Monolithic MEMS Microcircuit Fabrication via High-Temperature Contacts
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Solution Overview
Problem
The integration of MicroElectroMechanical Systems (MEMS) and microcircuits on a common substrate is challenging due to incompatible manufacturing processes, particularly the limitation of contact feature size and vertical stack-up caused by high temperature processes in MEMS fabrication.
Innovation Solution
A method for monolithic fabrication of MEMS and microcircuits involves forming high-temperature contacts through a dielectric layer, depositing and patterning conducting material for local interconnects, and using selective wet etch processes to protect MEMS structures during metallization, allowing for multiple metal layers and reduced surface area dedicated to microcircuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep contacts are formed after MEMS fabrication is substantially complete, then contact performance is maintained, but the minimum contact feature size is limited due to high aspect ratio
Solution Approach 1:
The patent forms contacts through the dielectric layer before completing the MEMS fabrication process, specifically before forming the movable structure. This preliminary action allows contacts to be created when the dielectric layer is thinner, reducing the aspect ratio and improving manufacturability while maintaining contact performance through proper material selection and process sequencing.
Solution Approach 2:
The fabrication process is segmented into distinct stages: first forming contacts through the dielectric layer, then completing the MEMS structure fabrication. This segmentation allows each stage to be optimized independently, with contact formation occurring when dimensional constraints are more favorable.
2Strength
If high temperature processes are used in MEMS fabrication, then MEMS structure integrity is maintained, but contact and metallization performance is compromised
Solution Approach 1:
The patent performs contact formation and metallization processes before subjecting the structure to high temperature MEMS fabrication steps. This sequencing ensures that temperature-sensitive contacts and metals are established while materials are in a more favorable state, avoiding degradation from subsequent high temperature processing.
Solution Approach 2:
The patent changes the temperature parameter over time by performing contact formation at lower temperatures initially, then introducing controlled high temperature steps later in the process. This dynamic parameter control allows both contact integrity and MEMS structure integrity to be maintained through appropriate thermal management.
3Device complexity
If multiple metal interconnect layers are deposited and patterned, then microcircuit complexity is increased, but MEMS structure is exposed to damaging dry etch processes
Solution Approach 1:
The patent introduces a protective dielectric layer as an intermediary between the MEMS structure and the dry etch processes used for patterning metal interconnect layers. This protective layer acts as a barrier that prevents direct exposure of the MEMS structure to damaging etchants while allowing the metal layers to be deposited and patterned above it.
Solution Approach 2:
The protective dielectric layer is deposited beforehand to cushion and protect the MEMS structure from subsequent dry etch damage. This preemptive protective measure ensures that when multiple metal layers are patterned using aggressive etching processes, the underlying MEMS structure remains intact and undamaged.
4Productivity
If contact feature size is reduced to increase channel counts, then integration density is improved, but aspect ratio increases and manufacturing becomes more difficult
Solution Approach 1:
The patent forms contacts at an earlier stage in the fabrication process when the dielectric layer thickness is smaller, which allows for reduced contact feature sizes without creating excessively high aspect ratios. This preliminary timing enables higher integration density while maintaining manufacturability.
Solution Approach 2:
The patent changes the dielectric layer thickness parameter by forming it in multiple stages or using different deposition techniques, allowing contact features to be sized smaller without proportionally increasing aspect ratio. This parameter optimization enables increased channel counts while keeping contacts manufacturable.
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 realization of complex microcircuits with multiple metallization levels while avoiding issues with high-aspect ratio contacts and material removal, enhancing the integration of MEMS and microcircuits on a single substrate.
Implementation Method 1
remaining dielectric material is removed from the MEMS structure using a highly selective buffered oxide (BOE) wet etch process
Implementation Method 2
depositing a layer of conducting material over the dielectric layer
Data Source
AI summary
A method of fabricating an integrated device including a MicroElectroMechanical system (MEMS) and an associated microcircuit is provided. In one embodiment, the method comprises: forming a high temperature contact through a dielectric layer to an underlying element of a microcircuit formed adjacent to a MicroElectroMechanical System (MEMS) structure on a substrate; and depositing a layer of conducting material over the dielectric layer, and patterning the layer of conducting material to form a local interconnect (LI) for the microcircuit overlying and electrically coupled to the contact and a bottom electrode for the adjacent MEMS structure. Other embodiments are also provided.