陽極氧化鋁之特性其在氧化鋁/氮化矽雙閘極介電層非晶矽薄膜電晶體之應用

Abstract

本文利用陽極氧化法成長陽極氧化鋁及電漿輔助化學氣相沈積法研製適用 大面積液晶顯示器 /氮化矽雙閘極介電層之非晶矽薄膜電晶體。在本研究 中，氧化鋁在各種酸鹼值及不同比例之氧化液之許多條件下成長，成長後 之氧化鋁並在各種不同溫度退火30分鐘。在本實驗中發現氧化鋁在酸鹼值 為6，純水為氧化液百分之三十且經300℃退火30分鐘研製的氧化鋁具有最 好的特性。在此研製成長的氣化鋁具有非常緻密之結構，及低的蝕刻率 （90A/min)，並且其破壞電場可達(7.8ＭＶ╱cm)，而其在( 3MV/cm)電場 的漏電流低於(10nA/cm2)。在本研究中，亦探討用鋁電極及不同閘極介電 層對非晶矽薄膜電晶體電性之影響。在本實驗中亦發現，用氧化鋁/氮化 矽雙閘極介電層之非晶矽薄膜電晶體較低的啟動電壓(1.8 6V)，較低的次 臨介變動(1.05V/dec)，較低的關電流(32.4pA)，及較低磁滯寬度(1.32) ，並且退火效應也會增進非晶矽薄膜電晶體支電特性，退火後氧化鋁/氮 化矽雙閘極介電層之非晶矽薄膜電晶體具有最低的啟動電壓(1.76V)，最 低的次臨介變動(1.00V/dec)，最低的關電流(4.52pA)且在經過10000sec 的+20V固定電壓應力，也具有最低啟動電壓偏移(2.9V )，及最低次臨介 變動偏移(1.04V/dec)。 Al2O3/SiNx dielectric film suitable for large size a-Si:H TFT L CD have been prepared by anodization and PECVD. Al2O3 layers we re formed at various pH values and H2O% in the electrolyte, and treated at various temperatures for 30 min in N2 ambient. The o ptimal quality for Al2O3 dielectric film was achieved at pH=6, H2O%=30 in the electrolyte and annealed at 300oC for 30 min. Th is high quality Al2O3 films have denser structure, low etch rat e(90 ＊min) and smooth surface morphology after etching. And th e electrical characteristics of Al2O3 measured from MIM capacit or show a high breakdown field of 7.8 MV/cm and a low leakage c urrent density of 10 nA/cm2 at electrical field of 3MV/cm. Furt hermore, the a-Si:H TFTs with Al gate and with different gate d ielectrics (Al2O3/SiNx and SiNx) were also fabricated and compa red. The a-Si:H TFT with Al2O3/SiNx gate dielectric had lower t hreshold voltage (1.86 V), lower subthreshold swing (1.05 V/dec ), lower off current (32.4 PA), and lower the width of hysteres is (less than 1.32V) than that with SiNx gate dielectric for ch annel width 40mm and channel length 50mm. And the annealing of Al2O3 film also improved the electrical characteristics of the a-Si:H TFT for threshold voltage (1.76V), subthreshold swing (1 .00V/dec) and off current (4.52pA). Furthermore, the threshold voltage shift (2.9V) and subthreshold swing shift (1.04V/dec) of a-Si:H TFT with Al2O3(annealed)/SiNx double-layered gate die lectric were better than those with Al2O3/SiNx and SiNx gate di electric under +20V stress for 10000sec.