Revolution of silicon micro

For some decades, the number and type of electronic components that could be achieved on a single piece of silicon has been a factor in the performance and progress. If in the years’60 to squeeze a few transistors chip size of the order tens of micrometers has been a revolution, 2000 we have over 100 million transistors, nanometer-sized, all on a piece of silicon a few millimeters square! Thus far, the visionary of Moore (Gordon Moore, one of the founders of Intel), under which integrated component density doubles every 24 months, was observed. But until when? Well, until the tranzistoarele will become so small that it will be like transistors. Already many undesirable effects of head beating give designers working with devices with dimensions of tens of nanometer. Border based on silicon technology will be achieved in a few years.

But not only the size (and implicitly the number) components of a face has changed over the past five decades, but also their type. A modern can integrate on the same plate for both semiconductor various types of transistors (bipolar, field effect), as well as resistors, diodes, capacitors and even small coils. Although most used semiconductor silicon remained, because of its advantages, there are technologies based on GaAs (galium-arsenic), SiGe (silicon-germanium) or InP (indium-phosphorus), with which you can create components for special applications, such as high frequencies and very high (even above 70 GHz).

The history of electronics has been the witness of many branches of development of this art engineering. If the first electronic applications have been in radio, today we already comes hard to make a classification. Technological advances have enabled an enormous increase of complexity systems, while the price has fallen steadily in. Possibilities opened by digital recently surpassed any imagination. May we find hardly any device today that does not contain a digital.

For reasons of cost, reliability and size, is not always desirable for digital circuits are physically separated from the analog. An important step was the implementation of mixed-signal technologies (ie “mixed signals”) that allows bringing the same chip as digital circuits, and the analog. It might not for who knows how much, but have stressed that the two types of circuits have very different requirements and their coexistence on the same silicon plate is not necessarily a matter banala. Today however, technology has become a regular. Further modules have been integrated analog power along the sensitive analog blocks and digital circuits. If it seems trite, maybe we should do a comparison: is like a watchmaker to put on a watch mestereasca (block sensitive) in a truck (power block) that hurducane on poorly paved road.

Such an integrated circuit, which gathers several “types” of electronics, called system on a chip – a system on chip (SOC). A typical example is found in the automotive industry (ie manufacturing industry for automotive electronics) electronic switch that a command of electro-motor, for example. Contains the power transistors working as an interruption and should allow a high current (and therefore occupy the largest area of silicon). But besides this component, on the same chip found in May a lot of other modules you need to carry protection “switch” and to ensure communication with the outside world. Thus, there are circuits that detect if the current-switch transistors has exceeded the maximum permitted value, if the chip temperature reached values not allowed, if it came from a short external pins or if pregnancy has been disconnected. All these events can cause irreversible damage to the integrated circuit and therefore they must be kept under control. Detection circuits (which are a sensitive analog) transmit “diagnosis” of the digital circuits, on the same chip, which forms a kind of small “brain”: they decide what to do, like switch off in case of emergency. All these digital circuits provide bidirectional communication with the outside world, so that image-breaker may receive commands from a microprocessor and can send the data on this condition. And above all, to function properly, each block component needs food. Another circuit provides various voltages and currents necessary for stabilizing the rest of integrative, and that in terms of the supply voltage of the entire chip can vary between very wide limits! … Here is how a simple switch to become a “smart circuit” … and this on only a few square millimeters of silicon!

Another challenge is the integration of radio blocks along the low-frequency blocks. SOC RF (radio-frequency system on a chip – the radio system on a chip) has emerged as a result of the development world of mobile communications, portable devices which must be small, cheap and reliable. A transceiver (transmitter-receiver, ie transmitter-receiver) SOC typically includes blocks in signal processing banda basic, oscillators, mixers, amplifiers, low noise circuit for reception and floors for transmitting power. I mean a “menu” very rich and heterogeneous, with each block other requests. And as we make an idea of how heterogeneous is to think that only the receiving circuit has to be able to collect signals with powers of the order picowatt (millions of millions of a watt) in a noisy environment, while transmitting circuit must be able to deliver power in the order of the watt antenna. I mean powers 1012 times higher! Now to add to problems such as noise (at reception), nonlinear distortion (in emission), so that the receiver, and the broadcaster using the same antenna and frequency is somewhere around 2 GHz, and the designer is already in a nightmare situation … And yet, such a chip transceivere were built and are found in most products!

