低噪声超导量子干涉器件磁强计设计与制备  

Design and fabrication of low-noise superconducting quantum interference device magnetometer

作　　者：韩昊轩 张国峰[1,2] 张雪[1,2,3] 梁恬恬[1,2,3] 应利良 王永良 彭炜[1,2,3] 王镇 Han Hao -Xuan;Zhang Guo -Feng;Zhang Xue;Liang Tian -Tian;Ying Li -Liang;Wang Yong -Liang;Peng Wei;Wang Zhen(State Key Laboratory of Functional Materials for Informatics,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,China;Chinese Academy of Sciences,Center for Excellence in Superconducting Electronics,Shanghai 200050,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院上海微系统与信息技术研究所,信息功能材料国家重点实验室,上海200050 [2]中国科学院超导电子学卓越创新中心,上海200050 [3]中国科学院大学,北京100049

出　　处：《物理学报》2019年第13期295-300,共6页Acta Physica Sinica

摘　　要：超导量子干涉器件(superconducting quantum interference device,SQUID)作为一种极灵敏的磁通传感器,在生物磁探测、低场核磁共振、地球物理等领域得到广泛应用.本文介绍了一种基于SQUID的高灵敏度磁强计,由SQUID和一组磁通变压器组成.SQUID采用一阶梯度构型,增强其抗干扰性.磁通变压器由多匝螺旋的输入线圈和大尺寸单匝探测线圈组成,其中输入线圈与SQUID通过互感进行磁通耦合.利用自主工艺平台,在4英寸硅衬底上完成了基于Nb/Al-AlOx/Nb约瑟夫森隧道结的SQUID磁强计制备.低温测试结果显示,该磁强计磁场灵敏度为0.36 nT/Ф0,白噪声段磁通噪声为8μФ0/√Hz,等效磁场噪声为2.88 fT/√Hz.Superconducting quantum interference device(SQUID)is the most sensitive magnetic flux sensor known,which is widely used in biomagnetism,low-field nuclear magnetic resonance,geophysics,etc.In this paper,we introduce a high-sensitivity SQUID magnetometer,which consists of an SQUID and a flux transformer.The SQUID is first-order gradiometer configuration,which is insensitive to interference noise.The flux transformer includes a multi-turn spiral input coil and a large-sized pickup coil.And the input coil is inductively coupled to the SQUID through mutual inductance.We present an SQUID magnetometer fabricated with Nb/Al-AlOx/Nb Josephson junction technology on a 4-inch silicon wafer at our superconducting electronics facilities.We develop a fabrication process based on selective niobium etching process consisting of five mask levels.In the first two mask levels,the trilayer is patterned by a dry etch to define base electrode,contact pads,and interconnects.The shunt resistor and a dielectric insulating layer are then deposited and patterned by using lift-off and dry etchant,respectively.Finally,the niobium wiring layer is deposited and patterned by using reactive ion etching to define input,pickup and feedback coils.The measurement of the SQUID magnetometer is performed inside a magnetically shielded room.The operating temperature is realized by immersing the SQUID into the liquid helium(4.2 K).Moreover,a superconducting niobium tube is employed to protect the SQUID from being disturbed by external environments.A homemade readout electronics instrument with low input voltage noise is used to characterize the SQUID magnetometer.The results of low-temperature measurements indicate that the magnetometer has a magnetic field sensitivity of 0.36 nT/Ф0and a white flux noise of 8μФ0/√Hz,corresponding to a white field noise of 2.88 fT/√Hz.This kind of SQUID magnetometer is suitable for multi-channel systems,e.g.,magnetocardiography,magnetoencephalography,etc.Although the SQUID process development benefits from the rapi

关 键 词：超导量子干涉器件 磁强计 磁通噪声 

分 类 号：TP212[自动化与计算机技术—检测技术与自动化装置] TM936[自动化与计算机技术—控制科学与工程]