Selective Deposition for Interdigitated Solar Cell Patterns
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Solution Overview
Problem
The creation of interdigitated patterns for silicon heterojunction interdigitated back-contact solar cells is complex and costly, making it challenging for mass production, as existing processes like photolithography and lift-off are difficult to adapt outside laboratory settings.
Innovation Solution
A method involving selective deposition of amorphous silicon layers using plasma deposition and etching processes, with different etch rates for sublayers on a hard mask and exposed regions, forming a second passivation layer stack that includes intrinsic and doped amorphous silicon layers, and optional thermal annealing to enhance surface passivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photolithography and lift-off processes are used to create interdigitated patterns, then pattern formation is achieved, but manufacturing cost increases and mass production becomes difficult
Solution Approach 1:
The patent replaces complex photolithography and lift-off mechanical processes with a simpler selective deposition process using plasma-enhanced chemical vapor deposition (PECVD). This substitution eliminates the need for photoresist coating, patterning, and lift-off steps, directly forming the interdigitated pattern through selective area deposition on the substrate.
Solution Approach 2:
The patent utilizes parameter changes in the PECVD process, specifically controlling deposition conditions such as temperature, pressure, and gas flow rates to achieve selective deposition only in desired regions. By adjusting these parameters, the process enables direct pattern formation without complex mechanical intervention.
2Manufacturing precision
If photolithography and lift-off processes are used, then interdigitated patterns are formed, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive photolithography and lift-off equipment with a more cost-effective selective PECVD deposition system. This mechanical substitution significantly reduces manufacturing costs while maintaining the ability to form precise interdigitated patterns through controlled selective deposition.
3Reliability
If selective deposition with different etch rates is used, then surface passivation is improved, but process steps increase
Solution Approach 1:
The patent applies local quality by creating different a-Si layers with distinct properties in different locations. The first a-Si layer provides intrinsic passivation, while the second doped a-Si layer provides selective passivation and contact formation. This local differentiation of material properties enhances overall surface passivation quality.
Solution Approach 2:
The patent segments the passivation function into multiple distinct layers: an intrinsic a-Si layer for general passivation and a doped a-Si layer for selective functional regions. This segmentation allows each layer to perform its specific function optimally, improving overall reliability.
4Reliability
If in-situ plasma cleaning is implemented, then vacuum breaking is eliminated, but process integration complexity increases
Solution Approach 1:
The patent merges the plasma cleaning step with the PECVD deposition process by performing cleaning in-situ within the same vacuum chamber before deposition begins. This integration eliminates the need to break vacuum between cleaning and deposition, maintaining process continuity and reducing contamination risk.
Solution Approach 2:
The patent maintains continuous vacuum conditions throughout the process by performing plasma cleaning in-situ without breaking vacuum. This continuity of the vacuum environment prevents contamination and maintains process reliability, even though it requires integrated process planning.
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 method enables efficient and cost-effective creation of interdigitated patterns for solar cells, improving surface passivation and minority carrier lifetime, while allowing for in-situ plasma cleaning without breaking the vacuum, thus facilitating mass production.
Implementation Method 1
selectively depositing a second passivation layer stack including at least a third layer of intrinsic amorphous silicon (a-Si, or a-Si:H) on the one or more exposed regions
Implementation Method 2
etching, using a plasma etch process, the added sublayer of the third layer on the hard mask and in the one or more exposed regions
Implementation Method 3
cleaning, using a plasma cleaning process, a surface of the remaining added sublayer of the third layer in the one or more exposed regions from contaminants
Implementation Method 4
optional thermal annealing to enhance surface passivation
Data Source
Figure 1a
Figure 1b~1e
Figure 1f~1h
AI summary
A method (100) for creating an interdigitated pattern for a solar cell is provided, including providing (S110) a substrate with one or more regions covered by a first passivation layer stack covered by a hard mask, and one or more exposed regions. A second passivation layer stack, including at least one layer, is selectively deposited on the exposed regions, including plasma depositing (S120) a sublayer of the at least one layer on the exposed regions and on the hard mask, and plasma etching (S130) the added sublayer with an etch rate that is higher on the hard mask than on the exposed regions, thereby substantially removing the sublayer from the hard mask while leaving a finite thickness of the sublayer on the exposed regions, plasma cleaning (S150) the remaining sublayer, and adding a further sublayer by repeating the steps of deposition (S120) and etching (S130). Cleaning, deposition and etching may be repeated (S142) until a desired thickness of the at least one layer of the second passivation layer stack is obtained.