Wafer Bonding via Bowing and Hydrophilization to Prevent Voids
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Solution Overview
Problem
In the field of electronics, there is a challenge in bonding substrates together, particularly planar wafers, as air can be trapped between the bonding surfaces, leading to voids and defects, and existing methods struggle to maintain high positional precision during the bonding process.
Innovation Solution
A method involving hydrophilization treatment to adhere water or OH-containing substances to the bonding surfaces, followed by bowing one substrate to protrude its central portion towards the other, aligning them precisely, and then bonding across the entirety of the surfaces while maintaining a non-bonded pressure condition to prevent voids and ensure high positional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the central portion of the wafer is bowed toward the opposing wafer to prevent air trapping, then void formation is prevented, but positional displacement between wafers occurs during the bowing and recovery process
Solution Approach 1:
The patent applies preliminary action by performing alignment correction before the bonding process. Specifically, alignment marks are detected and positional displacement is corrected while the wafer is still in the alignment stage, before bowing occurs. This ensures that even though displacement happens during bowing, the final bonded position maintains high precision because the alignment was established and corrected in advance.
Solution Approach 2:
The patent implements feedback by using alignment marks and detection mechanisms to monitor and measure positional displacement. The system detects the position of alignment marks on both wafers, calculates any displacement, and provides feedback for correction. This closed-loop feedback ensures that alignment precision is maintained despite the mechanical changes during bowing and recovery.
2Reliability
If the outer circumferential portion of the wafer is held to bow the central portion, then air is pushed out and voids are prevented, but the wafer shape is altered during the process
Solution Approach 1:
The patent applies dynamics by making the wafer shape changeable during the bonding process. The wafer transitions from a flat state during alignment to a bowed state during bonding, and then returns to flat after bonding. This dynamic shape change allows the system to optimize for different requirements: flatness for alignment precision, and bowing for complete surface contact and air evacuation.
Solution Approach 2:
The patent uses curvature by intentionally bowing the wafer into an arc shape during the bonding process. The outer circumferential portion is held fixed while the central portion is pressed to create a curved surface that contacts the opposing wafer. This curvature facilitates air evacuation and ensures complete surface contact, with the wafer returning to its original flat shape after the 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 approach effectively prevents void formation and allows for high-precision bonding of substrates by ensuring accurate alignment and controlled pressure, enhancing the quality of the bonding process.
Implementation Method 1
a step of performing hydrophilization treatment to cause water or an OH containing substance to adhere to a bonding surface of the first substrate and a bonding surface of the second substrate
Data Source
AI summary
A production of voids between substrates is prevented when the substrates are bonded together, and the substrates are bonded together at a high positional precision while suppressing a strain. A method for bonding a first substrate and a second substrate includes a step of performing hydrophilization treatment to cause water or an OH containing substance to adhere to bonding surface of the first substrate and the bonding surface of the second substrate, a step of disposing the first substrate and the second substrate with the respective bonding surfaces facing each other, and bowing the first substrate in such a way that a central portion of the bonding surface protrudes toward the second substrate side relative to an outer circumferential portion of the bonding surface, a step of abutting the bonding surface of the first substrate with the bonding surface of the second substrate at the respective central portions, and a step of abutting the bonding surface of the first substrate with the bonding surface of the second substrate across the entirety of the bonding surfaces, decreasing a distance between the outer circumferential portion of the first substrate and an outer circumferential portion of the second substrate with the respective central portions abutting each other at a pressure that maintains a non-bonded condition.