Semiconductor Microstructure Fabrication via Multi-Stage Etching
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Solution Overview
Problem
Fabricating semiconductor microstructures with complex designs is challenging due to variable etching characteristics of stacked materials, making it difficult to achieve desired microstructures with improper material and etchant combinations during dry or wet etching processes.
Innovation Solution
A method involving the formation of a lower material layer of Group III nitride on a semiconductor substrate, followed by a mold material layer and an etching mask, with anisotropic and isotropic etching using specific etchants like sulphuric acid, deionized water, and SC-1 solution to control the etching process and achieve desired microstructures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used with improper material and etchant combinations, then the fabrication process is simpler, but the manufacturing precision of the microstructure deteriorates
Solution Approach 1:
The etching process is divided into multiple sequential steps including anisotropic etching, isotropic etching, and over-etching stages. Each stage uses different etchants and parameters to achieve specific portions of the desired microstructure, thereby resolving the contradiction between precision and complexity by breaking down the complex precision requirement into manageable sequential steps
Solution Approach 2:
The patent systematically varies etching parameters including etchant composition (BF3, SF6, O2, Cl2, H2, H2O), temperature, pressure, and power settings across different etching stages. This parameter optimization enables precise control over etching rates and selectivity for different material layers, achieving high manufacturing precision while managing process complexity through structured parameter variation
2Adaptability or versatility
If multiple material layers are stacked for complex microstructure, then the microstructure design flexibility is improved, but the etching characteristic variability worsens
Solution Approach 1:
The patent applies different etching conditions to different regions and layers of the stacked structure. Each material layer (dielectric, semiconductor, metal) receives tailored etching treatment with specific etchants and parameters, ensuring that local etching characteristics match the local material properties, thereby maintaining precision despite design flexibility
Solution Approach 2:
The etching process dynamically adjusts parameters such as gas flow rates, pressure, temperature, and power based on the specific material layer being etched. This adaptive parameter control ensures consistent etching characteristics across variable material combinations while preserving the ability to design complex multi-layer microstructures
3Shape
If anisotropic etching is used for directional precision, then the shape control is improved, but the surface roughness worsens
Solution Approach 1:
The etching process is segmented into anisotropic etching followed by isotropic etching and over-etching stages. The anisotropic stage establishes the primary directional shape, while subsequent isotropic and over-etching stages smooth the surface and refine the final dimensions, thereby resolving the contradiction between shape control and surface finish through process segmentation
Solution Approach 2:
The patent employs continuous multi-stage etching where each stage builds upon the previous stage's results. The transition from anisotropic to isotropic to over-etching creates a continuous refinement process that maintains directional accuracy while progressively improving surface quality, ensuring both shape control and surface finish are achieved
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 allows for the precise fabrication of semiconductor microstructures, such as via holes, with controlled etching rates and structure formation, enabling the creation of semiconductor devices like capacitors with increased surface area and improved capacitance.
Implementation Method 1
isotropic-etching the mold material layer and the lower material layer
Implementation Method 2
anisotropic-etching the mold material layer and the lower material layer
Data Source
AI summary
Provided is a method of fabricating a semiconductor microstructure, the method including forming a lower material layer on a semiconductor substrate, the lower material layer including a nitride of a Group III-element; forming a mold material layer on the lower material layer; forming an etching mask on the mold material layer, the etching mask being for forming a structure in the mold material layer; anisotropic-etching the mold material layer and the lower material layer by using the etching mask; and isotropic-etching the mold material layer and the lower material layer.