富硅—氮化硅薄膜的PECVD制备及其退火处理研究

发布时间：2018-08-27 16:48

【摘要】：纳米材料的量子限制效应已在硅基纳米材料及其发光机制方面深入研究。硅基发光材料中的硅量子点是由于量子限制效应特性,而且量子点发光波长可随量子点尺度变化,在光电子器件中具有非常好的应用前景。将包含硅量子点的硅基材料逐渐引入到太阳能电池中。这样可以使太阳光的有效吸收增强,太阳电池的光电转换效率提高,能成为未来高效的第三代硅量子点太阳能电池最有可能的竞争者。基于这些优点,本论文利用等离子体增强化学气相沉积(PECVD)法制备富硅-氮化硅薄膜材料,研究沉积参数对富硅-氮化硅薄膜结构的影响,以及制备薄膜后再进行退火处理的发光特性质的研究,有益于得出最佳的工艺参数应用于材料的制备中。本文利用射频PECVD法制备富硅SiN_x薄膜材料,此方法具有制备方法简单、制备温度低、沉积速率快、能量损失少,生产效率高等特点。对所沉积的薄膜样品进行X射线衍射、傅里叶变换红外、光致发光、紫外可见光吸收谱等分析,对沉积条件在薄膜微结构、结晶情况、组分含量、发光特性等方面的影响进行研究,制备出氮化硅及富硅氮化硅薄膜,然后对富硅氮化硅薄膜进行后续退火处理。本论文实验研究结果分为如下几个部分:1.反应气源为SiH_4、NH_3、N_2,文章研究N_2流量的改变对制备氮化硅薄膜结构及性质的影响。实验结果分析表明:少量通入氮流量,薄膜Si-N键浓度增强,氮与硅含量比值增大;继续增加氮流量,薄膜逐渐呈富氮态,伴随缺陷态增多,辐射增强,光学带隙迅速展宽,带尾态能量逐渐减小;氮含量较高时,形成了包埋在非晶SiN_x母质中的Si3N4晶粒,且晶粒逐渐增加,实现了从非晶SiN_x到包含Si3N4小晶粒的薄膜材料的演变过程。2.反应气源为SiH_4、NH_3和H_2,文章研究NH_3流量的改变对制备富硅-氮化硅薄膜材料的影响。实验结果分析表明:氨气流量增加,N原子和H原子数量增多,Si-H键和Si-N振动强度逐渐增强。当氮原子含量较高时,容易形成N的悬挂键,而高电负性的N影响Si-H键电子云的分布且向高波数方向发生一定的蓝移,同时薄膜样品本身存有大量的结构缺陷。而光学带隙关联于薄膜中的缺陷态密度,缺陷越多,光学带隙越宽。随着氨气流量不断的增加,氢原子饱和多余的悬挂键,有益于硅氮键、硅氢键的形成,薄膜内各化学键密度和各原子密度均有单调递增的现象,Si/N原子比在0.903与0.994之间变化,薄膜逐渐成富硅-氮化硅材料。3.反应气源为SiH_4、NH_3、H_2,采用等离子体化学气相沉积技术低温沉积富硅-氮化硅薄膜,并置于退火炉内对样品热退火处理,退火温度为500℃、700℃和950℃,退火时间为90分钟。实验结果表明,700℃高温退火后,薄膜中Si-H键和N-H键完全断裂,H溢出薄膜。Si-H键的断裂产生大量的硅悬挂键,N-H键的断裂与周围硅原子结合成Si-N键,使薄膜内Si-N键增多,同时该峰亦逐渐向高波数方向移动,通过RBM模型分析表明硅原子键合氮原子数目增多,而薄膜的硅氮比值固定,导致薄膜有更多硅析出。在510-550nm处出现由硅量子点的限制效应引起的发光带,而薄膜内的缺陷态复合引起了P1,P2,P3,P5四个发光峰的出现。分析了硅量子点随退火温度的生长导致P4发光峰红移与蓝移。随着热退火温度增加,硅量子点的Raman峰逐渐向500cm-1靠近并计算出700℃和950℃温度退火下样品中硅量子点尺寸分别为3.01nm、3.05nm。
[Abstract]:Quantum confinement effect of nanomaterials has been studied in detail in silicon-based nanomaterials and their luminescent mechanism.Silicon quantum dots in silicon-based luminescent materials are due to their quantum confinement effect characteristics and the luminescent wavelength of quantum dots can vary with the size of quantum dots.Silicon containing silicon quantum dots has a very good application prospect in optoelectronic devices. Based on these advantages, plasma enhanced chemical vapor deposition (PECVD) is used to fabricate solar cells in this paper. Silicon-rich silicon nitride thin films were prepared, and the effects of deposition parameters on the structure of silicon-rich silicon nitride thin films were studied. The luminescent properties of silicon-rich silicon nitride thin films prepared by annealing were also studied. The optimum process parameters were obtained for the preparation of silicon-rich silicon nitride thin films. The preparation method is simple, the preparation temperature is low, the deposition rate is fast, the energy loss is small, and the production efficiency is high. Silicon nitride and silicon-rich silicon nitride thin films were prepared, and then silicon-rich silicon nitride thin films were annealed. The experimental results were divided into the following parts: 1. The reaction gas source was SiH_4, NH_3, N_2. The effect of N_2 flow rate on the structure and properties