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MEMS

Learn how SENTECH plasma systems and metrology tools are ideal for processing advanced micro-electromechanical systems and applications.

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MEMS Applications

Micro-electromechanical systems or MEMS is the umbrella term for many microfabricated devices that enable highly scalable, cost-efficient, mass-produced sensors, actuators, and optics. MEMS have many applications and are often found in for example pressure sensors, acceleration sensors, and microphones due to their extremely high sensitivity, small size, and very low power consumption and their suitability for integration with microelectronic systems.

Industries:
Sensors
Automotive
Aerospace
Consumer electronics
Data communication
Biomedical imaging

Conventional plasma etching processes are designed for etch depths of only a few microns and lack etch rate and mask selectivity. Deep reactive ion etching (DRIE) of silicon to create high aspect ratio microstructures is a key process in the advanced MEMS field. Two approaches are commonly known: the gas chopping process, the “Bosch process” and the cryogenic (cryo) etching. These processes are capable of producing deep features with exceptional anisotropy, etch rate, and etch mask selectivity. The Bosch process excels in etch rate and aspect ratio and is hence recognised as the main production technology. The cryo process overcomes the drawback of scalloping with the Bosch process and allows for smooth sidewalls.

SENTECH ICP-RIE systems can be configured for DRIE using Bosch, cryo, or both processes. Additionally, the SENTECH SI 500 enables a new level of MEMS functionality, for leading-edge applications including AlN and AlScN piezo MEMS etching, and the SENTECH SI 500 D for the high-quality, precise stress-controlled ICPECVD of Si3N4 and SiO2 deposition.

The SENTECH spectroscopic ellipsometry and reflectometry systems are ideally suited to characterise the quality of process steps on R&D and fully automated production level.  Applying pattern recognition, they enable automated measurements of film thickness, optical constants, and the uniformity also of patterned wafers to gain insight into the development and stage of any MEMS devices.

Learn more about SENTECH plasma process technology, process monitoring, endpoint detection, and thin-film characterisation solutions by requesting the full application note.

Etching of Scandium Aluminium Nitride (ScAlN) using the SENTECH SI 500 ICP-RIE System

Etching aluminium scandium nitride (AlScN) for piezo MEMS
Etching of Scandium Aluminium Nitride (ScAlN) using the SENTECH SI 500 ICP-RIE System
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Scandium Aluminium Nitride (ScAlN) has gained a lot of interest in recent years for its higher piezoelectric properties compared to pure Aluminium Nitride (AlN). This makes it useful for applications in micro-electromechanical systems (MEMS), such as bulk acoustic wave (BAW) filters for RF applications. It exhibits a greater electromechanical coupling efficiency than pure AlN, resulting in lower losses and a higher signal-to-noise ratio for high-frequency filters. Furthermore, it is easy to integrate into existing CMOS processes and lead-free, compared to the typically used PZT ceramics. The concentration of ScAlN can be described as ScₓAl1-ₓN, with x typically in the range between 10% and 40%. With a higher Scandium (Sc) content, the piezoelectric properties increase up to the maximum of x = 43%, where the ScAlN undergoes a phase transition and loses its properties. Due to the low vapour pressure of Scandium(III) chloride (ScCl₃), it becomes increasingly difficult to keep reasonable etch rates and profile angle at higher Sc content. The top and bottom electrodes are typically made out of Molybdenum (Mo), because of its similar crystallographic properties.
This means a high selectivity to Mo is critical to ensure low bottom electrode material loss. This application note presents a successful etching of ScAlN using the SENTECH SI 500 ICP-RIE process mode for the fabrication of MEMS for RF filtering applications.

Low-Temperature ICPECVD of Si₃N₄ Films using the SENTECH SI 500 D System

Si3N4 thickness uniformity
Low-Temperature ICPECVD of Si₃N₄ Films using the SENTECH SI 500 D System
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Silicon Nitride (Si₃N₄) layers are extensively used as passivation layers, etching masks, membranes, electrically isolating layers, and dielectrics for leading-edge applications, including microelectronic devices, sensors, and OLEDs. This application note demonstrates the successful inductively coupled plasma-enhanced chemical vapour deposition (ICPECVD) process results inSi₃N₄ films with excellent uniformity, high growth rate, and adjustable low film stress using the SENTECH SI 500 D ICPECVD System.

