WaferMasters Inc.

San Jose, CA, United States

WaferMasters Inc.

San Jose, CA, United States
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Kim J.H.,Korea Advanced Institute of Science and Technology | Kim J.H.,SK hynix | Yoo W.S.,WaferMasters Inc. | Han S.M.,Korea Advanced Institute of Science and Technology
Electronic Materials Letters | Year: 2017

Silicon near Cu through-silicon vias (TSVs) develops stresses during processing steps, and the local stress of Si around Cu TSVs of sizes ranging from 4 to 8 μm was characterized using micro-Raman spectroscopy as a function of processing steps. Micro-Raman measurements showed that the max stress sum, σr + σθ, is size dependent, where the stress sum of 88.7 MPa in the compressive direction was measured in Si for 8 μm sized Cu via, and this max stress sum, σr + σθ, decreased to 21 MPa in compression for 4 μm sized Cu via. With the deposition of oxide/nitride overlayers, the stress sum was found to switch sign to 138.9 MPa in the tensile direction for 8 μm sized Cu via after deposition of the SiN overlayers with residual compressive stress caused by ion bombardment. The measured stresses by micro-Raman was used to determine the keep-off-zone that can be used in device design to ensure reliability, and compared against the TCAD simulations results. [Figure not available: see fulltext.] © 2017, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.


Yoo W.S.,WaferMasters. Inc. | Ishigaki T.,WaferMasters. Inc. | Kang K.,WaferMasters. Inc.
ECS Transactions | Year: 2017

We have characterized 200-mm and 300-mm Si wafers with a single epitaxial layer and with a triple epitaxial layer stack atop using multi-wavelength, high-resolution Raman spectroscopy. 96-point wafer mapping measurements were performed on all wafers. Statistics of Raman signal intensity, shift and full-width-at-half-maximum (FWHM) values, under different excitation wavelengths, were extracted and compared with two types of reference Si wafers (prime Si wafers and reclaimed Si wafers). Significant variations in Raman signal intensity, shift and FWHM were measured between reference wafers and epitaxial wafers indicating potential Si lattice stress and crystallinity variations. Excitation wavelength dependence of Raman signal intensity, shift and FWHM also indicated variations in the Si lattice stress and the crystallinity of epitaxial layers in the depth direction. Non-contact multi-wavelength Raman spectroscopy was found to be very sensitive to the quality of epitaxial Si layers which makes this technique very effective in complimentary in-line process characterization and monitoring. © The Electrochemical Society.


Kwon W.S.,Institute of Microelectronics, Singapore | Alastair D.T.,Institute of Microelectronics, Singapore | Teo K.H.,Institute of Microelectronics, Singapore | Gao S.,Institute of Microelectronics, Singapore | And 4 more authors.
Applied Physics Letters | Year: 2011

Three-dimensional stress development was observed in silicon surrounding the Cu-filled through-silicon via (TSV) structures undergoing the thermal annealing process. We show here, using a multiwavelength micro-Raman spectroscopy system, that the behavior of stress development in silicon after annealing step is dependent on the initial stress state as well as the geometry and directionality of the TSV array. The warping of stress curve for postannealed state with a reference of preannealed state is distinctively observed. Furthermore, the introduction of stress-free point is also attributed to the destructive stress interaction from different geometry and direction and initial stress state. © 2011 American Institute of Physics.


Yoo W.S.,WaferMasters Inc. | Kim J.H.,Korea Advanced Institute of Science and Technology | Kim J.H.,SK hynix | Han S.M.,Korea Advanced Institute of Science and Technology
Journal of Micro/Nanolithography, MEMS, and MOEMS | Year: 2014

Characterization of silicon stress near copper (Cu)-filled through-silicon via(s) (TSVs) was demonstrated using high-resolution micro-Raman spectroscopy. For depth profiling of Si stress distribution near TSVs, a polychromator-based, multiwavelength excitation Raman measurement with different probing depths was used. The design concept of the polychromator-based, multiwavelength micro-Raman spectroscopy system, including the importance of the high-spectral resolution and multiwavelength excitation capability in three-dimensional (3-D) Si stress characterization, was described. Silicon stress near Cu-filled TSVs, with various sizes and layouts, was measured and analyzed before and after Cu annealing steps. Main factors impacting Si stress near Cu-filled TSVs are analyzed based on Raman characterization results on various types of TSV structures, layouts and Cu annealing conditions. Large variations in Si stress in TSV arrays were measured in wafers with poor Cu fill characteristics and in wafers annealed in nonoptimized conditions. The Cu annealing sequence and annealing conditions are found to be significantly important for managing Si stress and the reliability of Cu-filled TSVs. Substantially lower Si stress was measured near Cu-filled TSVs with voids. Multiwavelength micro-Raman spectroscopy can be used as a very effective noncontact, nondestructive, inline TSV process and Si stress monitoring technique. © The Authors.


Yoo W.S.,Wafe rMasters Inc. | Kim B.G.,SK hynix | Jin S.W.,SK hynix | Ishigaki T.,Wafe rMasters Inc. | Kang K.,Wafe rMasters Inc.
ECS Transactions | Year: 2014

Room temperature photoluminescence (RTPL) spectroscopy was proposed as an in-line monitoring technique for characterizing the dielectric/Si interface. Specifically, Si lattice stress beneath dielectric films and overall quality of the dielectric/Si interface (including passivation characteristics) are investigated. As an application example, ~7.0 nm thick ultra-thin SiO2 films on 300 mm Si wafers, prepared by various oxidation techniques and conditions, were characterized using multiwavelength RTPL spectroscopy. The overall SiO2/Si interface quality was seen to be very dependent on oxidation technique and process condition. Within wafer and wafer-to-wafer variations of SiO2/Si interface quality were successfully characterized by RTPL spectrum measurement and intensity wafer mapping under different excitation wavelengths. © 2014 by The Electrochemical Society. All rights reserved.


