Development of Low Temperature Deposition Process of Silicon Oxide Film by Low Frequency Plasma CVD (TEOS+O_2)

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Silicon oxide films have been used in the fabrication of integrated circuits as the insulation layr of metal-oxide-semiconductor structures or as a passivation layr. In the beginning, silicon oxide films used in integrated circuits were prepared by thermal oxidation of silicon substrates or thermal chemical vapor deposition (CVD). Recently, many kinds of methods to prepare the films, such as low pressure CVD, plasma oxidation, sputtering, and plasma CVD have been developed. Among these methods, plasma CVD can deposit high quality silicon oxide films at comparatively low substrate temperatures. Moreover, silicon oxide films with good step coverage are deposited by plasma CVD using TEOS (Tetraethoxysilane). In this work, the silicon oxide films was deposited using TEOS as a silicon source by using a low frequency (50Hz) plasma CVD.It is found in the present work that the substrate heating at deposition is required to obtain acceptable electrical properties when silicon oxide films are deposited from a TEOS and oxygen mixture, even by low frequency (50Hz) plasma CVD.The films deposited at 200。C from the plasma of a 3% TEOS mixture were found to be high quality insulating films ; the resistivity was 10^<16>OMEGA cm and the breakdown strength 7X10^6 V/cm. Moreover, Auger electron spectrum analysis revealed that carbon atoms were not detected from the films in spite of the presence of carbon atoms in the TEOS molecule. With optical emission spectrum analysis of the TEOS and oxygen mixture plasma, strong emissions from the CO and CO_2 molecules were observed.