Tuan Yaakub Tuan Norjihan, Yunas Jumril, Latif Rhonira, Hamzah Azrul Azlan, Razip Wee Mohd Farhanulhakim Mohd, Yeop Majlis Burhanuddin
Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia (UKM), 43600 UKM Bangi, Selangor, Malaysia.
Department of Electronics Engineering, Faculty of Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia.
Micromachines (Basel). 2018 May 7;9(5):222. doi: 10.3390/mi9050222.
A simple fabrication method for the surface modification of an electroosmotic silicon microchannel using thermal dry oxidation is presented. The surface modification is done by coating the silicon surface with a silicon dioxide (SiO₂) layer using a thermal oxidation process. The process aims not only to improve the surface quality of the channel to be suitable for electroosmotic fluid transport but also to reduce the channel width using a simple technique. Initially, the parallel microchannel array with dimensions of 0.5 mm length and a width ranging from 1.8 µm to 2 µm are created using plasma etching on the 2 cm × 2 cm silicon substrate <100>. The oxidation of the silicon channel in a thermal chamber is then conducted to create the SiO₂ layer. The layer properties and the quality of the surface are analyzed using scanning electron microscopy (SEM) and a surface profiler, respectively. The results show that the maximum oxidation growth rate occurs in the first 4 h of oxidation time and the rate decreases over time as the oxide layer becomes thicker. It is also found that the surface roughness is reduced with the increase of the process temperature and the oxide thickness. The scallop effect on the vertical wall due to the plasma etching process also improved with the presence of the oxide layer. After oxidation, the channel width is reduced by ~40%. The demonstrated method is suggested for the fabrication of a uniform channel cross section with high aspect ratio in sub-micro and nanometer scale that will be useful for the electroosmotic (EO) ion manipulation of the biomedical fluid sample.
本文提出了一种利用热干法氧化对电渗硅微通道进行表面改性的简单制造方法。表面改性是通过热氧化工艺在硅表面涂覆一层二氧化硅（SiO₂）层来实现的。该工艺不仅旨在改善通道的表面质量以适合电渗流体传输，还旨在使用一种简单技术减小通道宽度。首先，在2 cm×2 cm的<100>硅衬底上通过等离子体蚀刻创建长度为0.5 mm、宽度在1.8 µm至2 µm范围内的平行微通道阵列。然后在热室中对硅通道进行氧化以形成SiO₂层。分别使用扫描电子显微镜（SEM）和表面轮廓仪分析该层的特性和表面质量。结果表明，最大氧化生长速率出现在氧化时间的前4小时，并且随着氧化层变厚，速率随时间降低。还发现随着工艺温度和氧化层厚度的增加，表面粗糙度降低。由于等离子体蚀刻工艺在垂直壁上产生的扇贝效应也因氧化层的存在而得到改善。氧化后，通道宽度减小了约40%。所展示的方法建议用于制造亚微米和纳米尺度具有高纵横比的均匀通道横截面，这将有助于对生物医学流体样本进行电渗（EO）离子操纵。
