MEMS Vibrating Structures on Plane Substrates
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Solution Overview
Problem
Current methods for manufacturing microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) face challenges such as high costs, limited material options, and performance limitations due to temperature constraints, particularly when using Silicon on Insulator (SOI) substrates, which are expensive and result in components with low mechanical quality.
Innovation Solution
A method involving the formation of a substrate with a silicon area covered by an insulating layer, followed by selective epitaxy of a sacrificial silicon and germanium alloy layer, and simultaneous formation of a monocrystalline and polycrystalline silicon layer to create a vibrating structure and actuation electrodes in the same plane, allowing for improved performance and cost-effectiveness by etching a predetermined pattern and eliminating the sacrificial layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SOI substrates are used for MEMS manufacturing, then manufacturing cost is reduced, but material quality and mechanical performance deteriorate
Solution Approach 1:
The substrate is divided into two distinct regions: a first region with a silicon layer for high-quality mechanical structures requiring monocrystalline properties, and a second region without silicon layer for electrical circuits and components. This segmentation allows each region to be optimized independently - the first region uses expensive high-quality silicon for mechanical performance while the second region uses standard materials for cost-effective electronics, thereby resolving the contradiction between manufacturing cost and mechanical quality.
2Reliability
If low temperature deposition is used for MEMS manufacturing, then existing circuits are protected from damage, but material quality and crystalline structure deteriorate
Solution Approach 1:
The manufacturing process is segmented into two temperature zones: low temperature deposition for electrical circuit layers to protect existing circuits, and high temperature epitaxial growth for the silicon layer in the first region to achieve monocrystalline structure. This process segmentation allows simultaneous achievement of circuit protection and high material quality in different areas.
Solution Approach 2:
Different thermal conditions are applied to different regions of the substrate. The first region undergoes high temperature epitaxial growth to produce monocrystalline silicon with superior mechanical properties, while the second region maintains lower temperatures suitable for standard electronic material deposition. This local quality approach enables each region to have the thermal history optimal for its intended function.
3Ease of operation
If vibrating structures are made perpendicular to substrate, then actuation is simplified, but device complexity and manufacturing steps increase
Solution Approach 1:
The vibrating structures are reoriented from perpendicular (vertical) displacement to parallel (lateral) displacement relative to the substrate plane. This dimensional change allows the vibrating structures to be formed in the same plane as the electrical circuits, eliminating the need for additional suspended layers and complex three-dimensional assembly steps, thereby reducing device complexity while maintaining actuation functionality.
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/NEMS components with enhanced performance and reduced manufacturing costs by allowing for the creation of vibrating structures that can move in the plane of the substrate, improving vibration quality and enabling the integration of transistors and variable capacitances on the same substrate.
Implementation Method 1
epitaxying a sacrificial layer of a few nanometers thick (typically 20 nm to 50 nm) made of silicon and germanium SiGe alloy
Implementation Method 2
silicon is then epitaxied with the characteristic of being monocrystalline above the silicon and germanium layer
Implementation Method 3
The silicon and germanium layer is then selectively etched with respect to the silicon
Data Source
AI summary
Method for making an electromechanical component on a plane substrate and comprising at least one structure vibrating in the plane of the substrate and actuation electrodes. The method comprises at least the following steps in sequence:formation of the substrate comprising one silicon area partly covered by two insulating areas,formation of a sacrificial silicon and germanium alloy layer by selective epitaxy starting from the uncovered part of the silicon area,formation of a strongly doped silicon layer by epitaxy, comprising a monocrystalline area arranged on said sacrificial layer and two polycrystalline areas arranged on insulating areas,simultaneous formation of the vibrating structure and actuation electrodes, by etching of a predetermined pattern in the monocrystalline area designed to form spaces between the electrodes and the vibrating structure,elimination of said sacrificial silicon and germanium alloy layer by selective etching.