非晶硅薄膜热光特性理论与工艺研究
发布时间：2018-08-24 09:35
【摘要】：非晶硅由于热光系数高,成本低廉、易于集成等特点,被广泛应用于光学系统中。近年来,设计基于非晶硅薄膜热光效应的低损耗、高性能的光学器件成为半导体光学领域的研究重点,如热光可调谐薄膜滤波器、热光开关、红外探测器等。在基于非晶硅热光效应设计的器件中,要求薄膜具有较高的热光系数来实现器件设计功能。然而在其他情况下,非晶硅折射率随温度的变化可能会引起系统工作不稳定及器件性能下降,因而要求其具有相对较小的热光系数来避免这种热诱导效应。非晶硅材料具有连续不规则网格结构,这使得它的性质在不同的工艺条件下具有很高的灵活性,因此研究薄膜热光特性的工艺相关性具有相当的实用价值。首先,通过理论分析得出极化率为影响热光系数的主导因素并对其进行仿真。建立基于非晶硅内部组分的氢团簇模型,通过改变晶胞内不同硅氢基团的数量,研究了非晶硅带边770 nm及通信波段1330 nm和1550 nm处的极化率。结果表明,非晶硅热光特性对H含量十分敏感。增加H含量,即提升SiH2和SiH3基团比例,能够增强薄膜热光效应,其中Si H3基团效果更优,而过量的H会降低对薄膜热光系数的增幅,甚至会造成薄膜热光系数下降。其次,为研究薄膜热光特性工艺相关性,先重点解决非晶硅薄膜均匀制备工艺以及非晶硅薄膜热光系数精确测量两个亟需解决的关键性技术问题。本文从改善气流场、温度场、电磁场均匀性三个角度出发优化反应腔体设计,台阶仪测试结果显示薄膜均匀性得到明显改观。总结了国内外热光系数测量方法,结合热光系数测量要求,设计出了基于FILMeasure-20的薄膜热光系数测量平台。最后,使用搭建的热光系数精确测量平台研究了不同工艺条件:射频功率、沉积压强、退火温度处对薄膜性能及在1330 nm处热光特性的影响。测试结果与现有理论值接近,证明了测试平台的可靠性,并得出以下结论:(1)沉积时使用相对较高的射频功率、适中的沉积压强、对薄膜进行500℃短时间退火都是提高薄膜热光系数的有效手段,其中500℃短时间退火可使热光系数提升63.5%;(2)使用较低射频功率、较高的沉积压强、800℃以上高温退火都是降低薄膜热光系数的有效手段,其中900℃以上退火使薄膜热光系数降低到10-5 K-1量级。在应用中,可结合实际需要选择合适的薄膜沉积参数。
[Abstract]:Amorphous silicon is widely used in optical systems because of its high thermo-optical coefficient, low cost and easy integration. In recent years, the design of low loss and high performance optical devices based on the thermo-optical effect of amorphous silicon thin films has become the focus of semiconductor optics, such as thermo-optical tunable thin film filters, thermo-optical switches, infrared detectors and so on. In the device based on the thermo-optical effect of amorphous silicon, the thin film is required to have a high thermo-optical coefficient to achieve the device design function. However, in other cases, the variation of the refractive index of amorphous silicon with temperature may lead to the instability of the system and the degradation of the device performance. Therefore, it is required that the amorphous silicon has a relatively small thermo-optical coefficient to avoid this thermal induction effect. The amorphous silicon material has a continuous irregular mesh structure, which makes its properties have high flexibility under different technological conditions, so it is of great practical value to study the process correlation of thermo-optical properties of thin films. Firstly, the polarizability is the main factor affecting the thermo-optical coefficient, and the simulation is carried out. The hydrogen cluster model based on the internal components of amorphous silicon is established. The polarizability of amorphous silicon band edge at 770 nm and communication band of 1330 nm and 1550 nm is studied by changing the number of different hydrosilyl groups in the crystal cell. The results show that the thermo-optical properties of amorphous silicon are sensitive to H content. Increasing H content, that is, increasing the ratio of SiH2 and SiH3 groups, can enhance the thermo-optical effect of the film, and the effect of Si H _ 3 group is better, while excessive H can decrease the increase of the thermo-optical coefficient and even cause the decrease of the thermo-optical coefficient of the film. Secondly, in order to study the correlation of thermo-optical properties of amorphous silicon thin films, two key technical problems which need to be solved urgently are the uniform preparation process of amorphous silicon films and the accurate measurement of thermo-optical coefficients of amorphous silicon films. In this paper, the design of the reaction cavity is optimized from three aspects of improving the airflow field, temperature field and electromagnetic field uniformity. The results of the step meter test show that the film uniformity has been improved obviously. The measurement methods of thermo-optical coefficient at home and abroad are summarized. According to the requirement of thermo-optical coefficient measurement, a measurement platform of film thermo-optical coefficient based on FILMeasure-20 is designed. Finally, the effects of different technological conditions, such as RF power, deposition pressure, annealing temperature on the film properties and thermo-optical properties at 1330 nm, were studied by using an accurate measurement platform for thermo-optical coefficient. The test results are close to the existing theoretical values, which proves the reliability of the test platform. The conclusions are as follows: (1) the relatively high RF power and moderate deposition pressure are used in deposition. Annealing at 500 鈩，
