Continuous Porous Silicon Etching via Horizontal Transport
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Solution Overview
Problem
Existing methods for producing porous silicon layers face challenges such as incomplete wafer etching, high costs due to precious metal electrodes, and inefficiencies in throughput and electrode material usage, particularly in high-throughput systems, as well as issues with hydrogen bubbles and inhomogeneous etching.
Innovation Solution
A device and method for continuous one-sided etching of porous silicon layers using a transport device to move workpieces horizontally through multiple etching chambers with an electrolyte and cathode, where only one surface is wetted, eliminating the need for sealing rings and allowing for full-surface etching without edge wrap, using a cathode and anode contact unit with adjustable spacing and electrolyte convection to prevent bubble deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional electrochemical etching with contacted electrodes is used, then porous silicon layers can be produced, but the entire wafer surface cannot be etched completely and expensive precious metal electrodes are required
Solution Approach 1:
The etching process is segmented into multiple sequential etching chambers, each handling a portion of the wafer surface. This allows complete coverage of the entire wafer by dividing the etching task across multiple stations, eliminating the limitation of single-chamber contacted electrode methods.
Solution Approach 2:
The anode contact is extracted from the wafer surface and replaced with a conductive substrate or table that the wafer rests on. This eliminates the need for precious metal electrodes contacted to the wafer edges, reducing cost and complexity while enabling full-surface etching.
2Productivity
If high-throughput continuous etching is implemented, then productivity increases, but hydrogen bubble deposition causes inhomogeneous etching
Solution Approach 1:
The system uses dynamic transport of wafers through multiple etching chambers at controlled speeds, combined with electrolyte convection currents. This dynamic approach prevents hydrogen bubble accumulation by continuously moving the wafer surface through fresh electrolyte zones, maintaining etching uniformity at high throughput.
Solution Approach 2:
Electrolyte convection currents are introduced to actively remove hydrogen bubbles from the wafer surface during etching. The hydraulic flow of electrolyte through the etching chambers prevents bubble deposition, ensuring homogeneous etching even in high-throughput continuous operation.
3Reliability
If sealing rings are used to prevent electrolyte escape, then etching chamber containment is improved, but edge wrap etching occurs and throughput is reduced
Solution Approach 1:
The wafer is positioned horizontally on a conductive substrate rather than being vertically sealed in a chamber. This dimensional change eliminates the need for sealing rings, prevents edge wrap etching, and allows continuous high-speed throughput while maintaining electrolyte containment through the multi-chamber design.
4Manufacturing precision
If multiple etching chambers are arranged vertically above the workpiece, then complete surface etching is achieved, but the system cannot accommodate discrete workpieces and width is limited
Solution Approach 1:
Instead of arranging etching chambers vertically above the workpiece, the system inverts the approach by placing chambers horizontally below the workpiece. The workpiece rests on a conductive substrate that serves as the anode, allowing electrolyte to be supplied from below. This inversion enables accommodation of discrete workpieces with various geometries and widths while achieving complete surface etching.
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 homogeneous, high-throughput production of porous silicon layers with reduced material costs, accommodating various workpiece geometries, and eliminating the need for expensive electrodes, while allowing for multilayer etching and improved layer thickness uniformity.
Implementation Method 1
arranged so that only one surface of the workpiece to be etched is wettable with the electrolyte
Implementation Method 2
the workpiece being transported horizontally by means of a transport device with the front side of the workpiece to be etched past more than one etching chamber
Implementation Method 3
A device for the continuous production of porous silicon layers on workpieces made of silicon or workpieces with a silicon coating by means of one-sided etching
Data Source
Figure 1~3
Figure 4~6
AI summary
The invention concerns a device and a method for the continuous production of porous silicon layers (single or multiple layers) on workpieces made of silicon or workpieces coated with silicon. The method according to the invention is based on a one-sided etching method, the workpiece being guided past at least one etching chamber containing an electrolyte and a cathode by means of a transport device, horizontally with the workpiece front side to be etched. The method can be used in particular for producing PV cells.