L. Kwakman - Academia.edu (original) (raw)
Papers by L. Kwakman
AIP Conference Proceedings, 2001
In today's device fabrication the opaque metal film control is generally limited to full-... more In today's device fabrication the opaque metal film control is generally limited to full-sheet, single layer measurements on monitor wafers since the commonly used techniques require surfaces largely exceeding the typical device dimensions and cannot distinguish multiple layers in a stack. This indirect control method is apart from being expensive and time consuming- not adequate to ensure accurate process control
Microelectronic Engineering, 2002
In this communication, we used a modern analytical TEM–STEM fully equipped to carry out a complet... more In this communication, we used a modern analytical TEM–STEM fully equipped to carry out a complete physical and chemical study of Al/Ti/W/TiN interconnection evolution after 450°C annealing. Using energy filtered TEM, compositional mapping, scanning TEM (STEM) Z contrast imaging, EDX and EELS spectrum imaging and micro-diffraction, we evidence at the Al/W top contacts interface a reaction between Al and W
Metrology, Inspection, and Process Control for Microlithography XX, 2006
Full wafer dual beam FIB-SEM systems have received a lot of industrial interest in the last years... more Full wafer dual beam FIB-SEM systems have received a lot of industrial interest in the last years and by now are operational in several 200mm and 300mm fabs. These tools offer a 3D-physical characterization capability of defects and device structures and as such allow for more rapid yield learning and increased process control. Moreover, if SEM resolution is insufficient to
Solid State Phenomena, 1999
Solid State Phenomena, 2008
In integrated circuit manufacturing, surface cleanliness is mandatory to achieve high production ... more In integrated circuit manufacturing, surface cleanliness is mandatory to achieve high production volumes and device yield. Time-Of-Flight Mass Spectroscopy (ToF-SIMS) is an attractive technique for contamination control since it does provide information about both elemental and molecular species present on essentially any surface and offers high chemical sensitivity associated with sub-micrometer range spatial resolution and short acquisition time. The benefits of this technique to control surfaces after post copper chemical mechanical polishing (Cu-CMP) cleaning [1, 2] and after post via etch cleaning have already been reported. In this study, we have investigated ToF-SIMS spectra interpretation issues encountered when analyzing such surfaces: We will evidence whether Cu x O y H z peaks provides information on Cu oxidation and/or on surface cleanliness. We will try to interpret the presence of an intense CO 3 ion peak detected on some of the analyzed Cu surfaces. We will also illustrate the impact of airborne molecular contamination (AMC) on effective low detection limit for typical tracked compounds on Cu surfaces post cleaning (BTA, TA, carboxylic acids…) and as a consequence the importance of the delay before surface analysis / process steps. ToF-SIMS acquisitions are usually conducted in the so-called static mode meaning that the pulsed primary ion beam has damaged only a small amount of the surface at the end of the acquisition. However, when the to be analyzed area is limited in size (e.g. metrology boxes on product wafers), the primary ion dose density (PIDD) has to be increased for sufficient counting statistics. We will show that increasing the PIDD may degrade significantly the measurement reproducibility. To support this study we have followed an as-deposited PVD Cu surface over time with ToF-SIMS and Auger.
Surface Science, 1987
The charge state of Li, K and Cs ions scattered from cesium covered W(110) is measured as a funct... more The charge state of Li, K and Cs ions scattered from cesium covered W(110) is measured as a function of the surface work function. The particle energy ranges from 100 to 2000 eV. It is shown that the local electrostatic potential has a significant influence on the neutralization process. In the case of potassium and cesium scattering the neutralization is due to a collective effect of the adsorbed cesium ions. In the case of lithium scattering it is found that the adsorbed cesium ions act as independent neutralization centres. The corresponding neutralization cross section is of the order of 600a 2. * Present address: ASM Europe,
Applied Surface Science, 1989
The possibility of the chemical vapour deposition of tungsten for metallisation for microelectron... more The possibility of the chemical vapour deposition of tungsten for metallisation for microelectronic applications has been considered and investigated for about twenty years, but the process still remains problematical and has serious limitations. Many of the difficulties arise from a lack of a good understanding of the chemistry of the processes and on the effect of that chemistry on layer properties and characteristics. In particular, the very limited information about the thermodynamics and kinetics of the processes allows little more than an empirical approach to the control of reaction parameters or reactor design. In this paper we review the two predominant reactions of silicon and hydrogen reduction of tungsten hexafluoride and we make some observations and comments on the thermodynamics and kinetics of the two reactions. We also review the chemistry of selective deposition of tungsten. However, in order to fully exploit the chemistry of the deposition processes it is pointed out that for both basic studies and applications it is necessary to make use of high vacuum technology in order to minimise the effect of atmospheric impurities, particularly water, and reaction by-products.
