Wet Chemical Processing of Ge in Acidic H₂O₂ Solution: Nanoscale Etching and Surface Chemistry

Abstract

Herein, we investigate wet-chemical etching of Ge (100) in acidic H2O2 solutions for technologically advanced device processing. Nanoscale etching kinetics data were provided by inductively coupled plasma mass spectrometry (ICP-MS) measurements. Rotation rate- dependent measurement showed that the hydrodynamics of the system is important. The dependence of the etch rate on the HCl concentration was considered for the range 0.001–1 M HCl. A stark difference morphologically for >1 M HCl, which resulted in a rough surface confirmed by atomic force microscopy (AFM) images, has been observed. X-ray photoelectron spectroscopy (XPS) measurements provided insight in the surface chemistry of etching for device processing. Electrochemical measurements confirmed that the etching process follows a chemical mechanism. Based on X-ray photoelectron spectroscopy (XPS) data, we present reaction schemes that help to understand the results.

Sub-10 μm-Thick Ge Thin Film Fabrication from Bulk-Ge Substrates via a Wet Etching Method

“…With the continuous oxidation from H 2 O 2 and oxide removal from acid, Ge could be thinned down. It should be noted that an anion like Cl – may play a more important role in the etching process than proton concentration. , …”

“…Based on the etch rate reported from the literature, the only suitable choices were NH 4 OH-based H 2 O 2 solution, HCl-based H 2 O 2 solution, and H 2 SO 4 -based H 2 O 2 solution. Acidic H 2 O 2 solutions have been studied and widely used for Ge etching . Hence, H 2 SO 4 - and HCl-based H 2 O 2 solutions were selected.…”

“…It should be noted that an anion like Cl − may play a more important role in the etching process than proton concentration. 32,41 Unlike prior studies which etched germanium with a short time and a limited depth, this work thinned Ge from the original thickness of 535 μm to a thickness of ≤10 μm. Therefore, it could be difficult to do the nanoscale mechanism investigation because the surface changed dramatically for such a long etching time (≥50 h).…”

Efficient surface passivation of germanium nanostructures with 1% reflectance

“…It has been demonstrated that ALD Al 2 O 3 forms negative fixed charge at the Al 2 O 3 -Ge interface resulting in excellent surface passivation through field-effect [21,24]. Prior to ALD either HCl or HF alone is often used instead of RCA cleaning, which has been shown to be too vigorous for Ge [25][26][27][28]. In addition to cleaning the surface, another purpose of this treatment is to remove unstable native germanium oxides that easily form on the surface when exposed to air [29][30][31].…”

Validation of functionability of transition metal and its alloys at the simultaneous introduction of two oxidizing agents in the volume of liquid phase

“…The presence of two or more oxidizers in a system with a metal or alloy is quite common. For example, for successful etching of printed circuit boards [1][2][3], such mixtures are used for high-speed removal of a metal layer from the surface without any physical actions by immersing in the appropriate solution for a short time for several minutes. The presence of the second oxidizer in the liquid bulk phase is the reason for a sharp increase in the corrosion rate, leading to uncontrolled metal consumption [4 -6].…”