LONDON – Baolab Microsystems SL (Barcelona, Spain) a startup pioneering the creation of microelectromechancial systems (MEMS) within the back-end-of-line structure of CMOS wafers, has completed its first product design, a magnetic compass sensor.
However, Baolab (Terrassa, Spain) is breaking with MEMS tradition in more ways than one. Not only does it intend to use conventional metalization and the removal of interlayer dielectric to build MEMS structures, but it is using the Lorentz force in its CMOS MEMS sensor.
Conventional compass devices have used magneto-resistive materials or Hall-effect structures combined with magnetic field concentrators to detect the direction of the Earth’s magnetic field, the company said.
The MEMS structure, a moveable aluminium plate suspended by springs, is constructed using the metal interconnect layers of the CMOS chip by etching away the Inter Metal Dielectric (IMD) using vHF (vapour HF). When a current passes through the plate, it experiences a force (the Lorentz force) proportional to the surrounding Earth’s magnetic field. The resulting displacement is measured using capacitive detection between the moveable plate and fixed electrodes around it, sensing the magnetic field in the x, y and z directions with a single NanoEMS chip.
One of the main characteristic of Baolabs devices is that they are small – hence the use of NEMS terminology and can be integrated with conditioning circuitry and even digital processing on the same CMOS die.
Baolab’s first NanoEMS product range will be a portfolio of ow cost motion sensors. Initial samples will be available early in 2012 with volume by the end of the year, according to Dave Doyle, CEO.
The company claims that is 3-D digital compass matches performance benchmarks for sensitivity, power consumption and package size, but at a dramatically lower cost, than competitor products. The integration with conditioning and processing circuitry means that Baolab has been able to include an auto-calibration routine to maintain consistent accuracy.
The company also aims to produce complex hybrid sensors that include gyroscope, accelerometer and compass sensing in a single chip, all made using the Lorentz force sensing principle. "When several devices are integrated onto a single chip to create a multi-sensor device using NanoEMS, the cost savings compared to conventional MEMS become even more significant especially as different sensors require different production processes, unlike NanoEMS," said Doyle in a statement.
Engineering samples of the BLBC3-D NanoCompass will be available in 2012 along with an evaluation kit. The compass provides 5-degree heading resolution and 13-bits per axis. The commercial IC will have either an I2C or SPI digital serial interface and a choice of either a 3-mm by 3-mm by 0.9mm 10-pin DFN/0.5-mm pitch package, which provides drop in compatibility with existing solutions, or a 2-mm by 2-mm by 0.75-mm BGA package.
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