Pulsed Laser Liftoff of Multilayer Epitaxial Structures
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for recovering epitaxial structures from semiconductor wafers are inefficient, as they typically allow for the removal of only one layer per wafer reuse, leading to high costs and energy consumption, and can damage the substrate, limiting the number of device layers that can be produced.
Innovation Solution
A technique involving the formation of a multilayer structure with alternating epitaxial and sacrificial layers, where laser liftoff is used to sequentially release multiple epitaxial structures from the substrate, allowing for repeated wafer reuse and reducing energy consumption and material waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional thin film removal techniques are used, then a single layer can be removed from the wafer, but the wafer can only be reused once per layer removal cycle, limiting productivity
Solution Approach 1:
The patent segments the wafer surface into multiple distinct growth regions, each capable of producing separate epitaxial layers. By creating spatially separated growth zones on the wafer, multiple layers can be independently formed and subsequently removed through laser liftoff, enabling recovery of multiple layers per wafer reuse cycle and significantly improving productivity
Solution Approach 2:
The patent performs preliminary actions by pre-defining multiple growth regions on the wafer before the actual layer deposition process. These pre-configured regions are designed to accommodate multiple epitaxial layer formations, allowing the wafer to be prepared in advance for multi-layer recovery operations, thereby reducing cycle time and improving overall productivity
2Productivity
If conventional removal techniques are used, then layer removal can be achieved, but the process requires long substrate acid exposure and takes hours, increasing energy consumption
Solution Approach 1:
The patent replaces conventional mechanical and chemical removal methods (acid exposure, mechanical peeling) with laser-based liftoff technology. The laser pulse delivers energy precisely to the interface between the epitaxial layer and substrate, causing rapid separation through ablation or stress wave generation. This substitution reduces process time from hours to seconds and eliminates the need for prolonged acid exposure, thereby reducing energy consumption and improving productivity
Solution Approach 2:
The patent employs periodic pulsed laser action to remove epitaxial layers. Instead of continuous energy application, short-duration laser pulses are delivered at specific intervals to achieve layer separation. This periodic action allows for precise control of the removal process, minimizing energy consumption while maintaining high removal speed and preventing thermal damage to the substrate
3Productivity
If multiple layers are grown on the wafer, then productivity increases, but thermal stress and substrate damage accumulate, reducing reliability
Solution Approach 1:
The patent extracts the epitaxial layers from the substrate using laser liftoff technology after each growth cycle. By removing the grown layers promptly and cleanly, the substrate is restored to its original state without accumulated thermal stress or material buildup. This extraction process prevents damage accumulation and maintains substrate reliability for subsequent growth cycles, enabling high productivity without compromising quality
Solution Approach 2:
The patent implements a discard and recover cycle where epitaxial layers are removed (discarded from the substrate) and the substrate is recovered for reuse. The laser liftoff process enables clean separation where the grown layers are discarded as separate recoverable products, while the substrate is recovered in pristine condition. This cycle can be repeated multiple times without degrading substrate quality, maintaining reliability while increasing the number of devices produced per wafer
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 significantly increases the number of device layers that can be recovered per wafer reuse, lowers costs, and preserves the substrate quality, enabling the production of high-quality thin film devices like solar cells and LEDs with improved efficiency and reduced thermal stress.
Implementation Method 1
Illuminating the multilayer structure with one or more pulses of laser radiation such that absorption of the laser radiation in a selected one of the sacrificial structures provides ablative release from each other of structures sandwiching the selected one of the sacrificial structures
Implementation Method 2
absorption of the laser radiation in a selected one of the sacrificial structures provides ablative release
Data Source
AI summary
We provide a technique that can rapidly and sequentially separate multiple sets of thin films from a wafer, effectively multiplying the number of epitaxial structures that may be recovered per wafer reuse, and therefore increasing throughput and reducing costs. A multilayer structure is formed of alternating epitaxial structures and sacrificial structures, with the entire stack disposed on a substrate structure. Then laser liftoff is performed one sacrificial structure at a time, to individually release the epitaxial structures from the substrate (and from each other).