2011 IEEE International Interconnect Technology Conference, 2011
3D integration comes with the introduction of many new processes and materials that may affect be... more 3D integration comes with the introduction of many new processes and materials that may affect behavior and reliability of the overall system. For reliability testing of 3D integration technologies a 3-level test chip has been designed that includes Through Silicon Vias (TSV's) and assembly layers and that allows evaluation of yield and electrical parameters under steady state (DC) and RF signal conditions. Additionally, this (stacked) chip delivers reliability values when used within the standardized procedures defined by JDEC.
In an industrial environment, new techniques based on the surface photovoltage measurement (SCA a... more In an industrial environment, new techniques based on the surface photovoltage measurement (SCA and SPV), are shown to detect sodium, aluminum, iron contamination in the range of E + 10/cm2. Variations in the measurements due to wafer samples or oxidation recipe are determined. From these results, a procedure for preparing monitoring samples is established. It is demonstrated that these monitoring
Process, Equipment, and Materials Control in Integrated Circuit Manufacturing, 1995
Thin Solid Films, 2004
Accurate and reliable in-line monitoring of the different films thickness that occur throughout t... more Accurate and reliable in-line monitoring of the different films thickness that occur throughout the integrated circuit manufacturing process is mandatory to develop and produce advanced microelectronic devices. X-ray reflectivity (XRR) is a fundamental and suitable metrology technique to precisely determine the thickness of both transparent and metallic thin films. Furthermore, XRR is very sensitive to surface and interface roughness, and also provides information about the film density. X-ray fluorescence (XRF) is currently used as a metrology technique to control the thickness and the elemental composition of relatively thick films. The performance of a new in-line metrology tool, which gathers XRR and XRF data to monitor film thickness, has been assessed. Results on the monitoring of high k thin films, low k materials, copper barrier and copper seed layers are presented. ᮊ
Surface and Interface Analysis, 2008
Recent time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies using primary cluster io... more Recent time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies using primary cluster ion sources such as Au n + , SF n + , Bi n + or C 60 + have shown polyatomic ions to be more appropriate for the detection of high mass molecular secondary ions than monoatomic ion sources like Ga + , thanks to secondary ion yield and ion formation efficiency enhancements.
AIP Conference …, 2005
ABSTRACT An overview of our main Time-Of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) applic... more ABSTRACT An overview of our main Time-Of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) applications is first given that highlights the strengths but also reveals some development needs for this technique especially where it comes to contaminants quantification. In this work, as a step towards better quantified data, we have elaborated a method to quantify Airborne Molecular Contamination (AMC) on Silicon. For this a protocol using liquid nitrogen sample cooling was set up to reduce the desorption of the most volatile species under the Ultra High Vacuum (UHV) of the ToF-SIMS analysis chamber and thus to enable a more stable, reliable and representative measurement. Using this protocol for the ToF-SIMS analysis and a careful analytical sequence, good correlation between Wafer Thermal Desorption Gas Chromatography Mass Spectroscopy (W-TDGCMS) and ToF-SIMS results on wafers exposed for varying time under the clean-room air flow containing 2,2,4-trimethyl 1,3-pentanediol diisobutyrate (TXIB) and Phthalates - two main organic clean-room contaminants - is obtained. Relative Sensitivity Factors (RSF) are deduced. With the used measurement setups, the ToF-SIMS low detection limits (DL) lie around 1E11 - 1E12 atoms Carbon/cm2 (atC/cm2) depending on species and are comparable to that of W-TDGCMS at 1E11 atC/cm2.
