Wafer Bonding by Molecular Adhesion Defect Reduction
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Solution Overview
Problem
The existing bonding by molecular adhesion of multilayer semiconductor structures often results in localized bonding defects at the interface between wafers, leading to reduced bonding quality and non-optimized fabrication processes.
Innovation Solution
A method involving the positioning of wafers in a hermetically sealed vessel, evacuation to a low pressure to desorb surface water, adjustment of pressure to a higher level with a dry gas having low water concentration, and initiation of a bonding wave while maintaining the vessel at this pressure to reduce water trapped at the interface, thereby preventing bonding defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding by molecular adhesion is performed under conventional atmospheric conditions, then the bonding process is simple and fast, but localized bonding defects occur at the bonding interface due to water presence
Solution Approach 1:
The patent applies preliminary action by evacuating the bonding chamber to remove water vapor and surface water from the wafer surfaces before bonding occurs. This pre-treatment eliminates the harmful water presence that causes bonding defects, ensuring high bonding quality from the start without requiring complex post-bonding repairs or rework
Solution Approach 2:
The patent creates an inert environment by maintaining the bonding chamber under vacuum conditions during the molecular adhesion process. This inert atmosphere prevents water vapor from interfering with the bonding interface, eliminating the root cause of localized bonding defects while keeping the process relatively simple
2Reliability
If water is removed from the bonding environment through evacuation, then bonding defects are prevented, but the bonding process time increases and productivity decreases
Solution Approach 1:
The water removal and chamber evacuation are performed as preliminary actions before wafer loading and bonding. By completing the environment preparation in advance, the actual bonding process can proceed quickly without prolonged exposure to vacuum conditions, thus maintaining high productivity while ensuring defect-free bonding
Solution Approach 2:
The patent implements a rapid evacuation process that quickly removes water vapor from the bonding chamber without prolonged vacuum maintenance. This rushing through the water removal phase minimizes process time while still achieving the goal of preventing bonding defects, thereby maintaining high fabrication throughput
3Ease of manufacture
If pressure is maintained at atmospheric level during bonding, then the equipment and process are simple, but water trapped at the bonding interface causes localized bonding defects
Solution Approach 1:
The patent employs a vacuum environment as an inert atmosphere during the bonding process. This simple yet effective approach creates water-free conditions at the bonding interface, preventing localized bonding defects without requiring complex equipment modifications or multi-step processing sequences
Solution Approach 2:
The patent changes the pressure parameter from atmospheric to vacuum conditions during bonding. This parameter modification eliminates water vapor interference and surface water presence, ensuring uniform and reliable bonding across the entire wafer interface while maintaining process simplicity
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
Significantly reduces or eliminates bonding defects by controlling water presence and pressure conditions, enhancing the quality of the bonding interface and the overall multilayer structure fabrication.
Implementation Method 1
evacuation of the vessel to a first pressure lower than or equal to 400 hPa in order to desorb the water present on the surface of the wafers
Implementation Method 2
the forces of attraction between the two surfaces are sufficiently high to cause molecular adhesion (bonding induced by all the electronic interaction forces of attraction (van der Waals forces) between atoms or molecules of the two surfaces to be bonded)
Data Source
AI summary
The disclosure relates to a method of bonding by molecular adhesion comprising the positioning of a first wafer and of a second wafer within a hermetically sealed vessel, the evacuation of the vessel to a first pressure lower than or equal to 400 hPa, the adjustment of the pressure in the vessel to a second pressure higher than the first pressure by introduction of a dry gas, and bringing the first and second wafers into contact, followed by the initiation of the propagation of a bonding wave between the two wafers, while maintaining the vessel at the second pressure.