Al2O3/HFO2/Ta2O5堆疊閘極介電層於InGaZnO薄膜電晶體之研究及其在光感測的應用

Investigation of InGaZnO Thin Film Transistors Using Al2O3/HFO2/Ta2O5 Stacked Gate Dielectrics and Application on Optical Sensor

非晶氧化銦鎵鋅(a-IGZO)是近期受矚目的金屬氧化物材料，普遍應用於顯示器上，具有非晶矽與多晶矽的優點，有高的電子遷移率、較佳的均勻度、較低的製程成本與可在室溫下製程，當TFT應用在大尺寸高解析的顯示器上時，每個電晶體所分配到開關時間變少，電晶體電性的研究及改善也越顯得重要。
在本研究中，我們對氧化銦鎵鋅薄膜電晶體在以不同高介電材質之堆疊結構閘極介電層探討其應用電晶體技術之可行性。從電性結果顯示，採用Ta2O5/HfO2/Al2O3堆疊結構閘極介電層的電晶體與單層閘極介電層的元件相較之下有較好的電晶體元件特性，堆疊結構閘極介電層增加40%的驅動電流，改善閘極電容值，提高載子遷移率，增強Ion/Ioff ratio，有更小的臨界電壓與臨界擺幅(S.S.)，堆疊結構氧化銦鎵鋅薄膜電晶體飽和電流、載子遷移率、臨界電壓、次臨界斜率、電流開關比分別為1.4 x 10−4uA、109Xcm2/VS、0.4V、0.38V/dec、2.76X106，堆疊結構閘極介電層中的材料有較高的介電常數，因此堆疊結構閘極電容的改善確實也是電流驅動能力提升的原因，並且介電層間會因氧密度的差異性形成Diople，在通道層吸引電子，使得堆疊結構閘極介電層的電晶體電流與單層閘極介電層的元件相較之下，有較大的驅動電流和電子電洞載子遷移率的增加，並且降低臨界電壓，從電性結果顯示，堆疊結構介電層比單層介電層元件有更好的電特性，基於前述的優異電性表現與製程相容性，此堆疊結構閘極介電層目前普遍使用於半導體廠且完全相容於現有的積體電路製程技術，使得堆疊結構閘極介電層具有應用於高效能電晶體技術的潛力，成為應用於下一世代電晶體之前瞻技術。
使用氧化銦鎵鋅做為主動層材料具有多項優點且為寬能隙的材料，適合應用於透明顯示器，本研究中第二部份，我們對氧化銦鎵鋅薄膜電晶體在不同波長光照下進行了光反應之研究，發現其具有光敏特性且與光波長及元件之操作模式有明顯的相依性，顯示出氧化銦鎵鋅薄膜電晶體除了應用在開關元件上，在光感偵測器上的應用也具潛力。

Amorphous gallium zinc oxide (a-IGZO) is a target metal oxide material that has attracted attention recently. It has the advantages of amorphous silicon and polycrystalline silicon on common displays, with high electron mobility, best uniformity, and low cost of the process. When TFT is applied to a large-size and high-resolution display, the switching time allocated to each transistor becomes less, and the research and improvement of the electrical properties of the transistor are more likely to be important.
In this study, we explored the feasibility of applying transistor technology to indium gallium zinc oxide thin-film transistors using stacked gate dielectric layers of different high-k materials. The electrical results show that the gate dielectric layer of the Ta2O5/HfO2/Al2O3 stacked structure has better characteristics of the transistor than the single-layer gate dielectric layer. The Ta2O5/HfO2/Al2O3 stacked structure could increases the driving current by 40%, and improve gate capacitance value, carrier mobility, and Ion/Ioff ratio. Such stacked dielectric structure have different oxygen density among dielectric layers, which will form Diople[14], attract electrons in the channel layer, so that the stacked structure has a larger driving current and mobility compared with the single-layer gate dielectric layer. Based on the study, the stacked structure dielectric layer is currently widely used in semiconductor factories and is fully compatible with the existing integrated circuit process technology, making the stacked gate dielectric layer have the potential to be used in high-performance transistor technology and become the next generation of transistors. Forward-looking technology.
In the second part of this research, we conducted indium gallium zinc oxide thin film transistors under different wavelengths of light. After studying the photoreaction, it is found that it has photosensitivity and is obviously dependent on the wavelength of light. It shows that indium gallium zinc oxide thin film transistors are not only used in switching elements, but also in photo-detectors. The application also has potential.