Manufacturing of TFTs with High Deposition Rated Microcrystalline Silicon using Plasma Enhanced Chemical Vapor Depositio
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0989-A17-02
Manufacturing of TFTs with High Deposition Rated Microcrystalline Silicon using Plasma Enhanced Chemical Vapor Deposition Kyung-Bae Park, Ji-Sim Jung, Jong-Man Kim, Myung-kwan Ryu, Sang-Yoon Lee, and JangYeon Kwon Display Lab, Samsung Advanced Institute of Technology, Mt14-1, Nongseo-dong, Giheung-Gu, Gyeonggi-Do, Yongin-Si, 446-712, Korea, Republic of ABSTRACT Microcrystalline silicon was deposited on glass by standard plasma enhanced chemical vapor deposition using H2 diluted SiH4. Raman spectroscopy indicated a crystalline volume fraction of as high as 40% in films deposited at a substrate temperature 350oC. The deposition rate in films was as high as 10Å/sec. This process produced µc-Si TFTs with both an electron mobility of 10.9cm2/Vs, a threshold voltage of 1.2V, a subthreshold slop of 0.5V/dec at nchannel TFTs and a hole mobility of 3.2cm2/Vs, a threshold voltage of -5V, a subthreshold slop of 0.42V/dec at p-channel TFTs without post-fabrication annealing. INTRODUCTION Recently, directly-deposited microcrystalline silicon(µc-Si) has been intensively introduced as attractive material for the TFT active layer [1][2]. Compared to a-Si TFTs, µc-Si TFTs have demonstrated higher electron mobility and Active Matrix display for driving devices. However disadvantages of µc-Si are inhomogeneity due to a complex crystalline structure composed of grains, amorphous silicon layer and grain boundaries, which limit the transport properties and the TFT sizes [3]. It is important to obtain higher crystalline Si layers on large size panel with high deposition rates for reducing the production costs of device. In addition, because of the large and well-established manufacturing base for a-Si TFTs, there is an overwhelming need for µc-Si TFTs fabricated using the conventional 13.56 MHz PE-CVD technique [4].Presently a deposition rate of a-Si for fabrication of TFT-LCD is as high as 15Å/sec. but a deposition rate of µc-Si is lower than deposition rate of a-Si. In an effort to develop a high throughout process to fabricate a higher crystalline si using conventional PE-CVD with highly H2 diluted SiH4 plasma at 350oC. The µc-Si films were characterized using Raman scattering, UV reflectance, Scanning Electron Microscopy(SEM) and Transmission Electron Microscope(TEM). EXPERIMENT Microcrystalline Si films were deposited on Corning 1737 substrates at a substrate temperature 350oC in a RF Plasma Enhanced Chemical Vapor Deposition (PE-CVD) system with conventional discharge frequency 13.56MHz using the high purity SiH4, H2 as feed gas. In Raman scattering, SEM and TEM were used to determine the structure of the films. Both nchannel and p-channel thin film transistors are fabricated in a top-gated structure. All process temperature was done below 200oC except µc-Si deposition at 350oC. The buffer layer was silicon nitride deposited on Corning glass. Microcrystalline silicon was deposited from suitable
process condition from mixture of SiH4 and H2 in PE-CVD reactor. The microcrystalline Si film was patterned into the island s
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