The Experts below are selected from a list of 1566 Experts worldwide ranked by ideXlab platform
Lionel C Kimerling - One of the best experts on this subject based on the ideXlab platform.
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optical loss reduction in high index contrast chalcogenide glass waveguides via thermal reflow
Optics Express, 2010Co-Authors: Ningning Feng, Nathan Carlie, Laeticia Petit, Anu Agarwal, Kathleen Richardson, Lionel C KimerlingAbstract:A thermal reflow technique is applied to high-index-contrast, sub-micron waveguides in As2S3 chalcogenide glass to reduce the Sidewall Roughness and associated optical scattering loss. We show that the reflow process effectively decreases Sidewall Roughness of chalcogenide glass waveguides. A kinetic model is presented to quantitatively explain the Sidewall Roughness evolution during thermal reflow. Further, we develop a technique to calculate waveguide optical loss using the Roughness evolution model, and predict the ultimate low loss limit in reflowed high-index-contrast glass waveguides. Up to 50% optical loss reduction after reflow treatment is experimentally observed, and the practical loss limiting factors are discussed.
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transparent amorphous silicon channel waveguides with silicon nitride intercladding layer
Applied Physics Letters, 2009Co-Authors: Rong Sun, Kevin A Mccomber, Jing Cheng, Daniel K Sparacin, M Beals, Jurgen Michel, Lionel C KimerlingAbstract:We have experimentally demonstrated single mode amorphous silicon channel waveguides with low optical transmission loss of 2.7±0.4 dB/cm for TE mode in the 1550 nm range. This result was achieved by using hydrogen passivation of a-Si dangling bonds and a thin, low loss silicon nitride intercladding layer prepared by plasma enhanced chemical vapor deposition between the waveguide core and the oxide cladding layer. The silicon nitride intercladding layer reduces waveguide Sidewall Roughness scattering and preserves the hydrogen passivation.
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effect of size and Roughness on light transmission in a si sio2 waveguide experiments and model
Applied Physics Letters, 2000Co-Authors: Kevin K Lee, Desmond R Lim, Hsinchiao Luan, Anuradha M Agarwal, James Foresi, Lionel C KimerlingAbstract:In this letter, we experimentally evaluate the effect of miniaturization and surface Roughness on transmission losses within a Si/SiO2 waveguide system, and explain the results using a theoretical model. Micrometer/nanometer-sized waveguides are imperative for its potential use in dense integrated optics and optical interconnection for silicon integrated circuits. A theoretical model was employed to predict the relationship between the transmission losses of the dielectric silicon waveguide and its width. This model accurately predicts that loss increases as waveguide width decreases. Furthermore, we show that a major source of loss comes from Sidewall Roughness. We have constructed a complete contour map showing the interdependence of Sidewall Roughness and transmission loss, to assist users in their design of an optimal waveguide fabrication process that minimizes loss. Additionally, users can find an effective path to reduce the scattering loss from Sidewall Roughness. Using this map, we confirm that n...
James W Taylor - One of the best experts on this subject based on the ideXlab platform.
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direct measurement of x ray mask Sidewall Roughness and its contribution to the overall Sidewall Roughness of chemically amplified resist features
Journal of Vacuum Science & Technology B, 1999Co-Authors: Geoffrey W Reynolds, James W Taylor, Cameron J BrooksAbstract:As critical dimensions of resist features shrink, the Sidewall Roughness in resists may adversely affect the uniformity of the critical dimensions. Because x-ray lithography uses 1:1 size mapping of the mask pattern to the resist, it is plausible that any Roughness or defects in the mask would transfer into the resist, contributing to the overall Sidewall Roughness of the resist feature. This article will report on our efforts to ascertain the contribution of mask Sidewall Roughness to the overall Sidewall Roughness in chemically amplified resists exposed by x-ray lithography by comparing the directly measured Sidewall Roughness of x-ray mask features to that of resist Sidewall Roughness patterned with the x-ray mask. For instance, Shipley UV5 exposed with a gold-absorber mask has a Sidewall Roughness on the order of 2.8 nm rms while resist exposed with a TaSi mask has a Sidewall Roughness on the order of 3.0 nm rms. Preliminary atomic force microscopy measurements to determine directly the mask Sidewall ...