of silicon nitride thin films was studied. With the increase of nitrogen flow rate, the Si-N bond concentration and the ratio of nitrogen to silicon content of the films increase; with the increase of nitrogen flow rate, the films become nitrogen-rich gradually, and with the increase of defect state, the radiation increases, the optical band gap widens rapidly, and the band tail energy decreases gradually; when the nitrogen content is high, the Si_3N_4 grains embedded in the amorphous SiN_x parent material are formed, and the grains increase gradually. In addition, the evolution process from amorphous SiN x to thin film materials containing small Si3N4 grains is realized. 2. The reaction gas sources are SiH_4, NH_3 and H_2. The influence of NH_3 flow rate on the preparation of Si-rich silicon nitride thin film materials is studied. The experimental results show that the number of N atoms and H atoms increases with the increase of ammonia flow rate, and the vibration intensity of Si-H bonds and Si-N gradually increases. When the content of nitrogen atom is high, the suspended bond of N is easily formed, and the high electronegativity of N affects the distribution of electron cloud of Si-H bond and blue shift to high wavenumber. At the same time, there are a lot of structural defects in the film itself. The optical band gap is related to the density of defect states in the film, the more defects, the wider the optical band gap. With the increase of gas flow rate, hydrogen atom saturates the superfluous hanging bond, which is beneficial to the formation of silicon-nitrogen bond and silicon-hydrogen bond. The density of each chemical bond and each atom in the film increases monotonously. The Si/N atom ratio varies between 0.903 and 0.994, and the film gradually becomes silicon-rich silicon-nitride material. 3. Reaction gas source is SiH_4, NH_3, H_2, using plasma. Silicon-rich silicon nitride thin films were deposited by bulk chemical vapor deposition at low temperatures and annealed in an annealing furnace. The annealing temperatures were 500, 700 and 950, and the annealing time was 90 minutes. The breakage of N-H bond and Si-N bond make Si-N bond increase in the film, and the peak shifts to higher wave number. The RBM model analysis shows that the number of nitrogen atoms bonded by Si atoms increases, while the Si-N ratio of the film is fixed, resulting in more silicon precipitation in the film. Silicon quantum dots appear at 510-550 nm. Four luminescent peaks, P1, P2, P3 and P5, were induced by the recombination of defect states in the films. The red shift and blue shift of P4 luminescent peaks were analyzed with the growth of Si quantum dots at annealing temperature. The size of silicon quantum dots in the samples is 3.01nm, 3.05nm.
【学位授予单位】：内蒙古师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O484

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