Centimeter-scale low-damage micromachining on single-crystal 4H–SiC substrates using a femtosecond laser with square-shaped Flat-Top focus spots

Femtosecond (fs) lasers have been proved to be reliable tools for high-precision and high-quality micromachining of ceramic materials. Nevertheless, fs laser processing using a single-mode beam with a Gaussian intensity distribution is difficult to obtain large-area flat and uniform processed surfaces. In this study, we utilize a customized diffractive optical element (DOE) to redistribute the laser pulse energy from Gaussian to square-shaped Flat-Top profile to realize centimeter-scale low-damage micromachining on single-crystal 4H–SiC substrates. We systematically investigated the effects of processing parameters on the changes in surface morphology and composition, and an optimal processing strategy was provided. Mechanisms of the formation of surface nanoparticles and the removal of surface micro-burrs were discussed. We also examined the distribution of subsurface defects caused by fs laser processing by removing a thin surface layer with a certain depth through chemical mechanical polishing (CMP). Our results show that laser-induced periodic surface structures (LIPSSs) covered by fine SiO₂ nanoparticles form on the fs laser-processed areas. Under optimal parameters, the redeposition of SiO₂ nanoparticles can be minimized, and the surface roughness Sa of processed areas reaches 120 ± 8 nm after the removal of a 10 μm thick surface layer. After the laser processing, micro-burrs on original surfaces are effectively removed, and thus the average profile roughness Rz of 2 mm long surface profiles decreases from 920 ± 120 nm to 286 ± 90 nm. No visible micro-pits can be found after removing ~1 μm thick surface layer from the laser-processed substrates.     

柠条的纤维特性及其双螺杆CMP制浆性能研究

以柠条为原料，分析了其化学组分和纤维形态，并探讨了柠条双螺杆CMP法的制浆工艺以及浆料的纤维形态和成纸的物理性能。研究结果表明：与针、阔叶木相比，柠条原料中纤维素和综纤维素质量分数较低，苯醇抽出物和热水抽出物质量分数较高，柠条纤维长度总体偏短，木质部和皮部的纤维质量平均长度分别为0.621和0.819 mm，还存在部分杂细胞。采用3.5% Na₂SO₃和1.5% NaOH常温预浸12 h、90℃汽蒸1 h后再用双螺杆挤浆机在质量分数35%下进行搓丝，并结合高浓盘磨机磨浆，所得CMP浆得率可达73%。柠条CMP浆基本保持了纤维原有的长度，质量平均长度达0.650 mm，长宽比为32.7，纤维解离较好，但分丝帚化情况不理想，含有部分纤维束和杂细胞。当加拿大游离度为300 mL时，柠条CMP浆成纸的环压强度指数和松厚度较高，分别为8.67（N·m）/g和2.56 cm³/g，抗张指数为19.6（N·m）/g，本色浆白度较高，达50%（ISO）。柠条CMP浆适合配抄瓦楞原纸等包装用纸，漂白后可配抄新闻纸和白板纸。     

低压力下环保型络合剂和氧化剂对铝合金化学机械抛光的影响

在低平坦化压力下用壳寡糖(COS)环保型络合剂及H₂O₂氧化剂化学机械抛光铝合金，用原子力显微镜观测抛光后的表面质量，并用X射线光电子能谱仪分析其表面的钝化膜元素，用纳米压痕仪分析钝化膜的力学性能，研究COS及H₂O₂对铝合金CMP的作用机理。结果表明:H₂O₂质量分数为2%时，材料去除率随COS含量的增加而增大，当COS质量分数为0.32%时，材料的去除速率达861 nm/min，表面粗糙度最低为2.50 nm；COS质量分数为0.50%时，材料去除率随H₂O₂含量的增加先增大后减小，当H₂O₂质量分数为1.2%时，材料的抛光去除速率达840 nm/min，同时其表面粗糙度为3.52 nm。加入COS络合剂会在铝合金表面形成主要成分为Al-COS、Al₂O₃和Al(OH)₃的弱钝化膜。      

Highly efficient chemical mechanical polishing method for SiC substrates using enhanced slurry containing bubbles of ozone gas

In this study, a highly efficient method for chemical mechanical polishing (CMP) of silicon carbide (SiC) substrates using enhanced slurry was proposed and developed. The enhanced slurry contains bubbles of ozone gas generated by ozone gas generator in pure water mixed with a conventional commercially available slurry. Therefore, the enhanced slurry has an oxidizing effect on the Si-face of SiC substrates. To confirm the effectiveness of bubbles enclosing ozone gas, both nano-indentation test and X-ray photoelectron spectroscopy (XPS) analysis were conducted. As a result, the hardness decrease of the Si-face of the SiC substrate was confirmed through the nano-indentation test, and the generation of reaction products was confirmed on Si-face of SiC substrate in the XPS analysis. According to a series of experimental results of our proposed highly efficient CMP method for SiC substrates, the removal rate can be increased when the enhanced slurry was applied, comparing with that for the not only conventional commercially available slurry but also commercially available dedicated slurry.     

