| Designof a Single-Chip pH Sensor Using a Conventional 0.6-μm CMOS process |
| Paul A.Hammond |
| 关键词：CMOSanalog circuit, encapsulation, ion-sensitive field-effect transistor (ISFET), pH, system-on-chip (SoC) |
| 主要内容：A pH sensor fabricated on a single chip by an unmodified,commercial 0.6- m 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... |
| 《2004 IEEE》 |
| 全文下载请进入http://hightech.stlib.cn/tpi_1/sysasp/include/index.asp |
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