Selective Etching of Thin (Al, In, Ga)N Membranes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The fabrication of high-quality (Al, In, Ga)N devices is hindered by the difficulty in growing bulk nitride materials, leading to defects in heteroepitaxial growth, and the challenge of selectively removing nitride materials without damaging sensitive layers, particularly for microcavity structures and optoelectronic devices.
Innovation Solution
A selective etching technique involving ion implantation to create a damage layer in (Al, In, Ga)N templates, allowing for non-crystallographic removal of nitride materials from substrates without harming sensitive device layers, using a combination of ion implantation and chemical etching to separate thin nitride membranes and form free-standing wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heteroepitaxial growth is used to fabricate (Al, In, Ga)N devices, then device fabrication becomes possible, but defects such as threading dislocations, cracks, and voids are introduced into the nitride films
Solution Approach 1:
The invention segments the nitride film structure by introducing a dedicated buffer layer between the substrate and the active device layers. This buffer layer acts as a separate functional component that absorbs defects and prevents them from propagating into the active regions, thereby maintaining device reliability while enabling heteroepitaxial fabrication.
Solution Approach 2:
The invention performs preliminary defect management by growing a thick buffer layer first, before depositing the active device layers. This preliminary action allows defects to be concentrated in the buffer layer rather than in the active regions, effectively pre-filtering the defect distribution to improve overall film quality.
2Reliability
If thick films are grown to reduce defect densities, then defect reduction is achieved, but additional impurities, point defects, inhomogeneities, and strain are introduced into the composite structure
Solution Approach 1:
The invention applies local quality by creating a buffer layer with different thickness and composition characteristics than the active device layers. The buffer layer is specifically designed with higher aluminum content and greater thickness to handle defect absorption, while the active layers maintain precise compositional control for optimal device performance, thus resolving the conflict between defect reduction and film uniformity.
3Ease of manufacture
If chemical etching is used to remove nitride material, then selective removal is achieved, but the process is extremely difficult and time-consuming compared to silicon etching
Solution Approach 1:
The invention dramatically changes the chemical parameters of the etching process by using a eutectic mixture of nitric acid and hydrofluoric acid. This parameter change transforms the etching process from an extremely slow and difficult operation into a rapid and efficient process, achieving etch rates comparable to conventional silicon etching while maintaining high selectivity for nitride material removal.
4Ease of manufacture
If dry etching techniques are used for vertical etching of nitride films, then etching capability is achieved, but the processes are complex and expensive and can damage remaining material
Solution Approach 1:
The invention replaces the complex mechanical and plasma-based dry etching system with a simpler chemical wet etching process. By substituting the mechanical ion bombardment and plasma chemistry with a straightforward chemical dissolution process using the nitric acid-hydrofluoric acid eutectic mixture, the invention achieves comparable etching capability with significantly reduced process complexity and cost.
5Ease of manufacture
If PEC etching is used for lateral etching of (Al, In, Ga)N structures, then effective lateral etching is achieved, but the process is cumbersome and requires multiple steps including masking, electrode formation, and UV irradiation
Solution Approach 1:
The invention extracts and eliminates the unnecessary complexity from the PEC etching process by removing the requirements for masking, electrode formation, and UV irradiation. By using the chemically active eutectic acid mixture, the invention achieves lateral etching through simple chemical dissolution, taking out the cumbersome procedural elements while retaining the effective lateral etching capability.
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 method enables the reproducible formation of thin (Al, In, Ga)N membranes and free-standing wafers with minimal damage, suitable for microcavity light emitting structures, improving device efficiency by avoiding ion bombardment and mechanical stresses, and providing precise thickness control.
Implementation Method 1
ion implantation to create a damage layer in (Al, In, Ga)N templates, allowing for non-crystallographic removal of nitride materials
Data Source
AI summary
An etching technique for the fabrication of thin (Al, In, Ga)N layers. A suitable template or substrate is selected and implanted with foreign ions over a desired area to create ion implanted material. A regrowth of a device structure is then performed on the implanted template or substrate. The top growth surface of the template is bonded to a carrier wafer to created a bonded template/carrier wafer structure. The substrate is removed, as is any residual material, to expose the ion implanted material. The ion implanted material on the bonded template/carrier wafer structure is then exposed to a suitable etchant for a sufficient time to remove the ion implanted material.