Microscopy and Microanalysis, 2004
Micron, 2003
This paper presents a new technique using energy filtered TEM (EFTEM) for inelastic electron scat... more This paper presents a new technique using energy filtered TEM (EFTEM) for inelastic electron scattering contrast imaging of Germanium distribution in Si -SiGe nanostructures. Comparing electron energy loss spectra (EELS) obtained in both SiGe and Si single crystals, we found a spectrum area strongly sensitive to the presence of Ge in the range [50 -100 eV]. In this energy loss window, EELS spectrum shows a smooth steeply shaped background strongly depending on Ge concentration. Germanium mapping inside SiGe can thus be performed through imaging of the EELS background slope variation, obtained by processing the ratio of two energy filtered TEM images, respectively, acquired at 90 and 60 eV. This technique gives contrasted images strongly similar to those obtained using STEM Z-contrast, but presenting some advantages: elastic interaction (diffraction) is eliminated, and contrast is insensitive to polycrystalline grains orientation or specimen thickness. Moreover, since the extracted signal is a spectral signature (inelastic energy loss) we demonstrate that it can be used for observation and quantification of Ge concentration depth profile of SiGe buried layers. q
Applied Surface Science, 2006
X-ray reflectivity (XRR), X-ray fluorescence (XRF) and small angle X-ray scattering (SAXS) techni... more X-ray reflectivity (XRR), X-ray fluorescence (XRF) and small angle X-ray scattering (SAXS) techniques are used to the monitoring of Cu/porous low κ processes, which are developed for the next generation (≤65nm) integrated circuits. Sensitivity of XRR and XRF is sufficient to detect drifts of the copper barrier layer, copper seed layer and Cu CMP (chemical–mechanical polishing) processes. Their metrology key parameters comply with production requirements. SAXS allows determining the pore structure of low κ films: average pore size and pore size distribution.
Applied Surface Science, 2008
The user has requested enhancement of the downloaded file. This article appeared in a journal pub... more The user has requested enhancement of the downloaded file. This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Applied Surface Science, 2006
An epitaxial Si grown multi-layer stack consisting of boron delta-doped layers separated by 6.4 n... more An epitaxial Si grown multi-layer stack consisting of boron delta-doped layers separated by 6.4 nm thick undoped films has been profiled using a Cameca IMS Wf magnetic SIMS. Using low energy oblique O 2 + beam, the boron depth resolution is improved from 1.66 nm/decade at 500 eV down to 0.83 nm/decade at 150 eV. At very low impact energy O 2 + bombardment induces a near full oxidation of silicon and oxygen flooding is then no more needed in the analytical chamber to get a smooth sputtering of silicon at 458 incidence angle. #
AIP Conference Proceedings, 2001
In today's device fabrication the opaque metal film control is generally limited to full-... more In today's device fabrication the opaque metal film control is generally limited to full-sheet, single layer measurements on monitor wafers since the commonly used techniques require surfaces largely exceeding the typical device dimensions and cannot distinguish multiple layers in a stack. This indirect control method is apart from being expensive and time consuming- not adequate to ensure accurate process control
Microelectronic Engineering, 2002
In this communication, we used a modern analytical TEM–STEM fully equipped to carry out a complet... more In this communication, we used a modern analytical TEM–STEM fully equipped to carry out a complete physical and chemical study of Al/Ti/W/TiN interconnection evolution after 450°C annealing. Using energy filtered TEM, compositional mapping, scanning TEM (STEM) Z contrast imaging, EDX and EELS spectrum imaging and micro-diffraction, we evidence at the Al/W top contacts interface a reaction between Al and W
Metrology, Inspection, and Process Control for Microlithography XX, 2006
Full wafer dual beam FIB-SEM systems have received a lot of industrial interest in the last years... more Full wafer dual beam FIB-SEM systems have received a lot of industrial interest in the last years and by now are operational in several 200mm and 300mm fabs. These tools offer a 3D-physical characterization capability of defects and device structures and as such allow for more rapid yield learning and increased process control. Moreover, if SEM resolution is insufficient to
Solid State Phenomena, 1999
Solid State Phenomena, 2008
In integrated circuit manufacturing, surface cleanliness is mandatory to achieve high production ... more In integrated circuit manufacturing, surface cleanliness is mandatory to achieve high production volumes and device yield. Time-Of-Flight Mass Spectroscopy (ToF-SIMS) is an attractive technique for contamination control since it does provide information about both elemental and molecular species present on essentially any surface and offers high chemical sensitivity associated with sub-micrometer range spatial resolution and short acquisition time. The benefits of this technique to control surfaces after post copper chemical mechanical polishing (Cu-CMP) cleaning [1, 2] and after post via etch cleaning have already been reported. In this study, we have investigated ToF-SIMS spectra interpretation issues encountered when analyzing such surfaces: We will evidence whether Cu x O y H z peaks provides information on Cu oxidation and/or on surface cleanliness. We will try to interpret the presence of an intense CO 3 ion peak detected on some of the analyzed Cu surfaces. We will also illustrate the impact of airborne molecular contamination (AMC) on effective low detection limit for typical tracked compounds on Cu surfaces post cleaning (BTA, TA, carboxylic acids…) and as a consequence the importance of the delay before surface analysis / process steps. ToF-SIMS acquisitions are usually conducted in the so-called static mode meaning that the pulsed primary ion beam has damaged only a small amount of the surface at the end of the acquisition. However, when the to be analyzed area is limited in size (e.g. metrology boxes on product wafers), the primary ion dose density (PIDD) has to be increased for sufficient counting statistics. We will show that increasing the PIDD may degrade significantly the measurement reproducibility. To support this study we have followed an as-deposited PVD Cu surface over time with ToF-SIMS and Auger.
