arXiv subjects

Uwe Scheithauer

Publications and source records attributed to Uwe Scheithauer.

13 recordsLinked to original sources

arXiv2022

AES Analysis of Al Bond Pads in Electrically Insulating Surroundings Utilizing Metal Grid Contacting

Bond pads are the electrical interconnections of a microelectronic device to the outside world. A polyimide layer (PI) on top of a microelectronic device protects the whole device against environmental impacts. The bond pads are accessible though openings in this electrically insulating layer. The oxide layer thickness and contaminations at the Al bond pad surface influence as well the quality of the mechanical and electrical joint between bond pad and bond wire as the durability of this interconnection. If a bond pad surface has to be analyzed with high spatial resolution Auger electron spectroscopy (AES) is the method of choice. AES utilizes an electron beam for excitation, which induces serious sample charging because of the PI layer. Sample charging can be avoided by metal grids, which are common in transmission electron microscopy (TEM) sample preparation. A TEM grid is pressed onto the sample while the bond pad of interest is centered in the square openings of the grid. Exemplarily analyses of bond pads demonstrate the applicability of this approach for AES measurements.

physics.ins-det↗

arXiv2021

Depth resolution optimized sputter depth profiling of a polycrystalline Al layer

Depth profiling of thin films by inert gas sputtering is one of the most important applications of Auger electron spectroscopy and X-ray photoelectron spectroscopy. Such an analysis monitors the elemental in-depth composition of the thin film system and controls the quality of the manufacturing process. A challenging task of a sputter depth profile measurement is the determination of the interface contaminations. Interface contaminations are only detectable if the depth profile data were measured with a sufficient depth resolution. Interface contaminations are crucial, because they strongly influence the mechanical and electrical properties of the whole thin film system. The depth resolution of unidirectional sputter depth profiling for polycrystalline samples is limited by the sputter yield differences attributed to grains having different crystalline orientations relative to the incoming ion beam. Therefore depth resolution optimized sputter depth profiling of polycrystalline thin films requires dedicated experimental approaches. If the sample is rotated during ion sputtering the depth profile is recorded with a better depth resolution because the ion impact direction relative to the grains orientation varies. If depth profiling can be performed on a single grain only, the depth resolution is improved, too. These approaches are applied to the depth profiling and interface contamination analysis of a 5000 nm thick polycrystalline Al layer. An O contamination at the interface of the Al to the Si substrate was detected utilizing these high depth resolution depth profiling methods.

cond-mat.mtrl-sci↗

arXiv2020

Experimental setups for XPS measurements beyond the instrumental lateral resolution limit

The lateral resolution of an X-ray photoelectron spectroscopy instrument, which is equipped with a focused X-ray beam, is limited by the nominal X-ray beam diameter and the long tail intensity distri-bution of the X-ray beam. The long tail intensity distribution of the X-ray beam impedes to perform a measurement with good lateral resolution and low detection limits at the same time. Two experimental setups are described which allow examining sample structures that are smaller than the X-ray beam dimensions. The first method uses differential sample charging on partly non-conductive samples by low energy electron flooding. The spectra of the non-conductive sample areas are shifted towards lower binding energy. That way, the surface compositions of conductive and non-conductive sample areas are estimated independently. The second method utilizes the rather limited dimensions of the energy analyser acceptance volume. Here only the sample is placed inside the energy analyser acceptance volume. That way, signals from the illuminated sample contribute exclusively to the measured photoelectrons intensity, independent form the sample size.

physics.ins-det↗

arXiv2017

The Benefit of Wide Energy Range Spectrum Acquisition During Sputter Depth Profile Measurements

Thin film systems are often analysed by using sputter depth profiling. First the sample gets eroded by inert gas ion impact during sputter depth profiling. Then the elemental composition of the freshly unveiled surface is determined by using a surface sensitive analytical method as AES or XPS, for instance. This way the depth distributions of the elements are recorded as a function of sputter time. The time to record the spectral data in a certain sputter depth is kept as short as possible to avoid recontamination of the freshly sputtered surface by adsorption of gas particles from the vacuum during the measurement. Therefore in every sputter depth only those spectral regions are recorded, which belong to the elements expected to be in the sample. But in case the sample composition is entirely unknown, it is indispensable to measure wide energy range spectra. By this approach the depth distributions of all elements are estimated, which are detectable by the used analytical method. The measurement of wide energy range spectra during sputter depth profile acquisition is promising for samples, which are very insulating. If the surface potential varies in different sputter depths, the elemental peaks are shifted in an unpredictable way. If wide energy range spectra are recorded, the energy scale can be re-adjusted afterwards and the data can be re-evaluated. Both use cases are demonstrated exemplarily by sputter depth profile measurements.