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correlation of atomic force microscopy Sidewall Roughness measurements with scanning electron microscopy line edge Roughness measurements on chemically amplified resists exposed by x ray lithography
Journal of Vacuum Science & Technology B, 1999Co-Authors: Geoffrey W Reynolds, James W TaylorAbstract:As critical dimensions of resist features shrink, Roughness of the features may contribute significantly to the variation in critical dimension. Measuring and understanding the causes of this Roughness will become increasingly important with smaller sizes. To date, mainly two techniques have been used to measure the Roughness: atomic force microscopy (AFM) and scanning electron microscopy (SEM). Topdown SEM measurements provide an easy and expedient measure of the variation in the profile of the resist feature. These measurements are often called “line-edge Roughness” (LER). AFM measurements are considerably more time consuming, but provide information on the entire Sidewall surface of the resist, rather than just the profile in line-edge Roughness. Our recent AFM measurements on the positive-tone resist APEX-E and UV5 have shown that the Sidewall Roughness of the resist is depth dependent; resist near the substrate is smoother than resist at the top surface of the resist. For instance, APEX-E may have a ...
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comparison of measured Sidewall Roughness for positive tone chemically amplified resists exposed by x ray lithography
Proceedings of SPIE the International Society for Optical Engineering, 1999Co-Authors: Geoffrey W Reynolds, James W TaylorAbstract:As critical dimensions for resist features shrink, resist Roughness on the Sidewall may contribute relatively more to the correspondingly smaller CD error budget. Thus, some photoresists may be more suitable than others for smaller dimensions. This paper compares and contrasts the Sidewall Roughness values measured by atomic force microscopy of two positive-tones, chemically amplified resists used in X-ray lithography.
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factors contributing to Sidewall Roughness in a positive tone chemically amplified resist exposed by x ray lithography
Journal of Vacuum Science & Technology B, 1999Co-Authors: Geoffrey W Reynolds, James W TaylorAbstract:As device critical dimensions continue to decrease, Sidewall Roughness will become increasingly important. To address this issue, we have measured the Sidewall Roughness of a positive-tone, chemically amplified resist, Shipley APEX-E exposed by X-ray radiation. We have also examined factors that contribute to the overall Sidewall Roughness such as mask Roughness, the development process, variations in acid diffusion, shot noise, and the effects of acid volatility. The overall Sidewall Roughness for fully developed nested lines, under normal processing conditions, is on the order of 4.3 nm root-mean-square (rms) and shows no dose dependence. Isolated lines, however, do demonstrate a dose-dependent Sidewall Roughness. Samples exposed with doses of 60–100 mJ/cm2 exhibit a monotonically decreasing trend in Roughness from 6.5 to about 4.5 nm rms, respectively. The development process, in tandem with pattern-specific parameters, appears to cause this difference in the Roughness between nested and isolated lines...
Huilin Jiang - One of the best experts on this subject based on the ideXlab platform.
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investigation for Sidewall Roughness caused optical scattering loss of silicon on insulator waveguides with confocal laser scanning microscopy
THE Coatings, 2020Co-Authors: Hongpeng Shang, Degui Sun, Bin Wang, Huilin JiangAbstract:Sidewall Roughness-caused optical loss of waveguides is one of the critical limitations to the proliferation of the silicon photonic integrated circuits in fiber-optic communications and optical interconnects in computers, so it is imperative to investigate the distribution characteristics of Sidewall Roughness and its impact upon the optical losses. In this article, we investigated the distribution properties of waveguide Sidewall Roughness (SWR) with the analysis for the three-dimensional (3-D) SWR of dielectric waveguides, and, then the accurate SWR measurements for silicon-on-insulator (SOI) waveguide were carried out with confocal laser scanning microscopy (CLSM). Further, we composed a theoretical/experimental combinative model of the SWR-caused optical propagation loss. Consequently, with the systematic simulations for the characteristics of optical propagation loss of SOI waveguides, the two critical points were found: (i) the Sidewall Roughness-caused optical loss was synchronously dependent on the correlation length and the waveguide width in addition to the SWR and (ii) the theoretical upper limit of the correlation length was the bottleneck to compressing the Roughness-induced optical loss. The simulation results for the optical loss characteristics, including the differences between the TE and TM modes, were in accord with the experimental data published in the literature. The above research outcomes are very sustainable to the selection of coatings before/after the SOI waveguide fabrication.
