Group III Nitride Semiconductor Lift-Off with Laser-Absorbing Nucleus Layer
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Solution Overview
Problem
The laser lift-off technique for separating a sapphire substrate from an AlN semiconductor layer is challenging due to the strong Al—N bond, requiring high laser output that is difficult to achieve.
Innovation Solution
A method involving forming a crystal nucleus layer of AlGaN or AlN on a sapphire substrate, irradiating the back surface with laser light to generate heat, and decomposing the substrate near the interface to facilitate separation, reducing the need for high laser output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser lift-off is used to separate sapphire substrate from AlN semiconductor layer, then substrate separation is achieved, but very high laser output is required which is difficult to achieve
Solution Approach 1:
The patent applies preliminary action by forming a crystal nucleus layer of AlGaN or AlN between the sapphire substrate and the AlN semiconductor layer before the laser lift-off process. This pre-formed layer serves as an intermediate structure that facilitates subsequent substrate separation. The nucleus layer is grown using techniques such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), creating a controlled interface that will later enable easier separation with reduced laser power requirements.
Solution Approach 2:
The crystal nucleus layer acts as an intermediary between the sapphire substrate and the AlN semiconductor layer. This intermediate layer has properties that are intermediate between sapphire and AlN, allowing it to absorb laser energy more effectively than pure AlN while still maintaining strong bonding to both layers. The intermediary layer transfers and concentrates the laser energy at the substrate interface, enabling separation with lower overall laser output.
2Reliability
If high laser output is used to break Al—N bond, then substrate separation is achieved, but the process becomes difficult to implement
Solution Approach 1:
The patent applies parameter changes by modifying the optical and thermal parameters of the interface region through the crystal nucleus layer. The layer's composition (AlGaN or AlN) and thickness are specifically controlled to optimize laser absorption characteristics. By changing the material parameters at the substrate interface, the system achieves effective bond breaking at lower laser power levels, making the process more manufacturable.
Solution Approach 2:
The crystal nucleus layer introduces local quality changes at the substrate-semiconductor interface. Rather than attempting to break bonds uniformly across the entire AlN layer, the nucleus layer concentrates the laser energy interaction locally at the substrate interface where separation is needed. This localized approach reduces the total energy required and simplifies the manufacturing process.
3Reliability
If laser light is absorbed by crystal nucleus layer to generate heat, then substrate decomposition and separation are achieved, but laser energy must be precisely controlled
Solution Approach 1:
The patent applies dynamics by making the laser energy absorption process controllable through the crystal nucleus layer's properties. The layer's thickness and composition can be dynamically adjusted during fabrication to match different laser parameters. This dynamic adjustability allows the system to achieve reliable separation while accommodating variations in laser energy output, reducing the stringency of precision requirements.
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 efficient separation of the sapphire substrate from the AlN semiconductor layer with lower laser energy requirements, improving the quality and reducing threading dislocations in the resulting Group III nitride semiconductor.
Implementation Method 1
irradiating a back surface side of the substrate with laser light to pass the laser light through the substrate and cause the crystal nucleus layer to absorb the laser light to thereby generate heat in the crystal nucleus layer
Implementation Method 2
by conducting the heat from the crystal nucleus layer to the substrate to decompose a region of the substrate near an interface with the crystal nucleus layer
Implementation Method 3
irradiating a back surface side of the substrate with laser light to pass the laser light through the substrate and cause the crystal nucleus layer to absorb the laser light to thereby generate heat in the crystal nucleus layer
Implementation Method 4
by conducting the heat from the crystal nucleus layer to the substrate to decompose a region of the substrate near an interface with the crystal nucleus layer
Data Source
AI summary
A method for producing a Group III nitride semiconductor includes: forming a crystal nucleus layer by generating nuclei of AlGaN or AlN over a substrate containing sapphire; forming a semiconductor layer containing a Group III nitride semiconductor over the crystal nucleus layer; forming a void by irradiating a back surface side of the substrate with laser light to pass the laser light through the substrate and cause the crystal nucleus layer to absorb the laser light to thereby generate heat in the crystal nucleus layer, and by conducting the heat from the crystal nucleus layer to the substrate to decompose a region of the substrate near an interface with the crystal nucleus layer; and separating the substrate from the crystal nucleus layer at a position of the void.