Microsystem special equipment: integration and miniaturization in one bottle.

Microsystem special equipment: integration and miniaturization in one bottle..

MICROSYSTEM SPECIAL EQUIPMENT: INTEGRATION AND MINIATURE IN ONE BOTTLE 

The article examines modern possibilities for increasing the efficiency of special technical means through the use of new microsystem technologies.

A characteristic trend in global technological development over the last decade has been the emergence of integrated, including, microsystem technologies (MST) [1]. The initiating factor contributing to the dynamic development of microsystem technology was the emergence of the so-called microelectromechanical systems– MEMS, in which galvanic connections are in close interaction with mechanical movements [2]. A special feature of MEMS is the fact that electrical and mechanical units are formed from a common base (for example, a silicon substrate), and, as a result of using the technology of forming volumetric structures, it is possible to obtain microsystem equipment with high operational and technical characteristics (weight, size, energy, etc.), which immediately attracted the attention of specialists — developers of special equipment.

Analysis of the microsystem equipment market

The integration of advances in electronics, mechanics, computer science and measurement technology, united by the trend towards microminiaturization, determined the emergence of new integrated microsystem technologies in the late 80s — early 90s of the last century. A huge number of universities and commercial companies in the United States and Japan concentrated their efforts on the development of MEMS technologies. An analysis of the MEMS market dynamics carried out by NEXUS (a body of the European Commission) showed that the market volume is increasing annually by an average of 18% and currently amounts to over 40 billion dollars. A more detailed structure of the MEMS market is shown in Fig. 1.

 Fig. 1. Structure of the world market for microsystem technology

It should be noted that in recent years new classes of MEMS based on silicon have been developed, which have provided a revolutionary introduction of new technical means of cellular communication and optoelectronics, including:

• Radio frequency MEMS filters for cellular phones, providing a high quality factor in the frequency range of 3…300 MHz — 200…300 (instead of 20…30 in the microelectronic design);
• Micromirror switches (2×2.1×4 mm) for fiber-optic communication channels at frequencies of 3…30 GHz.

In the 1990s, the countries of Europe and Southeast Asia actively joined the rivalry between the two world leaders in the MEMS field (the USA and Japan). For example, the number of universities and commercial companies engaged in research and development in the field of MEMS creation in Germany by 1997 became 1.5 times greater than in the USA and almost equaled Japan. In 1998, by order of the US Defense Advanced Research Projects Agency, the MEMS program was adopted for the first time, which was called “MEMC Microelektromechanical Systems”. The United States annually allocates $35 million for the development of this program, which exceeds similar investments by other countries.

Main directions and features of development of microsystem technology products

Table 1. Main directions and features of development of microsystem technology products

It should be emphasized that in Russia the term “microsystem technology” began to be used in official documents after the adoption of the list of critical technologies at the Federal level in 1996. Microsystem technology is included in the list of priority areas for the development of science and technology for 2001–2010.

The basis for the development of MEMS is microelectronic technology, which is used in almost all silicon-based products. Unfortunately, the domestic microelectronic industry cannot boast of great achievements at the moment. However, a big positive factor is that the existing Russian microelectronic technology can now be widely used for MST. Therefore, domestic specialists have already obtained interesting results in this area. Currently, the number of Russian research teams engaged in nanomechanics, nanotools, nanotubes and photonic crystals has increased.

Analysis of the modern market of equipment for MST shows that the latter is formed due to the active development of biotechnology against the background of the fight against terrorism, tightening requirements for work with radioactive, toxic and explosive substances, which causes a transition to the use of ultra-small quantities of substances in limited volumes and the creation of “laboratories on a crystal” and biochips [4, 5]. Possible areas of use of MEMS and MST technical means for solving special problems are given in Table 2.

Table 2. Possible areas of use of MEMS in special equipment

It should be noted that three main circumstances contribute to the active development of microsystem technology in Russia:

• the availability of basic equipment, production capacities and organizational infrastructure for microelectronic production, suitable for the implementation of microsystem technology objects (with the existing level of technology at 1…10 μm);
• the availability of scientific and technological culture (primarily in the field of micro- and optoelectronics);
• a vast market of sensor systems of various directions (including in the field of security).

Prospects for further integration of microsystem technology

As mentioned above, the development of MEMS was most influenced by the integration of modern tools, systems and technologies, so to assess the prospects for the development of MEMS we will use the integration level coefficient K = T x M, where T is the number of transistors and M is the number of mechanical components [3]. The state and prospects of integration of microsystem technology are shown in Fig. 2.

Fig. 2. The state and prospects of integration of microsystem technology:

1 — most existing MEMS;
2 — ADXL-50 accelerometer;
3 — DMD optomechanical displays;

The presented figure illustrates well the integration capabilities of microsystem technology. For example, for the serially produced ADXL-50 accelerometer, manufactured using technology with topological norms of 2-10 μm (containing 100…200 transistors and 1 mechanical element), the integration coefficient is T x M = 102, and for the micromirror display chip (1 million mechanical screen elements and 1 million control transistors), we get T x M = 1012. Other integration areas are constructed similarly.

