Structured Contacts in Photovoltaic Components via Lift-Off
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Solution Overview
Problem
Existing methods for producing structured contacts in photovoltaic components, such as those used in a-Si/c-Si heterojunction solar cells, are costly and time-consuming, often requiring complex alignment and multiple structuring steps, which can lead to substrate damage and reduced process reliability.
Innovation Solution
A method utilizing a nanocrystalline or amorphous doped silicon-rich layer with a masking layer having a silicon gradient, allowing for a single lateral structuring step and a faster lift-off process through etching with HF solutions, eliminating the need for complex alignment and reducing substrate damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard photolithography is used for fabricating back-side contact systems, then manufacturing precision is improved, but device complexity and production cost increase
Solution Approach 1:
The patent extracts and removes the masking layer after the lift-off process to expose the structured first doped semiconductor layer. This eliminates the need for complex photolithography masking and alignment steps, simplifying the overall manufacturing process while maintaining contact structuring precision through direct conformal deposition and selective removal.
Solution Approach 2:
Instead of creating contacts by directly patterning the contact material through photolithography, the patent inverts the approach by first depositing a complete conformal layer of the second doped semiconductor layer, then selectively removing it in non-contact areas through lift-off. This reverse methodology simplifies the process by eliminating complex photolithography alignment steps.
2Manufacturing precision
If multiple structuring steps with complex alignment are used, then contact structuring precision is improved, but processing time increases
Solution Approach 1:
The patent merges multiple process steps into a single conformal deposition operation. The second doped semiconductor layer is deposited conformally over the entire surface in one continuous process, eliminating the need for multiple separate structuring steps and alignment operations, thereby reducing processing time while maintaining precision.
Solution Approach 2:
The masking layer is applied and structured beforehand before the conformal deposition of the second doped semiconductor layer. This preliminary structuring of the masking layer with contact opening definitions enables the subsequent single-step conformal deposition to automatically self-align, eliminating the need for complex real-time alignment during deposition.
3Productivity
If laser radiation is used for structuring, then processing speed is improved, but substrate damage occurs
Solution Approach 1:
The patent introduces a masking layer as an intermediary between the laser structuring process and the substrate. The masking layer absorbs the laser energy and undergoes lift-off, protecting the underlying substrate from direct laser damage while still enabling rapid laser-based structuring of the contact patterns through the masking layer.
Solution Approach 2:
The patent converts the potentially harmful laser radiation into a beneficial process by using it to selectively remove the masking layer in contact areas. The laser energy that could damage the substrate is instead used to modify the masking layer properties, enabling controlled lift-off and contact formation while protecting the substrate through the masking layer's sacrificial role.
4Manufacturing precision
If wet chemical etching is used for structuring, then manufacturing precision is improved, but processing time increases
Solution Approach 1:
The patent replaces the slow wet chemical etching process with a faster laser-based structuring method applied to the masking layer. The laser rapidly patterns the masking layer with high precision, and the subsequent lift-off process in HF solution quickly removes both the masking layer and the conformally deposited second doped semiconductor layer, significantly reducing total processing time while maintaining precision.
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 reduces processing time and enhances reliability by enabling a quick lift-off step, achieving up to 100 times faster results compared to prior methods, while ensuring effective structuring of contacts without substrate damage.
Implementation Method 1
a masking layer is opened using laser radiation to form narrow structures
Implementation Method 2
To remove such damage, the surface is etched using wet chemical processes or plasma
Implementation Method 3
subsequently at least partial removal of the remaining masking layer arrangement and the second doped semiconductor layer to expose the structured first doped semiconductor layer
Data Source
Figure 1A~1F
AI summary
The invention relates to a method, wherein a doped silicon-rich layer that is nanocrystalline or amorphous is used as a first doped semiconductor layer of a first conductivity type and/or as a second doped semiconductor layer having the opposite conductivity type. Two masking layers having materials of different selective etchability are applied for the masking layer arrangement, wherein the masking layer arranged closest to the substrate is a silicon-poor layer having greater etchability in HF-containing etchant than the second masking layer, which is silicon-rich and can be etched in Si-etching etchant. The etching of the structured masking layer arrangement is performed in a silicon-etching solution in at least one etching step at least in order to remove the first doped silicon-rich layer in the contact openings and in order to remove the Si-rich masking layer in the unstructured regions of the masking layer arrangement, wherein at the same time the remaining exposed surface of the Si-poor masking layer is roughened, and the at least partial removal of the still remaining silicon-poor masking layer and of the second doped silicon-rich layer arranged on the rough surface of said silicon-poor masking layer is performed by means of a lift-off process in an HF-containing solution in order to expose the structured first silicon-rich layer. The same result is achieved by using only one masking layer having a silicon gradient.