GaN Layer Detachment via Ion Implantation and Sensitization
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Solution Overview
Problem
The existing methods for transferring thin GaN layers face challenges such as limited temperature resistance of bonding, non-uniform bonding due to different thermal expansion coefficients, and the need for significant planarization post-fracture, which hinder efficient detachment and recycling of substrates.
Innovation Solution
A method involving the bombardment of a GaN substrate with Helium and Hydrogen ions, followed by a fracture treatment that allows for low-temperature detachment with minimal surface roughness, enabling the entire GaN layer to be transferred without significant planarization, and allowing the substrate to be recycled for further use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bonding is performed between GaN substrate and sapphire substrate, then heterostructure is formed, but temperature resistance is limited to approximately 230°C due to different thermal expansion coefficients
Solution Approach 1:
The patent applies a sensitization heat treatment at approximately 1000°C before bonding to pre-create microcavities and weaken the GaN lattice structure. This preliminary action prepares the GaN layer for subsequent low-temperature fracture (at 230°C or lower) after bonding, allowing the bonded heterostructure to undergo fracture treatment without exceeding the temperature limit imposed by thermal expansion mismatch.
Solution Approach 2:
The patent changes the physical and chemical parameters of the GaN substrate through high-temperature sensitization treatment, transforming it from a strong, intact crystal structure to a weakened state with microcavities and reduced bonding strength. This parameter change enables the GaN layer to be fractured at low temperatures after bonding, resolving the contradiction between forming heterostructures and maintaining temperature resistance.
2Temperature
If sensitization heat treatment is applied before bonding, then fracture temperature can be reduced, but surface deformation such as blisters and exfoliated areas occurs
Solution Approach 1:
The patent optimizes the sensitization treatment parameters (temperature of approximately 1000°C, duration of 1-24 hours, and atmospheric conditions) to achieve a balance between creating sufficient microcavities for low-temperature fracture and avoiding excessive surface deformation. The controlled application of these parameters allows fracture at low temperatures while maintaining acceptable surface quality.
3Manufacturing precision
If high temperature fracture treatment is applied to achieve complete detachment, then GaN layer can be fully transferred, but bonding integrity is compromised due to thermal expansion differences
Solution Approach 1:
The sensitization treatment performed before bonding pre-weakens the GaN lattice and creates microcavities that serve as fracture initiation sites. This preliminary action ensures that subsequent low-temperature fracture treatment (at 230°C or lower) can achieve complete detachment of the GaN layer without requiring high temperatures that would compromise bonding integrity between the GaN and sapphire substrates.
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 enables efficient detachment of GaN layers at low temperatures, maintaining surface quality and allowing for the reuse of substrates without extensive planarization, thus overcoming the limitations of existing techniques.
Implementation Method 1
bombardment of one face of an initial substrate with ions or gaseous species (H or rare gases), in order to implant these ions (or atoms) in sufficient concentration to create a layer of microcavities
Implementation Method 2
due to their intrinsic properties, different materials A and B generally have different coefficients of thermal expansion (CTE for short). The more different the CTEs, the less the integrity of the bonded structure can be maintained at high temperatures.
Implementation Method 3
fracture at the level of the microcavity layer, by the application of a heat treatment and/or a detachment stress
Data Source
Figure 1~2
Figure 3~7
AI summary
The invention relates to a method for preparing a thin layer of GaN from a starting substrate in which at least one thick surface area extending along a free face of the starting substrate is made of GaN, said method including the following steps: bombarding said free face of the substrate with helium and hydrogen atoms, the helium being implanted first into the thickness of said thick surface area and the hydrogen being implanted thereafter, the helium and hydrogen doses each varying between 1.1017 atoms/cm2 and 4.1017 atoms/cm2; submitting the starting substrate to a rupture process in order to induce the separation, relative to a residue of the starting substrate, of the entire portion of the thick area located between the free face and the helium and hydrogen implantation depth. The helium is advantageously implanted in a dose at least equal to that of hydrogen, and can also be implanted alone.