Low Temperature High Quality Growth of Silicon-Dioxide Using Oxygenation of Hydrogenation-Assisted Nano-Structured Silic
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0989-A05-08
Low Temperature High Quality Growth of Silicon-Dioxide Using Oxygenation of Hydrogenation-Assisted Nano-Structured Silicon Thin Films Nima Rouhi1, Behzad Esfandyarpour1, Shams Mohajerzadeh1, Pouya Hashemi1, Bahman Hekmat-Shoar1, and Michael D Robertson2 1 University of Tehran, Tehran, 14395, Iran 2 Acadia University, Wolfville, 14395, Canada
ABSTRACT We report a low temperature high quality oxide growth of nano-structured silicon thin films on silicon substrates obtained through a hydrogenation-assisted PECVD technique followed by a plasma enhanced oxidation process. A 100nm-thick electron-beam evaporated a-Si layer was hydrogenated at a plasma power of 2W/cm2 and a temperature of 250°C, followed by a post treatment at a temperature of 300°C for 30 min. with the plasma “off”. Nano-crystalline silicon layers were obtained through this process with an average grain size of less than 5nm, which their grain size and porosity could be well controlled by process conditions. After the hydrogenation process, a plasma oxidation step was performed in an RF-PECVD for an extended period of two hours. The treated layers were investigated and compared with respect to their electrical, optical and stoichiometrical properties by means of Ellipsometry, transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and by current voltage and capacitance voltage measurements on metal-oxidesemiconductor (MOS) structures. INTRODUCTION There have been many attempts to develop a high quality low temperature oxidation process required for inter-level dielectrics, gate dielectrics in MOSFETs and thin film transistors. Low temperature oxides or LTO for short are usually realized using a LPCVD method which requires temperatures as high as 410oC. Also the deposition of silicon-oxide and silicon-nitride layers by means of plasma enhanced CVD is regularly used. On the other hand the formation of silicon oxide films by means of a growth approach requires temperatures above 850oC which is not suitable for many substrates such as glass and plastic bases that must be processed at low temperatures. The oxidation technique reported in this paper is based on low temperature plasma assisted oxygen incorporation into high porosity nano-crystalline silicon thin films with an average grain size of less than 3nm. Micro-crystalline and nano-crystalline silicon films fabricated at low temperatures are promising materials in the areas of flexible electronics, optoelectronics, single-electron tunneling devices, solar cells and imaging sensors [1]. Several conventional approaches have been proposed for lowering the crystallization temperature of silicon, including metal-induced crystallization (MIC) [2], metal-induced lateral crystallization (MILC) [3] and excimer laser annealing (ELA) [4]. In these works, Pt and Ni-induced crystallization of amorphous silicon (a-Si) have been studied [5,6]. Recently, it is shown that RF plasma hydrogenation of evaporated amorphous Si films can lead to the formation of n
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