Analytical Instruments And Methods At The Stanford Nanofabrication Facility (SNF) With an Introduction to the Stanford Nano Center (SNC)

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

TYPES OF MEASUREMENTS OFTEN ASSOCIATED WITH PROCESS CONTROL, MONITORING AND DEVELPMENT

1) Electrical 1) Sheet Resistance 2) Contact, Via or Line Resistance 2) Physical 1) Thickness of Opaque films 2) Reflectivity of Metal Films 3) Stress of Deposited Films 4) Surface Roughness 5) Chemical Composition 6) Microstructure, Device Structure 7) Particles 8) Contact Angle 3) Optical 1) Thickness (transparent films) 2) Index of Refraction (n) 3) Extinction Coefficient (k)

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

PHYSICAL MEASUREMENTS

Thickness (opaque films) Sheet Resistance (doped polysilicon or metallic films): Prometrix 4-point Probe Step Height: Alphastep 500 Profilometer, Tencor P-2 Profilometer, Zygo 3D Surface Profiler, SEM, AFM Stress: Flexus 2320 Reflectivity: Nanospec’s Surface Roughness: Atomic Force Microscope (AFM) Thickness (transparent films): Nanospec’s, Rudolph Ellipsometer, Woollam Spectral Ellipsometer, SEM Index of Refraction (n) and Extinction Coefficient (k): Woollam Spectral Ellipsometer

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Prometrix Resistivity Mapping System

The Prometrix OmniMap Model RS35e Resistivity Mapping System collects sheet resistance data on various conductive layers such as implants, diffusions, epi, metals and bulk substrates. The system provides accurate and repeatable sheet resistance measurements from 5 mohm/sq to 5 Mohm/sq on 2-inch ( 50mm) to 8-inch (200mm) wafers. The OmniMap measures up to 1264 sites per wafer using standard or user defined patterns, and displays test results in the form of contour maps, 3-D maps, diameter scans. Cleanliness Group: All, but must use the correct probe head.

Measure Voltage Force Current

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

http://www.four-point-probes.com/faq.html

Ed Myers, April 19, 2011

4-Point Probe Limitations and Concerns

1) If you know the thickness you can calculate the resistivity (resistivity=sheet res x t) where t is the thickness in cm. 2) The geometry of the sample determines the correction factors that must be used, additionally the position of the probes on the sample and the spacing between the probes. The need for correction factors is caused by the proximity of a boundary which limits the possible current paths in the sample. The most basic sample would be semi-infinite in extent i.e., it extends to infinity in all directions below the plane in which the four probes are located. All other cases would restrict the current paths available, eg., an infinite plane sample of finite thickness requires a correction factor based on the thickness. 3) The general rule is that you can probe up to (20 x probe spacing) of the edge, eg 20mm with a 1mm spacing probe without applying any factor beyond the basic one of rho=4.5324 x (V/I). Further factors are available from literature.

4) With a rectangular sample there are similar correction factors. The pins should contact parallel to the longer of the sides. Again, the correction factors show that if the length of the rectangle is over 100s then there will be no error. At 40 times the spacing there is less than 1% error and 10s less than 10% error. As for irregular shapes I would consider what size circle/rectangle could be included within its perimeters and work from there. These correction factors (if you are working more or less on these limits mentioned) will only be valid for measurements at the center of the sample.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

4-Point Probe Limitations and Concerns Continued

Q. Let's say I have a sample that's infinite in 3 dimensions, and I use a 4-point probe measures resistance. Will the resistance be independent of probe spacing? The equations seem to imply this.

A.

Such a sample is usually defined as a "semi-infinite volume" if it extends to infinity in all directions below a plane on which four probes are located.

For equidistant probes: Resistivity = 2 x pi x s x (V/I) where s is the probe spacing in cm.

Compare this with a "thin" sample when Resistivity (rho) = pi/(logn2) x V/I x t where t is the thickness and pi/(logn2) x V/I is the sheet resistance.

