Hot Melt Ink Resist for Uniform Semiconductor Current Tracks
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Solution Overview
Problem
The formation of current tracks on semiconductors often results in undercutting during etching, leading to irregular widths and electrical shorts, which reduces the efficiency of semiconductor devices like photovoltaics and solar cells, especially when working with thinner wafers and smaller dimensions.
Innovation Solution
A method using a hot melt ink resist with hydrogenated rosin resins and fatty acids, combined with an inorganic acid etch containing polyols, is applied to inhibit undercutting, ensuring uniform current track dimensions and preventing capillary seepage of the etchant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to form current tracks, then metal coating and conductivity are achieved, but undercutting occurs leading to irregular track widths and electrical shorts
Solution Approach 1:
A resist layer is introduced as an intermediary between the etchant and the semiconductor substrate. This resist layer selectively protects the areas where current tracks should not form, preventing unwanted lateral etching and undercutting. The resist acts as a mediator that controls the interaction between the etchant and substrate, ensuring precise track geometry and preventing electrical shorts between adjacent tracks.
2Productivity
If the number of current tracks is increased on smaller wafers, then electrical output is improved, but shadowing of the active surface increases reducing photon capture
Solution Approach 1:
The front surface of the semiconductor is segmented into multiple discrete current tracks rather than a continuous metal layer. This segmentation allows light to pass through the gaps between tracks to reach the active semiconductor surface, reducing shadowing losses. Meanwhile, the tracks are strategically positioned and sized to collect sufficient current, maintaining high electrical output. The segmentation enables optimization of both light capture and current collection independently.
3Loss of substance
If thinner semiconductor wafers are used, then material usage and cost are reduced, but manufacturing precision and resistance to damage during processing deteriorate
Solution Approach 1:
The resist layer is applied and patterned before the etching process begins. This preliminary action establishes precise boundaries for the current tracks before any material removal occurs. The resist pattern serves as a pre-defined template that guides the subsequent etching, ensuring that even on thin, fragile substrates, the current tracks are formed with accurate dimensions and positions. This preliminary patterning compensates for the reduced mechanical stability of thinner wafers during processing.
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 approach allows for the formation of current tracks with reduced or no detectable undercutting, enhancing uniformity and electrical output, reducing shadowing, and increasing the number of current tracks on smaller wafers, thereby improving the efficiency of semiconductor devices.
Implementation Method 1
inhibit undercutting... preventing capillary seepage of the etchant
Implementation Method 2
applying an etch composition including one or more inorganic acids to the semiconductor to etch away exposed portions of the semiconductor antireflective layer
Data Source
AI summary
Methods of making current tracks for semiconductors are disclosed. The methods involve selectively depositing a hot melt ink resist containing rosin resins and waxes on a silicon dioxide or silicon nitride layer coating a semiconductor followed by etching uncoated portions of the silicon dioxide or silicon nitride layer with an inorganic acid etch to expose the semiconductor and simultaneously inhibit undercutting of the hot melt ink resist. The etched portions may then be metallizaed to form a plurality of substantially uniform current tracks.