Chiang C-C, Lee Benjamin T-H
Department of Mechanical Engineering, National Central University, Taoyuan City, Taiwan.
Sci Rep. 2019 Sep 2;9(1):12631. doi: 10.1038/s41598-019-49119-8.
A silicon layer that is tens of micrometers thick on a handle substrate is desired for applications involving power devices, microelectromechanical systems (MEMS), highly efficient silicon solar cells (<50 µm), etc. In general, if the initial silicon layer obtained from the layer transfer process using the etch-stop or ion-cut techniques, which may provide very accurate thickness control, is too thin, then additional epitaxial growth is required to increase the thickness of the silicon layer. However, epitaxial growth under strict predeposition conditions is a time-consuming and expensive process. On the other hand, producing porous silicon via anodization in a hydrofluoric acid solution offers an efficient way to control the dimensions of the generated pores directly on the nano- or macroscale via the current density. When sintering the porous layer via high-temperature argon annealing, the porosity of the porous layer determines whether this porous layer can serve as a device layer or a separation layer. In addition, it is clearly easier to create a transferred layer ten of micrometers thick via anodization than by ion implantation and/or epitaxial deposition.
对于涉及功率器件、微机电系统（MEMS）、高效硅太阳能电池（<50 µm）等的应用，需要在衬底上有一层几十微米厚的硅层。一般来说，如果使用蚀刻停止或离子切割技术从层转移过程中获得的初始硅层太薄（这些技术可能提供非常精确的厚度控制），那么就需要额外的外延生长来增加硅层的厚度。然而，在严格的预沉积条件下进行外延生长是一个耗时且昂贵的过程。另一方面，通过在氢氟酸溶液中进行阳极氧化来制备多孔硅，提供了一种通过电流密度直接在纳米或宏观尺度上控制所产生孔隙尺寸的有效方法。当通过高温氩气退火烧结多孔层时，多孔层的孔隙率决定了该多孔层是否可以用作器件层或分离层。此外，通过阳极氧化创建一个几十微米厚的转移层显然比通过离子注入和/或外延沉积更容易。
