3D Digital NanoCompass can be integrated into CMOS chips

3D compasses of the sort typically found in smartphones use technologies that employ magnetoresistive materials or Hall-effect structures combined with magnetic field concentrators to detect the direction of the Earth’s magnetic field.

Baolab Microsystems claims to have designed the first pure CMOS Lorentz force microelectromechanical systems (MEMS) in its new 3D Digital NanoCompass.

Speaking to The Engineer, Nigel Drew, technical representative at Baolab, said: ‘The key difference is that existing devices are quite difficult to make in that they involve an electronics chip but also some kind of magnetic detector as well, which is typically deposited on top of the chip at additional cost.

‘The fundamental thing that we’ve done is to be able to make MEMS devices, such as this compass, inside the CMOS process itself using the standard masks so there is no additional deposition; it just comes with the electronics and the MEMS on board.’

In the NanoCompass, the MEMS structure is a moveable aluminium plate suspended by springs and is constructed using the metal interconnect layers of the CMOS chip by etching away the Inter Metal Dielectric (IMD) using vapour HF (vHF). When a current passes through the plate, it experiences a force (the Lorentz force) proportional to the surrounding Earth’s magnetic field.