Etching Characteristics and Mechanism of ZnO and Ga-Doped ZnO Thin Films in Inductively Coupled HBr/Ar/CHF 3 Plasma

The etching characteristics and mechanism of In- and Ga-doped ZnO (IGZO) thin films in BCl3/Cl2/Ar inductively coupled plasma at a fixed gas pressure (6 mTorr) were investigated. It was found that the substitution of Cl2 for BCl3 in the BCl3/Cl2/Ar gas mixture results in the maximum IGZO etching rate in 40% BCl3 + 40% Cl2 + 20% Ar. In both Cl2-rich (20% BCl3 + 60% Cl2 + 20% Ar) and BCl3-rich (60% BCl3 + 20% Cl2 + 20% Ar) plasmas, increases in input power (500–800 W) and bias power (100–250 W) cause the monotonic acceleration of the IGZO etching process. Plasma diagnostics using Langmuir probes and zero-dimensional plasma modeling provided the data on plasma parameters and fluxes of active species. It was concluded that the IGZO etching process is not limited by the ion–surface interaction kinetics as well as involves BCl x radicals.

Section: Introductionmentioning

confidence: 72%

Etching Behavior and Mechanism of In- and Ga-Doped ZnO Thin Films in Inductively Coupled BCl₃/Cl₂/Ar Plasmas

Kwon

Efremov

Kang

et al. 2012

“…In our previous work, deep etching with HBr/N 2 /CH 3 F-based gas plasma was successfully demonstrated to fabricate the holes in poly-Si/SiO 2 stacks. [14][15][16][17][18][19][20][21][22][23][24] The vertical and deep hole profile was obtained by a combination of N 2 addition and the adjustment of the substrate temperature to under 20 °C. To understand the mechanism of the deep etching in our HBr/N 2 /CH 3 F-based gas chemistry, the surface composition was analyzed using blanket wafers and pattern samples.…”

Section: Introductionmentioning

confidence: 99%

Deposition profile of ammonium bromide in N₂/HBr plasmas for high-aspect-ratio multilayer etching

Iwase

Kofuji

Yokogawa

et al. 2019

The deposition profile of ammonium bromide in N2/HBr plasmas was evaluated as a function of depth in a macro-cavity structure for the high-aspect-ratio etching process. The macro cavity reproduces deep holes in 3D NAND structures. The profile was compared with the calculated results of that of fluorocarbon (FC) in CF2 radicals. The decay in the ammonium bromide deposition is smaller than that of FC over a depth of 50 mm in the cavity. The 50 mm depth corresponds to an aspect ratio of 60. To clarify the experiment, two models were investigated; ammonium bromide forms in the gas phase, and on a solid surface, respectively. It was found that the latter model reasonably clarifies the experiment when comparing the two models. These results imply that ammonium bromide sufficiently reaches the bottom of deep holes in 3D NAND high-aspect-ratio structures.

“…[14][15][16][17] The HBr and fluorocarbonbased gases were mixed to achieve uniform etching rates for both poly-Si and SiO 2 and thus obtain smooth side walls in the etched holes. [18][19][20][21][22] Furthermore, nitrogen gas was added to the etching gas, and the substrate temperature was adjusted to obtain a vertical hole profile. A film consisting of a fluorocarbon polymer was deposited on the substrate when the substrate was not bombarded with ions from the plasma, and a mixing layer (2-3 nm thick) containing carbon, fluorine, nitrogen, bromine, and substrate material formed when the substrate was bombarded with ions.…”

Section: Introductionmentioning

confidence: 99%

Eliminating dependence of hole depth on aspect ratio by forming ammonium bromide during plasma etching of deep holes in silicon nitride and silicon dioxide

Iwase

Yokogawa

Mori

2018

The reaction mechanism during etching to fabricate deep holes in SiN/SiO 2 stacks by using a HBr/N 2 /fluorocarbon-based gas plasma was investigated. To etch SiN and SiO 2 films simultaneously, HBr/fluorocarbon gas mixture ratio was controlled to achieve etching selectivity closest to one. Deep holes were formed in the SiN/SiO 2 stacks by one-step etching at several temperatures. The surface composition of the cross section of the holes was analyzed by time-of-flight secondary-ion mass spectrometry. It was found that bromine ions (considered to be derived from NH 4 Br) were detected throughout the holes in the case of low-temperature etching. It was also found that the dependence of hole depth on aspect ratio decreases as temperature decreases, and it becomes significantly weaker at a substrate temperature of 20 °C. It is therefore concluded that the formation of NH 4 Br supplies the SiN/SiO 2 etchant to the bottom of the holes. Such a finding will make it possible to alleviate the decrease in etching rate due to a high aspect ratio.