Multilayer Diaphragm Smoothing for Stable Transducer Release
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Solution Overview
Problem
The manufacturing of semiconductor transducer devices with suspended diaphragms often results in low yield due to membrane breakage and unstable conditions caused by rough surfaces and inhomogeneous stress distribution, which are exacerbated by the removal of sacrificial layers during the etching process.
Innovation Solution
A fabrication process that includes chemical-mechanical polishing to reduce the surface roughness of the first layer to a predefined value, followed by the application of additional layers for diffusion barrier and stress compensation, ensuring a smooth and stable diaphragm structure after etch release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deposition of metal layers is performed to form the diaphragm, then the diaphragm structure is created with necessary material properties, but the surface roughness increases leading to fracture initiation sites and low manufacturing yield
Solution Approach 1:
The patent applies preliminary action by performing chemical-mechanical polishing on the first metal layer before depositing subsequent layers. This pre-treatment removes surface roughness and potential fracture initiation sites early in the manufacturing process, ensuring a smooth foundation for subsequent layer deposition and preventing reliability issues in the final diaphragm structure
Solution Approach 2:
The patent changes the surface parameter of the deposited metal layer by applying chemical-mechanical polishing to reduce surface roughness from a high initial state to a controlled low state (Ra ≤ 5 nm). This parameter modification eliminates fracture initiation sites while maintaining the structural integrity and material properties of the diaphragm layers
2Ease of operation
If sacrificial layer removal is performed by HF vapor etching, then the diaphragm is released for functionality, but the membrane becomes prone to breakage reducing manufacturing yield
Solution Approach 1:
The patent applies preliminary action by smoothing the surface of the first metal layer through chemical-mechanical polishing before the sacrificial layer removal process. This pre-treatment ensures that when the diaphragm is released via HF vapor etching, the smoothed surface prevents fracture initiation and maintains membrane integrity throughout the release operation and subsequent handling
Solution Approach 2:
The patent applies beforehand cushioning by creating a smooth surface structure that acts as a protective measure against future mechanical stresses. The reduced surface roughness serves as a preventive buffer that cushions the diaphragm against fracture during the vulnerable release phase and subsequent operational phases
3Device complexity
If multiple metal layers are deposited for diaphragm formation, then the functional structure is achieved, but inhomogeneous stress distribution occurs causing unstable conditions
Solution Approach 1:
The patent changes the surface parameter of the first metal layer by reducing its roughness through chemical-mechanical polishing. This parameter modification creates a uniform baseline surface that promotes homogeneous stress distribution across the multilayer diaphragm structure, preventing localized stress concentrations that would lead to instability
Solution Approach 2:
The patent applies local quality by specifically treating the surface of the first metal layer with chemical-mechanical polishing to achieve uniform local properties. This localized surface smoothing ensures that each subsequent layer deposits on a uniform surface, creating consistent local stress conditions throughout the multilayer structure
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
Significantly improves the yield of the manufacturing process by reducing the risk of diaphragm fracture and enhancing mechanical stability, allowing for high-sensitivity pressure sensors and transducer devices with improved performance.
Implementation Method 1
reducing a roughness of a surface of the first layer facing away from the semiconductor body in order to achieve a processed surface
Implementation Method 2
removing the sacrificial layer by introducing an etchant, such as HF vapor, into openings of the diaphragm
Data Source
AI summary
In an embodiment a method includes providing a semiconductor body, forming a sacrificial layer above a surface of the semiconductor body, applying a diaphragm on the sacrificial layer and removing the sacrificial layer by introducing an etchant into openings of the diaphragm, wherein applying the diaphragm comprises applying a first layer, reducing a roughness of a surface of the first layer facing away from the semiconductor body thereby providing a processed surface, and patterning and structuring the first layer to form the openings.