Low Thermal Budget Amorphous Silicon for Fabrication of Photovoltaic and Non-volatile Memory Devices

• Main Authors: Huang, Wen-Hsien, 黃文賢
• Other Authors: Pan, Fu-Ming
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/61524689266630700346

博士 === 國立交通大學 === 材料科學與工程學系所 === 104 === The demand for system on panel (SoP) and monolithic 3D integration is increasing for realizing devices with high density and operation speed and low power consumption to fabricate future chip integration. However, the conventional high thermal processes constrain this realization; thus developing low thermal budget processes is essential. In this thesis, we investigated the material characteristics of low thermal budget amorphous Si (a-Si) thin-film for fabrication of low thermal budget photovoltaics and field effect transistors. Furthermore, we developed and integrated low thermal budget processes, such as light-trapping structures, plasma-deposited thin film, laser crystallization, and laser activation, to fabricate hydrogenated a-Si (a-Si:H) thin-film solar cells, poly-Si field-effect transistors (FETs), and charge-trap non-volatile memories (CTNVMs). For low thermal budget thin-film solar cells, highly efficient n-i-p and p-i-n a-Si:H thin-film solar cells were fabricated through inductively coupled plasma chemical vapor deposition at 140-200oC. The light-trapping capability of the n-i-p solar cells increased in the ultraviolet (UV)-visible region and a conversion efficiency of 8.5% was achieved, when the cells were incorporated with sub-micron (0.4 μm in diameter) self-assembly loosely-packed silica spheres (LPSS) monolayers (65% fill density). The LPSS monolayer behaves like a nearly omnidirectional antireflector and increases the solar efficiency at high incident angle of illumination. Incorporating the FTO/Au-NPs/AZO electrode in p-i-n thin-film solar cells imparted the light-trapping capability in the green-red band because of the plasmonic effect and resistance to photodegradation in the UV-blue band, which was due to the low defect of the p-/i-layer interface and intrinsic layer. This phenomenon substantially increased the conversion efficiency to 10.1% and reduced the photodegradation to 7%. For low thermal budget field effect transistor and non-volatile memories, green nanosecond laser spike annealing was used to transform a-Si to poly-Si, the thickness of which was reduced to 14 nm. Low temperature n- and p-FETs were fabricated by integrating a thin poly-Si channel, high-κ/metal gate (Al2O3/TiN) and far-infrared laser activation to obtain a high on-current (121 and 62 A/m, respectively), low subthreshold swing (88 and 121 mV/dec., respectively), and low threshold voltage (0.7 and 0.3 V, respectively). In addition, a metal/SiO2/Si-rich SiNx/AlOxNy/SiO2/Si CTNVM with a low thermal budget was implemented by combining low thermal budget field effect transistor with nano-scale to obtain a low operation voltage, low charge loss, and reliable endurance. These low thermal budget materials, processes and devices can be widely used in SoP, 3D integration, and Internet of Things.