Characteristics of ITO-resistive touch film deposited on a PET substrate by in-line DC magnetron sputtering

High-quality tin-doped indium oxide with moderate resistivity (1.7-2.0 × 10−3 Ω cm) for use on a resistive-type touch screen was deposited at room temperature on a polyethylene terephthalate substrate via in-line moveable magnetron sputtering. In order to examine its feasibility for use as an upper electrode screen of a touch panel, electrical and optical properties were investigated by measuring resistivity, transmission, Hall mobility and carrier density, etc. Working pressure and oxygen flow ratio to argon gas were varied under a moving speed of 120 cm/min for obtaining optimum film quality. Increasing the working pressure from 0.53 Pa to 1.06 Pa, resistivity decreases and mobility increases. Increasing the oxygen ratio from 1.6% to 3.4%, resistivity is minimized and mobility attains a peak value at 3.0% oxygen concentration. For application to an analog resistive-type touch screen, an operable touch panel with a 3.5-inch diagonal viewing area was fabricated and characterized.