摘要
为了在透明基板上制备出导电性能良好的微电路,研究了窄脉宽激光正向和背向选择性去除金属薄膜制备的微结构形貌特征,开展了纳秒激光选择性去除Cu薄膜(厚度为150 nm)的实验和温度场仿真研究,揭示了正、背面去除的烧蚀机理和材料的喷射机制。实验结果表明,当激光脉冲能量为0.270~0.542μJ,扫描速度为2 mm/s时,激光诱导背向去除金属薄膜在加工质量方面优于正向加工,其去除几何精度高,轮廓边缘平整,几乎没有溅射。采用优化后的纳秒激光加工工艺参数,激光脉冲能量为0.403μJ,扫描速度2 mm/s,扫描线间距为3μm,制备出均匀分布的铜阵列图案。在相同参数下对玻璃基板上的铜薄膜背向选择性去除,得到具有良好导电性和粘附性的微电路。
Nanosecond laser processing technology is widely used in Integrated Circuits(IC),optoelectronic devices,biology,medical,aerospace,and network technology due to its low cost,high precision,non-contact directional processing,and high efficiency.As the feature size of IC and Optoelectronics continues to decrease,copper(Cu)has become the mainstream interconnect material in electronic components,which has the advantages of low cost,low resistance,strong conductivity,high thermal conductivity and excellent ductility.Microcircuits prepared by narrow pulse laser induced selective ablation of Cu films on transparent substrates have attracted extensive attention from researchers because of their excellent optical and electrical properties.It has become a research hotspot in this field on how to obtain higher processing quality and efficiency,satisfy the processing requirements of various materials and structures.In recent years,the major processing method has been laser forward induced selective ablation of metal thin films to fabricate microstructures.However,this method inevitably produces heat-affected zones and nano-ripples during processing,this situation seriously reduces the quality and photoelectric properties of the metal film microstructure.In order to decrease the influence of laser thermal effect,avoid the accumulation of remelted material,and effectively improve the surface morphology and photoelectric properties of microstructure,this paper uses a narrow pulse width laser to selectively remove metal thin films and prepare microcircuits on the rear side.Firstly,the laser beam passes through the transparent substrate,and then irradiates the glass substrate and Cu film interface for laser selective induced ablation.Part of the Cu film in the ablation area is vaporized,and a huge pressure is generated in the closed space,thereby promoting the remaining metal film on the transparent substrate to be ejected.This unique ablation process has become an important preparation method for metal film microstructure owing to its high removal efficiency and high-quality processing effect.Based on the fabrication of microgrooves by nanosecond laser removing metal films,the effects of process parameters such as laser pulse energy and scanning speed on the front and rear side ablation of metal films by narrow pulse width laser(λ=532 nm,τ=1.8 ns)were investigated.By comparing the relationship between the groove width and the laser pulse energy at the same scanning speed,it can be concluded that the groove width increases with the enlargement of laser pulse energy on the front and rear side ablation.When the laser energy enlarges to a certain value,the groove width gradually reaches a certain level,and then remains stable.On the front side ablation,the width of the groove decreases with the increase of the scanning speed.At the same time,on the rear side ablation,the groove width is not sensitive to the scanning speed.As the scanning speed increases,the groove width does not change significantly.Since the width of the groove in the reverse removal is independent of the laser scanning speed,the edge shape of the groove can be improved by changing the laser scanning speed.By further optimizing the process parameters and analyzing the surface morphology of the microstructure in detail,it is proved that the performance of the microgrooves prepared by narrow pulse width laser(E=0.403μJ,v=2 mm/s)on the rear side ablation is better than the front side.It not only has a straight and steep edge morphology,but has almost no sputtering on the edge.Through the experiments comparison of the front and reverse removal,it can be seen that the groove removed by the laser from the rear side is narrower than that removed from the front,which is impertinence of the variation of laser power.The difference in groove width between the two laser induced ablation methods could be attributed to diverse beam propagation and material removal processes.In addition,the 3D morphology of the microgrooves is characterized by a Confocal Laser Scan Microscope(CLSM),and the removal depth of the microgrooves is about 150 nm.This indicates that the Cu film on the glass substrate is completely removed and the glass substrate is not damaged which is crucial for the electronic isolation and photoelectric properties of actual electronic devices.In consequence,under the existing experimental conditions of our group,the microstructure of metal film prepared on rear side ablation has preferable quality.Combined with the temperature field simulation results of metal film by narrow pulse laser selective removal,the ablation mechanism and material removal mechanism of front and rear side ablation are revealed from the perspective of experiment and theory.To verify the feasibility of this removal method,uniformly distributed Cu arrays and complex microcircuit patterns are prepared when the laser energy is set to 0.403μJ,and the scanning speed is 2 mm/s.The resistivity of the microcircuit measured by the double probe measuring instrument is 1.81μΩ·cm,which is equivalence with the resistivity of the copper body.As a result,the microcircuit has excellent conductivity.Finally,the sample is placed in deionized water for ultrasonic 10 min,and the morphology of the microcircuit has no change.It proves the microcircuit processed by laser reverse processing has good adhesion and could be used for IC.Furthermore,this method has good application prospects.
作者
崔佳琪
谢小柱
黄亚军
李兆艳
罗宇航
龙江游
CUI Jiaqi;XIE Xiaozhu;HUANG Yajun;LI Zhaoyan;LUO Yuhang;LONG Jiangyou(School of Physics and Optoelectronic Engineering,Guangdong University of Technology,Guangzhou 510006,China;Laser Micro/Nano Processing Lab,School of Electromechanical Engineering,Guangdong University of Technology,Guangzhou 510006,China;Department of Experiment Teaching,Guangdong University of Technology,Guangzhou 510006,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2023年第7期46-56,共11页
Acta Photonica Sinica
基金
国家自然科学基金(No.52075103)
广东省基础与应用基础研究基金区域联合基金重点项目(No.2020B1515120058)
广东省基础与应用基础研究基金项目(No.2022A1515010614)。
关键词
窄脉宽激光
背面去除
温度场仿真
金属薄膜
微电路
Narrow pulse width laser
Reverse removal
Temperature field simulation
Mental thin film
Microcircuit