REQUIRES CAREFUL CALIBRATION FOR THIN FILMS

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Alphastep 500 Profilometer

The Tencor Alphastep 500 is a stylus-based surface profiler to measure step heights of surfaces. A stylus is placed in contact with, and then gently dragged along the surface of the substrate. The vertical deflection measures the change in step height. Cleanliness Standard: Gold Equipment Group Performance of the Tool: vertical resolution of 25A Step heights from 500 Angstroms to 300 µm Scan length from 100 Angstroms up to 0.3 mm Stylus radius 5 µm (yellow ring) Max sample dimensions: 150 mm (6 inch) wide 15 mm (.59 inch) thick

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Tencor P-2 Profilometer

The Tencor P2 Long Scan Profiler is a computerized, high-sensitive surface profiler that measures step height and roughness in a variety of applications. Cleanliness Standard: CLEAN and SEMICLEAN EQUIPMENT GROUPS.

Performance of the Tencor P2: Stepheight 500 Å to 80µm Scan length 0.01 mm to 210 mm Pieces to 8 inch wafers Stylus Radius 12.5 µm

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

STRESS MEASUREMENTS

The Tencor Flexus 2320 determines wafer curvature by measuring the angle of deflection of a laser beam off the surface of the substrate. Film stress is determined by comparing the change in radius of curvature of the substrate, with and without the film. The substrate and the film must be optically reflective in the wavelength used. The Flexus 2320 has two wavelengths (670 nm and 750 nm), because semi-transparent films may absorb light (depending on the incident wavelength/angle and the film thickness/RI)

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Zygo White-Light 3D Surface Profiler

The Zygo White-Light 3D Surface Profiler provides fast, non-destructive, quantitative surface characterization of step heights, texture, roughness, and other surface topography parameters. The measurement technique is non-contact, three-dimensional, scanning white light and optical phase-shifting interferometry. The Zygo is based on scanning white-light interferometry, a traditional technique in which a pattern of bright and dark lines (fringes) result from an optical path difference between a reference and a sample beam. Incoming light is split inside an interferometer, one beam going to an internal reference surface and the other to your sample. After reflection, the beams recombine inside the interferometer, undergoing constructive and destructive interference and producing the light and dark fringe pattern. http://www.optics.arizona.edu/jcwyant/pdf/meeting_papers/whitelightinterferometry.pdf

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Zygo White-Light 3D Surface Profiler

Measurement technique: Non-contact, three-dimensional, scanning white light (600 +/- 20 nm) and optical phase-shifting interferometry. Vertical resolution is 0.1 nm Minimum lateral resolution is 0.11 µm (50X objective, 2X zoom) Objectives: 2.5X, 10X, 20X, and 50X Field of View: 2.5X: 2.82 x 2.11 mm, 10X: 0.7 x 0.53 mm, 20X: 0.35 x 0.26 mm, 50X: 0.14 x 0.11 mm Image zoom: 0.5, 0.75, 1.0, 1.5, 2.0 measurement length 5 µm to 100 µm, extended to 5300 µm

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Nanospec Spectro-Reflectometers

The Nanometrics Nanospecs are systems which use non-contact, spectro-reflectometry (measurement of the intensity of reflective light as a function of incident wavelength) to determine the thickness of transparent films (up to two) on substrates, such as silicon.

The system is comprised of a microspectrophotometer head, measuring in the wavelength range of 400 - 800 nm using a computer-controlled grating monochromator, a photomultiplier tube detector, and an amplifier. The amplifier output is converted to a digital signal by the computer, which then calculates film thickness with one of several algorithms.

There are a number of preloaded programs for standard semiconductor films. The parfocal objective yield small measurement spot sizes, down to tens of microns.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Nanospec Spectro-Reflectometers

Available programs 1) Oxide on Si 2) Nitride on Si 3) Negative resist on Si 4) Poly on Oxide (page 3-14) 5) Negative resist on Oxide 6) Nitride on Oxide 7) Thin Oxide on Si 8) Thin Nitride on Si 9) Polyimide on Si 10) Positive resist on Si 11) Positive resist on Oxide 12) Reflectivity Mode

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Atomic Force Microscope (AFM)

Scanning Probe Microscopy (SPM), more commonly known as Atomic Force Microscopy (AFM), provides atomic or near-atomic-resolution surface topography, which is ideal for determining angstrom-scale surface roughness on a sample. In addition to presenting a surface image, AFM can also provide quantitative measurements of feature sizes, such as step height, and other sample characteristics, such as capacitance measurements for identifying carrier and dopant distributions.