ICPECVD of Silicon Carbide Films using the SENTECH SI 500 D System

ICPECVD of SiC mapping
ICPECVD of Silicon Carbide Films using the SENTECH SI 500 D System
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Amorphous Silicon Carbide (a-SiC:H) films are extensively used in solar cells and as passivation layers in sensors for high-temperature applications. In addition, thanks to its good mechanical properties and chemical resistance silicon carbide (SiC) is widely used as a protection layer against abrasion and chemical corrosion such as in MEMS applications. This application note will demonstrate the successful deposition of a-SiC:H layers using the SENTECH SI 500 D ICPECVD System. The procedure comprises the deposition of a-SiC:H layers by ICPECVD on a silicon wafer with a thickness in the range of ca. 200-600 nm with different process conditions. Characterisation was done by determining the optical layer properties using ellipsometry and measurement of the layer stress. The results demonstrate the excellent deposition properties of an SI 500 D system with a SiH₄/CH₄-based deposition process for a-SiC:H films.

PEALD of SiO₂ for Highly Conformal Trench Filling at Low Temperatures Using the SENTECH SI PEALD System

PEALD of SiO2 conformal trench fill
PEALD of SiO₂ for Highly Conformal Trench Filling at Low Temperatures Using the SENTECH SI PEALD System
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This application note highlights the successful utilisation of the SENTECH SI PEALD system to perform a low-damage, low-temperature, and highly conformal trench-fill deposition process for silicon oxide (SiO₂) layers. Plasma-enhanced atomic layer deposition (PEALD) of SiO₂ is a state-of-the-art technique that achieves highly conformal and uniform film deposition, even within complex geometries like trenches, where precise control over thickness and coverage is essential.

Trenches and gratings are a cornerstone of modern semiconductor fabrication, enabling advancements in device scaling, performance, and reliability. The ability to perform conformal trench filling using PEALD of SiO₂ is critical for addressing challenges in creating smaller, faster, and more efficient semiconductor devices. The SENTECH SI PEALD system excels in delivering the precision and uniformity required for such processes, ensuring optimal film quality at low deposition temperatures.

This approach is particularly beneficial in advanced microfabrication and high-performance semiconductor devices across foundational and emerging industries. Applications include Quantum Devices, where precise interfaces are vital, Microelectromechanical Systems (MEMS), requiring robust dielectric layers, Photonic Integrated Circuits (PICs), which demand low-loss optical claddings, and Power Electronics, where high-quality dielectric isolation enhances device reliability.

Low-Temperature ICPECVD of SiO₂ Films using the SENTECH SI 500 D System

Deposition on SiO2 thickness mapping
Low-Temperature ICPECVD of SiO₂ Films using the SENTECH SI 500 D System
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Silicon Oxide (SiO₂) layers are extensively used as passivation layers, etching masks, membranes, electrically isolating layers, and dielectrics for leading-edge applications, including microelectronic devices, sensors, OLEDs. This application note demonstrates the successful inductively coupled plasma-enhanced chemical vapour deposition (ICPECVD) process results in SiO₂ films with excellent uniformity, high growth rate, and adjustable low film stress using the SENTECH SI 500 D ICPECVD System.

PEALD and Thermal ALD of Al₂O₃ using the SENTECH SI PEALD System

PEALD of Aluminium Oxide
PEALD and Thermal ALD of Al₂O₃ using the SENTECH SI PEALD System
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This application note explores the underlying physics and process optimisation strategies of plasma-enhanced atomic layer deposition (PEALD) and thermal atomic layer deposition (ALD) of aluminium oxide (Al₂O₃). The relentless drive for smaller, faster, and more efficient electronic devices in the semiconductor industry has elevated the importance of advanced thin-film deposition techniques. Among these, PEALD and thermal ALD of Al₂O₃ have emerged as cornerstone processes. Combining exceptional film uniformity with precise thickness control at the atomic scale, PEALD and ALD of Al₂O₃ play a vital role in enabling the production of next-generation microelectronic devices. Al₂O₃, a high-k dielectric material, offers outstanding electrical insulation properties, high thermal stability, and superior chemical resistance. Its deposition via PEALD and thermal ALD allows for unparalleled conformality on high-aspect-ratio structures, which are critical in cutting-edge semiconductor architectures such as MOSFETs.

