III-N MEMS on Silicon via Selective Etching
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Solution Overview
Problem
Current solutions fail to integrate group III material-nitride (III-N) microelectromechanical systems (MEMS) devices with silicon complementary metal-oxide-semiconductor (CMOS) devices in a single system-on-chip (SoC) implementation, limiting the potential of MEMS devices.
Innovation Solution
Techniques for forming III-N MEMS structures on group IV substrates, such as silicon, silicon germanium, or germanium, by selectively etching the substrate and shallow trench isolation material to create suspended III-N layers, allowing for the integration of piezoresistive elements and enabling the formation of accelerometers, gyroscopes, and pressure sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If III-N MEMS structures are formed on group IV substrates using selective etching, then integration with Si CMOS devices is enabled, but manufacturing complexity increases
Solution Approach 1:
The patent introduces shallow trench isolation (STI) material as an intermediary layer between the III-N MEMS structures and the Si CMOS devices. This STI material serves as a protective barrier during the selective etching process, enabling the formation of suspended III-N structures while maintaining compatibility with Si CMOS integration. The intermediary layer facilitates the complex integration process by providing a controlled interface between different material systems.
Solution Approach 2:
The manufacturing process is segmented into distinct stages: forming the III-N MEMS structures, selectively etching specific regions to create suspended portions, and then integrating with Si CMOS devices. This segmentation allows each step to be optimized independently, managing the overall manufacturing complexity through phased approach rather than attempting to perform all operations simultaneously.
2Ease of operation
If selective etching is used to create suspended III-N layers, then MEMS functionality is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The STI material acts as a protective intermediary during the selective etching process. By depositing this intermediary layer before etching, the process gains an additional layer of control and protection, reducing the stringency of precision requirements for the etching operation itself while still achieving the desired suspended structures.
Solution Approach 2:
The patent applies preliminary protective measures by depositing the STI material and applying a protective layer before performing the selective etching. This preliminary action prepares the structure in advance, making the subsequent etching process more manageable and less demanding in terms of precision control, as the protective layers prevent unintended etching and provide reference surfaces.
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 integration of III-N MEMS devices with Si CMOS devices in a SoC, enhancing the potential of MEMS devices by allowing for smaller form factors and various sensor applications, including mobile computing devices.
Implementation Method 1
The techniques include releasing the III-N layer by etching to form a free portion of the III-N layer suspended over the substrate
Implementation Method 2
Piezoresistive elements can be formed on the III-N layer to, for example, detect vibrations or deflection in the free/suspended portion of the III-N layer
Data Source
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AI summary
Techniques are disclosed for forming group III material-nitride (III-N) microelectromechanical systems (MEMS) structures on a group IV substrate, such as a silicon, silicon germanium, or germanium substrate. In some cases, the techniques include forming a III-N layer on the substrate and optionally on shallow trench isolation (STI) material, and then releasing the III-N layer by etching to form a free portion of the III-N layer suspended over the substrate. The techniques may include, for example, using a wet etch process that selectively etches the substrate and/or STI material, but does not etch the III-N material (or etches the III-N material at a substantially slower rate). Piezoresistive elements can be formed on the III-N layer to, for example, detect vibrations or deflection in the free/suspended portion of the III-N layer. Accordingly, MEMS sensors can be formed using the techniques, such as accelerometers, gyroscopes, and pressure sensors, for example.