Cleave Layer Removal for Bifacial Solar Cell Fabrication
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Solution Overview
Problem
Existing methods for removing metal stressor layers from spalled semiconductor films using wet or dry chemical etching are non-uniform, leading to potential cracks in the film and are time-consuming, which hinders the fabrication of high-temperature devices and flexible bifacial solar cells.
Innovation Solution
A method involving a cleave layer with a lower fracture toughness than the host substrate material, which is laterally etched or dissolved to detach and remove the stressor layer, facilitating the handling and processing of spalled semiconductor films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet or dry chemical etching is used to remove the metal stressor layer, then the stressor layer can be removed, but the etch rate is non-uniform which induces cracks in the spalled film and the process is time-consuming
Solution Approach 1:
A sacrificial cleave layer is introduced as an intermediary between the host substrate and the metal stressor layer. This cleave layer is designed to be selectively removable, allowing the stressor layer to be detached mechanically or chemically without directly etching through the entire stressor layer thickness. The cleave layer acts as a mediator that facilitates clean separation while preserving the integrity of the spalled film.
Solution Approach 2:
The removal process is segmented into two distinct stages: first, the cleave layer is selectively removed (compromised) to create a separation plane; second, the stressor layer is detached along this pre-created plane. This segmentation allows each step to be optimized independently, avoiding the need for time-consuming complete stressor layer etching while preventing film cracks through controlled separation.
2Ease of manufacture
If complete removal of the thick nickel layer using wet/dry etching is performed, then the stressor layer is fully removed, but the throughput is lowered due to the time-consuming nature of the process
Solution Approach 1:
The cleave layer is prepared in advance during the fabrication process, positioned between the host substrate and the metal stressor layer. This preliminary action creates a pre-defined separation plane that enables rapid subsequent removal of the stressor layer without requiring time-consuming complete etching of the thick nickel layer, thereby maintaining both removal completeness and high throughput.
3Ease of operation
If the metal stressor layer is kept on the spalled film, then handling is easier and more reliable, but the film cannot be used for high temperature device processing or applications requiring exposure of the original semiconductor substrate surface
Solution Approach 1:
The cleave layer serves as a temporary intermediary support structure that enables easy handling during fabrication but can be selectively removed when needed. This allows the spalled film to maintain handling advantages during processing while enabling transition to applications requiring direct substrate access or high temperature processing by removing the cleave and stressor layers.
Solution Approach 2:
The support structure (stressor layer with cleave layer) transitions from a permanent support role during fabrication to a removable component for final applications. The dynamic nature of this support system allows it to provide handling assistance when needed and be removed when the spalled film requires direct substrate access or high temperature processing, thus adapting to different operational requirements.
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 simplifies the post-spalling device fabrication process, enhances mechanical flexibility, allows for the reuse of host semiconductor substrates, and enables bifacial solar cell operation without compromising device performance.
Implementation Method 1
A method involving a cleave layer with a lower fracture toughness than the host substrate material, which is laterally etched or dissolved to detach and remove the stressor layer
Implementation Method 2
A method involving a cleave layer with a lower fracture toughness than the host substrate material, which is laterally etched or dissolved to detach and remove the stressor layer
Implementation Method 3
separating a portion of the semiconductor from the host substrate via controlled spalling
Data Source
AI summary
A stressor layer used in a controlled spalling method is removed through the use of a cleave layer that can be fractured or dissolved. The cleave layer is formed between a host semiconductor substrate and the metal stressor layer. A controlled spalling process separates a relatively thin residual host substrate layer from the host substrate. Following attachment of a handle substrate to the residual substrate layer or other layers subsequently formed thereon, the cleave layer is dissolved or otherwise compromised to facilitate removal of the stressor layer. Such removal allows the fabrication of a bifacial solar cell.