Anodic Bonding of Glass and Silicon Wafers via Surface Activation
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Solution Overview
Problem
Conventional anodic bonding methods face issues with organic substances adhering to surfaces, leading to weak bonding strength, air voids, and poor production efficiency, especially in high-precision applications like MEMS devices, where high temperatures and pressures are required to achieve firm bonds, and existing methods fail to simultaneously clean and chemically treat surfaces effectively.
Innovation Solution
A bonding method and device that utilize surface activation treatments with energy waves such as atom beams, ion beams, or plasmas to prepare bonding surfaces, allowing for low-temperature anodic bonding with increased strength, and separating preliminary bonding at room temperature from main bonding to improve efficiency, while using a hydrophilic treatment to enhance bonding without warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional anodic bonding is performed in atmospheric air, then the process is simple and fast, but organic substances adhere to surfaces causing weak bonding strength
Solution Approach 1:
The patent applies surface activation treatment using energy waves (ion beams, electron beams, or plasma) before bonding to remove organic substances and activate the bonding surfaces. This preliminary cleaning and activation step ensures that when bonding occurs, the surfaces are free from contaminants that would weaken the bond, thereby achieving both strong bonding and maintained productivity.
2Strength
If high temperature heating is applied to achieve firm bonding, then bonding strength increases, but production efficiency decreases due to long processing time
Solution Approach 1:
The patent changes the bonding parameters by performing surface activation with energy waves at relatively low temperatures (room temperature to 200°C) compared to conventional high-temperature bonding (400-500°C). This parameter change allows bonding to occur at lower temperatures while maintaining strong bond strength, significantly reducing processing time and improving production efficiency.
3Loss of time
If room temperature bonding is attempted using surface activation, then processing time is reduced, but firm bond cannot be achieved for Si and glass
Solution Approach 1:
The patent replaces the conventional thermal bonding mechanism with a surface activation mechanism using energy waves (ion beams, electron beams, or plasma). Instead of relying solely on high temperature to achieve bonding, the energy wave treatment activates the surfaces by removing contaminants and creating reactive sites, enabling strong bonding at lower temperatures and shorter times.
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 enables strong, void-free bonding at lower temperatures, increases production efficiency, and allows for bonding of three-layer structures without warping, using a compact and cost-effective setup that can handle atmospheric pressure and vacuum conditions.
Implementation Method 1
subjecting bonding surfaces of both the objects to be bonded to a surface activation treatment using an energy wave, such as an atom beam, an ion beam, or a plasma
Implementation Method 2
bonding a wafer made of Si and a wafer made of glass together by applying a voltage using a electrode for the glass wafer as a cathode while both the wafers are contacted with each other
Data Source
AI summary
Conventional heat bonding and anodic bonding require heating at high temperature and for a long time, leading to poor production efficiency and occurrence of a warp due to a difference in thermal expansion, resulting in a defective device. Such a problem is solved. An upper wafer 7 made of glass and a lower wafer 8 made of Si are surface-activated using an energy wave before performing anodic bonding, thereby performing bonding at low temperature and increasing a bonding strength. In addition, preliminary bonding due to surface activation is performed before main bonding due to anodic bonding is performed in a separate step or device, thereby increasing production efficiency, and enabling bonding of a three-layer structure without occurrence of a warp.