Surface Analysis

Surface Analysis Techniques

Auger Electron Spectroscopy

Physical Electronics PHI 660

  • Elemental mapping with high spatial resolution and is capable of performing scanning electron microscopy (SEM)
  • Coaxial LaB6 Filament Electron Gun, ~100 nm Min. Spot Size for Auger Analysis, 0.5-20 KeV
  • Single Pass Cylindical Mirror Analyzer
  • Single Channel Electron Multiplier
  • Differentially Pumped 1-5 KeV Ar Ion Gun with Automatic Leak Valve
  • Attached UHV Chamber for Sample Fracture or Heating

Staff Contact

Rick Haasch
(217) 244-2967

Location

B06 Materials Research Laboratory
(217) 244-2963

Background

Auger electron spectroscopy (AES) is a surface sensitive analytical technique used mainly to determine elemental compositions of materials and, in certain cases to identify the chemical states of surface atoms. With AES, a primary electron beam is used to excite secondary and Auger electrons. If a scanning primary beam is used, the secondary electron images yield information related to surface topography. Auger electrons, when analyzed as a function of energy, are used to identify the elements and chemical states present. The information depth for Auger analysis is the top 2-20 atomic layers, and can be used in depth profiling applications in conjunction with ion beam sputtering.

Instrumentation

The Physical Electronics model PHI 660 Scanning Auger Microprobe (SAM) has elemental mapping with high spatial resolution and is capable of performing scanning electron microscopy (SEM). The instrument is equipped with an in situ impact fracture stage for analysis of grain boundaries and other internal surfaces. Auger point analysis and scanning analysis can be performed with a spatial resolution down to 250 nm, while SEM resolution is around 100 nm. The Auger has a sputter ion gun for depth profiling analysis

Applications

This instrument is primarily used when high spatial resolution surface analysis is required, for example, failure analysis of integrated circuits, elemental mapping of fine particles, thin-film depth profiling, and studies of corrosion and oxidation scales and of fiber composites. Also of particular importance is the ability to perform in-vacuo fracture so that uncontaminated boundary surfaces can be analyzed.

Secondardy Ion Mass Spectrometry

Cameca ims 5f

  • In secondary ion mass spectrometry (SIMS) a focused ion beam is directed to a solid surface, removing material in the form of neutral and ionized atoms and molecules. Generated secondary ions and molecules accelerate into a mass spectrometer and separate according to their mass-to-charge ratio.
  • The primary strengths of SIMS are surface/near surface analysis with low detection limits, isotopic analysis, imaging, and rapid depth profiling. Sensitivity to hydrogen, lithium, and elemental isotopes can be exploited to determine diffusion rates and mechanisms in conductive samples. Semiconductor applications include the study of the redistribution of a dopant species and depth profiling modulated structures such as quantum well devices.
  • The Cameca ims 5f SIMS is a member of the class of instruments known as magnetic sector SIMS, which uses a combination of electrostatic and magnetic deflection of the secondary beam to select ions of a specific mass-to-charge ratio.  The mass range is from 1 to 280 amu.
  • The Cameca ims 5f SIMS can use either Cs+ or O2+ as the primary ion beam.  This choice will lead to signal enhancement of electronegative or electropositive ions, respectively.  Sensitivity is in the parts per billion for many elements and mass resolution up to 20,000 is attainable to distinguish elements and molecules with the same nominal mass.
  • Normal measurments of the Cameca ims 5f are depth profiles of one or several secondary ions.  Depth resolution during profiling is 3-15 nm.

Physical Electronics PHI Trift III

  • In secondary ion mass spectrometry (SIMS) a focused ion beam is directed to a solid surface, removing material in the form of neutral and ionized atoms and molecules. Generated secondary ions and molecules accelerate into a mass spectrometer and separate according to their mass-to-charge ratio.
  • The PHI TRIFT III is a Time of Flight SIMS, which uses a pulsed primary beam to generate secondary ions which are mass separated by the amount of time it takes for the secondary ion to reach the detector.  This produces a full mass spectrum from each primary pulse.
  • The primary strengths of TOF-SIMS are surface/near surface analysis with low detection limits, isotopic analysis, imaging, and rapid depth profiling. Sensitivity to hydrogen, lithium, and elemental isotopes allow for measurements on metal, semiconductor, polymer, and biological samples.
  • The TRIFT III at MRL uses a liquid metal ion source for the analysis ion beam. This gold source can produce Au+, Au2+, and Au3+ ions.
  • The TRIFT III normally operates in static mode, which allows for the analysis of both elemental and molecular species at the sample surface. Molecules of up to 1,000 amu have been analyzed by the SIMS.
  • A low energy (2-3 kV) dual ion source (Cs+ and O2+) can be used for material removal during elemental depth profiling work.
  • The PHI TRIFT III produces ion images from 25 to 400 microns with ion beam rastering and up to several mm with mosaic stage rastering.  Lateral resolution is limited by beam spot size which is on the order of 1 micron.

Staff Contact

Tim Spila
(217) 244-0298

Location

Cameca
B01 Materials Research Laboratory
(217) 244-2965

PHI Trift III
B04 Materials Research Laboratroy
(217) 244-2964

Background

In secondary ion mass spectrometry (SIMS) a focused ion beam is directed to a solid surface, removing material in the form of neutral and ionized atoms and molecules. The secondary ions are then accelerated into a mass spectrometer and separated according to their mass-to-charge ratio.