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effective metrology and standard of the surface Roughness of micro nanoscale waveguides with confocal laser scanning microscopy
Optics Letters, 2019Co-Authors: Degui Sun, Hongpeng Shang, Huilin JiangAbstract:Surface Roughness is one of the important parameters affecting the optical scattering loss of dielectric waveguides. Despite extensive research interests in correlating optical losses with surface Roughness, not much research focus has been dedicated to the study of an accurate metrology and measurement standard for the characterization of waveguide Roughness. In this Letter, we report an effective metrology for the measurement of waveguide surface Roughness, using confocal laser scanning microscopy (CLSM). We also provide the definition of surface Roughness relevant to CLSM terminology based on the measured peak-to-valley (P-V) values, which can be correlated to the conventional root-mean-square Roughness, by employing multi-dimensional statistical models. Finally, we demonstrate the use of CLSM metrology in measuring two-dimensional Roughness of 10 μm×6 μm silica waveguides, showing an average top surface Roughness of 0.151 μm and an average Sidewall Roughness of 0.203 μm. For comparison, the scanning electron microscopy (SEM) measurements are also carried out for the same waveguide samples, and then the measured Sidewall Roughness values are in the range of 0.08–0.12 μm. Since SEM measures only the amplitude of Roughness profile, while CLSM measures the P-V value, after doubling the SEM value, these two methods can provide comparable results of Roughness.
S.k. Pani - One of the best experts on this subject based on the ideXlab platform.
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Evolution of Sidewall Roughness during reactive-ion etching of polymer waveguides
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2006Co-Authors: S.k. Pani, C.c. Wong, K. Sudharsanam, C. S. Premachandran, M.k. IyerAbstract:Sidewall roughening of fluorinated polyether waveguides fabricated by reactive-ion etching in pure oxygen plasma was investigated. Variation of Sidewall Roughness (SWR) was observed by scanning electron microscopy, and was measured and confirmed by atomic force microscopy. Lower-pressure SWR variation along the vertical depth is due to the combination of both the shadowing and the first-order reemission effect, and higher-pressure SWR variation is postulated to be due to a continuous shadowing effect. It was discovered that the autocorrelation length (ACL) calculated from the experiment varies in a similar manner as the SWR does along the depth of the waveguides. This variation of ACL suggests that the surface-Roughness evolution at the Sidewalls during plasma etching possesses the same etch dynamics as that of planar thin-film etching. With the increase of pressure, the average value of Roughness exponent increases.
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pressure and depth dependence of Sidewall Roughness of polymer optical waveguides during reactive ion etching
Electronics Packaging Technology Conference, 2004Co-Authors: S.k. Pani, C.c. Wong, V. Lim, C. S. Premachandran, M.k. Iyer, P V Ramana, N RanganathanAbstract:Sidewall Roughness (SWR) of fluorinated polyether waveguides fabricated using reactive ion etching in pure oxygen gas was directly measured using atomic force microscope (AFM). We confirmed that SWR is not the replicate of line edge Roughness (LER) of the waveguides. We also confirmed the pressure dependence of SWR for shallow structures and discovered an additional etch depth dependence for deeper structures which counteracts the pressure dependence. Lower O/sub 2/ pressure etching produces SWR which increases with depth while higher O/sub 2/ pressure etching produces declining SWR with depth. The depth dependence at lower pressure is explained by the change in the arrival dynamics of etchant ions in a mechanism involving both shadowing and first order reemission effects.
