Interdigitated Electrode Formation via Laser Ablation
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Solution Overview
Problem
Industrial manufacturing of interdigitated back contact photovoltaic cells faces challenges in forming interdigitated electrodes without electrical shorts and shunts, particularly due to metal penetration into the silicon substrate during laser ablation and the complexity of additional etch barrier layer deposition.
Innovation Solution
A method involving a dielectric layer on a semiconductor substrate, where the metal seed layer is patterned by laser ablation and partially removing the dielectric layer in the separation region before thickening, using wet etching to prevent metal redeposition and reduce the risk of electrical shorts, thereby simplifying the process and reducing substrate damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser ablation is used to pattern the metal seed layer, then the interdigitated electrode pattern can be formed, but metal penetration into the silicon substrate occurs causing lifetime degradation
Solution Approach 1:
A dielectric layer is deposited on the silicon substrate before forming the metal seed layer. This preliminary protective layer prevents direct contact between the metal and silicon during laser ablation, thereby preventing metal penetration and lifetime degradation while still allowing the electrode patterning process to proceed
Solution Approach 2:
The dielectric layer serves as an intermediary barrier between the metal seed layer and the silicon substrate. During laser ablation, this intermediate layer absorbs some of the laser energy and prevents the metal from penetrating into the silicon, thus protecting the substrate while enabling the patterning process
2Ease of manufacture
If laser ablation is used to pattern the metal seed layer, then the electrode pattern is formed, but metal redeposition on the dielectric layer creates electrical shorts
Solution Approach 1:
The laser parameters (power, pulse duration, wavelength) are optimized to control the ablation process. By adjusting these parameters, the metal is vaporized and removed without excessive redeposition, maintaining electrical isolation between electrodes while still achieving effective patterning
Solution Approach 2:
Pulsed laser ablation is used instead of continuous laser exposure. The periodic pulsing allows for controlled vaporization of the metal with sufficient time between pulses for the vapor to clear, reducing metal redeposition on the dielectric layer and preventing electrical shorts
3Reliability
If an etch barrier layer is added to prevent metal penetration, then substrate damage is reduced, but process complexity increases
Solution Approach 1:
The dielectric layer performs multiple functions simultaneously: it protects the silicon substrate from metal penetration, serves as a base for metal deposition, and prevents metal redeposition during laser ablation. This multi-functionality eliminates the need for separate etch barrier and protective layers, reducing overall process complexity
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 achieves good electrical isolation between interdigitated electrodes, reduces the risk of metal penetration, and maintains process complexity comparable to prior-art methods, while allowing lower laser powers and easier alignment across process steps.
Implementation Method 1
patterning the metal seed layer by laser ablation
Implementation Method 2
Laser ablation thermally evaporates the thin metal seed layer
Implementation Method 3
thickening both electrodes by plating, such as e.g. Cu electroplating
Data Source
AI summary
The disclosed technology generally relates to photovoltaic devices and methods of fabricating photovoltaic devices, and more particularly relates to interdigitated back contact photovoltaic cells and methods of fabricating the same. In one aspect, a method of forming first and second interdigitated electrodes on a semiconductor substrate comprises providing a dielectric layer on the rear surface of the semiconductor substrate. The method additionally comprises providing a metal seed layer on the dielectric layer. The method additionally comprises patterning the metal seed layer by laser ablation, thereby separating it into a first seed layer and a second seed layer with a separation region interposed therebetween, wherein the first seed layer and the second seed layer are interdigitated and electrically isolated from each other. The method further comprises thickening the first seed layer and the second seed layer by plating, thereby forming the first electrode and the second electrode.