High sensitivity indium antimonide thin film micro-Hall sensor arrays for simultaneous multiple detection of magnetic beads for biomedical applications

In this report the fabrication of an InSb Hall sensor arrays to simultaneously detect multiple superparamagnetic microbeads for biomedical applications is described. One-dimensional InSb Hall sensor arrays with 8 micro-Hall devices were fabricated using photolithography and wet chemical etching. The electrical characteristics and noise spectrum of the micro-Hall sensors were determined by van der Pauw Hall measurements and fast Fourier transform (FFT) spectrum analysis respectively. Results show that the offset voltage of all 8 Hall sensors was small at ∼0.1 mV under a drive current (I_H) of 100 μA. The minimum detectable magnetic field is found to be 0.10 mG/(Hz)¹2/ at I_H = 1 mA. Calculations showed that the magnetic field from a single ferromagnetic particle with a radius of 50 nm at a distance of 200 nm from the sensor is about 4.4 G. Therefore, the sensitivity of the Hall array micro-Hall sensors is sufficient for detection of magnetic microbeads. In conclusion, the paper showed that real time simultaneous detection of multiple superparamagnetic beads using the InSb-Hall sensor array system is possible. These results suggest that possibility of using two dimensional Hall sensor array biochips for biomedical applications.