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Title: Prediction of ultraviolet-induced damage during plasma processes in dielectric films using on-wafer monitoring techniques

Abstract

We measured electron-hole pairs generated in dielectric film using our developed on-wafer monitoring technique to detect electrical currents in the film during the plasma etching processes. The electron-hole pairs were generated by plasma induced ultraviolet (UV) photons, and the number of electron-hole pairs depends on the UV wavelength. In SiO{sub 2} film, UV light, which has a wavelength of less than 140 nm, generates electron-hole pairs, because the band gap energy of the film is 8.8 eV. On the other hand, in Si{sub 3}N{sub 4} film, which has a band gap energy level of 5.0 eV, UV light below 250 nm induces the electron-hole pairs. Additionally, we evaluated the fluorocarbon gas plasma process that induces UV radiation damage using multilayer sensors that consisted of both SiO{sub 2} and Si{sub 3}N{sub 4} stacked films. In these cases, electron-hole pair generation depended on the dielectric film structure. There were more electron-hole pairs generated in the SiO{sub 2} deposited on the Si{sub 3}N{sub 4} film than in the Si{sub 3}N{sub 4} deposited on the SiO{sub 2} film. As a result, our developed on-wafer monitoring sensor was able to predict electron-hole pair generation and the device characteristics.

Authors:
; ; ;  [1];  [2];  [2]
  1. Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
20723198
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 23; Journal Issue: 6; Other Information: DOI: 10.1116/1.2049297; (c) 2005 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DIELECTRIC MATERIALS; ELECTRIC CURRENTS; ENERGY GAP; ETCHING; EV RANGE 01-10; HOLES; PHOTONS; PHYSICAL RADIATION EFFECTS; PLASMA; SILICON NITRIDES; SILICON OXIDES; THIN FILMS; ULTRAVIOLET RADIATION; WAVELENGTHS