本文编号：2200411
[Abstract]:Amorphous silicon is widely used in optical systems because of its high thermo-optical coefficient, low cost and easy integration. In recent years, the design of low loss and high performance optical devices based on the thermo-optical effect of amorphous silicon thin films has become the focus of semiconductor optics, such as thermo-optical tunable thin film filters, thermo-optical switches, infrared detectors and so on. In the device based on the thermo-optical effect of amorphous silicon, the thin film is required to have a high thermo-optical coefficient to achieve the device design function. However, in other cases, the variation of the refractive index of amorphous silicon with temperature may lead to the instability of the system and the degradation of the device performance. Therefore, it is required that the amorphous silicon has a relatively small thermo-optical coefficient to avoid this thermal induction effect. The amorphous silicon material has a continuous irregular mesh structure, which makes its properties have high flexibility under different technological conditions, so it is of great practical value to study the process correlation of thermo-optical properties of thin films. Firstly, the polarizability is the main factor affecting the thermo-optical coefficient, and the simulation is carried out. The hydrogen cluster model based on the internal components of amorphous silicon is established. The polarizability of amorphous silicon band edge at 770 nm and communication band of 1330 nm and 1550 nm is studied by changing the number of different hydrosilyl groups in the crystal cell. The results show that the thermo-optical properties of amorphous silicon are sensitive to H content. Increasing H content, that is, increasing the ratio of SiH2 and SiH3 groups, can enhance the thermo-optical effect of the film, and the effect of Si H _ 3 group is better, while excessive H can decrease the increase of the thermo-optical coefficient and even cause the decrease of the thermo-optical coefficient of the film. Secondly, in order to study the correlation of thermo-optical properties of amorphous silicon thin films, two key technical problems which need to be solved urgently are the uniform preparation process of amorphous silicon films and the accurate measurement of thermo-optical coefficients of amorphous silicon films. In this paper, the design of the reaction cavity is optimized from three aspects of improving the airflow field, temperature field and electromagnetic field uniformity. The results of the step meter test show that the film uniformity has been improved obviously. The measurement methods of thermo-optical coefficient at home and abroad are summarized. According to the requirement of thermo-optical coefficient measurement, a measurement platform of film thermo-optical coefficient based on FILMeasure-20 is designed. Finally, the effects of different technological conditions, such as RF power, deposition pressure, annealing temperature on the film properties and thermo-optical properties at 1330 nm, were studied by using an accurate measurement platform for thermo-optical coefficient. The test results are close to the existing theoretical values, which proves the reliability of the test platform. The conclusions are as follows: (1) the relatively high RF power and moderate deposition pressure are used in deposition. Annealing at 500 鈩，
本文编号：2200411
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