Surface Science, 1987
The charge state of Li, K and Cs ions scattered from cesium covered W(110) is measured as a funct... more The charge state of Li, K and Cs ions scattered from cesium covered W(110) is measured as a function of the surface work function. The particle energy ranges from 100 to 2000 eV. It is shown that the local electrostatic potential has a significant influence on the neutralization process. In the case of potassium and cesium scattering the neutralization is due to a collective effect of the adsorbed cesium ions. In the case of lithium scattering it is found that the adsorbed cesium ions act as independent neutralization centres. The corresponding neutralization cross section is of the order of 600a 2. * Present address: ASM Europe,
Applied Surface Science, 1989
The possibility of the chemical vapour deposition of tungsten for metallisation for microelectron... more The possibility of the chemical vapour deposition of tungsten for metallisation for microelectronic applications has been considered and investigated for about twenty years, but the process still remains problematical and has serious limitations. Many of the difficulties arise from a lack of a good understanding of the chemistry of the processes and on the effect of that chemistry on layer properties and characteristics. In particular, the very limited information about the thermodynamics and kinetics of the processes allows little more than an empirical approach to the control of reaction parameters or reactor design. In this paper we review the two predominant reactions of silicon and hydrogen reduction of tungsten hexafluoride and we make some observations and comments on the thermodynamics and kinetics of the two reactions. We also review the chemistry of selective deposition of tungsten. However, in order to fully exploit the chemistry of the deposition processes it is pointed out that for both basic studies and applications it is necessary to make use of high vacuum technology in order to minimise the effect of atmospheric impurities, particularly water, and reaction by-products.
2011 IEEE International Interconnect Technology Conference, 2011
3D integration comes with the introduction of many new processes and materials that may affect be... more 3D integration comes with the introduction of many new processes and materials that may affect behavior and reliability of the overall system. For reliability testing of 3D integration technologies a 3-level test chip has been designed that includes Through Silicon Vias (TSV's) and assembly layers and that allows evaluation of yield and electrical parameters under steady state (DC) and RF signal conditions. Additionally, this (stacked) chip delivers reliability values when used within the standardized procedures defined by JDEC.
In an industrial environment, new techniques based on the surface photovoltage measurement (SCA a... more In an industrial environment, new techniques based on the surface photovoltage measurement (SCA and SPV), are shown to detect sodium, aluminum, iron contamination in the range of E + 10/cm2. Variations in the measurements due to wafer samples or oxidation recipe are determined. From these results, a procedure for preparing monitoring samples is established. It is demonstrated that these monitoring
Process, Equipment, and Materials Control in Integrated Circuit Manufacturing, 1995
Thin Solid Films, 2004
Accurate and reliable in-line monitoring of the different films thickness that occur throughout t... more Accurate and reliable in-line monitoring of the different films thickness that occur throughout the integrated circuit manufacturing process is mandatory to develop and produce advanced microelectronic devices. X-ray reflectivity (XRR) is a fundamental and suitable metrology technique to precisely determine the thickness of both transparent and metallic thin films. Furthermore, XRR is very sensitive to surface and interface roughness, and also provides information about the film density. X-ray fluorescence (XRF) is currently used as a metrology technique to control the thickness and the elemental composition of relatively thick films. The performance of a new in-line metrology tool, which gathers XRR and XRF data to monitor film thickness, has been assessed. Results on the monitoring of high k thin films, low k materials, copper barrier and copper seed layers are presented. ᮊ
Surface and Interface Analysis, 2008
Recent time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies using primary cluster io... more Recent time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies using primary cluster ion sources such as Au n + , SF n + , Bi n + or C 60 + have shown polyatomic ions to be more appropriate for the detection of high mass molecular secondary ions than monoatomic ion sources like Ga + , thanks to secondary ion yield and ion formation efficiency enhancements.
