Vertical LED Impact Damping Layer for Laser Lift-Off Stress
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Solution Overview
Problem
The fabrication of GaN-based light emitting diodes (LEDs) with a vertical structure faces challenges in substrate separation due to high-production costs, poor heat release efficiency, and degradation of electrical characteristics caused by stress and impact during the laser lift-off process, which results in irregularities and poor bonding in the semiconductor layer.
Innovation Solution
A light emitting device with a vertical structure is manufactured using a semiconductor layer with a multilayer structure, featuring a metal support and an impact damping layer made of a ductile metal to absorb the impact generated during substrate separation, reducing stress and maintaining ohmic characteristics, and the process involves growing a GaN semiconductor layer over a sapphire substrate, etching to define device regions, forming electrodes, and using a diode pumped solid state laser to form grooves for controlled substrate removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser lift-off method is used for substrate separation, then chip separation efficiency is improved, but impact and stress damage the semiconductor layer and degrade electrical characteristics
Solution Approach 1:
A metal layer with high ductility (impact damping layer) is formed on the semiconductor layer before substrate separation. This layer acts as a cushion to absorb impact and stress during laser lift-off, preventing damage to the semiconductor layer and maintaining ohmic characteristics of electrodes.
Solution Approach 2:
The metal impact damping layer serves as an intermediary between the semiconductor layer and the external environment during substrate separation. It mediates the harmful effects of laser-induced stress and nitrogen gas expansion, protecting the semiconductor layer while allowing the separation process to proceed efficiently.
2Manufacturing precision
If laser irradiation is increased to improve substrate separation, then separation completeness is improved, but nitrogen gas expansion causes more impact and damage
Solution Approach 1:
The ductile metal impact damping layer is pre-formed to cushion against nitrogen gas expansion impact. This allows complete substrate separation with high laser irradiation while the metal layer absorbs the harmful expansion forces, preventing damage to the semiconductor layer.
Solution Approach 2:
The harmful nitrogen gas expansion force during laser lift-off is converted into a beneficial effect by the ductile metal layer, which uses its plasticity to absorb and dissipate the expansion energy as deformation, protecting the semiconductor layer from damage.
3Temperature
If vertical structure is adopted, then heat release efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into distinct steps: forming the semiconductor layer, forming electrodes, forming the metal impact damping layer, forming the metal support, and substrate separation. This systematic segmentation manages complexity while achieving the heat release benefits of vertical structure.
Solution Approach 2:
The metal impact damping layer and metal support are formed preliminarily before substrate separation. This preliminary action ensures that protective structures are in place before the challenging separation step, simplifying the overall manufacturing process by preventing damage that would require rework.
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 effectively reduces the impact on the semiconductor layer, maintains electrical characteristics, and simplifies the chip separation process, improving the manufacturing efficiency and reducing production costs by minimizing laser irradiation and nitrogen gas expansion effects.
Implementation Method 1
irradiating a laser to the unit device regions of the semiconductor layer, to form grooves in the semiconductor layer
Implementation Method 2
an impact damping layer arranged between the first electrode and the metal support, and made of a metal having a ductility higher than a ductility of a metal of the metal support
Data Source
AI summary
A light emitting device having a vertical structure and a method for manufacturing the same, which are capable of damping impact generated during a substrate separation process and achieving an improvement in mass productivity, are disclosed. The light emitting device includes a semiconductor layer having a multilayer structure, a first electrode arranged at one surface of the semiconductor layer, a metal support arranged on the first electrode, and an impact damping layer arranged between the first electrode and the metal support, and made of a metal having a ductility higher than a ductility of a metal for the metal support.