热丝法制备富硅氮化硅薄膜及其结构与性能

发布时间：2018-02-24 02:29

  本文关键词： 热丝化学气相沉积 SiNx H薄膜 光致发光 键合结构　出处：《内蒙古师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：氮化硅薄膜作为一种重要的功能薄膜材料已经成为国内外研究的热点。因其具有良好的绝缘性、致密性、稳定性及抗水汽渗透能力,且能够有效的阻止B、P、Na等杂质的扩散,可作为微电子材料和器件的钝化膜、绝缘层、扩散掩膜。近年来,随着多孔硅在室温下强可见光致发光现象的发现,突破了以往具有间接带隙的体硅不能有效发光的禁区,氮化硅薄膜的又一种应用被人们所认识。目前,已经有大量的研究报道,纳米Si团簇包埋于氧化硅或氮化硅中可以获得稳定而有效的发光。作为包埋母体材料,氧化硅带隙较宽,为9.0eV, 氮化硅的带隙为5.4eV,遂穿势垒较低,更有利于载流子的注入,是纳米硅团簇最为优良的包埋母体材料。当前富硅氮化硅是硅量子点形成的必要条件,而富硅氮化硅薄膜的制备方法有很多,常见的有低压化学气相沉积法(LPCVD)、等离子化学气相沉积法(PECVD)以及磁控溅射法等多种制备手段并加以退火处理。热丝化学气相沉积技术(HWCVD)是一门较新的沉积技术,目前被广泛用于微晶硅与多晶硅薄膜的研究,但却很少见于氮化硅薄膜的制备。热丝化学气相沉积法具有较低的衬底温度,沉积速率高,易于结晶并且对薄膜不具有离子轰击作用等特点,使得该技术硅量子点的制备也存在较大的前景。本文采用热丝气相沉积技术来制备富硅氮化硅薄膜,气源采用N2、SiH4以及N2、SiH4和H2的组合做出了三组实验数据,研究N2流量以及NH3流量、热丝温度对富硅氮化硅的性能的影响。其主要研究结论如下：(1)采用N2和SiH4作为反应气源时,发现N2不易在热丝化学气相反应中分解,制备样品含氮量不高,薄膜主要以非晶硅形式存在,样品容易被氧化,缺陷态多,薄膜质量差。(2)采用NH3、SiH4和H2作为反应气源,调整NH3与SiH4比例观察薄膜的特性的变化。随着气体比例的提高,薄膜带隙也发生缓慢展宽,充分发挥热丝优点,实现薄膜从富硅到富氮的良好控制。同时,随N原子的增多,薄膜有序度不断增大,折射率不断减小且变化明显。红外透射谱显示：Si-N键、N-H键随其流量增大而增大,而Si-H键恰好相反。随N原子的增加缺陷态明显增多。(3)采用NH3、Si H4和H2作为反应气源,发现热丝温度对薄膜内的N、H含量有明显的影响,且非单调性变化,主要归咎于不同气体分解温度。扫描电镜观测发现1500℃时薄膜中出现大小约为1.5um的硅晶粒,分析出氢含量的多少直接影响薄膜结晶效果。
[Abstract]:Silicon nitride thin film, as an important functional thin film material, has become a hot research topic at home and abroad. Because of its good insulation, compactness, stability and water vapor permeability, it can effectively prevent the diffusion of impurities such as BPN, Na and so on. It can be used as passivation film, insulating layer and diffusion mask for microelectronic materials and devices. In recent years, with the discovery of strong visible photoluminescence phenomena in porous silicon at room temperature, it has broken through the forbidden zone where bulk silicon with indirect band gap can not effectively emit light in the past. Another application of silicon nitride thin films has been recognized. At present, there have been a lot of research reports that nanocrystalline Si clusters embedded in silicon oxide or silicon nitride can obtain stable and effective luminescence. The band gap of silicon oxide is 9.0eV, the band gap of silicon nitride is 5.4 EV, and the barrier of penetration is lower, which is more favorable to carrier injection and is the best embedded parent material of silicon nanoclusters. Silicon nitride rich silicon nitride is a necessary condition for the formation of silicon quantum dots. And there are a lot of ways to prepare silicon nitride films, The common methods are low pressure chemical vapor deposition (LPCVD), plasma chemical vapor deposition (PECVD), magnetron sputtering and annealing. Hot filament chemical vapor deposition (HWCVD) is a new deposition technology. At present, it has been widely used in the study of microcrystalline silicon and polycrystalline silicon films, but rarely in the preparation of silicon nitride thin films. The hot filament chemical vapor deposition method has low substrate temperature and high deposition rate. It is easy to crystallize and has no ion bombardment, which makes the preparation of silicon quantum dots have great prospects. In this paper, silicon nitride thin films are prepared by hot filament vapor deposition. Three groups of experimental data were made by using the combination of N2SiH4, N2OSiH4 and H2 to study the effects of flow rate of N2, flow rate of NH3 and temperature of hot filament on the performance of silicon nitride rich silicon nitride. The main conclusions are as follows: 1) when N 2 and SiH4 are used as reaction gas source, It is found that N _ 2 is not easily decomposed in the chemical gas phase reaction of hot filament, the nitrogen content of the prepared sample is not high, the film mainly exists in the form of amorphous silicon, the sample is easy to be oxidized, the film has many defects, and the film mass is poor. (2) NH _ 3O _ 3SiH _ 4 and H _ 2 are used as the reaction gas source. Adjusting the ratio of NH3 to SiH4 to observe the change of the film characteristics. With the increase of the gas ratio, the band gap of the film also develops slowly, giving full play to the advantages of hot filament, and realizing the good control of the film from silicon to nitrogen. At the same time, with the increase of N atoms, The order degree of the film is increasing, the refractive index is decreasing and the change is obvious. The infrared transmission spectrum shows that the N-H bond increases with the increase of the flow rate of the Si-N bond. However, the Si-H bond is opposite. With the increase of N atom, the defect states increase obviously. (3) NH _ 3Si _ 4 and H _ 2 are used as reaction gas sources. It is found that the temperature of hot filament has a significant effect on the content of Na-H in the film, and the change is not monotonic. Scanning electron microscopy (SEM) showed that silicon grains of about 1.5 um were found in the films at 1500 鈩，

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