Takahiro Nakahigashi

Study of Deposition Process in Modulated RF Silane Plasma

The influences of plasma parameters on the deposition of a-Si:H film and particle growth have been studied with silane discharge using amplitude-modulated RF methods. Plasma parameters have been measured with the Langmuir probe system and optical emission spectrometer. Behaviors and generation processes of particles have been observed by the laser scattering method. The deposited thin film has been characterized by various techniques such as Fourier-transform infrared (FT-IR) spectrometry, ESR and the constant photocurrent method (CPM). High deposition rate with low particle density as well as high film quality has been realized for a-Si:H film by amplitude-modulated RF methods.

Properties of a-Si:H Film Deposited by Amplitude-Modulated RF Plasma Chemical Vapour Deposition for Thin Film Transistor.

The method of amplitude-modulated RF plasma enhanced chemical vapour deposition (p-CVD) has been used to deposit the a-Si:H film. Various properties of the deposited a-Si:H film such as uniformity of thickness, stress of film and hydrogen concentration in the film are studied. These film properties are improved in the case of amplitude-modulated RF p-CVD compared with the CW case, particularly at the high deposition rate. Further investigation has been carried out by constructing a bottom gate thin film transistor (TFT) device without an etch stop layer. The measured electron mobility and threshold voltage, are also improved up to the deposition rate of 32 nm/min by the method of amplitude modulated RF p-CVD at the modulation frequency of 68 kHz.