Moreover, the plasma enhancement in PEALD facilitates low-temperature processing, a necessity for sensitive substrates and emerging applications, including flexible electronics and heterogeneous integration.

Low-Damage Etching of Al Layers on Si for Advanced MEMS Sensors and Quantum Device Fabrication using the SENTECH SI 500 ICP-RIE System

Al layers on Si vertical sidewalls
Low-Damage Etching of Al Layers on Si for Advanced MEMS Sensors and Quantum Device Fabrication using the SENTECH SI 500 ICP-RIE System
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Aluminium (Al) is a key material in advanced semiconductor, MEMS sensors, and quantum device fabrication, where low interface roughness, vertical sidewall profiles, and stringent etch uniformity are critical for device performance and yield. In particular, Al-on-Silicon (Si) processes used in superconducting quantum circuits, high-frequency devices, and precision sensors place stringent demands on plasma etching to minimise substrate damage and maintain reproducible feature geometry. This application note demonstrates a robust, low-damage, inductively coupled plasma  reactive ion etching (ICP-RIE) process for Al layers on a 100 mm Si wafer using the SENTECH SI 500 ICP-RIE system. The process achieves smooth underlying Si surfaces after Al removal, vertical sidewalls, and an Al etch depth non-uniformity of ±2% across the wafer, including over-etch, highlighting the capability of the SI 500 for demanding Al etch applications.

ICPECVD of Silicon Nitride Films with Low-Hydrogen using the SENTECH SI 500 D System

Drain leakage current of the GaN HEMT with ICPECVD
ICPECVD of Silicon Nitride Films with Low-Hydrogen using the SENTECH SI 500 D System
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Silicon Nitride (SiₓNy) layers are extensively used as passivation layers, etching masks, membranes, electrically isolating layers, and dielectrics for microelectronic devices, sensors, OLEDs, and much more. The hydrogen incorporation in SiₓNy films plays a very important role in the mechanical, chemical, and electrical properties and their long-term stability. Therefore, the performance of the devices using SiₓNᵧ films is very much influenced by this hydrogen incorporation. The proprietary plasma source PTSA 200 and the separation of gas inlets of SENTECH ICPECVD allow the deposition of SiₓNy films with low hydrogen concentration. SiₓNy deposited at low temperature in the SENTECH SI 500 D ICPECVD tool with low hydrogen content have been successfully demonstrated using SiH₄/NH₃ chemistry. Impressive applications of such ICPECVD films with low hydrogen content have been demonstrated by Fraunhofer IAF Freiburg (Germany) for gate passivation of GaN HEMTs and the use as dielectric of MIM capacitors.

ICPECVD of TEOS/SiO₂ Films using the SENTECH SI 500 D System

SEM image of ICPECVD TEOS silicon oxide films
ICPECVD of TEOS/SiO₂ Films using the SENTECH SI 500 D System
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This application note will demonstrate how the SENTECH SI 500 D ICPECVD Plasma Deposition System with the optional Tetraethoxysilane (TEOS) box for the supply and vaporisation of liquid TEOS, achieved deposition of Silicon Oxide (SiO₂) by TEOS/O₂ with high sidewall step coverage, with low residual stress and good uniformity at a low temperature. We also reference research for ICPECVD deposition of SiO₂ by TEOS. E.g. Chang et al. and by Kusuda, by means of a cathode-coupled PECVD system, SiO₂ films are extensively used as passivation layers, etching masks, and electrically isolating layers for microelectronic devices, as well as barrier coatings, membranes, and in various other application fields, including MEMS. SiO₂ films grown using TEOS exhibit better conformity. Being a liquid, TEOS is safer and easier to handle, and it is more chemically stable compared to other silicon precursors such as Silane (SiH₄). However, low temperatures are required to support advanced device geometries, as well as good step coverage and gap-fill, lower film stress and higher uniformity.

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