基于标准CMOS工艺的新型pH值传感器

基于0.6μmCMOS工艺设计了一种新型的pH值传感器。多晶硅和双层金属电极形成复合的悬浮栅结构,Si3N4钝化层作为敏感层。传感单元为W/L=500μm/20μm的PMOS管,其阈值电压随溶液pH值线性变化,并通过恒定PMOS管源漏电压和源漏电流控制电路转换成PMOS管源电压线性输出。PMOS管源电压线性输出范围达到4.6V,很好满足在不同pH值溶液中测试的要求。采用波长396nm紫外灯管照射来消除浮栅上电荷,增大阈值电压并有效调整溶液栅电压线性区工作范围。紫外照射后溶液栅电压可偏置在0V,减少溶液中噪声影响。CMOSpH值传感器的平均灵敏度为35.8mV/pH。

New pH Sensor Based on Conventional CMOS Process

A new pH sensor is designed based on 0.6 μm CMOS process. Floating gate is made up of poly silicon and double metal layers,while silicon nitride passivation layer acts as sensitive layer. The sensing unit is PMOS transistor with W/L=500 μm/20 μm and the threshold voltage can be changed linearly with the pH value of solution. This change becomes the change of source voltage of PMOS transistor proportionably through keeping source-drain voltage and source-drain current constant respectively. The linear voltage range of PMOS transistor reaches to 4.6 V,which greatly satisfies the testing request for different pH value solution. Exposure to UV lamp with 396 nm wavelength can erase the charge trapped on the floating gate,which can increase the threshold voltage and can adjust the linear range of gate voltage in solution effectively. The gate voltage in solution can be set in zero after UV exposure,and the noise from solution is reduced. The average sensitivity of the CMOS pH sensor is 35.8 mV/pH.