Deveiopment of Room Temperature Deposition Process of Silicon Nitride Film by Low Frequency Plasma CVD.

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Silicon nitride films are being used extensively in the semiconductor technology for interlayer insulation and device surface passivation. Stoichiome-tric silicon nitrode Si_3n_4 can be deposited by thermal deposition at about 900 ゜C, and nearly stoichimetric silicon nitride films have been deposited by the high frequency plasma CVD method at low substrate temperature (200-300゜c). The purpose of the present study is to deposite of silicon nitride films at room temperature using low frequency(50Hz) plasma CVD with silane and nitrogen mixtures. The results obtained may be summarized as below.1) Silicon nitride films have been deposited by low frequency(50Hz) plasma CVD using a nitsogen and silane mixture at room temperature. To deposit high quality silicon nitride, the silane fraction in the nitrogen and silane mixture has to be less than 5%.2) The refractive index, breakdown field strenght and resistivity of the obtained silicon nitride film were 2.0, 1.2 x 1 0^1 V/cm and 6 x 1 0^<15> cm, respectively.3) The distribution of film thickness on 5 inches Si wafer was 1000 <plus-minus> 30 <Ang>. 4) Fixed charge density and surface state density of Al/SiNx/SiO_2 /Si(MNOS) were about 1.5 x 1 0^<11> cm^<-2> and 8 x 10^<10> cm^<-2> ev^<-1> , respectively. substrate temperature dependence of the film properties were observed, and as high the temperature(<200゜c) is, the films become Si tich. However electrical properties were not changed.5) The emission.intensity from silicon and nitrogen neutral and ionized molecule in nitrogen and silane mixture plasma with low frequency(50Hz) is large compared with that from RF(13.56MHz) plasma.6) Since low frequency plasma can generate high electron energy plasma, which is required for good silicon nitride formation, high quality silicon nitride films can be grown without any assistance from heating of the substrate.