Lateral Resolution/Probe Size: 5 - 50 Angstroms

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Ellipsometery

Ellipsometry measures a change in polarization as light reflects or transmits from a material structure. The polarization change is represented as an amplitude ratio, Ψ, and the phase difference, Δ. The measured response depends on optical properties and thickness of individual materials. Thus, ellipsometry is primarily used to determine film thickness and optical constants. However, it is also applied to characterize composition, crystallinity, roughness, doping concentration, and other material properties associated with a change in optical response. Ellipsometry is primarily interested in how p- and s- components change upon reflection or transmission in relation to each other. In this manner, the reference beam is part of the experiment. A known polarization is reflected or transmitted from the sample and the output polarization is measured. The change in polarization is the ellipsometry measurement, commonly written as: A sample ellipsometry measurement is shown below. The incident light is linear with both p- and s components. The reflected light has undergone amplitude and phase changes for both p- and s- polarized light, and ellipsometry measures their changes.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

http://www.jawoollam.com/tutorial_1.html

Ed Myers, April 19, 2011

Ellipsometery

JA Woollam Spectral Ellipsometer

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

data analysis screen for three layer film Ed Myers, April 19, 2011

Particles

Tencor 4500 Surfscan Particle Monitor Capable of 2"-6" wafers. Set up for 4-5-6 inch wafers. Substrate Thickness: Semi standard thickness. Material Type: In the most sensitive range, any opaque, polished surface that scatters less than 0.025% of incident collimated light averaged over the substrate. High angle optics. Non-patterned surface Inspection System. Defect Sensitivity, 0.2 micron or approximately 0.015 micron squared. Based on 95% capture on silicon PSL Standards. 0.4 ppm Haze Sensitivity.

Contamination: No more than 2 particles with scattering cross-section greater than 0.5 micron squared per 50 passes, 96% confidence. Accuracy within 1% measured on a VLSI Relative Standard 1402. HeNe laser, 632 nanometer.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Scanning Electron Microscope (SEM)

Hitachi 4160 Full Wafer SEM

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Hitachi S-800 Piece SEM Ed Myers, April 19, 2011

Introduction to the Stanford Nano Center (SNC)

www.snc.stanford.edu

Housed in the Center for Nanoscale Science and Technology (CNST) popularly known as the "Nano Building"

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Stanford Nano Center (SNC)

Stanford Nano Patterning (SNP) SNL/Soft Materials The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070 Flexible Clean Room

Ed Myers, April 19, 2011

Stanford Nanocharacterization Lab (SNL)

Cameca NanoSIMS

The NanoSIMS creates nanoscale maps of elemental composition, combining the high mass resolution, isotopic identification, and subparts-per-million sensitivity of conventional SIMS with spatial resolution down to 50 nm and the identification of up to seven masses in parallel from the same small volume. Secondary ion mass spectrometry (SIMS) is a technique used to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions. These secondary ions are measured with a mass spectrometer to determine the elemental, isotopic, or molecular composition of the surface.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Stanford Nanocharacterization Lab (SNL) FEI Titan TEM

The Nano Center houses a spherical aberration corrected FEI 80-300 environmental Titan (S)TEM with the following capabilities: High brightness field emission gun source, Spherical aberration (image) corrector (information limit 0.08nm at 300kV), Monochromator with energy resolution of ~ 0.2eV, Gatan Tridiem 866 electron energy-loss spectrometer (for Energy-Filtered TEM imaging and electron energy loss spectroscopy), High-angle annular dark field (HAADF) detector, Bright-field/Dark-field STEM detectors, Energy-dispersive X-ray spectroscopy, Magnetic biprism for electron holography, Dual tilt axis tomography holder (for electron tomography), SuperTwin objective pole piece, Environmental cell for controlled gas inlet into the sample holder area and analysis of the chemical composition of the atmosphere (up to 20mbar), US1000 CCD camera, Orius fast frame rate camera, Operates at 80, 200 and 300kV.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Stanford Nanocharacterization Lab (SNL) FEI Magellan SEM

FEI Magellan 400 XHR Scanning Electron Microscope with FEG source, EDAX Pegasus integrated EDS and EBSD system.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Soft and Hybrid Materials Facility (SMF) Housed in the SNL Nano Center SMF Equipment List

