GaN Dielectric Etching via Ion Implantation Selectivity
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Solution Overview
Problem
Current etching processes for gallium nitride (GaN)-based devices, particularly AlGaN/GaN heterostructures, face challenges such as degradation of electrical properties, over-etching, and non-uniformities due to fluorocarbon chemistry, leading to defects and reduced device performance.
Innovation Solution
A method involving partial etching of a dielectric layer, followed by hydrogen or helium ion implantation to modify the material throughout the residual portion and the GaN-based layer, and subsequent selective etching and annealing to restore the GaN-based material's properties, allowing for precise removal of the dielectric layer without residue and protecting the GaN-based layer from oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorocarbon chemistry plasma etching is used to open the passivation layer, then the etching process can be performed, but the electrical properties of the AlGaN layer are degraded due to fluorinated ion incorporation
Solution Approach 1:
The etching process is divided into multiple sequential steps: first etching to create a partial opening, then ion implantation to modify the residual portion, and finally selective removal of the modified material. This segmentation allows the etching to proceed without directly exposing the AlGaN layer to fluorocarbon chemistry, thereby preventing fluorinated ion incorporation while still achieving complete passivation layer removal.
Solution Approach 2:
Ion implantation is performed as a preliminary action before the final etching step. The ions (such as hydrogen or helium) are implanted into the residual passivation layer material to modify its properties, making it selectively removable in the subsequent step. This preliminary modification protects the AlGaN layer from direct exposure to etching chemistry.
2Manufacturing precision
If complete etching of the passivation layer is performed, then the opening is fully formed, but over-etching occurs leading to unintentional consumption of the AlGaN layer surface
Solution Approach 1:
The etching process is segmented into a first etching step that creates a partial opening with a residual portion of the passivation layer, and a second selective etching step that removes only the modified residual material. This prevents continuous etching that would lead to over-etching and AlGaN layer consumption.
Solution Approach 2:
Ion-modified residual passivation layer material serves as an intermediary layer between the etching process and the AlGaN layer. This intermediate layer is selectively removed in the second etching step, providing a buffer that prevents direct contact between the etching chemistry and the AlGaN layer surface.
3Productivity
If fluorocarbon chemistry etching is used, then the passivation layer can be etched, but charging effects occur leading to non-uniformities in engraving density
Solution Approach 1:
The etching process parameters are changed by switching from direct fluorocarbon chemistry etching to a two-step process involving ion implantation followed by selective etching. This parameter change eliminates charging effects that cause non-uniformities, as the ion implantation step modifies the material properties without creating the same charging issues as continuous fluorocarbon etching.
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 significantly enhances the selectivity of the etching process, maintains the electrical properties of the GaN-based material, and improves the performance and reliability of GaN-based devices by preventing residue and oxidation, making the process more efficient and cost-effective.
Implementation Method 1
implantation of ions in line with the partial opening over a thickness greater than thickness e 202 so as to: modify the material of the dielectric layer in line with the opening over the entire thickness e 202 of the residual portion; modify the material of the GaN-based layer
Implementation Method 2
annealing at least the GaN-based layer for a duration greater than D1 and a temperature between T1 and T2, with D1 = 30s, T1 = 300°C and T2 = 900°C, preferably T2 = 600°C
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3F
AI summary
The invention relates to a method for etching a dielectric layer (200) overlying a GaN-based layer (100), the method comprising at least the following steps: - first etching the dielectric layer (200) over only a portion of the thickness e200 of the dielectric layer (200) to define in the dielectric layer (200) at least one partial opening (401) and at least one residual portion (202) located at the opening (401), - implantation (700) of ions at the partial opening (401) over a thickness greater than the thickness e202 so as to: ∘modify the material of the dielectric layer (200) at the opening (401) over the entire thickness e202 of the residual portion (202), ∘modify the material of the GaN-based layer (100), - removal of the residual portion (202) using a second engraving,selective of the modified dielectric layer material (200) with respect to the unmodified dielectric layer material (200) and with respect to the modified GaN-based layer material (100); - annealing at least of the GaN-based layer (100).