Citation Formats

Ishikawa, Yasushi, Katoh, Yuji, Okigawa, Mitsuru, Samukawa, Seiji, Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577 Japan and Sanyo Electric Co., Ltd., Component Group, Semiconductor Company, CCD Business Unit, Development Department, 180 Ohmori, Anpachi-cho, Anpachi-gun, Gifu, 503-0195, and Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577. Prediction of ultraviolet-induced damage during plasma processes in dielectric films using on-wafer monitoring techniques. United States: N. p., 2005. Web. doi:10.1116/1.2049297.
Ishikawa, Yasushi, Katoh, Yuji, Okigawa, Mitsuru, Samukawa, Seiji, Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577 Japan and Sanyo Electric Co., Ltd., Component Group, Semiconductor Company, CCD Business Unit, Development Department, 180 Ohmori, Anpachi-cho, Anpachi-gun, Gifu, 503-0195, & Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577. Prediction of ultraviolet-induced damage during plasma processes in dielectric films using on-wafer monitoring techniques. United States. doi:10.1116/1.2049297.
Ishikawa, Yasushi, Katoh, Yuji, Okigawa, Mitsuru, Samukawa, Seiji, Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577 Japan and Sanyo Electric Co., Ltd., Component Group, Semiconductor Company, CCD Business Unit, Development Department, 180 Ohmori, Anpachi-cho, Anpachi-gun, Gifu, 503-0195, and Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577. Tue . "Prediction of ultraviolet-induced damage during plasma processes in dielectric films using on-wafer monitoring techniques". United States. doi:10.1116/1.2049297.
@article{osti_20723198,
title = {Prediction of ultraviolet-induced damage during plasma processes in dielectric films using on-wafer monitoring techniques},
author = {Ishikawa, Yasushi and Katoh, Yuji and Okigawa, Mitsuru and Samukawa, Seiji and Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577 Japan and Sanyo Electric Co., Ltd., Component Group, Semiconductor Company, CCD Business Unit, Development Department, 180 Ohmori, Anpachi-cho, Anpachi-gun, Gifu, 503-0195 and Intelligent Nano-Process Laboratory, Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577},
abstractNote = {We measured electron-hole pairs generated in dielectric film using our developed on-wafer monitoring technique to detect electrical currents in the film during the plasma etching processes. The electron-hole pairs were generated by plasma induced ultraviolet (UV) photons, and the number of electron-hole pairs depends on the UV wavelength. In SiO{sub 2} film, UV light, which has a wavelength of less than 140 nm, generates electron-hole pairs, because the band gap energy of the film is 8.8 eV. On the other hand, in Si{sub 3}N{sub 4} film, which has a band gap energy level of 5.0 eV, UV light below 250 nm induces the electron-hole pairs. Additionally, we evaluated the fluorocarbon gas plasma process that induces UV radiation damage using multilayer sensors that consisted of both SiO{sub 2} and Si{sub 3}N{sub 4} stacked films. In these cases, electron-hole pair generation depended on the dielectric film structure. There were more electron-hole pairs generated in the SiO{sub 2} deposited on the Si{sub 3}N{sub 4} film than in the Si{sub 3}N{sub 4} deposited on the SiO{sub 2} film. As a result, our developed on-wafer monitoring sensor was able to predict electron-hole pair generation and the device characteristics.},
doi = {10.1116/1.2049297},
journal = {Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films},
number = 6,
volume = 23,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
  • UV radiation during plasma processing affects the surface of materials. Nevertheless, the interaction of UV photons with surface is not clearly understood because of the difficulty in monitoring photons during plasma processing. For this purpose, we have previously proposed an on-wafer monitoring technique for UV photons. For this study, using the combination of this on-wafer monitoring technique and a neural network, we established a relationship between the data obtained from the on-wafer monitoring technique and UV spectra. Also, we obtained absolute intensities of UV radiation by calibrating arbitrary units of UV intensity with a 126 nm excimer lamp. As amore » result, UV spectra and their absolute intensities could be predicted with the on-wafer monitoring. Furthermore, we developed a prediction system with the on-wafer monitoring technique to simulate UV-radiation damage in dielectric films during plasma etching. UV-induced damage in SiOC films was predicted in this study. Our prediction results of damage in SiOC films shows that UV spectra and their absolute intensities are the key cause of damage in SiOC films. In addition, UV-radiation damage in SiOC films strongly depends on the geometry of the etching structure. The on-wafer monitoring technique should be useful in understanding the interaction of UV radiation with surface and in optimizing plasma processing by controlling UV radiation.« less
  • The authors modeled SiN film etching with hydrofluorocarbon (CH{sub x}F{sub y}/Ar/O{sub 2}) plasma considering physical (ion bombardment) and chemical reactions in detail, including the reactivity of radicals (C, F, O, N, and H), the area ratio of Si dangling bonds, the outflux of N and H, the dependence of the H/N ratio on the polymer layer, and generation of by-products (HCN, C{sub 2}N{sub 2}, NH, HF, OH, and CH, in addition to CO, CF{sub 2}, SiF{sub 2}, and SiF{sub 4}) as ion assistance process parameters for the first time. The model was consistent with the measured C-F polymer layer thickness,more » etch rate, and selectivity dependence on process variation for SiN, SiO{sub 2}, and Si film etching. To analyze the three-dimensional (3D) damage distribution affected by the etched profile, the authors developed an advanced 3D voxel model that can predict the time-evolution of the etched profile and damage distribution. The model includes some new concepts for gas transportation in the pattern using a fluid model and the property of voxels called “smart voxels,” which contain details of the history of the etching situation. Using this 3D model, the authors demonstrated metal–oxide–semiconductor field-effect transistor SiN side-wall etching that consisted of the main-etch step with CF{sub 4}/Ar/O{sub 2} plasma and an over-etch step with CH{sub 3}F/Ar/O{sub 2} plasma under the assumption of a realistic process and pattern size. A large amount of Si damage induced by irradiated hydrogen occurred in the source/drain region, a Si recess depth of 5 nm was generated, and the dislocated Si was distributed in a 10 nm deeper region than the Si recess, which was consistent with experimental data for a capacitively coupled plasma. An especially large amount of Si damage was also found at the bottom edge region of the metal–oxide–semiconductor field-effect transistors. Furthermore, our simulation results for bulk fin-type field-effect transistor side-wall etching showed that the Si fin (source/drain region) was directly damaged by high energy hydrogen and had local variations in the damage distribution, which may lead to a shift in the threshold voltage and the off-state leakage current. Therefore, side-wall etching and ion implantation processes must be carefully designed by considering the Si damage distribution to achieve low damage and high transistor performance for complementary metal–oxide–semiconductor devices.« less
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  • A noninvasive, nonperturbing technique for real-time monitoring of ion energy distributions and total ion current at a wafer surface during plasma processing has been used to monitor rapid changes in CF{sub 4}/Ar etching plasmas in an inductively coupled, rf-biased plasma reactor. To mimic the effects of process recipe steps or reactor malfunctions, perturbations were made in the inductive source power, gas flow, and pressure, and the resulting effects on total ion current, sheath voltage, and ion energy were monitored. During etching of a thermal silicon dioxide film, smaller changes, which are caused by the etch process itself, were also observed.more » Sheath voltages determined by the noninvasive technique were in good agreement with simultaneous measurements made using a capacitive probe. In addition to providing a demonstration of the speed and accuracy of the technique, the results also provide useful information about the relative importance of different types of equipment malfunctions and suggest methods for minimizing their effects. In particular, operating at constant bias voltage, instead of constant bias power, gave more stable ion energies. The physical mechanisms that cause the observed changes in ion energy are discussed, and a comparison to other process monitoring methods is presented. No other noninvasive, nonperturbing method yields ion current or ion energies as accurately as the technique presented here.« less
  • We investigate differential charging of high aspect ratio dielectric trenches under plasma exposure using a two-dimensional computational model. Rather than considering average fluxes, we track individual ion and electron trajectories within the electric field arising from surface charges on the trench, updating the potentials within the computational domain after each particle. Our results show that, as the trench width shrinks to 100 nm and below, the potentials within the trench oscillate over an ever-wider range. The stochastic charging behavior in turn leads to noticeable changes in the flux and energies of ions passing through the trench.