase, ensuring that oxide films do not reform on the solder surfaces even at melting temperatures, thereby maintaining both bonding strength and oxide-free interfaces throughout the entire process
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 achieves stable connection shapes and enhanced connection strength between semiconductor chips by removing oxide films effectively, preventing resistance increases and connection failures, and maintaining the necessary solder volume for reliable bonding.
Implementation Method 1
an oxide film on a surface of the solder bump is removed, by setting a temperature of the inside of the furnace to fall within a range of a reduction temperature or more at which a carboxylic acid expresses a reduction action
Implementation Method 2
the temperature of the inside of the furnace is raised up to the melting temperature, and a carboxylic acid gas concentration of the inside of the furnace is concurrently lowered down to a second carboxylic acid gas concentration. Thereafter, a process of connecting the solder bump and the second bump electrode to each other is performed, by keeping the temperature of the inside of the furnace at the melting temperature or more to melt the solder bump
Data Source
AI summary
According to an embodiment, a temperature of an inside of a furnace is set to fall within a range of a reduction temperature or more of a carboxylic acid and less than a melting temperature of a solder bump, and the inside is concurrently set to have a first carboxylic acid gas concentration. Thereafter, the temperature of the inside is raised up to the melting temperature, and the inside is concurrently set to have a second carboxylic acid gas concentration. The second carboxylic acid gas concentration is lower than the first carboxylic acid gas concentration, and is a concentration containing a minimum amount of carboxylic acid gas defined to achieve reduction on an oxide film of the solder bump. The inside has the second carboxylic acid gas concentration at least at a time when the temperature of the inside reaches the melting temperature.