Instrumentation

The CMM has two secondary ion mass spectrometers, a Cameca ims 5f and a Physical Electronics PHI Trift III. The Cameca can be operated as a true ion microscope with a spatial resolution of 1 micron or as an ion microprobe with a lateral resolution on the order of 200 nm. It has a sensitivity in the parts per billion range for many elements and can perform depth profiles with 3-15 nm depth resolution.

Features

The SIMS is equipped with cesium and duoplasmatron sources for the incident primary ion beam, which maximizes sensitivity for both electronegative and electropositive elements. Each source can be used in the microbeam mode. The instrument is usually used for dynamic SIMS, but static SIMS can also be done. A normal incidence electron gun gives charge neutralization to facilitate the analysis of insulators. Mass resolution up to 20,000 is attainable. The mass range normally is 1-280 amu with extension to 1-500 amu under some conditions. Quantitation of dopant levels is possible with standards. The instrument is equipped for imaging in both the microscope and microprobe modes. With sputter depth profiling and successive 2-dimensional image collection, 3-dimensional analysis can be obtained.

Applications

The primary strengths of SIMS are surface/near surface analysis with low detection limits, isotopic analysis, imaging, and rapid depth profiling. Isotopic sensitivity has been exploited to determine diffusion rates and mechanisms. Hydrogen in metals, ceramics, semiconductors, and polymers has been studied. Semiconductor applications include the study of the redistribution of a dopant species and depth profiling modulated structures such as quantum well devices.

Surface Profilometry

Sloan Dektak3ST

Staff Contact

Steve Burdin
(217) 265-0767

Location

B80 Materials Research Laboratory

General

Surface profilometry is a technique in which a diamond-tipped stylus is used to measure surface topography as it moves across the surface of a specimen.

Instrumentation

The Facility operates a Sloan Dektak3ST Profilometer. This 2-D Profilometer has the capability to measure features ranging from a few nanometers to approximately 105 microns in height.

Dektak 3 ST
Dektak 3 ST

Features

The Dektak profilometer uses a 2.5-micron (radius), conical stylus (90-degree cone angle). The stylus contact-force is adjustable from 10 to 400 microNewtons, allowing the instrument to measure a wide variety of materials without damaging them. The Dektak is controlled by a Windows PC. The software includes commonly used data processing and analysis capability. Data can be converted to ASCII (text) format and saved to a USB flash drive.

Applications

It is common to use a profilometer to measure film thickness and surface texture. Examples include thickness measurements made after spin coating or magnetron sputter deposition and height measurements that are used to calibrate the thickness monitor on a deposition system. Another important application is the measurement of crater depths for surface analysis methods that use depth profiling, such as Secondary Ion Mass Spectrometry (SIMS). Materials such as semiconductors, polymers, metals, and ceramics are commonly measured using this instrument.

X-ray Photoelectron Spectroscopy

Kratos Axis ULTRA

  • Excitation Sources
    Dual Anode X-ray Source: Mg, Al
    Monochromatic Xray Source: Al
  • Detection System
    Small Area Extraction Optics: Hybrid Spherical Capacitor Electron Energy Analyzer for Spectroscopy and 2-D Imaging

Physical Electronics PHI 5400

  • Excitation Sources
    Dual Anode X-ray Source: Mg, Al
    Monochromatic Xray Source:Al
    Ultraviolet Source: He I, He II
  • Detection System
    Small Area Extraction Optics: 0.2, 0.5, 1.0, and 1 mm x 3.5 mm
    Spherical Capacitor Electron Energy Analyzer
    Dual Channel Plate Position Sensitive Detector
  • Sputtering System
    Differentially Pumped 1-5 KeV Ion Gun with Automatic Leak Valve

Staff Contact

Rick Haasch
(217) 244-2974

Location

Kratos
B81 Materials Research Laboratory
(217) 244-2974

PHI 5400 XPS
B08 Materials Research Laboratroy
(217) 244-2974

Background

In X-ray photoelectron spectroscopy (XPS)- also called electron spectroscopy for chemical analysis (ESCA)- X-rays excite photoelectrons, and the emitted electron signal is plotted as a spectrum of binding energies. Differing chemical states resulting from compound formation are reflected in the photoelectron peak positions and shapes. Spectral information is collected from a depth of 2-20 atomic layers, depending on the material studied.

Instrumentation

The Center for Microanalysis of Materials has two instruments for X-ray photoelectron spectroscopy: a Kratos Axis ULTRA and a Physical Electronics PHI 5400. Both instruments have monochromated X-ray sources for high-energy resolution analysis and are capable of small area detection. The Axis ULTRA and PHI 5400 are high-resolution analytical spectrometers which allow sample tilting for depth resolved analysis. The Axis ULTRA and PHI 5400 also have attached sample processing chambers for heating and thin film deposition.

Applications

The strength of XPS is its ability to identify different chemical states. This ability is useful in a range of physical studies, for example, oxidation/corrosion products, adsorbed species, and thin-film growth processes. Analysis of insulators is possible with the Kratos Axis ULTRA. XPS is also capable of semiquantitative analysis.