Microcrystalline Si TFTs with low off-current and high reliability

Microcrystalline Si (μc-Si) TFTs were fabricated using a conventional bottom gate amorphous Si (aSi) process. A unique μc-Si deposition technique and TFT architecture was proposed to enhance the reliability of the TFTs. This three-mask TFT fabrication process is comparable with existing a-Si TFT procesess. In order to suppress nucleation at the bottom interface of Si, before deposition of the μc-Si an N₂ plasma passivation was conducted. A typical transfer characteristic of the TFTs shows a low off-current with a value of less than 1 pA and a sub-threshold slop of 0.7 V/dec. The DC stress was applied to verify the use of μc-Si TFTs for AMOLED displays. After 10,000 s of application of the stress, the off-current was even lowered and sub-threshold slope variation was less than 5%. For AMOLED displays, OLED pixel simulation was performed. A pixel current of 13 μA was achieved with V_data of 10 V. After the simulation, a linear equation for the pixel current was suggested.