Rear-Side Laser Marking for Solar Cell Traceability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for marking semiconductor wafers, particularly solar cell stacks, lack efficiency and reliability in providing unique identification, often requiring multiple adjustments and risking damage from heat input and impurities during the marking process.
Innovation Solution
A marking method using laser ablation on the underside of semiconductor wafers to create a unique topography, which can be enhanced by etching for increased contrast and protection, allowing for efficient and early identification of solar cell stacks with minimal additional complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If marking is applied on the front side of solar cells, then traceability is achieved, but the active area is reduced and manufacturing complexity increases
Solution Approach 1:
The patent applies marking on the rear side of the solar cell instead of the front side, inverting the conventional approach. This allows traceability to be achieved without reducing the active area of the front side, as the marking is placed on the previously unused rear surface.
Solution Approach 2:
The marking is integrated into the rear-side contacting structure, utilizing the vertical dimension and existing structural features on the rear side. This approach adds functionality (traceability) without occupying additional horizontal space that would reduce the active area.
2Reliability
If laser ablation is used for marking, then unique identification is created, but heat input may cause damage and impurities are introduced
Solution Approach 1:
The patent uses a pulsed laser with specific wavelength parameters (1030-1070 nm) and pulse duration (500 fs - 30 ns) to control the energy input. By optimizing these parameters, the laser creates sufficient topographic contrast for unique identification while minimizing excessive heat input that could cause damage or impurity formation.
Solution Approach 2:
The use of pulsed laser radiation instead of continuous laser provides periodic action with controlled duty cycles. This allows the material to cool between pulses, reducing cumulative heat input and preventing thermal damage while still achieving the desired topographic marking.
3Reliability
If marking is done after final inspection, then traceability is established, but additional process steps and time are required
Solution Approach 1:
The marking is performed on the rear side during the manufacturing process, specifically integrated with the rear-side contacting structure formation. This preliminary action establishes traceability early in the process rather than as a final step, eliminating the need for separate post-inspection marking operations.
Solution Approach 2:
The marking process is merged with the existing rear-side contacting structure manufacturing process. By combining these two operations into a single integrated process step, the patent achieves traceability without adding separate process steps or increasing overall manufacturing time.
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
Enables reliable and early unique identification of solar cell stacks with reduced risk of damage, using existing process technologies and minimizing additional complexity, while ensuring the identification remains recognizable and protected against environmental influences.
Implementation Method 1
generating an identification with a unique topography by means of laser ablation, using a first laser, on a surface area of the underside of each solar cell stack
Data Source
AI summary
A marking method for applying a unique identification to each individual solar cell stack of a semiconductor wafer, at least comprising the steps: Providing a semiconductor wafer having an upper side and an underside, which comprises a Ge substrate forming the underside; and generating an identification with a unique topography by means of laser ablation, using a first laser, on a surface area of the underside of each solar cell stack of the semiconductor wafer, the surface area being formed in each case by the Ge substrate or by an insulating layer covering the Ge substrate.