Micromechanical Sensor Hollow Structure for Deep Buried Cavities
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Solution Overview
Problem
Existing methods for creating hollow structures in substrates, such as those used in micromechanical sensors, face limitations in flexibility and control over cavity dimensions, particularly in achieving deep cavities with small surface areas and independent depth from layer thickness.
Innovation Solution
A method involving the creation of a lattice structure with trench structures, followed by applying a passivation layer, selectively removing it from the bottom surface, and performing isotropic etching to form contiguous cavities below, allowing for flexible control over cavity dimensions and independent depth from layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional etching methods are used to create hollow structures, then the cavity depth is limited by the layer thickness, but the flexibility and control over cavity dimensions are reduced
Solution Approach 1:
The cavity formation process is segmented into multiple independent stages: first creating a lattice structure with trenches, then forming an initial cavity, applying a passivation layer, and finally performing a second etching step to extend the cavity deeper. This segmentation allows each stage to be optimized independently, enabling deep cavities with precise dimensional control that are not limited by single-layer thickness constraints
Solution Approach 2:
The lattice structure with trenches is created in advance before the final cavity formation. This preliminary structure serves as a template that guides the subsequent etching process, allowing precise control over the final cavity dimensions while enabling depths that exceed the thickness of any single structural layer
2Length of stationary object
If deep cavity structures are created with small surface areas, then the cavity depth-to-area ratio is improved, but the manufacturing complexity increases
Solution Approach 1:
The lattice structure with trenches serves multiple functions: it defines the cavity geometry, guides the etching process, and enables deep cavity formation. This multi-functional approach simplifies the overall manufacturing process by combining several functions into a single structural element, reducing the need for additional complex manufacturing steps
Solution Approach 2:
The method employs parameter changes in the etching process, using different etching conditions for the initial cavity formation versus the final deep cavity extension. By adjusting etching parameters such as chemistry, temperature, and duration, the process achieves precise control over cavity depth and shape while maintaining manufacturing simplicity
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
Enables the production of deep cavity structures with smaller surface areas, facilitating the development of micromechanical sensors like pressure sensors, microphones, and gyroscopes with improved flexibility and precision in cavity design.
Implementation Method 1
applying a passivation layer at least to the surfaces of the cavity
Implementation Method 2
The etching process can comprise wet etching and/or dry etching
Implementation Method 3
The etching process can comprise wet etching and/or dry etching, in particular plasma etching
Implementation Method 4
An anisotropic etching process is then carried out, consisting of alternating cycles of etching and passivation. This leads to the formation of trench holes with high aspect ratios
Data Source
AI summary
A method for making a hollow structure in a substrate. The method includes creating a lattice structure with at least two mutually spaced trench structures, creating a cavity structure below the lattice structure with respect to a normal direction by forming a buried, contiguous cavity that spans at least the area of the two trench structures. A micromechanical sensor is also described.