MEMS technology

At a glance
In the previous section (part 2) we got to know the vibration measuring method. This section deals with the establishment of MEMS technology at TrueDyne Sensors AG. The technology has brought about the MEMS sensor, the heart of which is an oscillating silicon measuring channel. Compared to conventional resonator technology, it combines numerous advantages. These range from its small size and a wide range of applications to the exact determination of the density of gases, even at low pressure, and an extremely fast reaction time.


  • What is MEMS technology?
  • Where are MEMS technologies used?
  • How is the Omega chip structured?
  • What opportunities does MEMS technology offer?

What is MEMS technology?

MEMS stands for Micro-Electro-Mechanical Systems. The technology combines microelectronic and micromechanical components in a complex microsystem based on silicon semiconductor technology.

For the semiconductor technology, several electronic components are structured on a semiconductor substrate (often made of silicon) using various process technologies, e.g. photolithography and thin-film technology, and assembled into a chip. Since the individual steps for the production of a chip are very complex, these steps are multiplied and several chips are produced simultaneously. This is done with a circular or square, disc-shaped wafer which consists of the material of the required substrate.

Semiconductor technology allows for the miniaturization of electronic circuits, which in classic electronics consist of mechanically manufactured components. One TrueDyne Sensors AG MEMS chip not only includes electronic but also mechanical and fluidic functions.

Due to the high demands on the individual components, a TrueDyne Sensors AG MEMS chip is usually not limited to a silicon substrate. Instead, diverse materials are used for the different components, which are brought together using various assembly and connection techniques.¹

Graphic - Wafer
1. Waver, 2. Chip
Circular wafer – Source:

Where are MEMS technologies used?

MEMS technologies are becoming increasingly important. They are used in the most diverse areas and are omnipresent in our everyday life. MEMS systems are increasingly used in automotive industry applications, e.g. for theft protection, airbag control or vehicle rollover detection systems. In addition, they are used in the mobile communications sector for navigation, display orientation or mobile gaming. There is also great application potential for microfluidic systems in medical engineering, especially in biomolecular analytics. Keywords here are lab-on-a-chip or BioMEMS.

How has MEMS technology developed at
TrueDyne Sensors AG?

For several years, TrueDyne Sensors AG has been working on the development and implementation of the Coriolis measuring principle as a fluidic microsystem or as MEMS chip. The fluidic channel required for the Coriolis measuring principle is formed from a silicon substrate and integrated into a MEMS chip.

This system has not proven itself effective for measuring the flow rate at TrueDyne Sensors AG. However, it has been shown that the vibrating silicon channel can be used very effecticely as a resonator densimeter .

How is the TrueDyne Sensors AG MEMS chip constructed?

Nowadays, a TrueDyne Sensors AG MEMS chip is very small, no more than 6.9 x 6.9 x 1.5 mm in size. It contains electronic components, a fluidic measuring channel and a temperature sensor.

The TrueDyne Sensors AG MEMS chip is manufactured using a total of four wafers:

  • Two silicon wafers form the measuring channel. The measuring channel is formed using plasma etching technology. For this purpose, half of each channel is etched into a silicon wafer. The channel is created by connecting the two halves (bonding method).
  • A glass wafer contains metallic electrodes, fluidic openings and the temperature sensor.
  • Another silicon wafer is used to package the measuring channel in a vacuum. This allows the measuring channel to oscillate without air damping.

How is the TrueDyne Sensors AG MEMS chip constructed?

Numerous advantages and new areas of application are available due to the miniaturization (measuring channel = 0.5 µl volume) and the material qualities (silicon) of the channel.

Miniaturization is gaining ground particularly in applications where small sample quantities and a compact structure are of great importance.

The thermal and mechanical properties of silicon mean that a powerful sensor is also provided.

Silicon is a good conductor of heat. The channel is therefore not exposed to large temperature differences. The temperature information required for density measurement can thus be determined precisely and easily.

1. Thin film temperature sensorTemperatursensor, 2. Chimney, 3. Measuring channel, 4. Vacuum, 5. Electrodes
TrueDyne Sensors AG MEMS-Chip – Source: TrueDyne Sensors AG
The mechanical properties of silicon are also advantageous for density measurement. The low deadweight and the low rigidity of the silicon channel mean that a very high measuring sensitivity is achieved. This property is particularly important for light liquids and gasses. Thus, a gas measurement with low pressure (the currently specified pressure range is between 1 and 20 bar) can still be carried out with a high (level of measuring) sensitivity.

The silicon channel can vibrate at a very high frequency. This leads to a short measuring time and makes the measuring signal independent of external, mechanical interference vibrations.

¹Source: Praxiswissen Mikrosystemtechnik, F. Völklein und T. Zetterer, 2006, Vieweg+Teubner Verlag

Applications that might interest you

Monitoring of fuel concentrations
From volume (l) to mass (kg)
Monitoring of welding gas mixtures
Monitoring of gas mixtures for food packages