WaferMasters Inc.

San Jose, CA, United States

WaferMasters Inc.

San Jose, CA, United States

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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. | Ueda T.,WaferMasters Inc. | Ishigaki T.,WaferMasters Inc. | Kang K.,WaferMasters Inc. | And 4 more authors.
Journal of the Electrochemical Society | Year: 2011

Ultra-shallow boron implanted (B+ 1 keV 1.0× 10 15 cm-2) n-type Si wafers were prepared and characterized by multi-wavelength Raman and photoluminescence (PL) spectroscopy before and after rapid thermal annealing (RTA). The Raman and PL characterization results were compared with sheet resistance from four point probe measurements and boron depth profiles from secondary ion mass spectroscopy. We have found a very strong correlation between the rapid, non-contact optical characterization results and important parameters of ultra-shallow junctions (USJs) obtained from conventional invasive techniques. Ultraviolet Raman was very sensitive to subsurface (∼5 nm) B profiles near or above the solid solubility (>1× 1020 cm-3) of B in Si. Visible wavelength excitation PL indicated the presence of significant levels of nonradiative recombination centers beyond the USJ depth and implant end-of-range damage even after RTA. Multi-wavelength Raman and PL are found to be very promising as complementary and/or alternative diagnostic metrology tools for implant process control and in-line device performance screening. © 2010 The Electrochemical Society.


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.,Wafer Masters Inc. | Kim B.G.,SK hynix | Jin S.W.,SK hynix | Ishigaki T.,Wafer Masters Inc. | Kang K.,Wafer Masters Inc.
ECS Journal of Solid State Science and Technology | Year: 2014

Multiwavelength room temperature photoluminescence (RTPL) and Raman spectroscopy were proposed as in-line monitoring techniques for characterizing the dielectric/Si interface. 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 and Raman spectroscopy. Specifically, overall quality of the ultra-thin SiO2/Si interface (including passivation characteristics) and Si lattice stress beneath SiO2 films are investigated. The overall SiO2/Si interface quality was seen to be very dependent on oxidation technique and process conditions. Within wafer and wafer-to-wafer variations of SiO2/Si interface quality were successfully characterized by RTPL and Raman spectra measurements. For electrical analysis of SiO2/Si-based structures, non-contact corona charge-based, in-line (capacitance-voltage (C-V) and stress induced leakage current (SILC)) measurements were performed and compared with RTPL and Raman characterization results. Surprisingly, significant variations in RTPL intensity at and near the corona charge-based measurement sites, indicated that the corona-based electrical measurement technique, though non-contact, was indeed invasive. The effect of corona-charge based electrical measurements on SiO2/Si interface was permanent and even clearly visible from the back side of the wafer. RTPL intensity variations at and near the measurement sites remained, even after a forming gas anneal. © 2014 The Electrochemical Society.


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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