Metrological large range magnetic force microscopy

A new metrological large range magnetic force microscope (Met. LR-MFM) has been developed. In its design, the scanner motion is measured by using three laser interferometers along the x, y, and z axes. