Reinventing MEMS on the nanoscale

Current MEMS sensors have limitations

Sensors play an increasingly important roll in everybody’s lives as they provide the interface between the everyday analog world we live in and the digital world of the computers that are everywhere. They sense things such as movement, pressure changes, temperature magnetic fields, etc., and then generate digital signals for processing by electronics. The mobile phone is full of them which is what makes it a smartphone. Similarly, earbuds, wearables and a host of other devices are made smarter with sensors.

These sensors actually have tiny mechanical parts that move due to a specific stimulus and that movement is detected to form an electrical signal hence the name MEMS (Micro-Electro-Mechanical Systems). Each design of MEMS is made on a specially created production line which has advantages and disadvantages. On the plus side, once up and running, a line can produce MEMS chips in the millions but, as demand is outstripping supply in many cases, the only way to increase production is to build another identical line which takes time. Similarly, creating a new MEMS sensor means designing and commissioning a brand-new line. Lastly, these solutions are one type of sensor per chip.

Unique radical approach for building sensors

Nanusens has taken a completely different approach to creating MEMS that solves the drawbacks of the current method of production. Instead of building a MEMS structure on top of a sliver of silicon, Nanusens creates it by using metal layers within a CMOS chip. CMOS chips can be made in any of the many CMOS fabs around the world so Nanusens has no limitations on the number of sensors that it can make using this approach which solves the production limitations of current MEMS. It also gives Nanusens access to the huge economies of scale that these giant fabs provide.

Building within the CMOS chip means that the structures are not Microscopic in size but nanoscopic. This reduces the power consumption of each sensor and, moreover, several different kinds of sensors can be built within the chip at the same time to enable true multi-sensor chips to be created for the first time. This shrinks down the size of a multi-sensor solution to free up more space for additional features and batteries.

Smaller is better

There are many other advantages to these NEMS (Nano-Electro-Mechanical Systems) such as increased performance due to very small parasitic capacitances. This is because, in a typical MEMS sensor, it is detecting very tiny capacitance variations in the region of one picofarad from one die that is connected via wire bonds to the MEMS die. Simply wire bonding or building the typical MEMS structure on top of a CMOS wafer introduces a parasitic capacitance of around a thousand femtofarads. With Nanusens’ MEMS-within-CMOS approach, this is reduced to around ten femtofarads which is a huge noise to signal ration reduction giving much better sensitivity.

Building with just standard CMOS processes also means that the control electronic can be built into the CMOS chip alongside the sensor structures to create an integrated, single chip solution. Excitingly, Nanusens has designed a way to detected the capacitance changes using a digital circuit rather than the traditional analog one so that both the sensor designs and the digital circuit can be ported to smaller nodes as required to reduce power consumption and size even more.

Unlocking the higher band for 5G and 6G

Apart from sensors, the company has used its nanotechnology to create a novel solution for RF Front Ends for mobile phone antenna tuners. Now that antenna is located within a mobile phone, the user’s head and hand from part of the antenna and affect the way it operates so it is important to be able to match the power amplifier and the antenna, which is called the antenna tuner. Without this circuit, part of the power delivered to the antenna would bounce back and, instead of radiating the signal, the power would be used to heat the user’s brain, which wouldn't be very healthy, plus it would be discharging the battery unnecessarily. So, to avoid that, today, all the phones have this antenna tuner circuit, but it's implemented in solid state with SOI switches that switch external stand-alone capacitors. However, this is a relatively large overall solution and become less efficient at frequencies above 2GHz.

Nanusens uses its multi-patented technology to build a number of RF Digitally Tunable Capacitors (DTCs) to handle many different bands with the CMOS layers of a single chip giving a much smaller solution compared to currently so more room is available inside the phone for larger batteries. It can also handle the higher frequency bands making them now able to meet the increasing need to handle the additional data demands of 5G and 6G phones.

This novel approach also means that antenna efficiency can be increased giving up to 30% longer talk times and the range increased by up to 14% which mean less poor reception and fewer dropped calls.

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