Wafer Bonding Gas Stream Defect Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wafer bonding by molecular adhesion often results in localized bonding defects at the interface between wafers, which reduce the quality of the bond and indicate a non-optimized fabrication process.
Innovation Solution
A method involving the projection of a gas stream between wafers during the propagation of the bonding wave to slow down its progression, using a dry gas with low water concentration and controlled temperature to facilitate desorption and prevent condensation, thereby reducing the occurrence of bonding defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bonding wave is propagated between two wafers by molecular adhesion, then bonding is achieved, but localized bonding defects appear at the bonding interface
Solution Approach 1:
A gas stream is introduced as an intermediary medium between the two wafers during bonding wave propagation. The gas stream modifies the bonding environment to prevent localized defects by controlling the interaction between wafers, thereby improving bonding interface uniformity while maintaining bonding quality.
Solution Approach 2:
The bonding process parameters are changed by introducing a gas stream with controlled properties (flow rate, composition, temperature). This parameter modification prevents condensation and improves evaporation, leading to more uniform bonding across the interface while maintaining overall bonding reliability.
2Productivity
If the bonding wave propagates quickly between wafers, then productivity is improved, but heterogeneous deformations increase
Solution Approach 1:
The gas stream acts as a mediator that allows faster bonding wave propagation while maintaining wafer stability. It provides a controlled environment that prevents excessive heterogeneous deformations even at higher bonding speeds, thus improving productivity without compromising structural integrity.
Solution Approach 2:
A gas stream (pneumatic system) is used to control the bonding environment. The gas flow dynamics enable faster bonding wave propagation while the gas pressure and flow distribution prevent heterogeneous deformations, resolving the contradiction between bonding speed and deformation uniformity.
3Reliability
If water concentration is high at the bonding interface, then molecular adhesion is facilitated, but condensation occurs causing bonding defects
Solution Approach 1:
The water concentration parameter at the bonding interface is precisely controlled by introducing a gas stream with specific humidity characteristics. This parameter optimization maintains sufficient molecular adhesion while preventing condensation, thereby eliminating bonding defects caused by excessive moisture.
Solution Approach 2:
A controlled gas atmosphere (such as nitrogen or dry air) is introduced between the wafers to create an inert environment. This atmosphere prevents unwanted condensation while allowing molecular adhesion to proceed, resolving the contradiction between maintaining adhesion and preventing condensation-related defects.
4Device complexity
If no gas stream is used during bonding, then device complexity is reduced, but bonding defects increase
Solution Approach 1:
A gas stream is introduced as a simple intermediary medium that significantly improves bonding quality by preventing defects. The gas delivery system adds minimal complexity to the bonding device while providing substantial improvements in bonding reliability and interface uniformity.
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 effectively reduces the appearance of bonding defects and limits heterogeneous deformations, enhancing the quality of the bond between wafers and optimizing the fabrication process.
Implementation Method 1
projecting a gas stream between the two wafers, in order to slow down the propagation of the bonding wave... The gas stream may be a stream of dry gas with a view to causing desorption of water over at least one of the bonding surfaces for the two wafers
Implementation Method 2
projecting a gas stream between the two wafers... with a view to preventing condensation of water between the wafers
Implementation Method 3
bonding by molecular adhesion or 'direct bonding' (bonding induced by the various electronic interaction attractive forces (Van der Waals forces) between atoms or molecules of the two surfaces to be bonded together)
Data Source
AI summary
The invention provides a method of bonding a first wafer onto a second wafer by molecular adhesion, the method comprising applying a point of initiation of a bonding wave between the first and second wafers, the method further comprising projecting a gas stream between the first wafer and the second wafer generally toward the point of initiation of the bonding wave while the bonding wave is propagating between the wafers. The invention also provides a bonding apparatus for carrying out the bonding method.