Thin Film Laser Patterning with Integrated Heat and Light Blocking Layers
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Solution Overview
Problem
Laser direct patterning of thin film structures and devices, such as thin film batteries, electrochromics, and solar cells, often results in heat transfer from semiconductors or dielectrics to underlying metals, leading to vaporization and functional impairment due to high thermal diffusivity of metals, which reduces efficiency and damages the current collector layers.
Innovation Solution
Incorporating heat and light blocking layers in the device stack below the layers to be removed, with the heat blocking layer having low thermal diffusivity and the light blocking layer being a high-melting-point metal layer to absorb or reflect laser energy, ensuring the underlying layers remain below their melting and recrystallization temperatures during laser ablation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser direct patterning is used to remove dielectric and semiconductor layers, then layer removal efficiency is improved, but underlying metal layers are damaged due to heat transfer and high thermal diffusivity
Solution Approach 1:
A heat blocking layer is introduced as an intermediary between the dielectric/semiconductor layers and the underlying metal layers. This heat blocking layer has low thermal diffusivity and acts as a thermal barrier, preventing heat generated during laser ablation from transferring to the metal layers, thus protecting them from damage while allowing efficient layer removal
Solution Approach 2:
The device stack is segmented into distinct functional layers including dielectric layers, semiconductor layers, heat blocking layers, and metal layers. This segmentation allows each layer to perform its specific function independently, with the heat blocking layer specifically designed to manage thermal effects during laser processing
2Manufacturing precision
If laser energy is concentrated for selective ablation, then ablation precision is improved, but temperature of underlying layers reaches vaporization point causing melting and vaporization
Solution Approach 1:
The heat blocking layer serves as a thermal intermediary that absorbs and contains heat in the upper layers during laser ablation. Its low thermal diffusivity prevents heat from reaching the underlying metal layers, keeping their temperature below the vaporization point even when high laser energy is concentrated for precise ablation
Solution Approach 2:
The thermal diffusivity parameter of the heat blocking layer is specifically selected to be low, creating a thermal gradient that confines heat to the upper layers. This parameter change enables precise control over heat distribution, allowing high laser energy concentration for precise ablation without overheating underlying layers
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 selective removal of specified layers without damaging underlying metal layers, maintaining device functionality and increasing laser ablation efficiency by concentrating heat in the targeted layers.
Implementation Method 1
The light blocking layer may be a layer of metal with a high melting point and of sufficient thickness to absorb and/or reflect all the laser light penetrating through the specified layers
Implementation Method 2
The light blocking layer may be a layer of metal with a high melting point and of sufficient thickness to absorb and/or reflect all the laser light penetrating through the specified layers
Implementation Method 3
the heat blocking layer may be a conductive layer with thermal diffusivity low enough to ensure a majority of the heat from the laser is contained in the layers to be removed
Implementation Method 4
Laser processes for thin film structures and devices such as thin film batteries (TFBs), electrochromic (EC) devices, solar cells, etc. are used to selectively ablate/scribe various layers from the front side (thin film side) of the substrate
Data Source
AI summary
Selective removal of specified layers of thin film structures and devices, such as solar cells, electrochromics, and thin film batteries, by laser direct patterning is achieved by including heat and light blocking layers in the device/structure stack immediately adjacent to the specified layers which are to be removed by laser ablation. The light blocking layer is a layer of metal that absorbs or reflects a portion of the laser energy penetrating through the dielectric/semiconductor layers and the heat blocking layer is a conductive layer with thermal diffusivity low enough to reduce heat flow into underlying metal layer(s), such that the temperature of the underlying metal layer(s) does not reach the melting temperature, Tm, or in some embodiments does not reach (Tm)/3, of the underlying metal layer(s) during laser direct patterning.