Gold etching for microfabrication

Abstract

The etching of gold is a key enabling technology in the fabrication of many microdevices and is widely used in the electronic, optoelectronic and microelectromechanical systems (MEMS) industries. In this review, we examine some of the available methods for patterning gold thin films using dry and wet etching techniques. Dry methods which utilise reactive ion etching (RIE) have a number of important advantages over other methods, but the low volatility of gold etch products has made the development of suitable processes problematic. More recently, the adoption of high-density plasma reactors with optimised chlorine-based chemistries has allowed improved processes to be developed, and etching in hydrogen plasmas also shows promise. Wet etching methods for gold have also been critically reviewed. Traditionally, iodine-and cyanide-based etch processes have been used, but in the last decade, a number of alternative etchants have been studied. Of particular interest is the recent development of a range of novel nonaqueous-based gold etchants, and the suitability of these etchants for microfabrication is assessed.

Reactions of a Polyhalide Ionic Liquid with Copper, Silver, and Gold

“…For comparison with common dissolution rates, such as metal mass loss per exposed surface area per unit time [mg dm −2 d −1 ] and changes in foil height per unit time [μ min −1 ], the corresponding values are also given in Table . Note in the case of the most noble metal, gold, the etching rate for 6 h is of the same order of magnitude as typical wet‐chemical etching rates of 0.1 to 1 μm min −1 in aqueous I 2 /I − or alkaline cyanide etching processes …”

“…Note in the case of the most noble metal, gold, the etching rate for 6h is of the same order of magnitude as typical wet-chemical etching rates of 0.1 to 1 mmmin À1 in aqueous I 2 /I À or alkalinec yanide etchingp rocesses. [13] Due to the high metal contentsi nt he IL solutionso btained after dissolution,m etal core-level signals were expected to be clearlyd etectable XPS. After the 6hcorrosione xperiments,t he solutionsw ere placed onto am olybdenum XPS sample holder and transferred to the XPS system.T he chemical nature of the dissolved metal species, as deduced by using XPS, will be discussedi nd etail in Section 2.2.…”

“…[25] To rule out the possibility that the corrosion process found here requires or involves the formation of as table Au Icarbene (which most likelyw ould occur by abstracting the most acidic proton at the 2-position of the imidazolium ring), ChemistryOpen 2019, 8,15-22 www.chemistryopen.org 2019 The Authors. Publishedb yWiley-VCH Verlag GmbH &Co. KGaA, Weinheim we measured the 1 Ha nd 13 CNMR spectra of the IL before and after Au corrosion.T hese NMR spectra did not reveala ny significant changes due to the gold corrosion.A sa ne xample, we show the corresponding 1 Ha nd 13 CNMR spectra in FiguresS5 and S6, respectively.I np articular,t he signals of the most acidic 2-protona td = 7.8 ppm and of the 2-carbon at d = 137 ppm did not decrease, which would be the case in carbene formation. Additionally,w et estedatrihalide homologue, [C 4 C 1 C 1 Im][Br 2 I],t hat was methylated at the 2-position to prevent proton abstraction.D ue to the higher meltingp oint of this IL, we carriedo ut the corresponding corrosion experiment at 50 8C, and the foil mass loss results are given in Ta ble S1.…”

Continuous sheathless microparticle and cell patterning using CL-SSAWs (conductive liquid-based standing surface acoustic waves)

“…In previous studies, most metal electrodes were fabricated by expensive and complex steps, including conventional photolithography, metal deposition, and liftoff processes. 17 To overcome the limitations of patterned metal electrodes, microfluidic electrode channels filled with a conductive liquid (CL) have gained attention. Because the electrode channels can be produced through soft-lithographic techniques, the fabrication can be inexpensive and simple.…”

Formation, Characterization, And Optimization Of Antibody-Gold Nanoparticle Conjugates

“…The Au is dissolved by the oxidant (I3 -) which is formed through the reaction of I2 and I -. 66 Flame atomic adsorption spectroscopy was used to confirm that the AuNPs were fully dissolved by the KI/I2 etchant solution. A calibration curve for the quantitation of Au was constructed using standard solutions prepared from gold (III) chloride ( Figure 10).…”