Microcrystalline silicon growth using a inductive coupled plasma CVD on plastic substrate

Abstract

Summary form only given. Recently, the plastic materials are very useful as the substrate of the flexible, light and portable electronics. Although the plastic substrates have many advantages such as thin film solar cell, thin film transistor and thin film sensors, its application has a difficulty of the limitation of temperature, surface hardness, and corrosion resistance on the acid or alkali. In general, hydrogenated amorphous silicon (a-Si:H) films are found in a broad range of electronic devices such as radiation detectors, photovoltaic (PV) devices, thin film transistors (TFTs), display devices, and memory device applications. However, a-Si:H detectors and TFTs show some limitations because of their low carrier mobility. a-Si:H solar cells have exhibited problems on stability of conversion efficiency. These problems regarding a-Si:H films can be solved by replacing a-Si:H with microcrystalline silicon (/spl mu/c-Si) film. The goal of our research is to determine the best process conditions for the growth of /spl mu/c-Si on a plastic substrate. The films of /spl mu/c-Si with thickness in the range 20-120 nm were deposited in inductive coupled plasma chemical vapor deposition (ICP-CVD) system from mixture of diluted silane (SiH/sub 4/ 20% in He) and H/sub 2/ at low temperature of 100/spl deg/ Polycarbonate (PC) substrate (1mm thickness) 50/spl times/ 50 mm/sup 2/ was used as substrate. PC substrate has a higher heat resist of 130/spl deg/ than other plastic substrate and no problem to the alkali liquid. To verify the growth of /spl mu/c-Si film using an ICP-CVD, we investigated crystalline seeding layer on the plastic substrate and the optimized growth parameters of ICP. They were ultrasonically cleaned in methanol, D I water rinsed, and nitrogen-gas blown dry. The investigated process parameters for the Si film growth include plasma ignition conditions, rf power, input gas ratio, process pressure, with or without carrier gas An atomic force microscope (AFM) was employed for the surface morphology study and growth mechanism. An argon laser drive-Raman spectroscopy (Jobin Yvon /T64000, power=400 mW) was employed to determine the degree of crystallization and crystallized volume fraction of the /spl mu/c-Si film.