Search query: Large-field step-structure surface measurement using a femtosecond laser

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abstract: We present a femtosecond laser based interferometry for step structure surface measurement with a large field of view. A height axial scanning range of 348 um is achieved by using the method of repetition frequency scanning with reference to the Rb atomic clock and the optical path length difference design for 21 times of the pulse interval. A combined method, which includes the envelope peak positioning method for rough measurement, synthetic wavelength interferometry for connection, and carrier wave interferometry for fine measurement, is proposed to reconstruct the surface. A three step specimen with heights of approximately 20, 50, and 70 um was successfully measured with a height precision of 7 nm, and the accuracy was verified by a commercial white light interferometer. The diameter of the field of view that was demonstrated was 17.3 mm, which could be much larger owing to the high spatial coherence of the femtosecond laser. The results show that the femtosecond laser system combines the step structure measurement performance of white light interferometry and the high precision large field performance of phase shifting interferometry, indicating its potential for widespread use in ultra precision manufacturing of micro/nano devices, such as semiconductor chips, integrated circuits, and micro electro mechanical systems.
author_names: Yue Wang

Guangyao Xu

Shilin Xiong

Guanhao Wu
title: Large field step structure surface measurement using a femtosecond laser.
venue: Optics express
year: 2020

abstract: We present a femtosecond laser based interferometer for step structure surface measurement. The synthetic wavelength method is adopted to bridge the envelope positioning and carrier phase extraction methods. A three step surface is precisely reconstructed.
author_names: Yue Wang

Guangyao Xu

Shilin Xiong

Guanhao Wu
title: Large Field Step Structure Surface Profilometry using a Femtosecond Laser
venue: 2020 Conference on Lasers and Electro Optics (CLEO)
year: 2020

abstract: We test an erbium doped fiber femtosecond laser for its potential as a light source for a coherence scanning interferometer for large field of view profiling of rough silicon carbide (SiC) surfaces. This infrared fiber pulse laser is able to provide a relatively long temporal coherence length of ~30 mm to be appropriate for coherence scanning of rough surfaces. At the same time, it offers a high degree of spatial coherence comparable to that of a monochromatic continuous wave laser to achieve a large measurement field of view. In addition, the highly maintained linear polarization of the pulse laser source permits overcoming the low specular reflectance of rough SiC surfaces by polarization based optical power splitting control between the reference and measurement arms.
author_names: Yang Lu

Jiyong Park

Liandong Yu

Seung-Woo Kim
title: 3D profiling of rough silicon carbide surfaces by coherence scanning interferometry using a femtosecond laser.
venue: Applied optics
year: 2018

abstract: In this work we investigated the optical and electrical properties of Au Ag nanoalloys in various volume ratios. The nanoparticles have been prepared from gold and silver ions reduced by direct irradiation femtosecond laser. The samples were added into a quartz cuvette and irradiated for 10 minutes. Each sample was observed the optical property where surface plasmon resonance (SPR) peak was existed. In addition, electrical conductivity of the colloids was derived from the measurement of the correspond zeta potential by dynamic light scattering (DLS) method. The results showed that the SPR peak of Au Ag nanoalloy were shifted almost linearly in between 409 nm for Ag and 530 nm for Au depending on their volume fraction. The conductivity measurement showed that Au0Ag100 (pure Ag) nanoparticles has the highest value and Au100Ag0 (pure Au) nanoparticles has the lowest value, and interestingly, Au Ag nanoalloys have the values between Au0Ag100 and Au100Ag0. Briefly, this work revealed that both optical and electrical properties of Au Ag nanoalloys can be easily tuned by regulating the volume fraction between the two elements.
author_names: A Z Nur Hidayah

Yuliati Herbani
title: Optical and Electrical Properties of Gold Silver Nanoalloys Synthesized through Photochemical Reduction using Femtosecond Laser
venue: The Journal of Pure and Applied Chemistry Research
year: 2020

abstract: Fast, precise 3 D measurement of discontinuous step structures fabricated on microelectronic products is essential for quality assurance of semiconductor chips, flat panel displays, and photovoltaic cells. Optical surface profilers of low coherence interferometry have long been used for the purpose, but the vertical scanning range and speed are limited by the micro actuators available today. Besides, the lateral field of view extendable for a single measurement is restricted by the low spatial coherence of broadband light sources. Here, we cope with the limitations of the conventional low coherence interferometer by exploiting unique characteristics of femtosecond laser pulses, i.e. low temporal but high spatial coherence. By scanning the pulse repetition rate with direct reference to the Rb atomic clock, step heights of ~69.6 mm are determined with a repeatability of 10.3 nm. The spatial coherence of femtosecond pulses provides a large field of view with superior visibility, allowing for a high volume measurement rate of ~24,000 mm3/s.
author_names: Woo-Deok Joo

