氨气预氮化制备超薄氮化硅薄膜及电学性能

Electronic Properties of the Ultrathin Silicon Nitride Films Fabricated with Ammonia Plasma Prenitridation

为寻求制备性能良好的纳米厚度氮化硅(SiN_x)薄膜的方法,采用NH_3等离子体氮化、SiH_4/NH_3等离子增强化学淀积法及先氮化后淀积的方法制备了三种SiN_x薄膜,研究比较了三种薄膜的性质。用X射线光电子谱检测了NH_3等离子体氮化Si片得到的SiN_x薄膜的组分,利用椭圆偏振光谱仪测量薄膜厚度,估算了氮化速率。用NH_3和SiH_4作为反应气,分别在原始硅片和经过NH_3预氮化后的硅片上淀积厚度为5 nm、10 nm和50 nm的SiN_x薄膜。用电容-电压法研究了薄膜样品的电学性质,发现单纯用NH_3等离子体氮化的薄膜不适合做介质膜,而先用NH_3氮化再淀积SiN_x的样品比直接淀积SiN_x的样品界面性能明显改善,界面态密度降低到1～2×10^(11)eV^(-1) cm^(-2)。

In this paper, we investigate and compare the interface state densities and electronic reliabilities of three kinds of uhrathin silicon nitride （SiNx） film, fabricated in a plasma-enhanced chemical vapor deposition （PECVD） system by using 1） direct nitridation of single-crystal silicon by ammonia （NH3） plasma; 2） deposition of SiNx from Sill4 and NHa plasma and 3） method combined of direct nitridation with deposition. The composition and thickness of the films are investigated using XPS （X-ray photoelectron spectroscopy）, and spectroscopic ellipsometry （SE）, respectively. The interface state density is determined by C-V characteristic measurements. We found that the SiNx film prepared by combined method has the lowest interface state density as 1～2×10^11eV^-1cm^-2 and has much more reliable electronic insulating properties, compared with the film obtained from direct nitridation and deposition only. Our results will be helpful for the design and fabrication of electronic devices with lower interface state density and improved reliability.