physics.ins-det↗

arXiv2017

Analysis of a Sputtered Si Surface for Ar Sputter Gas Supply Purity Monitoring

For sputter depth profiling often sample erosion by Ar+ ions is used. Only a high purity of the sputter gas and a low contamination level of the ion gun avoids misleading depth profile measurements results. Here a new measurement procedure is presented, which monitors these parameters. A Si sample is sputtered inside the instrument and then the surface concentration of the elements Ar, C, N and O is measured. Results of such measurements of an XPS microprobe PHI Quantum 2000, which were recorded over a period of 10 years, are presented.

physics.ins-det↗

arXiv2017

Vacuum Quality Monitoring of Analytical Sputter Depth Profile Equipment by Recontamination Measurements of a Sputtered Ti Surface

Often a surface sensitive analytical technique in combination with sample erosion by inert ion sputtering is used for compositional in-depth analysis of solid state samples. Layer by layer the sample gets eroded and then the composition of the actual surface is estimated. The elemental detection limits can be increased by spending more time for the measurement in each sputter depth of the profile measurement. But during this time a significant sample surface recontamination with the element under investigation via adsorption form the vacuum has to be avoided. Commonly the vacuum quality of an analytical instrument is monitored using the base pressure of the UHV system. This article presents a novel method, which improves this crude approach. The recontamination of a sputtered Ti surface by adsorbed residual gas particles was used to monitor the sputter depth profile specific vacuum condition of an XPS microprobe Quantum 2000 over a 4 years period. This new method is suitable to monitor the condition of every sputter depth profiling instrument.

physics.ins-det↗

arXiv2015

In-Situ Low-Angle Cross Sectioning: Bevel Slope Flattening due to Self-Alignment Effects

Low-angle cross sections are produced inside an Auger microprobe using the equipped depth profile ion sputter gun. Simply the sample is partly covered by a mask. Utilizing the edge of this mask the sample is sputtered with ions. Due to the shading of the mask a cross section is produced in the sample. The slope of this cross section is considerably shallower than given by the geometrical setup. This is attributed to self-alignment effects, which are due to missing sputter cascades in the transition area between sputtered and shaded sample regions and a chamfering of the mask edge. These self-alignment effects are studied here using a 104.6 nm thick SiO2 layer thermally grown on a Si substrate. In this study on one hand for a fixed ion impact angle of 15.8{\deg} as function of the sputter time several in-situ low-angle cross sections were produced. This way slope angles between an ultimate low slope angle of 0.014{\deg} and 0.085{\deg} were achieved. On the other hand for a fixed sputter time the ion impact angle was varied between 14.8{\deg}and 70.8{\deg}. For these samples cross section slope angles between 0.031{\deg}and 0.32{\deg}are observed. These results demonstrate the distinct slope flatting of in-situ cross sectioning.

cond-mat.mtrl-sci↗

arXiv2015

Long Time Stability of the Energy Scale Calibration of a Quantum 2000

According to the international standard ISO 15472 the energy scale of an XPS instrument, type Physical Electronics Quantum 2000, was calibrated. It is shown, how the procedures of the ISO 15472 were adapted to the hardware and software design of the Quantum 2000. The long time stability of the energy scale calibration of the XPS instrument was investigated. The instrumented was operated with a satisfying energy scale calibration over a period of 8 years. All the time energy differences between certain peaks could be measured with the chosen precision of the energy scale calibration.

