Plasma-Modified Bonded Substrates for Void-Suppressed Wafer Joining
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Solution Overview
Problem
The formation of voids and poor bonding strength between substrates such as quartz and lithium tantalate, or lithium niobate substrates, during the manufacturing of surface acoustic wave elements and optical modulation elements is a challenge.
Innovation Solution
A method involving plasma treatment to form modified layers on the bonding surfaces of substrates, followed by temporary bonding and annealing to enhance bonding strength, thereby suppressing void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If substrates are bonded directly without surface modification, then the bonding process is simple, but voids are formed and bonding strength is poor
Solution Approach 1:
The patent applies preliminary surface modification through plasma treatment before bonding to enhance bonding strength. The plasma treatment creates modified layers on the substrate surfaces that improve adhesion and prevent void formation during the subsequent bonding process, thereby resolving the contradiction between achieving strong bonding and maintaining process simplicity.
Solution Approach 2:
The patent changes the physical and chemical parameters of the substrate surfaces by introducing modified layers through plasma treatment. This parameter change in surface properties enables stronger bonding and reduced void formation, addressing the technical contradiction between bonding strength and process complexity.
2Reliability
If plasma treatment is applied to form modified layers, then bonding strength is improved and void formation is suppressed, but the manufacturing process becomes more complex
Solution Approach 1:
The plasma treatment is performed as a preliminary step before bonding to prepare the substrate surfaces. This preliminary action creates modified layers that ensure high bonding quality and suppress void formation, justifying the additional process steps by delivering reliable bonding results.
Solution Approach 2:
The plasma treatment modifies surface parameters such as surface energy, roughness, and chemical composition, creating optimized surface conditions for bonding. These parameter changes directly improve bonding quality and reduce defects, making the enhanced process complexity worthwhile.
3Strength
If annealing is performed after temporary bonding, then void formation is suppressed and bonding strength is enhanced, but manufacturing time increases
Solution Approach 1:
The annealing process changes thermal parameters to enhance bonding. By controlling temperature and time parameters during annealing, the process suppresses void formation and enhances bonding strength. The parameter optimization balances the time investment with the quality improvement.
Solution Approach 2:
The annealing process utilizes thermal phase transitions and diffusion mechanisms to enhance bonding between substrates. The controlled heating enables atomic diffusion and bond formation at the interface, suppressing void formation and strengthening the bond, thereby justifying the additional manufacturing time.
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
The method results in a bonded substrate with high bonding strength and reduced void formation, ensuring stable and effective integration of quartz and lithium tantalate or lithium niobate substrates.
Implementation Method 1
a step of plasma-treating a surface of the first substrate and thereby forming a first modified layer over the surface of the first substrate
Implementation Method 2
a step of annealing the temporarily-bonded substrates and thereby bonding the first and second substrates to each other
Data Source
AI summary
A bonded substrate having a high bonding strength in which the formation of voids is suppressed is provided. A bonded substrate according to an aspect of the present disclosure is a bonded substrate in which a first substrate and a second substrate are bonded to each other through their bonding surfaces. The first substrate includes a first modified layer on the side thereof on which its bonding surface is located, and the second substrate includes a second modified layer on the side thereof on which its bonding surface is located. A method for manufacturing a bonded substrate according to an aspect of the present disclosure is a method for manufacturing a bonded substrate in which a first substrate and a second substrate are bonded to each other, the method including: a step of plasma-treating a surface of the first substrate and thereby forming a first modified layer over the surface of the first substrate; a step of plasma-treating a surface of the second substrate and thereby forming a second modified layer over the surface of the second substrate; a step of temporarily bonding the first and second substrates to each other in a state where the first and second modified layers face each other; and a step of annealing the temporarily-bonded substrates and thereby bonding the first and second substrates to each other.