AIP Conference …, 2005
ABSTRACT An overview of our main Time-Of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) applic... more ABSTRACT An overview of our main Time-Of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) applications is first given that highlights the strengths but also reveals some development needs for this technique especially where it comes to contaminants quantification. In this work, as a step towards better quantified data, we have elaborated a method to quantify Airborne Molecular Contamination (AMC) on Silicon. For this a protocol using liquid nitrogen sample cooling was set up to reduce the desorption of the most volatile species under the Ultra High Vacuum (UHV) of the ToF-SIMS analysis chamber and thus to enable a more stable, reliable and representative measurement. Using this protocol for the ToF-SIMS analysis and a careful analytical sequence, good correlation between Wafer Thermal Desorption Gas Chromatography Mass Spectroscopy (W-TDGCMS) and ToF-SIMS results on wafers exposed for varying time under the clean-room air flow containing 2,2,4-trimethyl 1,3-pentanediol diisobutyrate (TXIB) and Phthalates - two main organic clean-room contaminants - is obtained. Relative Sensitivity Factors (RSF) are deduced. With the used measurement setups, the ToF-SIMS low detection limits (DL) lie around 1E11 - 1E12 atoms Carbon/cm2 (atC/cm2) depending on species and are comparable to that of W-TDGCMS at 1E11 atC/cm2.
Microscopy and Microanalysis, 2004
Micron, 2003
This paper presents a new technique using energy filtered TEM (EFTEM) for inelastic electron scat... more This paper presents a new technique using energy filtered TEM (EFTEM) for inelastic electron scattering contrast imaging of Germanium distribution in Si -SiGe nanostructures. Comparing electron energy loss spectra (EELS) obtained in both SiGe and Si single crystals, we found a spectrum area strongly sensitive to the presence of Ge in the range [50 -100 eV]. In this energy loss window, EELS spectrum shows a smooth steeply shaped background strongly depending on Ge concentration. Germanium mapping inside SiGe can thus be performed through imaging of the EELS background slope variation, obtained by processing the ratio of two energy filtered TEM images, respectively, acquired at 90 and 60 eV. This technique gives contrasted images strongly similar to those obtained using STEM Z-contrast, but presenting some advantages: elastic interaction (diffraction) is eliminated, and contrast is insensitive to polycrystalline grains orientation or specimen thickness. Moreover, since the extracted signal is a spectral signature (inelastic energy loss) we demonstrate that it can be used for observation and quantification of Ge concentration depth profile of SiGe buried layers. q
Applied Surface Science, 2006
X-ray reflectivity (XRR), X-ray fluorescence (XRF) and small angle X-ray scattering (SAXS) techni... more X-ray reflectivity (XRR), X-ray fluorescence (XRF) and small angle X-ray scattering (SAXS) techniques are used to the monitoring of Cu/porous low κ processes, which are developed for the next generation (≤65nm) integrated circuits. Sensitivity of XRR and XRF is sufficient to detect drifts of the copper barrier layer, copper seed layer and Cu CMP (chemical–mechanical polishing) processes. Their metrology key parameters comply with production requirements. SAXS allows determining the pore structure of low κ films: average pore size and pore size distribution.
Applied Surface Science, 2008
The user has requested enhancement of the downloaded file. This article appeared in a journal pub... more The user has requested enhancement of the downloaded file. This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Applied Surface Science, 2006
An epitaxial Si grown multi-layer stack consisting of boron delta-doped layers separated by 6.4 n... more An epitaxial Si grown multi-layer stack consisting of boron delta-doped layers separated by 6.4 nm thick undoped films has been profiled using a Cameca IMS Wf magnetic SIMS. Using low energy oblique O 2 + beam, the boron depth resolution is improved from 1.66 nm/decade at 500 eV down to 0.83 nm/decade at 150 eV. At very low impact energy O 2 + bombardment induces a near full oxidation of silicon and oxygen flooding is then no more needed in the analytical chamber to get a smooth sputtering of silicon at 458 incidence angle. #