MEMS Fabrication via Segmented Sacrificial Layers
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Solution Overview
Problem
Manufacturing large sacrificial cavities for microelectromechanical structures is challenging due to undesirable deformation of carrier substrates during deposition of thick sacrificial layers, requiring complex and expensive stress-compensating layers.
Innovation Solution
A method for manufacturing multilayer MEMS structures using silicon, where functional and sacrificial areas are simultaneously structured and separated with passivation layers, allowing for precise adjustment of layer sequences and removal of sacrificial areas through gas phase etching, eliminating the need for wafer bonding and enabling independent mechanical and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If thick sacrificial layers are deposited to form large sacrificial cavities, then large-volume sacrificial areas can be created, but undesirable deformation of the carrier substrate occurs
Solution Approach 1:
The sacrificial layer is divided into multiple thinner layers deposited in sequence, with intermediate passivation layers between them. This segmentation prevents the substrate deformation that would occur with a single thick layer while still achieving the required large-volume sacrificial cavities after selective removal.
Solution Approach 2:
Passivation layers are introduced as intermediary layers between the sacrificial layers. These passivation layers act as stress-compensating mediators that prevent direct contact and deformation between the thick sacrificial structure and the carrier substrate, eliminating the need for additional stress-compensating layers.
2Stability of the object's composition
If complex stress-compensating layers are added to prevent substrate deformation, then substrate stability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The passivation layers serve dual functions: they provide stress compensation to prevent substrate deformation and simultaneously act as etch-stop layers during the sacrificial area removal process. This merging of functions eliminates the need for separate stress-compensating layers, reducing manufacturing complexity.
Solution Approach 2:
The passivation layers perform multiple roles throughout the manufacturing process: as stress-compensating layers during deposition, as etch-stop layers during sacrificial area removal, and as structural layers in the final MEMS device. This multi-functionality reduces the overall number of layers and steps required.
3Length of stationary object
If wafer bonding is used to create stacked structures, then large vertical extensions can be achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The stacked multilayer structure is built up layer by layer during the epitaxial growth process, with each layer formed and passivated before moving to the next layer. This preliminary sequential construction avoids the need for subsequent wafer bonding steps, simplifying the manufacturing process while achieving large vertical extensions.
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 creation of complex MEMS structures with large vertical extensions, allowing for precise control of layer sequences and connections, preventing substrate deformation, and facilitating the removal of sacrificial areas without complex stress-compensating layers, thus enhancing manufacturing efficiency and miniaturization capabilities.
Implementation Method 1
Areas of the silicon layer which are not to be etched are protected from the etching attack using passivation techniques such as, for example, thermal oxidation
Implementation Method 2
The resultant sacrificial areas may be removed, for example, with the aid of gas phase etching after completion of the method for manufacturing microelectromechanical structures
Implementation Method 3
a first silicon layer is epitaxially grown on a carrier substrate
Data Source
AI summary
A method for manufacturing microelectromechanical structures in a layer sequence and a corresponding electronic component having a microelectromechanical structure. The method includes provision of a carrier substrate including a first surface, an application of an insulation layer onto the first surface, an epitaxial growth of a first silicon layer onto the insulation layer, a structuring of the first silicon layer for forming trenches in the first silicon layer, a passivation of the first silicon layer, whereby the trenches are filled and a passivation layer is formed on a side facing away from the first surface, a structuring of the passivation layer, sacrificial areas and functional areas being formed in the first silicon layer, and the sacrificial areas are free of the passivation layer, at least at some points, on a side facing away from the carrier substrate, and, finally, removal of the sacrificial areas.