Vartanian V.,SEMATECH | Ueda T.,WaferMasters Inc. | Ishigaki T.,WaferMasters Inc. | Kang K.,WaferMasters Inc. | Yoo W.S.,WaferMasters Inc.
ECS Transactions | Year: 2011

Micro-Raman spectroscopy is a very attractive non-destructive in-line technique for characterizing stress/strain of the crystal, as well as crystallinity and Ge content in Si1-xGex. Additionally it requires no sample preparation, provides sub-micron spatial resolution, and requires relatively short measurement time. A polychromator-based, high resolution, multi-wavelength Raman spectroscopy system was evaluated from a manufacturing perspective as a candidate for in-line stress/strain monitoring equipment. Short-term and long-term measurement repeatability and system stability were extensively evaluated using five patterned Si 1-xGex/Si(100) wafers with nominal Ge content in the range of 15-35 at% (in 5 at% increments). Three major spectral lines (457.9, 488.0 and 514.5 nm) from a multi-wavelength Ar ion laser were used as the excitation source. The short-term and long-term measurement repeatability was evaluated for three months. A very small range of total variation, less than 0.05cm -1, was measured at all three excitation wavelengths. ©The Electrochemical Society.


Yoo W.S.,WaferMasters Inc. | Ueda T.,WaferMasters Inc. | Ishigaki T.,WaferMasters Inc. | Kang K.,WaferMasters Inc.
ECS Transactions | Year: 2010

A multi-wavelength, micro Raman spectroscopy system was designed and used for non-contact and non-destructive thickness and Ge content characterization of Si1-xGex/Si. The thickness and Ge content estimated by Raman measurements were compared to those values obtained from X-ray diffraction (XRD) and X-ray reflectance (XRR) measurements for cross-reference and showed very good agreement. The multi-wavelength excitation capability of the Raman system allows non-contact and non-destructive probing of Ge concentration as well as Si stress in Si1-xGex/Si along the depth direction. The Ge concentration gradient of small size test pads (as small as 10μm x 10μm) in depth direction were successfully measured using the multi-wavelength Raman system. The multi-wavelength Raman system with high spectral and spatial resolution is found to be very attractive and powerful for characterizing advanced semiconductor materials, such as Si1-xGex/Si and strained Si. It is also very useful for monitoring and controlling process equipment and process conditions. ©The Electrochemical Society.


Yoo W.S.,WaferMasters Inc. | Ueda T.,WaferMasters Inc. | Ishigaki T.,WaferMasters Inc. | Kang K.,WaferMasters Inc.
ECS Transactions | Year: 2010

A multi-wavelength, micro-Raman spectroscopy system was designed and used as a non-contact and non-destructive, in-line material and process monitoring tool. A large number of Si1-xGex/Si wafers with varied Ge and B content were prepared and characterized. Ge and B content in the Si 1-xGex/Si and Si1-xGex epitaxial layer were estimated from Raman measurements and were compared to those values obtained from secondary ion mass spectroscopy (SIMS), high resolution X-ray diffraction (HRXRD), X-ray reflectance (XRR) measurements for cross-reference. The estimated values were generally in good agreement with average values from other characterization techniques. Multi-wavelength Raman spectroscopy allows non-contact and non-destructive analysis, but with the added advantage of depth profiling capabilities. It is very effective in monitoring and controlling process equipment and process conditions in line. ©The Electrochemical Society.


Yoo W.S.,WaferMasters Inc. | Ueda T.,WaferMasters Inc. | Ishigaki T.,WaferMasters Inc. | Kang K.,WaferMasters Inc.
AIP Conference Proceedings | Year: 2010

Boron implanted (B 5 keV 3×1015cm-2) Si wafers before and after rapid thermal annealing (RTA) were characterized using multi-wavelength Raman spectroscopy and photoluminescence (PL) measurement techniques. Strong correlation among Raman, PL spectra and RTA conditions are observed. By selecting appropriate excitation wavelengths, approximate dopant profiles, crystallinity, dopant activation, and location and density of non-radiative recombination centers (originated by defects and damage) of B implanted wafers were successfully characterized by Raman and PL measurements without making contact. Multi-wavelength Raman and PL can provide advantages as inline process and material monitoring techniques in addition to conventional characterization techniques. © 2010 American Institute of Physics.


Yoo W.S.,WaferMasters Inc. | Kang K.,WaferMasters Inc.
ECS Journal of Solid State Science and Technology | Year: 2016

A surface heat-treatment method for semiconductor wafers using a xenon arc lamp is described. High absorption coefficients of silicon wafers in ultra violet (UV) region and short process time made selective surface heating possible. The surface melting of entire 150 mm diameter Si wafers was demonstrated in less than 2 s at a lamp power of 15 kW. By focusing UV light into a limited area on Si wafer surface, surface melting of a selectively exposed area was demonstrated at a much lower lamp power. The surface temperature ramp rate is estimated to be on the order of 1000°C/s. Si wafers, with various implanted species (P+, As+, B+ and BF2 +) and energies (1 keV-70 keV), were annealed for implant damage recovery and electrical activation using the Xe lamp under different scanning speeds. Sheet resistance and secondary ion mass spectroscopy (SIMS) depth profiling measurement results from the scanning rapid thermal annealing (RTA) successfully demonstrated the feasibility of the technique in semiconductor RTA processing applications. Electrical activation with desired levels of dopant diffusion can be achieved by optimizing process variables such as lamp power, distance between the lamp and Si wafer, area of light exposure and scanning speed. © The Author(s) 2015. All rights reserved.

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