離子感測電晶體與參照電晶體之感測層材料研究

Abstract

離子感測電晶體中利用不同的材料代替金氧半電晶體的金屬或是複晶矽閘極，使待測溶液直接接觸閘極材料，溶液中將被選擇的離子種類與閘極材料(感測層)發生反應，使閘極捕抓電荷產生電性上的飄移。藉由量測電性的改變量（閘極電壓-汲極電流曲線的平移量）來反推閘極上的反應程度而標定待測溶液的反應離子濃度。 本論文以數種材料作為閘極感測層對於標準酸鹼溶液進行探討。元件的製程均在國家奈米元件實驗室與國立交通大學奈米中心的一萬級無塵室中進行與完成。每一個晶圓上有14個元件；每一個元件由兩個對稱的離子感測電晶體共用一個源極組成；感測層則以HfO2、ZrO2、TiO2、Al2O3、Si3N4等五種材料做組合。當所有製程結束後，所有元件在國立交通大學電子所光積電元件實驗室進行量測與分析。量測利用HP4156在黑箱中進行，首先先量測汲極電壓-汲極電流特性確定元件是否可正常操作，之後對不同酸鹼值的標準液量測其閘極電壓-汲極電流曲線，藉由討論各曲線間的差距來定義元件的靈敏度。並探討在相同製程條件下，同一個元件上的兩種感測材料的特性表現。 此篇論文將詳細敘述酸鹼離子感測元件與參照元件的製作流程及量測條件，接著討論含有參照電晶體的元件在特性上與單一個離子感測電晶體有怎麼樣的改進，並且藉由實驗數據來評估不同的感測材料對於酸鹼離子反應的敏感度，最後對後續工作與未來發展做一個初步的規劃。

The ion-sensitive field effect transistors (ISFET) were first presented by P.Bergveld in 1970. They have different materials instead of the general metal/poli-Si gate of traditional MOS. As the unknown solution contacts the sensing material, specific ions would act with the sensing material, therefore, trapped charge lead to a shift on electrical properties. We have measured these changes to determine the degree of the reaction, and then, the concentration of the specific ions should be leveled by analysis the result data. In this thesis, five different materials (HfO2, ZrO2, TiO2, Al2O3, Si3N4 ) are used to be the sensing layers on ISFETs. All the devices fabrications were completed in the clean room (class 10000) of NDL and NFC of NCTU.4 inches p-type wafers were used in these procedures. Each wafer has fourteen devices. Differ to ordinary ISFETs device ,the device in this thesis has symmetrical pattern(i.e. two ISFETs with common source).As all the fabricating step are finished, the performance of these devices were measured and defined in OEM-Lab. The working point of each device was dependent on its ID-VD curve. At this defined working point, the devices were soaked in solutions with different PH value in sequence. ID-VG curves were recorded to define the sensitivity of these ISFETs. In this thesis, the following chapters will describe details on the fabrication process and measure conditions. Also, the property improvement will be discussed. According to the result, some ideas of future work will be mentioned.