Direct Imprinting of Porous Silicon via Metal-Assisted Chemical Etching
Direct Imprinting of Porous Silicon via Metal-Assisted Chemical Etching
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DOI：
10.1002/adfm.201505153
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发表时间：
2016-05-03
影响因子：
19
通讯作者：
Ferreira, Placid
中科院分区：
文献类型：
--
作者：
Azeredo, Bruno P.;Lin, Yu-Wei;Ferreira, Placid
用于块状半导体的传统光刻技术在用于微孔和介孔材料（如多孔硅（PS））时效果非常差。在这项工作中，首次报道了一种不涉及塑性变形或高温加工的高通量、单步、直接印迹PS工艺。基于金属辅助化学蚀刻（MACE）的基本机制，该工艺使用涂有贵金属催化剂的预图型聚合物戳记来蚀刻浸在hf -氧化剂混合物中的PS。该工艺不仅克服了PS图案的困难，而且根据其化学和机械降解，它可以重复使用多次。该工艺被证明能够以低于20纳米的分辨率进行厘米级平行3D图案。研究发现，PS有利于反应物和生成物的大量输运，整体蚀刻速率受限于反应物的局部耗损。这种直接压印技术的多功能性通过其产生曲线和平面3D特征（例如，抛物面，抛物面圆柱体，正弦波和直侧壁通道）的能力得到证明。微型光学元件，如衍射光栅和微聚光器的建立和特点，突出了PS在硅光子学中的潜在应用。
Conventional lithographical techniques used for bulk semiconductors produce dramatically poor results when used for micro and mesoporous materials such as porous silicon (PS). In this work, for the first time, a high-throughput, single-step, direct imprinting process for PS not involving plastic deformation or high-temperature processing is reported. Based on the underlying mechanism of metal-assisted chemical etching (MACE), this process uses a pre-patterned polymer stamp coated with a noble metal catalyst to etch PS immersed in an HF-oxidizer mixture. The process not only overcomes the difficulties in patterning PS but it does so with a stamp that may be reused multiple times depending on its chemical and mechanical degradation. The process is shown to be capable of centimeter-scale parallel 3D patterning with sub-20 nm resolution. It is found that PS facilitates mass transport of reactants and products, and the overall etch rate is limited by local depletion of reactants. The versatility of this direct imprinting technique is demonstrated by its ability to produce curvilinear and planar 3D features (e.g., paraboloids, parabolic cylinders, sinusoidal waves, and straight sidewall channels). Miniaturized optical elements such as diffraction gratings and microconcentrators are built and characterized highlighting potential use of PS in silicon photonics.