Wafer Bonding via Function Layer Solid Diffusion
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Solution Overview
Problem
Current bonding methods for semiconductor wafers require high temperatures, leading to thermal stresses, contamination, and potential destruction of microchip structures, while also failing to achieve a strong and reproducible bond, especially when dealing with materials of different thermal expansion coefficients.
Innovation Solution
A method involving the application of a function layer on one or both substrates that reacts with the other substrate to form a permanent bond through solid diffusion or phase transformation, minimizing temperature and mechanical stress, and using specific material combinations like Cu—Fe, Cu—Ge, and others to enhance bond strength at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperatures are used for bonding, then bond strength is improved, but thermal stresses and destruction of microchip structures occur
Solution Approach 1:
The patent changes the bonding parameters by using lower temperatures (below 200°C, preferably below 150°C) combined with a function layer that enables bonding through solid diffusion or phase transformation rather than traditional high-temperature welding. This parameter change allows achieving sufficient bond strength while avoiding thermal stress damage to temperature-sensitive microchip structures.
Solution Approach 2:
The patent introduces a function layer as an intermediary between the two substrates to be bonded. This function layer contains a second material that reacts with the first material from the other substrate through solid diffusion or phase transformation, enabling bonding at lower temperatures. The function layer mediates the bonding process, allowing strong bonds without the high temperatures that cause thermal stress.
2Strength
If high temperatures are used for bonding, then bond strength is improved, but contamination and energy consumption increase
Solution Approach 1:
The patent reduces the bonding temperature parameter to below 200°C, which significantly reduces contamination risks and energy consumption compared to traditional high-temperature bonding methods. The function layer enables this parameter change while maintaining bond strength through alternative bonding mechanisms (solid diffusion and phase transformation).
3Strength
If high temperatures are used for bonding, then bond strength is improved, but microchip structures are destroyed
Solution Approach 1:
The patent changes the temperature parameter to a lower range (below 200°C, preferably below 150°C) that preserves the integrity of temperature-sensitive microchip structures while still achieving strong bonds through the function layer-mediated solid diffusion and phase transformation processes.
Solution Approach 2:
The function layer serves as a protective intermediary that enables bonding through chemical reactions (solid diffusion and phase transformation) at lower temperatures, thereby protecting the microchip structures from thermal damage while achieving the required bond strength.
4Strength
If conventional bonding methods are used, then bond strength is achieved, but reproducibility is poor
Solution Approach 1:
The patent applies a function layer in advance on one or both substrates before the bonding process. This preliminary action ensures that the reactive second material is already present in controlled amounts and distributions, enabling reproducible bonding results through solid diffusion or phase transformation at lower temperatures, unlike conventional methods that rely on high-temperature welding with poor reproducibility.
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 allows for a strong, irreversible bond at lower temperatures, reducing thermal stresses and contamination, and achieving bond strengths greater than 1.5 J/m2, while minimizing surface roughness and preventing unwanted reactions, thus improving the reliability and longevity of semiconductor structures.
Implementation Method 1
a function layer with a second material which reacts with a first material of the other solid substrate especially after contact-making or production of a prebond between the solid substrates, and thus forms an irreversible or permanent bond between the solid substrates. The reaction is solid diffusion and/or a phase transformation.
Implementation Method 2
The reaction is solid diffusion and/or a phase transformation.
Data Source
AI summary
A method for bonding of a first solid substrate to a second solid substrate which contains a first material with the following steps, especially the following sequence: formation or application of a function layer which contains a second material to the second solid substrate, making contact of the first solid substrate with the second solid substrate on the function layer, pressing together the solid substrates for forming a permanent bond between the first and second solid substrate, at least partially reinforced by solid diffusion and/or phase transformation of the first material with the second material, an increase of volume on the function layer being caused.