Perspectives on Black Silicon in Semiconductor Manufacturing: Experimental Comparison of Plasma Etching, MACE, and Fs-Laser Etching

Abstract

In semiconductor manufacturing, black silicon (bSi) has traditionally been considered as a sign of unsuccessful etching. However, after more careful consideration, many of its properties have turned out to be so superior that its integration into devices has become increasingly attractive. In devices where bSi covers the whole wafer surface, such as solar cells, the integration is already rather mature and different bSi fabrication technologies have been studied extensively. Regarding the integration into devices where bSi should cover only small selected areas, existing research focuses on device properties with one specific bSi fabrication method. Here, we fabricate bSi patterns with varying dimensions ranging from millimeters to micrometers using three common bSi fabrication techniques, i.e., plasma etching, metal-assisted chemical etching (MACE) and femtosecond-laser etching, and study the corresponding fabrication characteristics and resulting material properties. Our results show that plasma etching is the most suitable method in the case of µm-scale devices, while MACE reached surprisingly almost the same performance. Femtosecondlaser has potential due to its maskless nature and capability for hyperdoping, however, in this study its moderate accuracy, large silicon consumption and spreading of the etching damage outside the bSi region left room for improvement.

External Gettering of Metallic Impurities by Black Silicon Layer

“…In particular, the RIE and MACE methods do not introduce significant damage in the nanostructures, and in the case of the fs‐laser method, the b‐Si layer has a high level of damage. [ 28 ] For each specific case, it is necessary to carefully analyze the various aspects of their application and the properties of the b‐Si layers.…”

“…Both of these nanostructural modifications of crystalline Si are used in solar cells, hydrogen generators, photodiodes, sensitive photodetectors, visible‐light emitters, display devices, and biological and chemical sensors. [ 26–30 ]…”

“…[14,15] Black Si (b-Si) is a nanostructured layer of crystalline Si consisting of thin needles with a high density, the height of which can be 0.3-10.0 μm, and the diameter-of 0.05-1.0 μm. [23][24][25][26][27][28] The presence of needles gives this material a darkened black hue, hence its name. Black Si can be fabricated by many methods including plasma-based reactive ion etching (RIE), metal-assisted chemical etching (MACE), and femtosecond-pulsed laser (fs-laser) treatment.…”

“…Black Si can be fabricated by many methods including plasma-based reactive ion etching (RIE), metal-assisted chemical etching (MACE), and femtosecond-pulsed laser (fs-laser) treatment. [26][27][28] In the literature, b-Si is often characterized as a variety of porous Si. Like porous Si, it also has many attractive properties, such as low reflectance, a large surface area, DOI: 10.1002/pssa.202200793 Black silicon (b-Si) has many attractive properties and is currently being adopted in various fields of semiconductor technology.…”

Chemical Excitation of Silicon Photoconductors by Metal-Assisted Chemical Etching

“…Metal-assisted chemical etching (MACE) as an effective method to fabricate semiconductor (especially Si) nanostructures has been widely studied over the past twenty years and is attracting more and more interest from both the scientific and technological communities. − The Si nanostructures produced by MACE have been widely used in energy harvesting and storage, − sensors, and biomedical technologies. − In addition, inspired by the MACE reaction, plasmon-enhanced nanomotors moving at the silicon/MACE etching solution interface have been developed based on the attractive plasmon resonance of noble metal, e.g., Ag and Au, nanocrystals. ,− The MACE process is based on the highly site-selective oxidation of Si when it is brought into contact with metal nanoparticles (typically silver nanoparticles, AgNPs) and oxidants (typically hydrogen peroxide, H 2 O 2 ) in a fluorine-containing solution. , The oxidized products of Si can be easily etched away by a fluoride solution and thus high-aspect-ratio silicon nanostructures are produced in the end. After twenty years of studies, the chemical transformations that take place during MACE have been well characterized, but the dynamics of the detailed charge transfer process taking place during the process have not been reported so far.…”