Plasma Substrate Bonding Oxide Removal Vacuum
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for bonding metallic or semiconductor substrates face challenges such as oxide layer interference, temperature-related thermal stresses, and material compatibility issues, leading to inefficient and defective multi-layer cell production, particularly in photovoltaic applications.
Innovation Solution
A plasma-treatment method using reducing gases like hydrogen in a controlled plasma chamber to alter or remove oxide layers, allowing for in-situ treatment and subsequent bonding in a vacuum environment, which prevents oxidation and minimizes thermal stress, enabling efficient and high-quality bonding across various substrate materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet etching processes with hydrofluoric acid are used to remove oxide layers, then oxide removal is achieved, but the process becomes time-consuming and requires subsequent high-temperature heat treatment
Solution Approach 1:
The patent replaces the chemical wet etching process with a physical plasma-based oxide removal process. The plasma treatment removes oxides through physical sputtering and chemical reactions in a controlled plasma environment, eliminating the need for liquid chemical etchants and subsequent extensive washing and drying steps, thereby significantly reducing process time while maintaining bonding quality
Solution Approach 2:
The patent changes the process parameters by conducting oxide removal in a plasma environment at lower temperatures compared to the high-temperature heat treatment (700°C) required after wet etching. The plasma process operates at temperatures that prevent oxide regrowth without requiring subsequent high-temperature processing, thus reducing total process time
2Strength
If high temperatures are used during bonding to ensure permanent connection, then bonding strength is improved, but thermal expansion causes misalignment and substrate damage
Solution Approach 1:
The patent performs preliminary oxide removal using plasma treatment before the bonding process. By removing oxides in advance through plasma at lower temperatures, the substrates can be bonded without requiring high-temperature heat treatment, thus maintaining alignment accuracy while achieving sufficient bonding strength through the plasma-prepared surfaces
Solution Approach 2:
The patent changes the bonding process parameters by enabling bonding at lower temperatures through plasma treatment. The plasma-modified surfaces allow for direct bonding or bonding at reduced temperatures, avoiding the thermal expansion and misalignment issues associated with high-temperature bonding while still achieving permanent connections
3Ease of manufacture
If multiple layers are produced through direct epitaxial growth, then manufacturing simplicity is maintained, but lattice structure incompatibility causes defects and reduces quantum efficiency
Solution Approach 1:
The patent extracts the oxide layers from the substrate surfaces using plasma treatment before bonding. By removing the oxide barrier, the plasma process enables direct bonding of substrates with different materials and lattice structures without the defects that would otherwise result from epitaxial growth across incompatible interfaces, thus improving layer quality while maintaining manufacturing simplicity
Solution Approach 2:
The patent enables the creation of composite multi-layer structures by plasma-bonding different semiconductor materials together. The plasma treatment allows direct bonding of dissimilar materials (e.g., silicon with different bandgaps) that would be incompatible through epitaxial growth, creating defect-free composite structures with optimized quantum efficiency for multi-junction solar cells
4Reliability
If hydrofluoric acid is used for oxide removal, then oxide reduction is achieved, but contamination and oxide regrowth occur
Solution Approach 1:
The patent uses plasma in a controlled inert or reducing atmosphere to remove oxides. The plasma environment prevents oxide regrowth during the process, and by conducting the treatment in a vacuum or controlled gas environment, contamination from ambient air is minimized, achieving clean oxide-free surfaces without the contamination issues of liquid HF
Solution Approach 2:
The patent replaces liquid chemical etching with plasma-based oxide removal. The plasma process physically and chemically removes oxides without leaving residual chemical contaminants that would require extensive washing. The plasma-treated surfaces are clean and ready for immediate bonding without regrowth, eliminating the contamination problems associated with hydrofluoric acid processing
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 results in a fast, universally applicable, high-quality bonding process that is environmentally friendly, reduces substrate damage, and allows for the use of diverse materials, enhancing the efficiency and stability of multi-layer cell production.
Implementation Method 1
A plasma-treatment method using reducing gases like hydrogen in a controlled plasma chamber
Implementation Method 2
alter or remove oxide layers, allowing for in-situ treatment
Implementation Method 3
subsequent bonding in a vacuum environment, which prevents oxidation
Data Source
AI summary
A device and method is described for producing an electrically conductive direct bond between a bonding side of a first substrate and a bonding side of a second substrate. A workspace is included that can be closed, gas-tight, against the environment and can be supplied with a vacuum. The workspace includes a) at least one plasma chamber for modifying at least one of the bonding sides and at least one bonding chamber for bonding the bonding sides, and/or b) at least one combined bonding/plasma chamber for modifying at least one of the bonding sides and for bonding the bonding sides.