But what pushes companies to invest enormous sums to develop these technologies extremes? Well costs. When you have as many functional blocks integrated into a single chip, the total price of the product decreases drastically. Why? It’s easy: an integrated circuit can be manufactured in mass, which makes it very cheap. Fewer components on a PCB board area means a smaller plate (thus cheaper and more compact), fewer interconnections (cheaper again) and a smaller effort by equipping the plate with the individual components (which again reduces costs ). In the current mass production of every cent counts, because it multiplies a million times. Besides this, fewer discrete components means the highest reliability of the finished product. And here are some reasons why everyone tries to build the super-on-a-chip.

Well, so far we only talked about integration of various electronic components. But what if we push them through some mechanical components?

Gears under a microscope …

MEMS means primarily spectacular. After an integrated way about all that can be integrated in the power (but that does not mean that would not be anything done in this direction!), It’s time to integrate and “arms” that mechanical intelligent circuits they command.

To understand better what this is about, to appeal to the most popular class of MEMS circuits which can be found currently on the market: MEMS sensors. Includes a sensor, if general, a transducer that converts a physical size of a small electric measurable, and conditioned by a signal which takes electrical signal provided by the transducer and processed before it’s delivered to the user. Typically, traductorul is implemented as a separate piece from conditionatorul signal. For example, a temperature transducer may be a termocuplu or a resistor whose electrical resistance varies with temperature, or a semiconductor device that will change an electrical parameter with temperature.

When traductorul itself is an electronic component that can be normally integrated into a chip, the problem is solved. But what do we do with a pressure transducer or a throttle? Well, MEMS offers incredible opportunity to bring such and transducers on the same chip with electronic circuits rest!

For example, a MEMS pressure sensor comprises an elastic membrane of silicon and aluminum which deforms under pressure from outside. If the membrane is just one of the fittings of a micro-electric condenser, a mechanical deformation to cause electric condenser capacity, variation that can be easily measured. And everything on a single chip! A related application is capacitive microphone, which ultimately also a pressure transducer.

Obtaining three-dimensional mechanical structures in silicon is possible by combining and modifying various technological methods used in microelectronics (deposition, corrosion, by ion bombardment, fotolitografiere etc..). The materials used are silicon, polymers and metals. MEMS process that is an extension of traditional processes is crucial, since it is compatible with such technologies VLSI (very large scale integration – integration scale wide) CMOS, allowing implementation on the same chip as the mechanical part, and of the electronic.

Design mechanical parts of the face must take into account the effects that occur in the case of so small size of them, because now will manifest electrostatic forces and the superficial tension. When advanced to NEMS can exist even ciocnirii with the laws of the cosmos little strange. Moreover, recently announced it was creating a device that draws the border of quantum physics. It is a “sliver” of aluminum caught at both ends of a substrate of silicon and nitrura which can vibrate. Nearby, a transistor with a superconducting single electron must detect vibrations chips. Because of tiny size of the device, the principle of Heisenberg begin to make their presence felt: the position and momentum can not be determined simultaneously with an accuracy as good.

Turning to applications but more “banal” of MEMS, other types of sensors spread of this kind are accelerometrele. They find various uses, such as in the systems of air-bag when automobile collision case they must detect the situation where rescue act pillow. Construction of micro-mechanics is again very simple (in principle): a micro-piece of material (which forms the inertial mass) is suspended by means of micro-springs (which are nothing but metallic conductors, suspended and shaped in the form the coil). Could move under the effect of inertia, inertial mass is to change the geometry of micro-capacitors (which have one of furniture fittings), which leads to modification of their electrical capacity. Changing the capacity is easily measurable by an electronic circuit, integrated on the same chip, which provides more of the decision about the acceleration. In a similar way accelerometrului have been built and giroscoape MEMS simple.

Another prototype promises apparently impossible: a mini power to replace batteries used in laptops and other portable equipment! The team of researchers claims that such a micro-jet could provide five times more power than a battery current, and that in terms of similar dimensions. As with reactor “macro” usual micro-pump injects fuel into the air at high pressure, after which the mixture is ignited. Incandescent gas spring acting a micro-turbine, which in turn turns a micro-power generator! Science-fiction? Until now have been completed and tested the individual components, but to the central micro pocket are fully functional enough to beat obstacles, such as thermal insulation of the combustion chamber as compared to the rest of the parties. And remains to be seen if the final product will be as safe in operation as they see now and if its creators will be included in environmental standards.