physics.ins-det↗

arXiv2015

Reducing the Aspect Ratio of Contact Holes by In-Situ Low-Angle Cross Sectioning

Auger analysis of high-aspect ratio contact holes of integrated microelectronic devices is a challenging analytical task. Due to geometrical shadowing the primary electron beam and the energy analyser have not the required direct line of sight to the analysis area simultaneously. To solve this problem sample preparation is needed to flatten the 3-dimensional geometry. Here the new approach of in-situ low-angle cross sectioning is applied. By this method material gets removed inside the Auger instrument while the sample is sputtered by Ar+ ions at nearly grazing incidence utilizing the edge of a mask, which partly covers the sample. A very shallow bevel with respect to the sample surface is produced. Thus along the bevel contact holes with suitable aspect ratios are available for the Auger analysis.

cond-mat.mtrl-sci↗

arXiv2015

Improved Sputter Depth Resolution in Auger Thin Film Analysis Using In Situ Low Angle Cross-Sections

A none conventional approach for depth profiling of thin film systems with enhanced depth resolution has been developed using standard Auger microprobe instruments. For the preparation of an in situ low angle cross-section, the sample is partly covered by an appropriate mask. Utilising the edge of this mask, the sample is sputtered in the Auger microprobe with ions at nearly grazing incidence. In the shadow of the mask, this produces a low angle cross section through the thin film system. Then, a conventional depth profile is measured at the point of interest where part of the thin film system is covered only by a thin top layer. As demonstrated a considerable improvement of depth resolution delta z / z can be obtained by this method.

cond-mat.mtrl-sci↗

arXiv2015

Examples for the improvements in AES Depth Profiling of Multilayer Thin Film Systems by Application of Factor Analysis Data Evaluation

Factor Analysis has proved to be a powerful tool for the full exploitation of the chemical information included in the peak shapes and peak positions of spectra measured by AES depth profiling. Due to its ability to extract the number of independent chemical components, their spectra and their depth distributions, its information content exceeds the one of the usual peak-to-peak height evaluation of AES depth profile data. Using modern software with a graphically interactive user interface the analyst is put into a position, where he can work with Factor Analysis on a physically intuitive level despite of all the matrix algebra mathematics which it is based upon. The progress brought about by Factor Analysis to AES depth profiles of thin films is demonstrated by the analysis of two thin film systems. The first one is a Pt/Ti metallisation used as bottom electrode for ferroelectric thin films, the second one is multilayer system where a Ti silicide formation of burried Ti/Si bilayers has been induced. Both examples show that Factor Analysis evaluation of AES depth profile data is capable to give access to stoichiometry information and to reveal interfacial layer phases, information which is hardly obtained from the conventional peak-to-peak height data evaluation.

cond-mat.mtrl-sci↗

arXiv2015

Application of the analytical methods REM/EDX, AES and SNMS to a chlorine induced aluminium corrosion

Scanning electron microscopy - SEM - with energy dispersive X-ray detection - EDX -, Auger electron spectroscopy - AES - and sputtered neutral mass spectrometry - SNMS - have been used to characterize a chlorine induced corrosion of an aluminium metallisation. SEM/EDX detects the characteristic X-rays that are emitted from the first few micrometers beneath the specimens surface after inner shell ionisation by the primary electrons. AES detects the alternatively ejected Auger electrons that are generated within the topmost atomic layers of the sample. To obtain elemental concentration depth profiles, the surface layers are removed by ion sputtering. Whereas AES detects the composition of the remaining surface, SNMS measures sputtered fluxes and does not suffer from preferential sputtering. As demonstrated by the example of a chlorine induced aluminium corrosion, these analytical methods are complementary with respect to quantification, chemical information and information depth. Only by simultaneous use measuring artefacts are detectable and able to be excluded from interpretation.

cond-mat.mtrl-sci↗

arXiv2013

Sputter-Induced Cross-Contaminations in Analytical AES and XPS Instrumentation: Utilization of the effect for the In-situ Deposition of Ultrathin Functional Layers

Cross contaminations are observed on sample surfaces by AES and XPS, if multiple samples are mounted on one sample holder and a neighbouring sample was sputter depth profiled. During sputter depth profiling sputtered material is deposited on inner surfaces of the instrument. In a secondary sputter process, which is due to species leaving the primary sputter target with higher kinetic energy, the previously deposited material is transported from the inner surfaces to the other samples mounted on the sample holder. This Reflective Sputtering is utilized to deposit ultra-thin layers on sample surfaces for XPS binding energy referencing purpose and to build up ultra-thin conductive layers to enable AES measurements on insulating samples.

cond-mat.mtrl-sci↗