Semiconductor Wafer Metallization via Printing Process
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Solution Overview
Problem
Current metallization methods for semiconductor wafers, particularly in metal wrap through solar cells, face challenges in reliably and cost-effectively metallizing through-contact openings across the wafer surface, including the side surfaces and bottom, with existing methods being complex and inefficient.
Innovation Solution
A method involving a semiconductor wafer with Ge and III-V sub-cells, where a photoresist layer is applied using a printing process to create a coherent pattern, allowing for simultaneous metallization of through-openings and the wafer surface in a single step, using a metal layer applied over the photoresist and then removed to leave a precise metal pattern, enabling reliable and cost-effective metallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metallization methods (screen printing, dispensing heads) are used to metallize through-contact openings, then the metallization can be applied to the wafer surface, but the process becomes complex and inefficient, failing to achieve reliable metallization of through-contact openings across the wafer surface
Solution Approach 1:
The patent combines the metallization of through-contact openings with the metallization of the wafer surface into a single integrated process. By applying metal layer simultaneously to both the lacquer pattern (which defines through-contact openings) and the exposed wafer surface, the method eliminates the need for separate metallization steps, thereby reducing process complexity while maintaining metallization reliability.
Solution Approach 2:
The patent applies a lacquer pattern to the wafer surface before metallization to pre-define the geometry of through-contact openings. This preliminary structuring allows the metal layer to be deposited precisely where needed, ensuring reliable metallization of through-contact openings while simplifying the overall process by eliminating subsequent complex patterning steps.
2Productivity
If multiple separate steps are used to metallize through-contact openings and wafer surface, then each area can be treated individually, but the process time increases and efficiency decreases
Solution Approach 1:
The patent merges multiple metallization operations into a single simultaneous deposition step. The metal layer is applied to both the lacquer pattern and exposed wafer surface in one process action, doubling the productivity gain by eliminating the need for separate metallization steps for through-contact openings and surface areas, thereby significantly reducing total process time.
3Manufacturing precision
If a coherent lacquer pattern is applied using printing process, then precise metal pattern can be achieved, but the application process requires additional precision control
Solution Approach 1:
The patent uses a lacquer pattern as an intermediary element that bridges the gap between simple printing application and precise metal patterning. The lacquer layer serves as a temporary mask and structural guide that can be applied using relatively simple printing processes, yet it defines precise through-contact opening geometries that guide subsequent metal deposition, achieving high manufacturing precision without requiring complex application equipment.
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 allows for precise, reliable, and cost-effective metallization of through-openings and the wafer surface, improving the efficiency and coherence of the metallization process, enabling reliable cut-out of through-contact holes and surface coverage.
Implementation Method 1
selectively applying a lacquer layer as a lacquer pattern by means of a printing process on the top surface or on the bottom surface of the semiconductor wafer
Implementation Method 2
the metal is applied over a surface, e.g., by physical vapor deposition
Data Source
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AI summary
Metallization process for a semiconductor wafer comprising at least the following steps: providing a semiconductor wafer with a top side, a bottom side, and comprising several solar cell stacks, each solar cell stack comprising a Ge substrate forming the bottom side of the semiconductor wafer, a Ge subcell, and at least two III-V subcells in the aforementioned order, as well as at least one through-hole extending from the top side to the bottom side of the semiconductor wafer with a continuous side wall and an oval cross-sectional circumference; selectively applying a photoresist layer as a lacquer pattern by means of a printing process to the top side and/or bottom side of the semiconductor wafer; and applying a metal layer over the entire surface to exposed areas of the photoresist-coated surface of the semiconductor wafer and to the lacquer layer.Detachment of the lacquer pattern, along with the portion of the metal layer on it, from the semiconductor wafer.