Dry etching in the presence of physisorption of neutrals at lower temperatures

Lill, Thorsten; Berry, Ivan L.; Shen, Meihua; Hoang, John; Fischer, Andreas; Panagopoulos, Theodoros; Chang, Jane P.; Vahedi, Vahid

doi:10.1116/6.0002230

Cited by 12 publications

(6 citation statements)

References 177 publications

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“…The factor influencing the increase in both the aspect ratio and etch rate of SiO 2 in Figure 5 is the reduction of necking at a lower temperature, which enhanced the fluxes of neutrals (including radicals) and ions onto the etch front of SiO 2 [ 18 ]. Specifically, it is believed that the flux of neutrals onto the etch front of SiO 2 was more enhanced at lower temperatures than the flux of ions [ 6 ]. The flux of ions was independent of the CD of the pattern and temperature rather than that of neutrals [ 16 , 19 ].…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, research and development efforts concerning the HAR process have attempted to overcome this problem using methods such as increasing the bias power, tuning the gas chemistry, and varying the substrate temperature [ 3 , 4 , 5 ]. Currently, the most promising method is the low-temperature HAR etching process [ 2 , 6 ]. This technology facilitates a high etch rate with higher AR structures compared with conventional HAR etching at room temperature [ 2 ].…”

Section: Introductionmentioning

confidence: 99%

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Necking Reduction at Low Temperature in Aspect Ratio Etching of SiO2 at CF4/H2/Ar Plasma

Kwon,

Bang,

Kim

et al. 2024

Nanomaterials

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This study investigated the effect of temperature on the aspect-ratio etching of SiO2 in CF4/H2/Ar plasma using patterned samples of a 200 nm trench in a low-temperature reactive-ion etching system. Lower temperatures resulted in higher etch rates and aspect ratios for SiO2. However, the plasma property was constant with the chuck temperature, indicated by the line intensity ratio from optical emission spectroscopy monitoring of the plasma. The variables obtained from the characterization of the etched profile for the 200 nm trench after etching were analyzed as a function of temperature. A reduction in the necking ratio affected the etch rate and aspect ratio of SiO2. The etching mechanism of the aspect ratio etching of SiO2 was discussed based on the results of the surface composition at necking via energy-dispersive X-ray spectroscopy with temperature. The results suggested that the neutral species reaching the etch front of SiO2 had a low sticking coefficient. The bowing ratio decreased with lowering temperature, indicating the presence of directional ions during etching. Therefore, a lower temperature for the aspect ratio etching of SiO2 could achieve a faster etch rate and a higher aspect ratio of SiO2 via the reduction of necking than higher temperatures.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Necking Reduction at Low Temperature in Aspect Ratio Etching of SiO2 at CF4/H2/Ar Plasma

Kwon,

Bang,

Kim

et al. 2024

Nanomaterials

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“…19) An additional explanation for the improved ARDE performance at lower temperatures is potentially surface diffusion of neutrals. 20) Knudsen transport and surface diffusion can be viewed as separate, independent fluxes or as synergistic, interdependent modes of neutral transport. 20,21) Another benefit of the leaner chemistry used in lowtemperature etching is an improved mask morphology, which translates into improved circularity and sidewall roughness of the etched holes, as shown in Fig.…”

Section: Har Etch Mechanismsmentioning

confidence: 99%

Progress report on high aspect ratio patterning for memory devices

Shen

Lill

Hoang

et al. 2023

Jpn. J. Appl. Phys.

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High aspect ratio (HAR) ONON channel hole patterning in 3D NAND flash presents grand challenges. This report summarizes some of the recent progresses in patterning from a HAR etch and Deposition-Etch-Co-Optimization (DECO) perspective. HAR etch mechanisms will be discussed focusing on how to reduce aspect ratio dependent etching (ARDE) effect. Highlights of the new low temperature etch process will be presented where significant improvement on ARDE is observed. New simulation results from a Monte Carlo feature scale model provide insights in ion scattering and mask interactions on channel hole profile control. Deposition and etch co-optimization (DECO) is a new frontier to enable better channel hole shape control at HAR. Film tier optimization and carbon liner insertion results show improvement in channel hole profile control.

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“…We therefore conjecture that the same can be valid for SiO 2 etching with fluorocarbon-based plasmas or other plasma-surface chemistries. It is also worth noting that physisorption is considered a contributing mechanism in many ALD processes and a major mechanism in cryogenic etching [55][56][57][58].…”

Section: Effect Of Polymer Depositionmentioning

confidence: 99%

Assessing neutral transport mechanisms in aspect ratio dependent etching by means of experiments and multiscale plasma modeling

Vanraes

Venugopalan

Besemer

et al. 2023

Plasma Sources Sci. Technol.

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Since the onset of pattern transfer technologies for chip manufacturing, various strategies have been developed to circumvent or overcome aspect ratio dependent etching (ARDE). These methods have, however, their own limitations in terms of etch non-idealities, throughput or costs. Moreover, they have mainly been optimized for individual in-device features and die-scale patterns, while occasionally ending up with poor patterning of metrology marks, affecting the alignment and overlay in lithography. Obtaining a better understanding of the underlying mechanisms of ARDE and how to mitigate them therefore remains a relevant challenge to date, for both marks and advanced nodes. In this work, we accordingly assessed the neutral transport mechanisms in ARDE by means of experiments and multiscale modeling for SiO2 etching with CHF3/Ar and CF4/Ar plasmas. The experiments revealed a local maximum in the etch rate for an aspect ratio around unity, i.e. the simultaneous occurrence of regular and inverse reactive ion etching lag for a given etch condition. We were able to reproduce this ARDE trend in the simulations without taking into account charging effects and the polymer layer thickness, suggesting shadowing and diffuse reflection of neutrals as the primary underlying mechanisms. Subsequently, we explored four methods with the simulations to regulate ARDE, by varying the incident plasma species fluxes, the amount of polymer deposition, the ion energy and angular distribution and the initial hardmask sidewall angle, for which the latter was found to be promising in particular. Although our study focusses on feature dimensions characteristic to metrology marks and BEOL integration, the obtained insights have a broader relevance, e.g. to the patterning of advanced nodes. Additionally, this work supports the insight that physisorption may be more important in plasma etching at room temperature than originally thought, in line with other recent studies, a topic on which we recommend further research.

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Dry etching in the presence of physisorption of neutrals at lower temperatures

Cited by 12 publications

References 177 publications

Necking Reduction at Low Temperature in Aspect Ratio Etching of SiO2 at CF4/H2/Ar Plasma

Necking Reduction at Low Temperature in Aspect Ratio Etching of SiO2 at CF4/H2/Ar Plasma

Progress report on high aspect ratio patterning for memory devices

Assessing neutral transport mechanisms in aspect ratio dependent etching by means of experiments and multiscale plasma modeling

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