【作者】 刘伟；

【导师】 陆健； 张宏超；

【作者基本信息】 南京理工大学 ， 电子信息， 2024， 硕士

【摘要】 单晶硅是我国集成电路、光伏等重要产业中的核心材料之一,激光加工单晶硅具有广阔的应用前景。但激光加工会产生应力损伤影响性能,因此检测单晶硅激光加工应力损伤就显得格外重要。基于激光超声的空间分辨声光谱法(SARS)是一种具有无损、非接触、空间分辨率较高、成本较低等优势的应力损伤检测方法。本文对激光超声在单晶硅激光加工中的应力损伤检测机理展开了研究。通过建立仿真模型对点源、单线源、线阵激光激发的表面波进行了时频域分析,结果表明线阵激光激发的表面波振幅更强、振幅在传播方向上衰减更慢。随着线阵数量的增加,表面波中心频率半高宽减小、频域精度和信噪比增大。建立了单晶硅任意晶向弹性矩阵的仿真模型,结果表明单晶硅表面波速度按照[111]、[100]、[110]的方向递增,最大速度差约400 m/s,速度变化幅度约10%。对单晶硅(100)晶面上的表面波在10 GPa单轴应力作用下的速度变化进行仿真研究,结果表明表面波速度下降2%左右,从[100]晶向到[110]晶向速度下降幅度逐渐增加。建立了基于光偏转法测量SARS窄带表面波的实验系统,测量了无损伤单晶硅(100)晶面上的窄带表面波速度并绘制了速度方向图,结果表明表面波速度从[100]晶向到[110]晶向呈递增趋势,速度变化幅度约8%。研究了连续激光加工单晶硅的损伤过程,较低功率时将出现融坑和从融坑延伸出来的裂纹,当激光功率2700 W时单晶硅表面将不会出现融坑,而是单纯的应力损伤。测量了单晶硅(100)晶面应力损伤区域的窄带表面波速度并绘制了速度方向图,测量结果显示速度无明显的方向性,这意味着应力损伤使损伤区域的晶向混乱、整体变得均匀。本文的工作可以为后续的激光超声检测单晶硅应力损伤、单晶硅超声表面波各向异性等研究提供参考。更多还原

【Abstract】 Monocrythic silicon is one of the core materials in many important industries such as integrated circuit and photovoltaic in our country.Laser processing monocrythic silicon has a broad application prospect.However,the stress damage caused by laser processing will affect the performance,so it is particularly important to detect the stress damage of single crystal silicon laser processing.Spatially resolved acoustic spectroscopy(SARS)based on laser ultrasound is a stress damage detection method with the advantages of non-destructive,non-contact,high spatial resolution and low cost.In this paper,the stress damage detection mechanism of laser ultrasound in single crystal silicon laser processing is studied.The time-frequency domain analysis of surface waves excited by point source,single line source and line array laser is carried out by building simulation models.The results show that the amplitude of surface waves excited by line array laser is stronger and the amplitude attenuation is slower in the propagation direction.With the increase of the number of linear arrays,the FWHM of the center frequency of the surface wave decreases,and the frequency domain accuracy and signal-to-noise ratio increase.The simulation model of elastic matrix in arbitrary direction of single crystal silicon is established.The results show that the surface wave velocity of single crystal silicon increases according to the direction of[111],[100]and[110],the maximum velocity difference is about 400 m/s,and the velocity variation range is about 10%.The velocity change of the surface wave on the crystal plane of single crystal silicon(100)under the uniaxial stress of 10 GPa is simulated.The results show that the velocity of the surface wave decreases by about 2%,and the velocity decrease increases gradually from[100]to[110].An experimental system for measuring SARS narrow-band surface wave based on optical deflection method is established.The velocity of narrow-band surface wave on the crystal plane of unscrared single crystal silicon(100)is measured and the velocity direction map is drawn.The results show that the surface wave velocity increases from[100]to[110]crystal direction,and the velocity variation is about 8%.The damage process of continuous laser processing of monocrystals is studied.At lower power,melting pits and cracks extending from melting pits will appear.When the laser power is 2700 W,no melting pits will appear on the surface of monocrystals,but the stress damage is simple.The narrow-band surface wave velocity in the stress-damaged region of single crystal silicon(100)was measured and the velocity direction map was drawn.The measured results show that the velocity has no obvious direction,which means that the stress damage makes the crystal orientation in the damaged region chaotic and the whole becomes uniform.The work in this paper can provide reference for the subsequent research on laser ultrasonic detection of stress damage of monocrystals and ultrasonic surface wave anisotropy of monocrystals.更多还原