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effect of process parameters on Sidewall Roughness in polymeric optical waveguides
Thin Solid Films, 2004Co-Authors: S.k. Pani, C.c. Wong, K. Sudharsanam, V. Lim, Subodh Mhaisalkar, S Mohanraj, P V RamanaAbstract:Abstract Most polymeric optical devices are mainly fabricated by photolithography and reactive ion etching (RIE). This paper describes the fabrication of fluorinated polyether (FPE) waveguides by using a metallic hard mask and proximity exposure followed by RIE. In particular, we focused on the effects of various fabrication parameters on the Sidewall Roughness. According to our study, a high-power, low-pressure oxygen RF plasma environment will provide vertical and smooth Sidewalls desired in a cladded waveguide. The Sidewall Roughness increases with pressure in pure oxygen plasma, while adding nitrogen gas to oxygen during RIE, creates a more vertical profile and smoother Sidewalls along with low vertical and lateral etch rates. A simple technique is presented to quantify Sidewall Roughness using an atomic force microscope (AFM).
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Direct measurement of Sidewall Roughness of polymeric optical waveguides
Applied Surface Science, 2004Co-Authors: S.k. Pani, C.c. Wong, K. Sudharsanam, V. LimAbstract:Sidewall Roughness (SWR) of fluorinated polyether waveguides fabricated using reactive ion etching in pure oxygen gas was directly measured using atomic force microscopy (AFM). We confirm that SWR is not the replicate of line edge Roughness (LER) of the waveguides. Statistical information such as standard deviation of Roughness, autocovariance function (ACF), and autocorrelation length (ACL) have been obtained from AFM measurements. The ACL varies in the similar manner as SWR along the depth of the waveguide, and both are dependent on the etch depth. The depth dependence can be explained by the change in the arrival dynamics of etchant ions in a mechanism involving both shadowing and first-order reemission effects.
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variation of Sidewall Roughness of polymeric waveguides during reactive ion etching
Applied Physics Letters, 2004Co-Authors: S.k. Pani, C.c. Wong, K. SudharsanamAbstract:Sidewall Roughness (SWR) of fluorinated polyether waveguides fabricated using reactive ion etching was directly measured using atomic force microscopy. We confirmed the pressure dependence of SWR for shallow structures and discovered an additional etch depth dependence for deeper structures which counteracts the pressure dependence. Lower O2 pressure etching produces SWR which increases with depth while higher O2 pressure etching produces declining SWR with depth. Addition of N2 to the etch ambient suppresses SWR for high pressure etches at intermediate depths. The role of N2 is possibly related to the formation of a N-containing passivating film, confirmed by secondary ion mass spectroscopy measurements.
Jaehyun Ryou - One of the best experts on this subject based on the ideXlab platform.
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light extraction efficiency control in algan based deep ultraviolet flip chip light emitting diodes a comparison to ingan based visible flip chip light emitting diodes
Optics Express, 2015Co-Authors: Keon Hwa Lee, Hyun Jung Park, Seung Hwan Kim, Mojtaba Asadirad, Yongtae Moon, Joon Seop Kwak, Jaehyun RyouAbstract:We study light-extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) using flip-chip (FC) devices with varied thickness in remaining sapphire substrate by experimental output power measurement and computational methods using 3-dimensional finite-difference time-domain (3D-FDTD) and Monte Carlo ray-tracing simulations. Light-output power of DUV-FCLEDs compared at a current of 20 mA increases with thicker sapphire, showing higher LEE for an LED with 250-μm-thick sapphire by ~39% than that with 100-μm-thick sapphire. In contrast, LEEs of visible FCLEDs show only marginal improvement with increasing sapphire thickness, that is, ~6% improvement for an LED with 250-μm-thick sapphire. 3D-FDTD simulation reveals a mechanism of enhanced light extraction with various Sidewall Roughness and thickness in sapphire substrates. Ray tracing simulation examines the light propagation behavior of DUV-FCLED structures. The enhanced output power and higher LEE strongly depends on the Sidewall Roughness of the sapphire substrate rather than thickness itself. The thickness starts playing a role only when the sapphire Sidewalls become rough. The roughened surface of sapphire Sidewall during chip-separation process is critical for TM-polarized photons from AlGaN quantum wells to escape in lateral directions before they are absorbed by p-GaN and Au-metal. Furthermore, the ray tracing results show a reasonably good agreement with the experimental result of the LEE.