Silicon Laser Doping with Dual Glass Layers for Mask-Free Junctions
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Solution Overview
Problem
Conventional methods for doping silicon substrates for solar cells require multiple steps, including masking processes, which are time-consuming and complex, and often necessitate separate high-temperature treatments for generating differently doped regions.
Innovation Solution
A method involving coating a silicon substrate with a layer stack of boron-containing and phosphorus-containing glass layers, followed by laser irradiation to introduce dopants into the substrate, and subsequent heating in a furnace to achieve doped regions with varying polarity and concentration without the need for masking steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional doping methods with masking processes are used, then doped regions can be generated, but the process becomes time-consuming and complex
Solution Approach 1:
The glass layers containing dopants are deposited on the silicon substrate surface before the doping process. This preliminary preparation allows the dopants to be positioned exactly where needed, eliminating the need for masking processes during the actual doping step and significantly reducing process time while maintaining precision
Solution Approach 2:
The masking function is extracted and replaced by the glass layer structure itself. The glass layers are selectively removed or activated to release dopants only in desired regions, thereby eliminating separate masking steps and reducing overall process complexity and time
2Manufacturing precision
If multiple separate high-temperature treatments are used for generating differently doped regions, then precise doping control is achieved, but the process complexity increases
Solution Approach 1:
Multiple doping functions are merged into a single high-temperature treatment step. The glass layers containing different dopants are simultaneously activated or selectively removed in one process, allowing multiple doped regions to be created in a single heating cycle rather than requiring separate treatments for each region
Solution Approach 2:
The glass layer structure serves multiple functions: it acts as a dopant source, a protective layer, and a selective mask. This multi-functionality allows a single high-temperature step to achieve what would otherwise require multiple specialized processes, reducing overall process complexity
3Manufacturing precision
If masking layers are used to protect regions from doping, then selective doping is achieved, but the process steps increase
Solution Approach 1:
The glass layers are deposited in advance with dopants already positioned in the desired locations. This preliminary action eliminates the need for subsequent masking steps, as the glass layer structure itself defines where doping will occur when activated
Solution Approach 2:
The glass layers serve as an intermediary structure that combines the functions of both dopant source and protective mask. By using this intermediate layer, the process achieves selective doping without requiring separate masking materials and steps
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 simplifies the doping process, allowing for the creation of multiple doped regions in a single process step, reduces the complexity and time required, and enables the formation of efficient p-n junctions suitable for solar cells, such as IBC solar cells, while minimizing the influence on existing doped regions.
Implementation Method 1
the region of the silicon substrate close to the surface is melted during the irradiation with laser radiation
Implementation Method 2
the layer stack is ablated in order to obtain a doped first region from which the layer stack is ablated
Implementation Method 3
dopant predominantly from the glass layer of the two glass layers that is closer to the surface of the silicon substrate than the other of the two glass layers is introduced into the silicon substrate close to the surface
Implementation Method 4
heating the silicon substrate in a furnace to a temperature of at least 700° C., such that dopant predominantly from one of the two glass layers is introduced into the silicon substrate close to the surface
Data Source
AI summary
A method for doping a silicon substrate, in particular for a solar cell, includes coating a surface of the silicon substrate with a layer stack composed of at least two glass layers such that the layer stack at least covers a first region to be doped and a second region to be doped of the silicon substrate. the layer stack includes a first glass layer containing boron as p-type dopant and a second glass layer containing phosphorus as n-type dopant; and irradiating the first region covered with the layer stack with laser radiation such that dopant predominantly from the glass layer of the two glass layers that is closer to the surface of the silicon substrate than the other of the two glass layers is introduced into the silicon substrate close to the surface.