Design of a Single-Chip pH Sensor Using a Conventional 0 . 6-m CMOS Process
Design of a Single-Chip pH Sensor Using a Conventional 0 . 6-m CMOS Process
复制标题
使用传统 0 的单芯片 pH 传感器的设计。
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
D. Cumming
中科院分区：
文献类型：
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作者：
P. Hammond;D. Ali;D. Cumming
本文介绍了一种采用0.6mCMOS工艺在单片上制作的pH传感器。该传感器包括用于在离子敏感场效应晶体管（ISFET）和参考FET（REFET）之间进行差分测量的电路。ISFET具有浮栅结构，并使用氮化硅钝化层作为pH敏感绝缘体。在制造时，它具有大的阈值电压，该阈值电压被假定为由浮置栅极上的捕获电荷引起。紫外线辐射和块衬底偏置用于永久地修改阈值电压，使得ISFET可以用于电池供电的电路中。一种新的后处理方法，使用一个单一的光致抗蚀剂层被用来定义的传感区域，并提供强大的封装芯片。整个电路采用3 V单电源供电，可提供与pH值成比例的输出电压，并可在不需要时关断。
A pH sensor fabricated on a single chip by an unmodified, commercial 0.6m CMOS process is presented. The sensor comprises a circuit for making differential measurements between an ion-sensitive field-effect transistor (ISFET) and a reference FET (REFET). The ISFET has a floating-gate structure and uses the silicon nitride passivation layer as a pH-sensitive insulator. As fabricated, it has a large threshold voltage that is postulated to be caused by a trapped charge on the floating gate. Ultraviolet radiation and bulk-substrate biasing is used to permanently modify the threshold voltage so that the ISFET can be used in a battery-operated circuit. A novel post-processing method using a single layer of photoresist is used to define the sensing areas and to provide robust encapsulation for the chip. The complete circuit, operating from a single 3-V supply, provides an output voltage proportional to pH and can be powered down when not required.