AVS 45th International Symposium
    Thin Films Division Friday Sessions
       Session TF-FrM

Paper TF-FrM5
Effects of Temperature (350 - 25°C) on OH Incorporation and Electrical Performance of Plasma Deposited Silicon Dioxide Thin Films for Applications on Plastic Substrates

Friday, November 6, 1998, 9:40 am, Room 310

Session: Thin Film Deposition from Chemical Precursors
Presenter: A. Gupta, North Carolina State University
Authors: A. Gupta, North Carolina State University
C.G. Makosiej, North Carolina State University
G.N. Parsons, North Carolina State University
Correspondent: Click to Email
Very low temperature PECVD SiO@sub 2@ may be useful on plastic substrates for gate dielectrics for polysilicon thin film transisitors, or for barrier or insulating layers in organic LED displays. We have used SiH@sub 4@/N@sub 2@O/He/H@sub 2@ mixtures in a parallel plate rf plasma CVD reactor to form SiO@sub 2@ on silicon, and examined the effect of substrate temperature between 350°C and 25°C, rf power, and gas ratios on the chemical composition, refractive index, etch rate, chemical stability, deposition rate, and I-V and C-V characteristics. Low temperature films have also been deposited on PET and polycarbonate substrates to examine adhesion and stress. Films deposited at 350°C show good insulating properties with breakdown fields >8 MV/cm. As temperature is decreased to 100°C, an increase in charge trapping is observed. The decrease in temperature also results in an increase in deposition rate from 65 to 100 Å/min, and a decrease in refractive index from 1.47 to 1.43, indicating a less dense structure. Infrared spectroscopy shows a correlation between OH concentration and the Si-O stretch peak position. At 90W, as the temperature decreases from 350 to 250°C, the Si-O stretch mode position decreases from 1063 to 1056 cm@super -1@, indicating an increase in bond strain. As temperature is decreased from 250 to 25°C, the Si-O peak increases from 1056 to 1065 cm@super -1@, due to an increase in OH incorporation during deposition. After deposition, the OH concentration increases with ambient exposure, and decreases slightly during annealing at 300°C. Process variations, including H@sub 2@ and He dilution, and time modulated deposition and H@sub 2@ exposure cycles to decrease OH incorporation have been tested. Films with less OH in the as deposited condition show a greater resistance to post-deposition oxidation, and show improved electrical properties. Films with good leakage characteristics (<10@super -7@ A/cm@super 2@ at 2 MV/cm) have been obtained at 100°C. We will show mass spectroscopy results of the effect of gas phase composition on water production and OH incorporation in silicon dioxide films formed at very low temperature.