Inverse metal-assisted chemical etching of germanium with gold and hydrogen peroxide

Abstract

Metal-assisted chemical etching (MACE) is a flexible technique for texturing the surface of semiconductors. In this work, we study the spatial variation of the etch profile, the effect of angular orientation relative to the crystallographic planes, and the effect of doping type. We employ gold in direct contact with germanium as the metal catalyst, and dilute hydrogen peroxide solution as the chemical etchant. With this catalyst-etchant combination, we observe inverse-MACE, where the area directly under gold is not etched, but the neighboring, exposed germanium experiences enhanced etching. This enhancement in etching decays exponentially with the lateral distance from the gold structure. An empirical formula for the gold-enhanced etching depth as a function of lateral distance from the edge of the gold film is extracted from the experimentally measured etch profiles. The lateral range of enhanced etching is approximately 10–20 µm and is independent of etchant concentration. At length scales beyond a few microns, the etching enhancement is independent of the orientation with respect to the germanium crystallographic planes. The etch rate as a function of etchant concentration follows a power law with exponent smaller than 1. The observed etch rates and profiles are independent of whether the germanium substrate is n-type, p-type, or nearly intrinsic.

Communication—Controlling Etching of Germanium through Surface Charge Manipulation

“…Hole assisted etching was previously observed experimentally in the vicinity of metal particles located on the surface of germanium. 16 Figure 2 is a cyclic voltammogram (CV) recorded for germanium in the KOH-based etchant by rapidly scanning biases and collecting instantaneous current. The polarity of the sample surface switches during CV acquisition, leading to the observed hysteresis behavior.…”

Metal-assisted chemical etching beyond Si: applications to III–V compounds and wide-bandgap semiconductors

“…Lidsky et al 211 investigated the variation in Au-catalyzed MacEtch rate enhancement with oxidant concentration. Rings of Au were fabricated on (100) Ge substrates prior to immersion in etch baths consisting of H 2 O and H 2 O 2 with concentrations ranging between 0.03 M and 0.61 M. An empirical formula for the etch rate with distance from catalyst was derived from the etch profiles as measured by profilometery.…”

Surface Engineering of Metals: Techniques, Characterizations and Applications

“…Chemical etching is often used for decorative purposes, precision machining, or the removal of surface defects. It offers advantages such as high precision, intricate detailing, and the ability to etch complex geometries [46]. Applications of chemical etching include jewelry, nameplates, microelectromechanical systems (MEMSs), and integrated circuits.…”

“…The etchin process can be controlled to create specific patterns, textures, or designs on the surfac Chemical etching is often used for decorative purposes, precision machining, or the r moval of surface defects. It offers advantages such as high precision, intricate detailin and the ability to etch complex geometries [46]. Applications of chemical etching includ jewelry, nameplates, microelectromechanical systems (MEMSs), and integrated circuits A comparison of the four types of chemical surface engineering techniques presente in this section is offered in Table 2.…”