The development of the 3D magnetic sensor using the nano-SQUID

我们开发了一种可应用于三维磁传感器的铌基纳米SQUID的制备工艺。SQUID使用Nb、Nb/W、Nb/Au膜制造，并通过常规光刻和聚焦离子束（FIB）工艺图案化。双层膜被认为是有效的，以减少自加热的影响，并避免由于在FIB过程中的Ga离子扩散的退化。我们成功地制备了具有非滞后I-V特性的双层纳米SQUID，在4.2K下IC低至30 mA。IC值可以很容易地通过改变FIB模式来调整。因此，本制造工艺具有针对各种测量环境（诸如针对高磁场（~ 1 T）和针对低温（0.1K））优化SQUID设计的灵活性。

We develop a fabrication process of Nb based nano-SQUIDs that can be applied for three dimensional magnetic sensor. The SQUIDs were fabricated using Nb, Nb/W, Nb/Au films and patterned by a conventional lithography and a focused ion beam (FIB) process. The bilayer films were found to be effective to reduce the effects of the self-heating and to avoid the degradation due to the Ga ion diffusion during the FIB process. We succeeded in fabricating bilayer nano-SQUIDs having nonhysteretic I-V characteristics with Ic down to 30mA at 4.2K. Ic values could be easily tuned by changing the FIB pattern. Therefore, the present fabrication process has the flexibility to optimize the SQUID design for various measurement environments, such as for high magnetic field (～1T) and for low temperature (0.1K).