MEMS Non-Magnetic Electric Heating Chip for Spin-Exchange-Relaxation-Free (SERF) Magnetometer

The alkali metal atoms in spin-exchange-relaxation-free (SERF) atomic magnetometers require high temperature and non-magnetic environment. Increasing the temperature of the alkali metal atoms causes higher atomic density, which can enhance the intensity of the output signal. However, heating current introduces additional magnetic flux density and unexpected gradient, which will reduce the device's sensitivity. Therefore, it is necessary to develop a non-magnetic heating chip for the SERF magnetometer. In this paper, a new design for non-magnetic heating chips, fabricated by the microelectromechanical system (MEMS) technique with platinum deposited on the semiconductor substrates, is proposed. The designed chip is composed of two layers of the same serpentine-shaped resistors to suppress the magnetic flux density, with an insulation layer in the middle. There are two sets of wires in each layer used as a thermometer resistor and a heating resistor forming a feedback loop of temperature control. The simulation results show that the magnetic effect between the layers can be reduced by four orders than in one layer. The experimental results show that the temperature coefficient of resistance (TCR) is approximately 0.224%/degrees C. The consistency of the resistance is better than 97.7%. The fluctuation of temperature at 110 degrees C is under 10 mK. The magnetic flux density introduced by the current in the z-direction is 0.22146 nT/mA.