Hydrophilic Substrate Bonding Layer for Low-Temperature Interface Closure
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Solution Overview
Problem
Existing substrate bonding processes require high-temperature heat treatments to close the bonding interface, which are costly, time-consuming, and can damage semiconductors, leading to defects such as localized debonding and preferential etching due to incomplete interface closure.
Innovation Solution
A process involving the deposition of a thin, non-metallic, dihydrogen-permeable bonding layer with a yield strength lower than the substrates, allowing hydrophilic bonding at temperatures below 900°C, typically 600°C, to close the interface by flattening asperities and enabling dihydrogen diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature heat treatment is applied to close the bonding interface, then the interface closure quality is improved, but the thermal budget increases and substrate damage risk increases
Solution Approach 1:
A bonding layer made of silicon oxide or silicon oxynitride is deposited between the first and second substrates at the bonding interface. This intermediate layer has lower yield strength than the substrates, allowing it to deform and flatten asperities at reduced temperatures (below 900°C, typically around 600°C), thereby closing the bonding interface without requiring high-temperature heat treatment that would damage the semiconductor substrates.
Solution Approach 2:
The invention changes the mechanical properties parameter (yield strength) by introducing a bonding layer with specifically controlled thickness (1-6 nm) and material composition. This bonding layer has lower yield strength than the substrates, enabling interface closure at lower temperatures by allowing plastic deformation of the bonding layer rather than requiring high-temperature deformation of the rigid substrates.
2Manufacturing precision
If high-temperature heat treatment is applied to close the bonding interface, then the interface closure is improved, but the treatment time increases and production cost increases
Solution Approach 1:
The bonding layer serves as a mediator that enables interface closure at lower temperatures. Since the bonding layer has lower yield strength and can deform more easily than the substrates, it allows asperity flattening and interface closure to occur at reduced temperatures (around 600°C instead of 1100-1200°C), significantly reducing heat treatment time and associated production costs while maintaining interface closure quality.
3Manufacturing precision
If the bonding layer thickness is increased, then the interface closure capability is improved, but the dihydrogen diffusion is hindered
Solution Approach 1:
The invention optimizes the bonding layer thickness to a specific range of 1-6 nm. This thin thickness is sufficient to provide the necessary yield strength reduction for interface closure while remaining thin enough to allow dihydrogen atoms to diffuse through the layer. The bonding layer is permeable to dihydrogen, enabling the dihydrogen produced during hydrophilic bonding to escape without accumulating and causing defects, while still providing adequate mechanical compliance for interface closure.
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
Achieves high-quality bonding with reduced thermal stress, minimizing defects and etching issues, while maintaining compatibility with hydrophilic bonding techniques.
Implementation Method 1
a bonding layer made of a non-metallic material that is permeable to dihydrogen
Implementation Method 2
when a high-temperature heat treatment is applied, the contact surface grows until the asperities are flattened, this leading to removal of the cavities
Implementation Method 3
a yield strength lower than that of at least one of the materials of the first substrate and of the second substrate located at the bonding interface
Data Source
AI summary
A process for hydrophilic bonding first and second substrates, comprising: —bringing the first and second substrates into contact to form a bonding interface between main surfaces of the first and second substrates, and—applying a heat treatment to close the bonding interface. The process further comprises, before the step of bringing into contact, depositing, on the main surface of the first and/or second substrate, a bonding layer comprising a non-metallic material that is permeable to dihydrogen and that has, at the temperature of the heat treatment, a yield strength lower than that of at least one of the materials of the first substrate and of the second substrate located at the bonding interface. The layer has a thickness between 1 and 6 nm, and the heat treatment is carried out at a temperature lower than or equal to 900° C., and preferably lower than or equal to 600° C.