Wafer Bonding via Low-Temperature Recrystallization
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Solution Overview
Problem
Current bonding methods for solid substrates, especially in the semiconductor industry, face challenges such as high temperature requirements, thermal stress, and irreproducibility, which can damage microchips and structures, and fail to achieve a strong, reproducible connection between materials with different thermal expansion coefficients while maintaining compatibility with existing components.
Innovation Solution
The method involves planarizing the bonding surfaces to minimize roughness, producing a metastable microstructure with high dislocation density or an amorphous layer to facilitate recrystallization, using machining processes and controlled temperature and speed to create a seamless, permanent bond at lower temperatures, and optimizing surface roughness to less than 1 nm for efficient recrystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperatures (>300°C) are used for bonding, then bonding force is improved, but thermal stress and risk of destroying microchip structures increase
Solution Approach 1:
The patent changes the bonding parameters by using temperatures below 300°C (specifically 20-250°C) combined with high pressure (1-1000 bar) and controlled speed (0.1-10 m/s) to achieve strong bonding without thermal stress. This parameter transformation allows bonding of materials with different thermal expansion coefficients without destroying microchip structures.
Solution Approach 2:
The patent replaces thermal bonding mechanisms with mechanical bonding through high pressure and friction. The mechanical energy from pressing force and relative motion between surfaces creates bonding without thermal effects, thus avoiding thermal stress on temperature-sensitive microchip components.
2Strength
If high temperatures are used for bonding, then bonding force is improved, but energy consumption increases
Solution Approach 1:
The patent substitutes thermal energy with mechanical energy for bonding. High pressure (1-1000 bar) and controlled relative motion (0.1-10 m/s) between bonding surfaces create friction and plastic deformation that leads to strong bonding, eliminating the need for high temperature heating and thus reducing energy consumption.
Solution Approach 2:
The patent changes the energy input parameters from thermal (temperature >300°C) to mechanical (pressure 1-1000 bar, speed 0.1-10 m/s), achieving bonding force through mechanical work rather than thermal energy, thereby significantly reducing overall energy consumption.
3Strength
If high temperatures are used for bonding, then bonding force is improved, but reproducibility decreases due to thermal expansion differences
Solution Approach 1:
The patent changes bonding parameters to low temperature (20-250°C), high pressure (1-1000 bar), and controlled speed (0.1-10 m/s). This eliminates thermal expansion effects that cause irreproducibility, allowing consistent bonding of materials with different thermal expansion coefficients while maintaining strong bonding force.
4Manufacturing precision
If machining processes are used to planarize surfaces, then surface roughness is improved, but production time increases
Solution Approach 1:
The patent uses periodic reciprocating motion (0.1-10 m/s) between the bonding surfaces during pressing, which simultaneously achieves planarization and bonding. The oscillating friction acts as a self-finishing process that reduces surface roughness to below 1 μm while maintaining production efficiency, eliminating separate machining steps.
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 a strong, reproducible, and thermally stable connection between metal surfaces with minimal thermal stress, preserving existing structures and ensuring compatibility with active components, while reducing energy consumption and avoiding material destruction.
Implementation Method 1
producing a metastable microstructure with high dislocation density or an amorphous layer to facilitate recrystallization
Implementation Method 2
temperature loading of the contacted solid substrates to form a permanent bond on the bonding surfaces, caused at least predominantly by recrystallization
Implementation Method 3
Recrystallization is understood to mean the formation of a new structure through grain growth. A prerequisite for such grain growth are high degrees of deformation, which increase the dislocation density of a material
Data Source
Figure 1a~1e
Figure 2a~2c
Figure 3a~3c
AI summary
The invention relates to a method for bonding a first bonding surface (1o) of a first solid body substrate (1) consisting of a first material to a second bonding surface (2o) of a second solid body substrate (2) consisting of a second material, comprising the following steps, in particular in the following sequence: machining of the first and/or second bonding surfaces (1o, 2o) by means of a cutting tool (5) at a speed vs below a critical speed Vk and at a temperature Ts above a critical temperature Tk and up to a surface roughness O of less than 1 μm; bringing the first solid body substrate (1) into contact with the second solid body substrate (2) at the bonding surfaces (1o, 2o); and thermally treating the solid body substrates (1, 2) in contact to form a permanent bond induced at least mainly by recrystallisation at the bonding surfaces (1o, 2o), in each case as far as a recrystallisation depth R greater than the surface roughness O of the bonding surfaces (1o, 2o) at a bonding temperature TB above the recrystallisation temperature. The invention further relates to a corresponding device and to a cutting tool for machining the first and/or second bonding surfaces at a speed vs below a critical speed Vk and at a temperature Ts above a critical temperature Tk and up to a surface roughness O of less than 1 μm.