Sacrificial Layer Bonding for Low-Temperature Substrate Joining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current bonding technologies in the semiconductor industry require high temperatures and pressures, leading to potential damage to functional units and malfunctions, especially in microchips and memory chips, due to thermal expansion coefficients differences and the need for precise alignment without movement post-alignment.
Innovation Solution
The method involves depositing an ultra-thin sacrificial layer on the substrate contact surfaces, which is dissolved during bonding, allowing for low-temperature and low-pressure bonding through a pre-bonding process using a sacrificial layer, preferably a liquid like water, to form a strong connection without damaging the substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperature and pressure bonding is used to bond metal substrates, then bonding strength is improved, but functional units and microchips may be damaged due to thermal stress
Solution Approach 1:
A sacrificial layer (liquid or solid) is introduced as an intermediary between the metal substrates. This sacrificial layer enables bonding at reduced temperatures by forming a pre-bond connection, eliminating the need for high-temperature thermal activation that would otherwise damage sensitive functional units and microchips.
Solution Approach 2:
The bonding process parameters are fundamentally changed by introducing a sacrificial layer that alters the bonding mechanism. Instead of relying on high-temperature diffusion bonding of metal surfaces, the process uses low-temperature pre-bonding through the sacrificial layer, followed by its controlled dissolution to create the final metal-to-metal bond.
2Stability of the object's composition
If high temperature heat treatment is applied to create permanent bond, then irreversible connection is achieved, but alignment precision may be compromised due to thermal expansion differences
Solution Approach 1:
Alignment is performed at room temperature before bonding, when no thermal expansion occurs. The sacrificial layer is then applied and bonding is initiated at low temperatures, preserving the alignment precision achieved during the alignment step without the disruptive thermal expansion that would occur with high-temperature bonding.
Solution Approach 2:
The sacrificial layer acts as a mediator that enables bond formation at temperatures low enough to prevent thermal expansion mismatches from compromising alignment precision, while still achieving irreversible bonding through the dissolution process.
3Strength
If liquid sacrificial layer is used to enhance adhesion, then pre-bond strength is improved, but additional process steps are required
Solution Approach 1:
The sacrificial layer undergoes a phase transition from liquid to solid during the bonding process. The liquid state enables enhanced adhesion and pre-bond formation, while the solid state provides structural stability. The subsequent dissolution of the solid sacrificial layer completes the bonding 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 enables efficient bonding at reduced temperatures, minimizing thermal stress and damage, while maintaining the strength of the bond, even at room temperature, by promoting atomic diffusion and dissolution of the sacrificial layer, thus facilitating a durable connection without high thermal activation.
Implementation Method 1
The sacrificial layer is dissolved in the material of the bonding area or the bulk material with the lowest possible temperature treatment
Implementation Method 2
promoting atomic diffusion and dissolution of the sacrificial layer
Implementation Method 3
The prebond is believed to be mainly based on Van der Waals forces, which are present at the surface of the substrates due to permanent and induced dipoles
Implementation Method 4
Thermal activation creates covalent bonds between the surfaces, creating an irreversible bond
Implementation Method 5
The reason is, in the case of water, mainly the provision of oxygen as a connecting atom between the atoms of the substrate surfaces that are to be bonded to one another
Data Source
Figure 1~3
Figure 4
Figure 5
AI summary
The present invention relates to a method for bonding a first partially metallic contact surface of a first substrate (1, 1') to a second partially metallic contact surface of a second substrate, comprising the following steps, in particular the following sequence: - applying several ultrathin sacrificial layers (4) (preferably a solid sacrificial layer and a liquid sacrificial layer deposited thereon, e.g., water) one above the other onto at least one of the contact surfaces, - bonding the substrates (1, 1'), wherein the sacrificial layers (4) are dissolved in the surrounding material or consumed at the interface during bonding. The contact surfaces can be formed from several bonding areas (3') surrounded by bulk material (5) or arranged in substrate cavities (2). The liquid sacrificial layer can be used to create a pre-bond between the substrates (1, 1').