Low-cost and low-topography fabrication of multilayer interconnections for microfluidic devices
Low-cost and low-topography fabrication of multilayer interconnections for microfluidic devices
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DOI：
10.1088/1361-6439/ab8c9e
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发表时间：
2020-05
影响因子：
2.3
通讯作者：
Jia Li;Supin Chen;C. Kim
中科院分区：
文献类型：
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作者：
Jia Li;Supin Chen;C. Kim
具有大量独立电极的微器件需要多层互连。通常采用多级互连工艺来提供集成电路器件中的多层互连，但是对于微流体经常需要的大面积或一次性器件来说，该工艺通常太昂贵。印刷电路板（PCB）可以以低成本提供多层互连，但其粗糙的形貌对小液滴的滑动提出了挑战。在这里，我们报告了一个低成本的低地形多层互连的薄膜金属层的选择性和控制阳极氧化。该工艺利用金属（本文中为钽）的阳极氧化，或者更具体地，重复部分阳极氧化以在导电层之间形成绝缘层，以及完全阳极氧化以在电极之间形成隔离区域，从而取代沉积、平坦化和蚀刻绝缘层的通常工艺。在验证了预期的电连接和绝缘后，开发的方法被应用于电介质上的电润湿（EWOD），其复杂的微流体产品目前构建在PCB或薄膜晶体管基板上。为了证明实用性，我们制造了具有小于1微米的台阶（表面形貌）的三金属层EWOD设备（与PCB EWOD设备的> 10微米相比），并确认了基本的数字微流体操作。
Multilayer interconnections are needed for microdevices with a large number of independent electrodes. A multi-level photolithographic process is commonly employed to provide multilayer interconnections in integrated circuit devices, but it is often too expensive for large-area or disposable devices frequently needed for microfluidics. The printed circuit board (PCB) can provide multilayer interconnection at low cost, but its rough topography poses a challenge for small droplets to slide over. Here we report a low-cost fabrication of low-topography multilayer interconnects by selective and controlled anodization of thin-film metal layers. The process utilizes anodization of metal (tantalum in this paper) or, more specifically, repetitions of a partial anodization to form insulation layers between conductive layers and a full anodization to form isolating regions between electrodes, replacing the usual process of depositing, planarizing, and etching insulation layers. After verifying the electric connections and insulations as intended, the developed method is applied to electrowetting-on-dielectric (EWOD), whose complex microfluidic products are currently built on PCB or thin-film transistor substrates. To demonstrate the utility, we fabricate a three metal-layer EWOD device with steps (surface topography) less than 1 micrometer (vs. > 10 micrometers of PCB EWOD devices) and confirm basic digital microfluidic operations.