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Differential Scanning Calorimetry (DSC)

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Dynamic Light Scattering (DLS)

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Langmuir-Blodgett (LB) Trough Instrument

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Imaging Ellipsometer

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Profilometer

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Mechanical Testing Equipment (Instron)

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Oxygen Plasma Cleaner

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Impedance Analyzer

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Atomic Force Microscopy (AFM)

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UV/Vis and FT-IR

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Stanford Nano Patterning Facility (SNP) Electron Beam Lithography - JEOL 6300

The JEOL JBX 6300 lithography system uses a high-brightness field emission electron source, a 100 keV acceleration potential, a 25 Mega-Hertz deflection system and magnetic lenses to define a beam diameter as small as 2 nm and patterns in resist as small as 8 nm. The laser-controlled stage is capable of loading 1 cm square compound semiconductor chips, up to 200 mm (8 inch) diameter silicon substrates.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Stanford Nano Patterning Facility (SNP) Scanning Electron Microscope FEI Nova NanoSEM

The FEI Nova NanoSEM provides high quality nanoscale research tools for a variety of applications that involve sample characterization. Dedicated SEM for the analysis of E-Beam written patterns.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Stanford Nano Patterning Facility (SNP) Agilent TN5500 SPM

The Agilent 5500 SPM is a multiple-user research system for Scanning Probe Microscopy (SPM) and Atomic Force Microscope (AFM). The 5500 SPM provides a wealth of unique technological features including a multi-purpose low coherence scanners, along with a 1 nA/V current sensing CSAFM nose-cone, with a Triple lock-in AC mode controller. Also include is a STM 10um Scanner and precision temperature controlled , and a liquid cell sample plates. The Agilent 5500 SPM offers features lithography and nanomanipulation software for research in materials science, polymers, nanolithography and general surface characterization. The combination of hardware allows for numerous characterization techniques including Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM), Contact mode AFM, Intermittent Contact AFM, Current Sensing Mode (CSAFM), Force Modulation Microscopy (FM), Lateral Force Microscopy (LFM), Dynamic Lateral Force Microscopy (DLFM), Magnetic Force Microscopy (MFM), Electrostatic Force Microscopy (EFM) and Kelvin Force Microscopy (KFM)

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Stanford Nano Patterning Facility (SNP) Housed in the Flexible Clean Room Intlvac Ion Beam Mill Etcher

The Intlvac Nanoquest Research Ion Beam Milling System is a Versatile R&D platform. The ion beam processing is a controllable thin film etching technique with independent control of ion energy, ion current density, and incidence angle. Designed as a general purpose R&D tool, the Nanoquest I is capable of performing processes ranging from a simple etch to multi-angle, utilizing substrate rotation and substrate offset to achieve a superior etch. The Nanoquest System combines a 4 inch water-cooled, rotating stage, a Kaufman ion source, an easily accessible stainless steel vacuum chamber with Turbo Molecular pumping.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Flexible Clean Room

The Flexible Cleanroom is a ~ 2000 square foot class 100 cleanroom facility used by graduate students and Stanford researchers from a wide range of backgrounds to do nano-fabrication related work, such as photolithography, wet etching, chemical processing, rapid thermal annealing, plasma cleaning, sample preparation, liftoff, chemical etching, thickness measurement, characterization, probing, testing, precision cleaning, optical assembling, delicate assembly work, etc. The lab is flexible in the sense that we work with many odd materials which are generally banned in a rigid CMOS type of facility, and we generally work with smaller chips, crystals, polymers, micro machined devices, etc. The lab users have a lot of interaction with each other and take an ownership of the facility by volunteering to help with training on certain machines.

The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011

Microfab Shop Housed in the Flexible Clean Room

The Microfab Shop, which is located mostly within the Flexible Cleanroom, is a service center which provides thin film deposition by evaporation and sputtering. It also provides related technical support work such as design and fabrication of special mounting fixtures, bonding fixtures, prototype device fabrication, mold-making, casting, bonding, precision cleaning, etc. The Stanford Nanofabrication Facility Paul Allen Center for Integrated Systems Stanford, CA. 94305-4070

Ed Myers, April 19, 2011