A Study on Hydrogenated Amorphous Silicon Thin-Film Transistor

• Main Authors: Lin, Chiung-Wei, 林烱暐
• Other Authors: Chang, Chun-Yen
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/67354200432431969748

碩士 === 國立交通大學 === 電子研究所 === 81 === 　　Thin film transistors with high performce at low deposition temperature in the range of 250℃∼350℃ were successfully fabricated. Our silicon nitride film was deposited by decomposing silane and ammonia mixture. Due to the introduction of hydrogen gas, the silicon nitride is of high film quality with dielectric constant 4.6∼5.09, refractive index 1.73∼1.88. The thickness of a-Si: H(4500 A) is thick enough to avoid the external damage, thus our devices are free from making passivation layer to simplify the fabrication process. Annealing the devices in different temperatures will show different results. Accoding to our investigation, 180℃ is the optimal annealing temperature to enhance the performance of pesent devices. During the annealing process, we used 10% H2 in 90% N2 as the forming gas was used. It introduces H atoms to the a-Si :H/SiNX interface and reduce the density of fast states. Indeed, we observed that after PMA, the threshold voltage shifts to a smaller value, thus is can be sure that the instability mechanism of presnet devices is dominated by the fast state creation. Finally, good performance of inverted staggered a-Si:H TFT''s was obtained, they have threshold voltages of 2.73∼4.68 volt, ON/OFF current ratio is nearly to seven orders, filed effect mobility of 0.644∼1.27cm2/v.s, subthreshold swing about 0.481∼0.836V/decade, and IoN/W ratio of 5.7×10-2A/m which are suitable for the application in active matrix liquid crystal displays (LCD).