Micro-electromechanical systems (MEMS)
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 SENDURO®MEMS and RM 1000 QC metrology 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.
Gain insight into Piezoelectric MEMS resonator process challenges and our application solutions
Piezoelectric aluminium nitride (AlN) is a well-known dielectric material with an advantageous combination of electromechanical properties, making it ideal for low-power consumption and high-level integration in MEMS and CMOS processes.
The etching of AlN-based MEMS devices is usually realised by sandwiching a thin AlN film between two metal electrodes. via an opening to a metal electrode.
The added roughness in etched areas is one of the main challenges associated with AlN etching. Thus, the etch selectivity between AlN and the metal underlayer at higher etch rates as well as generated roughness can be two main limiting factors for MEMS applications.
Smooth sidewalls and low surface roughness at a high etch rate while maintaining good etch selectivity to the metal underlayer are presented for the ICP-RIE of AlN MEMS using the SENTECH SI 500 ICP-RIE etch system equipped with proprietary SENTECH Planar Triple Spiral Antenna (PTSA) inductively coupled plasma (ICP) source.
Extreme narrow ion-energy distribution at low ion energies, stable plasma at low pressures, and low plasma power are the key features for successful etching using the SENTECH SI 500 system with the SENTECH PTSA ICP Plasma Source.
