Piezoelectric Element With Intermediate Layer for CMOS Compatibility
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Solution Overview
Problem
Piezoelectric components, such as ultrasonic transducers, face challenges in integration with CMOS processes due to incompatibility with lead zirconate titanate (PZT) and limitations in material choices like aluminum nitride (AlN), which result in limited frequency range, high electrical control voltages, and compatibility issues with CMOS and RHoS regulations.
Innovation Solution
A piezoelectric element with a substrate structure featuring an intermediate layer between two substrate layers, allowing a layer stack to oscillate and be controlled via electrode layers, using ferroelectric, piezoelectric, and/or flexoelectric materials like undoped hafnium oxide or zirconium oxide, enabling low-voltage operation and CMOS compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead zirconate titanate (PZT) is used for piezoelectric components, then high piezoelectric performance is achieved, but CMOS compatibility and RHoS compliance are lost
Solution Approach 1:
The patent changes the material parameters by using aluminum nitride (AlN) instead of PZT, accepting lower piezoelectric coefficients in exchange for CMOS compatibility and RHoS compliance. This parameter change enables integration into standard semiconductor manufacturing processes while meeting environmental regulations.
Solution Approach 2:
The patent employs composite material structures including aluminum nitride layers combined with silicon-based substrates and various electrode materials (tungsten, molybdenum, copper, aluminum). This composite approach allows optimization of both piezoelectric performance and process compatibility.
2Adaptability or versatility
If aluminum nitride (AlN) is used for piezoelectric components, then CMOS compatibility is achieved, but piezoelectric coefficient and crystal phase stability deteriorate
Solution Approach 1:
The patent optimizes AlN layer parameters including thickness (50-200 nm), doping concentrations, and deposition conditions to enhance piezoelectric coefficients while maintaining CMOS compatibility. Scandium doping is used to improve the piezoelectric response of AlN.
Solution Approach 2:
The patent applies different materials and structures to different regions: AlN for piezoelectric function, silicon-based layers for structural support and CMOS integration, and various electrode materials for electrical connection. This local optimization allows each layer to perform its specific function efficiently.
3Reliability
If conventional piezoelectric ultrasonic transducers are used, then ultrasonic sensing function is achieved, but area filling and measurement resolution are limited
Solution Approach 1:
The patent divides the piezoelectric structure into multiple thin layers (AlN, electrodes, buffer layers) that can be independently optimized. This segmentation allows for higher frequency operation and improved measurement resolution while maintaining full area utilization on the substrate.
Solution Approach 2:
The patent transitions from bulk piezoelectric materials to thin-film structures, utilizing the vertical dimension for layer stacking and the horizontal dimension for full area coverage. This dimensional transition enables high-frequency operation and improved resolution.
4Force
If high electrical control voltages are used in piezoelectric transducers, then sufficient actuation is achieved, but applicability in IoT and direct contact applications is reduced
Solution Approach 1:
The patent reduces the required control voltage by optimizing the piezoelectric layer thickness to 50-200 nm and using scandium-doped AlN with enhanced piezoelectric coefficients. This allows sufficient actuation force at low voltages suitable for IoT and wearable applications.
Solution Approach 2:
The patent replaces high-voltage electrical actuation with optimized thin-film piezoelectric structures that achieve mechanical displacement at low voltages. This substitution enables integration with low-power electronics and battery-operated devices.
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 solution allows for reliable, low-power operation of piezoelectric elements with enhanced frequency range and resolution, compatibility with CMOS and RHoS standards, and miniaturization capabilities, suitable for various applications including high-frequency systems and IoT devices.
Implementation Method 1
A ferroelectric, piezoelectric and/or flexoelectric layer (103), in particular made from undoped hafnium oxide or zirconium oxide, is applied on the first electrode layer (102)
Implementation Method 2
A ferroelectric, piezoelectric and/or flexoelectric layer (103), in particular made from undoped hafnium oxide or zirconium oxide, is applied on the first electrode layer (102)
Implementation Method 3
The layer stack can be moved in a translatory manner along its normal directed along the layer sequence. By structuring the substrate in such a way that the layer stack together with the region of the second substrate layer connected thereto can be moved in a translatory manner, i.e. in particular can oscillate, a system capable of oscillation is realized which, in addition, can be controlled or regulated in its movement via the electrode layers and the ferroelectric, piezoelectric and/or flexoelectric layer by applying and changing an electrical voltage.
Data Source
AI summary
A piezoelectric element and a method of manufacturing the piezoelectric element are provided. The piezoelectric element is provided with a substrate having an intermediate layer disposed between a first substrate layer and a second substrate layer, a first electrode layer of an electrically conductive non-ferroelectric material disposed on the second substrate layer, a ferroelectric, piezoelectric and/or flexoelectric layer disposed on the first electrode layer, and a second electrode layer of an electrically conductive non-ferroelectric material disposed on the ferroelectric, piezoelectric and/or flexoelectric layer. The intermediate layer and/or the first substrate layer is removed below a layer stack formed by the first electrode layer, the ferroelectric, piezoelectric and/or flexoelectric layer, and the second electrode layer so that the layer stack can be moved in a translatory manner along its normal directed along the layer sequence.