本論文利用標準0.35μm互補式金屬氧化物半導體(Complementary Metal Oxide Semiconductor，CMOS )製程技術，直接實現ㄧ具潛在可量產、低偏壓及高光電效率的微結構光感測器(Optical Sensor)。微結構光感測器依其結構可分成「電流式主動感光元件(Current Active Optical Sensor，CAOS)」 和「電壓式主動感光元件 (Voltage Active Optical Sensor，VAOS)」 兩部份。 在元件的設計理念上，CAOS為一整合傳統之光電二極體於標準負極金屬氧化物半導體(Negative Metal Oxide Semiconductor，NMOS)閘極區域之新型元件結構，藉由元件特殊設計可將光電二極體所產生之光產生電洞累積至NMOS閘極，除了可降低原本NMOS導通時所需之外加閘極偏壓外(即有助於壓抑元件暗電流)，更可經由NMOS來放大整體元件的光電流輸出；VAOS為整合一具有將光電流直接轉換成光電壓功能之光偵測器於標準NMOS閘極區域，特別的是VAOS可經部分的製程步驟設計後，正極金屬氧化物半導體(Positive Metal Oxide Semiconductor，PMOS)部份將被視為一類光電二極體，藉由電荷耦合電壓來控制NMOS，同樣也不需輔助放大電路即可直接做有效的放大電流輸出，可直接將CMOS當作光偵測器使用。所以經過元件特別之設計，CAOS及VAOS皆可於低偏壓條件下操作，不需再外接訊號放大電路，有別於傳統上感光元件之電流放大方式，可達到較小元件面積設計及減少整體功率消耗以外，CAOS及VAOS還皆兼具內建感測陣列中之像素選擇(Pixel Selection)功能，有利於元件組成影像感測陣列。 實驗結果證明，所設計元件除了具有輸出電流直接放大效應的優勢(可提高至少一百倍)，也有效增加了光響應能力(Photoresponsivity)；元件設計除了改善光電轉換效率以外，其操作電壓更可壓低至0.25 V，遠小於一般之工作偏壓1 V，這將非常適合應用於手持移動式的產品。另外，設計VAOS元件時所需要之光電壓直接產生元件其光電壓增加量也同時被量測而得知，直接就證明了論文所提出之光電元件結構可滿足將光電流直接轉換成光電壓輸出，不需利用傳統的電阻性負載或是額外聯接一轉阻放大電路(Trans-impedance Amplifier，TIA)來實現一電壓輸出之目的；同時，此光電壓之存在更進一步提供了CAOS或是VAOS可低壓操作之證據。 因CAOS及VOAS獨特的結構，可組合出較傳統元件面積為小的設計，而且優秀的光電特性以及不更動標準製程步驟的設計理念，除了具有可低成本量產之優勢外，也使得本論文的元件結構設計可立即與CMOS周邊支援電路順利整合並實際應用於許多需要偵測光強度之應用上。 In this study, low voltage operation and high photoelectric conversion capability of optical sensors, Current Active Optical Sensor (CAOS) and Voltage Active Optical Sensor (VAOS), were proposed and realized using a standard 0.35 μm Complementary Metal Oxide Semiconductor (CMOS) process technology . In the design concept for CAOS, that is integrated conventional photodiode with standard Negative Metal Oxide Semiconductor (NMOS), gate bias voltage of NMOS can be reduced to maintain the amplification capability of NMOS by the existence of photo generation holes accumulated within the gate region of NMOS. The VAOS was consisted of a standard NMOS for enlarging photocurrent and a novel photodetector which can be realized by a modified Positive Metal Oxide Semiconductor (PMOS) for providing photo-voltage output above the gate electrode of NMOS to reduce the gate bias voltage. Therefore, the CMOS structure benefits design of VAOS. CAOS and VAOS not only provide low bias operation potentially but also differ from the conventional optical sensor on the photocurrent amplification for enhance photoelectric conversion further. Additionally, CAOS and VAOS own the pixel selection function intrinsically through the n-well bias of PMOS and drain voltage of NMOS as these devices are employed in the application of image sensing array. Experimental results show that the output of the design elements in addition to the advantages of direct current amplification effect (can be increased by at least a hundred times), but also effectively increase the Photoresponsivity. The component designs can not only improve the photoelectric conversion efficiency, in which an operating voltage but also down to 0.25 V, the work is far less than the general bias 1 V, which is very suitable for handheld mobile products. And the photo-voltage was also measured in the novel optical sensor of VAOS to confirm the mechanism about converting photocurrent into photo-voltage without any resistance loading and external circuit like trans-impedance amplifier (TIA). At the same time, the measured photo-voltage provides strong evidence for low bias voltage operation in CAOS and VAOS benefiting the immunity of gate leakage and the reduction of power consumption. CAOS and VAOS due to the unique structure of the more traditional elements can be combined area of small design , and have excellent optical characteristics and process steps without changing the standard design, in addition to having the advantages of low-cost mass production, but also make this paper design elements can be immediately supported with CMOS circuits smooth integration of peripheral and actually used in many applications need to detect the light intensity.
