Profile simulation of high aspect ratio contact etch

Kim, Doosik; Hudson, Eric A.; Cooperberg, David; Edelberg, Erik A.; Srinivasan, Mukund

doi:10.1016/j.tsf.2006.10.023

Cited by 28 publications

(21 citation statements)

References 5 publications

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“…A semiempirical profile simulator was employed to investigate the necking and bowing of etching of HAR features. 33 The necking resulted from a balance between polymer removal and deposition processes, while the bowing was caused by surface scattering of ions from secondary facets. Nonuniform necking was found to cause an imbalance in the ion flux to the bottom of the feature, resulting in twisting irrespective of charging.…”

Section: Introductionmentioning

confidence: 99%

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Huang

Huard

Shim

et al. 2019

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Plasma etching of high aspect ratio (HAR) features, typically vias, is a critical step in the fabrication of high capacity memory. With aspect ratios (ARs) exceeding 50 (and approaching 100), maintaining critical dimensions (CDs) while eliminating or diminishing twisting, contact-edge-roughening, and aspect ratio dependent etching (ARDE) becomes challenging. Integrated reactor and feature scale modeling was used to investigate the etching of HAR features in SiO 2 with ARs up to 80 using tri-frequency capacitively coupled plasmas sustained in Ar/C 4 F 8 /O 2 mixtures. In these systems, the fluxes of neutral radicals to the wafer exceed the fluxes of ions by 1-2 orders of magnitude due to lower threshold energies for dissociation compared with ionization. At low ARs (<5), these abundant fluxes of CF x and C x F y radicals to the etch front passivate the oxide to form a complex which is then removed by energetic species (ions and hot neutrals) through chemically enhanced reactive etching, resulting in the formation of gas phase SiF x , CO x , and COF. As the etching proceeds into higher ARs, the fractional contribution of physical sputtering to oxide removal increases as the fluxes of energetic species to the etch front surpass those of the conduction constrained CF x and C x F y radicals. The instantaneous etch rate of oxide decreases with increasing aspect ratio (ARDE effect) due to decreased fluxes of energetic species and decreased power delivered by these species to the etch front. As the etch rate of photoresist (PR) is independent of AR, maintaining CDs by avoiding undercut and bowing requires high SiO 2-over-PR selectivity, which in turn requires a minimum thickness of the PR at the end of etching. Positive ions with narrow angular distributions typically deposit charge on the bottom of low AR features, producing a maximum in positive electric potential on the bottom of the feature. For high AR features, grazing incidence collisions of ions on sidewalls depositing charge produce electric potentials with maxima on the sidewalls (as opposed to the bottom) of the feature.

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Section: Introductionmentioning

confidence: 99%

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Huang

Huard

Shim

et al. 2019

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…An increase in W b intuitively points to an increase in the mean ion energy. The formation of double facets has been attributed to competition between ion etching and deposition, 3,4 and it was not captured in this work due to the limited kinetics data on the etching of silicon nitride and effect of plasma depositing species on it. 37,38 This coupling may slightly change the mean ion energy as well as the IAD.…”

Section: Model Calibration Simulation and Discussionmentioning

confidence: 99%

Feature profile evolution during shallow trench isolation etch in chlorine-based plasmas. I. Feature scale modeling

Hoang

Hsu

Chang

2008

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Feature profile evolution during shallow trench isolation etch in chlorine-based plasmas. II. Coupling reactor and feature scale models Modeling of fluorine-based high-density plasma etching of anisotropic silicon trenches with oxygen sidewall passivation J. Appl. Phys. 94, 6311 (2003); 10.1063/1.1621713Deep-submicron trench profile control using a magnetron enhanced reactive ion etching system for shallow trench isolationThe authors developed a cellular based Monte Carlo ͑MC͒ feature scale model capable of direct coupling to the dominant plasma species ratios from a reactor scale model in order to simulate the profile evolution of shallow trench isolation etch in chlorine-based plasmas and its variation from the center to the edge of the wafer. Carefully planned experiments along with scanning electron microscopy ͑SEM͒ were used to calibrate the MC model, where one to two plasma parameters were systematically varied. Simulated feature profiles were found to agree well with experimental observations, capturing details such as microtrenching, faceting, tapering, and bowing. The particle counts used to achieve these fits agreed well with those estimated from SEM, corroborating the chemistry and physics used in the feature scale model. In addition, the feature scale model uses a novel surface representation that eliminates the artificial flux fluctuations originating from the discrete cells used in the simulation and enables a much more precise calculation of the surface normal, which dictates the trajectory of reflected species.

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“…10 In addition, to decrease the amount of a nonuniform C-F based polymer layer that is deposited on the sidewall of the contact hole during the HARC etching process, the characteristics of C-F based gas dissociation have been investigated by experimentation and simulation. 11,12 However, the mechanism of contact hole distortion during HARC etching has not fully been investigated.…”

Section: Introductionmentioning

confidence: 99%

Study on contact distortion during high aspect ratio contact SiO2 etching

Kim

Lee

Cho

et al. 2014

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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As pattern density is increased in semiconductor integrated circuits (ICs) and pattern sizes are decreased to nanometer scale, high aspect ratio contact etching has become one of the most difficult processes in nanoscale IC fabrication. The increase in aspect ratio of the contact oxide etching raises problems such as low mask selectivity, microloading, pattern degradation, and etch stops. In this study, the authors investigated the effect of various oxide etch conditions such as mask materials, mask thickness, and oxide etch processes, on contact profile degradation. The results showed that greater contact pattern distortion occurred as the aspect ratio of the etched oxide was increased. The use of amorphous carbon instead of amorphous silicon as the etch mask, and the use of a more carbon-rich gas composition, lessened pattern distortion. The polymer deposited at the interface between the mask layer and the oxide layer appeared to significantly affect the degree of contact pattern distortion. By adding an in-situ polymer removal step during the overetch of a multistep contact oxide etch process with a 20:1 aspect ratio, about a 7% improvement in pattern distortion could be obtained without changing other conditions. V

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Profile simulation of high aspect ratio contact etch

Cited by 28 publications

References 5 publications

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Feature profile evolution during shallow trench isolation etch in chlorine-based plasmas. I. Feature scale modeling

Study on contact distortion during high aspect ratio contact SiO2 etching

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