Wang Yipeng, Zhou Weijian, Ma Tieying
College of Optical and Electronic Technology, China Jiliang University, Hangzhou 310013, China.
Micromachines (Basel). 2021 Dec 14;12(12):1557. doi: 10.3390/mi12121557.
A four-step etching method is used to prepare the double-layer cross Si microchannel structure. In the first etching step, a <100> V-groove structure is etched on (100) silicon, and the top channel is formed after thermal oxidation with the depth of the channel and the slope of its sidewall being modulated by the etching time. The second etching step is to form a sinking substrate, and then the third step is to etch the bottom channel at 90° (<100> direction) and 45° (<110> direction) with the top channel, respectively. Hence, the bottom channel on the sink substrate is half-buried into the top channel. Undercut characteristic of 25% TMAH is used to perform the fourth step, etching through the overlapping part of the two layers of channels to form a double-layer microchannel structure. Different from the traditional single-layer microchannels, the double-layer crossed microchannels are prepared by the four-step etching method intersect in space but are not connected, which has structural advantages. Finally, when the angle between the top and bottom is 90°, the root cutting time at the intersection is up to 6 h, making the width of the bottom channel 4-5 times that of the top channel. When the angle between the top and bottom is 45°, the root cutting time at the intersection is only 4 h, and due to the corrosion along (111), the corrosion speed of the sidewall is very slow and the consistency of the width of the upper and lower channels is better than 90° after the end. Compared with the same-plane cross channel structure, the semiburied microchannel structure avoids the V-shaped path at the intersection, and the fluid can pass through the bottom channel in a straight line and cross with the top channel without overlapping, which has a structural advantage. If applied to microfluidic technology, high-efficiency delivery of two substances can be carried out independently in the same area; if applied to microchannel heat dissipation technology, the heat conduction area of the fluid can be doubled under the same heat dissipation area, thereby increasing the heat dissipation efficiency.
采用四步蚀刻法制备双层交叉硅微通道结构。在第一步蚀刻中，在（100）硅片上蚀刻出<100> V形槽结构，经过热氧化后形成顶部通道，通道深度和侧壁斜率由蚀刻时间调制。第二步蚀刻是形成下沉衬底，然后第三步分别以90°（<100>方向）和45°（<110>方向）与顶部通道蚀刻底部通道。这样，下沉衬底上的底部通道半埋入顶部通道。利用25% TMAH的侧向蚀刻特性进行第四步蚀刻，蚀刻穿过两层通道的重叠部分，形成双层微通道结构。与传统的单层微通道不同，双层交叉微通道通过四步蚀刻法制备，在空间中相交但不连通，具有结构优势。最后，当顶部和底部夹角为90°时，交叉处的根部蚀刻时间长达6小时，使得底部通道宽度是顶部通道的4 - 5倍。当顶部和底部夹角为45°时，交叉处的根部蚀刻时间仅为4小时，并且由于沿（111）方向的腐蚀，侧壁腐蚀速度非常慢，最终上下通道宽度的一致性优于90°情况。与同平面交叉通道结构相比，半埋微通道结构避免了交叉处的V形路径，流体可以直线穿过底部通道并与顶部通道交叉而不重叠，具有结构优势。如果应用于微流控技术，可以在同一区域内独立高效地输送两种物质；如果应用于微通道散热技术，在相同散热面积下，流体的热传导面积可以翻倍，从而提高散热效率。