Now it's time to «ground ourselves», i.e. to descend from the microsystem heavens to the sinful Earth and examine in more detail specific developments implemented in real equipment samples.

Monolithic accelerometers

Combining the functions of various sensors in a single device, including a signal generation circuit, a microprocessor and a memory device, opened the way to the creation of universal cybernetic “receptors”. In the development and production of fully monolithic accelerometers, the greatest success was achieved by Analog Devices, which in 1991 was the first in the world to master the serial production of a fully integrated monolithic single-axis accelerometer ADXL50, combining a signal generator and an autonomous testing circuit. To form the sensor’s sensitive element, a thin-layer etching technology was used, which was called an integrated microelectromechanical system iMEMS (Integrated Vicro-Electro-Mechanical Systems). This technology has allowed Analog Devices to take a leading position in the accelerometer market (Fig. 3).

Fig. 3. The “cost – resolution” ratio for different types of accelerometers

The application of thin-layer polycrystalline silicon on an oxide substrate with its subsequent etching is compatible with the technological methods used in the production of integrated circuits, which makes it possible to design sensor devices integrated on a single crystal. It is along this path that Analog Devices has recently managed to develop single- and dual-axis accelerometers ADXL150 and ADXL250, which have high accuracy (relative error of 0.02%) and a very attractive price. Having first penetrated the automotive industry market as airbag command sensors, these accelerometers are now increasingly used in the main units of modern cars, including anti-lock braking systems, security and alarm systems, automatic headlight tilt correction, active suspension control and many other systems. Their use in so-called “black boxes” that continuously record vehicle motion parameters is promising.

Integrated gyroscopes in the ADXRS microcircuit

This gyroscope from Analog Devices is the first commercially available device that combines a rotation angle sensor and signal processing electronics on a single silicon wafer. The developers used iMEMS technology. Due to this, it was possible to make the gyroscope more accurate, more reliable, more economical and miniature than any other rotation angle sensor of a similar class. The chip is placed in a case with ball leads, the dimensions of which are 7x7x3 mm. With a supply of 5 V, the power consumption is only 30 mW. The chip provides a stable output signal even in the presence of mechanical noise up to 2000g in a wide frequency range. The device has a self-checking device for mechanical and electrical parts. The external appearance of the microcircuit crystal is shown in photo 1.

Photo 1. External appearance of the gyroscope microcircuit crystal.

The gyroscope is available in two modifications (with a dynamic range of 1500/s and 3000/s). The use of this microcircuit will increase the accuracy and reliability of global positioning system devices, as well as control the movement of various moving vehicles: cars, airplanes, industrial robots, antennas, industrial equipment.

Special intelligent sensors

The use of MEMS technologies in modern electronic systems allows for a significant increase in their functionality. Using technological processes that are almost identical to the production of silicon microcircuits, developers of MEMS devices create miniature mechanical structures that can interact with the environment and act as sensors that transmit the impact to the integrated electronic circuit. Sensors are the most common example of the use of MEMS technology: they are used in gyroscopes, accelerometers, pressure gauges, and other devices.

Almost all modern cars currently use the above-mentioned MEMS accelerometers to activate airbags. Microelectromechanical pressure sensors are widely used in the automotive and aviation industries. Gyroscopes are used in a variety of devices, from complex navigation equipment for spacecraft to joysticks for computer games. MEMS — devices with microscopic mirrors — are used to produce displays and optical switches (photo 2).

Photo 2. Element of the micromirror matrix of optical switches.

Microswitches and resonant devices made using MEMS technology demonstrate lower ohmic losses and high quality factor with reduced power consumption and dimensions, better repeatability and a wider range of variable parameters. In biotechnology, the use of MEMS devices allows the creation of cheap but productive single-crystal devices for decoding DNA chains, developing new drugs and other special preparations (“laboratory on a crystal”). In addition, it is also necessary to note the capacious market of inkjet printers, the cartridges of which use microfluidic MEMS devices that create and release microdroplets of ink under the control of electrical signals.

In conclusion, we note that, according to experts, the development of microsystem technology (especially for Russia) can have the same impact on scientific and technological progress as the emergence of microelectronics had on the formation and current state of the leading areas of science and technology.

Literature

1. Ukov V.S., Vodolazkiy V.V. Modern security technologies. Moscow: Knowledge”, 2000.
2. Klimov D.M. and others. Prospects for the Development of Microsystem Technology in the 21st Century/Microsystem Technology, 1999, No. 1.
3. Bocharov L. Yu., Mal'tsev P. P. The State and Prospects of Development of Microelectromechanical Systems Abroad/Microsystem Technology, 1999, No. 1.
4. Mal'tsev P. P. et al. “Smart Dust” Based on Microsystem Technology/Microsystem Technology, 2000, No. 4.
5. Rubtsov I. V., Nesterov V. E., Rubtsov V. I. Modern Foreign Military Micro- and Mini-Robotics/Microsystem Technology, 2000, 3.