Seungman Kim

Jiyong Park

Keun-woo Lee

Joo-hyung Lee

Seungchul Kim

Young-Jin Kim

Seung-Woo Kim
title: Femtosecond laser pulses for fast 3 D surface profilometry of microelectronic step structures.
venue: Optics express
year: 2013

abstract: Abstract. The intermode beats generated by direct detection of a mode locked femtosecond laser represent inherent high quality and high frequency modulations suitable for electro optical distance measurement (EDM) This approach has already been demonstrated as a robust alternative to standard long distance EDM techniques. However, we extend this idea to intermode beating of a wideband source obtained by spectral broadening of a femtosecond laser. We aim at establishing a technological basis for accurate and flexible multiwavelength distance measurement. Results are presented from experiments using beat notes at 1 GHz generated by two bandpass filtered regions from both extremes of a coherent supercontinuum ranging from 550 to 1050 nm. The displacement measurements performed simultaneously on both colors on a short distance setup show that noise and coherence of the wideband laser are adequate for achieving accuracies of about 0.01 mm on each channel with a potential improvement by accessing higher beat notes. Pointing and power instabilities have been identified as dominant sources of systematic deviations. Nevertheless, the results demonstrate the basic feasibility of the proposed technique. We consider this a promising starting point for the further development of multiwavelength EDM enabling increased accuracy over long distances through dispersion based integral refractivity compensation and for remote surface material probing along with distance measurement in laser scanning.
author_names: David Salido-Monzu

Andreas Wieser
title: Simultaneous distance measurement at multiple wavelengths using the intermode beats from a femtosecond laser coherent supercontinuum
year: 2018

abstract: We present experimental measurements of the femtosecond time scale generation of strong magnetic field fluctuations during the interaction of ultrashort, moderately relativistic laser pulses with solid targets. These fields were probed using low emittance, highly relativistic electron bunches from a laser wakefield accelerator, and a line integrated $B$ field of $2.70 \pm 0.39\\rm kT\\mu m$ was measured. Three dimensional, fully relativistic particle in cell simulations indicate that such fluctuations originate from a Weibel type current filamentation instability developing at submicron scales around the irradiated target surface, and that they grow to amplitudes strong enough to broaden the angular distribution of the probe electron bunch a few tens of femtoseconds after the laser pulse maximum. Our results highlight the potential of wakefield accelerated electron beams for ultrafast probing of relativistic laser driven phenomena.
author_names: Gaurav Raj

Olena Kononenko

M F Gilljohann

Antoine Doche

Xavier Davoine

Clement Caizergues

Y -Y Chang

J P Couperus Cabadag

Alexander Debus

H Ding

Michael Forster

J-P Goddet

Thomas Heinemann

Thomas Kluge

Thomas Kurz

Richard Pausch

Pascal Rousseau

P San Miguel Claveria

S Schobel

A Siciak

K Steiniger

Amar Tafzi

S Yu

B Hidding

Alberto Martinez de la Ossa

A Irman

S Karsch

A Dopp

Ulrich Schramm

Laurent Gremillet

Sebastien Corde
title: Probing ultrafast magnetic field generation by current filamentation instability in femtosecond relativistic laser matter interactions
year: 2020

abstract: Femtosecond pulse lasers provide novel possibilities to high precision optical profilometry for quality assurance of step structures on 3D microelectronic products based on its time and frequency domain characteristics.
author_names: Young-Jin Kim

Minah Choi

Jiyong Park

Sang-won Hyun

Woo-Deok Joo

Seung-Woo Kim
title: High precision 3 D surface measurement of step structures using femtosecond lasers
venue: 2015 11th Conference on Lasers and Electro Optics Pacific Rim (CLEO PR)
year: 2015

abstract: Fast, precise 3 D measurement of step structures fabricated on microelectronic products is essential for quality assurance of semiconductor, flat panel display and photovoltaic products. Optical interferometers have long been used, but not that wide spread for step structures due to their phase ambiguity or low spatial coherence. Femtosecond pulse lasers can provide novel possibilities to optical profilometry both in the time and the frequency domain. In the time domain, step surfaces can be measured over wide area by exploiting low temporal but high spatial coherence of femtosecond pulses; in the frequency domain, multi wavelength interferometry permits the absolute measurement over the discontinued surface profiles while maintaining the sub wavelength measurement precision.
author_names: Young-Jin Kim

Minah Choi

Keun-woo Lee

Heesuk Jang

Jiyong Park

Seung-Woo Kim
title: Precision 3D surface measurement of step structures using mode locked femtosecond pulses
venue: Other Conferences
year: 2015

abstract: Abstract This paper investigates the effects of femtosecond laser surface texturing on the interfacial bond strength of steel and a thermoplastic polymer PA 6 film. Ultimately the textures will be used for hybrids that are manufactured using a near infrared (NIR) laser assisted automated tape placement (ATP) process and carbon fibre PA 6 composites, therefore the NIR absorptance of the textured metal substrate is also of interest. To identify the influence of different surface structures on the bonding strength, lap shear samples were manufactured with laser textures varying in pulse length, hatch distance and ablated depth and tested by ASTM D 3165. The surface structures were analysed with white light interferometry (WLI) and scanning electron microscopy (SEM) Additional optical measurements in the infrared radiation range of 900 nm to 1100 nm were executed with a spectrophotometer to evaluate the laser absorptance for the NIR automated tape placement process. The lap shear strength increased to the highest value of 31.9 MPa with a tooth shaped laser texture using a 275 fs laser pulse width, a hatch distance of 600 mm an ablated depth of 40 mm. Also the absorptance for this sample increased by approximately 13% to 73% compared to the unprocessed pickled steel.
author_names: Victoria Zinnecker

Christopher Stokes-Griffin

Steve J Madden

Andrei V Rode

Paul P Compston
title: Investigation of the effects of femtosecond laser metal surface texturing on bonding of PA 6 to steel
year: 2019