碱性铜粗抛液中氧化剂对化学机械平坦化的影响

针对不合腐蚀抑制剂苯并三氮唑(BTA)的碱性铜粗抛液,通过对3英寸(1英寸=2.54 cm)铜片上的动态抛光速率和静态腐蚀速率的研究来模拟评估氧化剂对晶圆表面平坦化的影响.在12英寸铜镀膜片和TM1图形片上分别研究氧化剂体积分数对表面平坦化的影响.实验结果表明:动态抛光速率和静态腐蚀速率均随着氧化剂体积分数的增加先逐渐增大,达到最大值,然后下降,趋于平缓.片内非均匀性和剩余高低差均随H2O2体积分数的增加,先呈下降趋势,后缓慢上升.当氧化剂体积分数为3％时,动态去除速率(vRR)为398.988 nm/min,静态腐蚀速率vER为6.834 nm/min,vRR/vER比值最大,片内非均匀性最小为3.82％,台阶高低差最小为104.6 nm/min,此时晶圆片有较好的平坦化效果.     

碱性Cu抛光液中非离子表面活性剂和氧化剂作用的研究

化学机械抛光是集成电路制造工艺中十分精密的技术。在本文中,为了改善抛光效果,分表讨论了非离子表面活性剂和氧化剂在CMP过程中作用。我们主要分析了非离子表面活性剂对片内非均匀性和表面粗糙度的影响。同时,我们从静态腐蚀速率、电化学曲线和剩余高低差的角度,讨论了在不加BTA条件下,不同氧化剂浓度的抛光液的钝化特性。实验结果明显地表明：加入了非离子表面活性剂的抛光液,更有利于改善抛光后的片内非均匀性和表面粗糙度,并确定2vol%体积分数是比较合适的浓度。当抛光液中氧化剂浓度超过3vol%,抛光液拥有较好的钝化能力,能够有效减小高低差,并有助于获得平整和光滑的表面。根据这些实验结果,非离子表面活性剂和氧化剂的作用进一步被了解,将有助于抛光液性能的改善。     

Experimental investigation of process parameters for roll-type linear chemical mechanical polishing (Roll-CMP) system

The fabrication processes for electronic components are now demanding a higher degree of planarity for integration and multistacking, with chemical mechanical polishing (CMP) processes replacing conventional etching or mechanical polishing owing to their ability to attain global planarization. As CMP has been applied to more and more fields, new types of CMP machines have been developed. This study introduces a novel roll-type linear CMP (Roll-CMP) process that uses a line-contact material removal mechanism to for the polish flexible substrates, and examines the effect of the process parameters on the material removal rate (MRR) and its nonuniformity (NU). The parameters affecting the Roll-CMP process include down force, roll speed, table feed rate, slurry flow rate, slurry temperature, and the table oscillation length. Increasing the down force, roll speed, slurry flow rate, and slurry temperature resulted in a high average MRR (MRR_avg). Further, the MRR_avg was found to decrease with an increase in the oscillation length because of the effect of the polishing area. A large down force, high roll speed, high table feed rate, and high slurry flow rate were effective for reducing the NU. These results will be helpful for understanding the newly developed Roll-CMP process.     

Removal of residual oxide layer formed during chemical–mechanical-planarization process for lowering contact resistance

In the present work, we report the formation of residual oxide layer during chemical–mechanical-planarization (CMP) process in the carbon nanotube (CNT) via interconnects and some feasible solutions for its removal. Residual oxide layer makes electrically poor contact between CNTs and metal resulting in high contact resistance in CNT via interconnects. We adopt post-CMP processes such as hydrofluoric acid (HF) or Ar plasma treatment to remove the residual oxide layer. X-ray photoelectron spectroscopy (XPS) was used to confirm the chemical state of samples before and after the post-CMP process. Silicon and oxygen peaks from silicon-based oxide layer observed after the CMP process were disappeared and reduced in its intensity by the post-CMP process, respectively. Furthermore, via resistance decreased more than 1 order of magnitude after the post-CMP process. It is found that the post-CMP process provides good electrical contact between CNTs and metal by removing the residual oxide layer.     

高阻燃通信线缆的应用状况分析

介绍通信线缆的应用现状,提出应重视通信线缆的阻燃性能,并通过对CM、CMR、CMP和LSOH线缆进行燃烧实验对比其阻燃性能,实验证明CMP线缆具有在最短时间内自我熄灭且不续燃的功能。