Amorphous and microcrystalline silicon deposited by hot-wire chemical vapor deposition at low substrate temperatures: application to devices and thin-film microelectromechanical systems

Amorphous silicon and microcrystalline silicon have been deposited on glass and plastic (PET) substrates using hot-wire chemical vapor deposition (HW) at substrate temperatures (T-sub) of 100 degreesC and 25 degreesC. The opt oelectronic and structural properties of intrinsic and doped films are revi ewed. Intrinsic H-W a-SM is incorporated into a p-i-n diode processed at a maximum temperature of 100 degreesC, achieving a rectification ratio of 10( 6). The mechanical (residual stress) properties of low-T-sub HW layers are compared to those Of low-T-sub radio-frequency-deposited layers. Doped-micr ocrystalline films of low-T-sub HW layers deposited on plastic substrates s how piezoresistive behavior. The resistance of n-type films decreases with applied tensile stress and increases with applied compressive stress, while p-type films show the opposite behavior. The mechanical properties of low- T-sub HW layers are adequate for their use as structural layers in thin-fil m microelectromechanical systems (MEMS). The electrical actuation of surfac e micromachined bridge structures and the mechanical actuation of thin-film microresonators on large area substrates are demonstrated. (C) 2001 Elsevi er Science B.V. All rights reserved.