Monocrystalline Silicon Sacrificial Stack for 3D MEMS Structuring
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Solution Overview
Problem
Current MEMS production technologies face limitations in using monocrystalline silicon due to difficulties in structuring the mechanical layer in three dimensions and achieving high selectivity in chemical etching, which restricts the thickness and complexity of MEMS components.
Innovation Solution
A method involving a heterogeneous substrate with a sacrificial layer stack of monocrystalline Si between two layers of monocrystalline SiGe, allowing for selective etching and compatibility with epitaxy, enabling the production of monocrystalline mechanical layers with greater thicknesses and three-dimensional structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If monocrystalline silicon is used as the mechanical layer, then mechanical properties and thickness control are improved, but structuring in three dimensions and achieving high selectivity in chemical etching become difficult
Solution Approach 1:
The mechanical layer is segmented into multiple monocrystalline silicon layers separated by sacrificial layers, allowing independent structuring and release of each layer to overcome three-dimensional structuring difficulties
Solution Approach 2:
A sacrificial layer made of SiGe or SiO2 is introduced as an intermediary between monocrystalline silicon layers, enabling selective chemical etching and three-dimensional structuring that would be difficult to achieve with monocrystalline silicon alone
2Manufacturing precision
If a sacrificial layer is used to enable selective etching, then anchoring zones can be controlled, but the complexity of the substrate stack increases
Solution Approach 1:
The sacrificial layer is extracted as a separate, removable component from the final device structure, allowing precise control of anchoring zones during manufacturing while being completely removed before the device is completed
Solution Approach 2:
The chemical composition parameters of the sacrificial layer (SiGe with specific Ge concentration or SiO2) are optimized to achieve high selectivity in chemical etching, enabling precise anchoring zone control without proportionally increasing overall complexity
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 approach enables the production of MEMS with improved mechanical properties and selectivity in etching, allowing for thicker monocrystalline layers and integration of diverse materials like PZT, enhancing the complexity and sensitivity of MEMS components.
Implementation Method 1
the selective chemical etching of the sacrificial layer making it possible to produce in the mechanical layer active structures
Implementation Method 2
a first layer of monocrystalline SiGe is produced by epitaxy on a substrate in monocrystalline silicon
Implementation Method 3
a layer of monocrystalline Si is produced by epitaxy on the layer of monocrystalline SiGe
Data Source
Figure 1a~1f
Figure 1g~1j
Figure 1k~1o
AI summary
The substrate has a sacrificial layer constituted by a stack of monocrystalline silicon layers (3) located between monocrystalline silicon-germanium layers. The stack is located between two monocrystalline parts. One of the monocrystalline parts is compatible with an epitaxy of a silicon-germanium material. Another monocrystalline part is selected among silicon, strontium titanate/lead zirconate titanate, or strontium/strontium ruthenate/lead zirconate titanate. Independent claims are also included for the following: (1) a method for realizing a heterogeneous substrate (2) a method for realizing a component from the heterogeneous substrate.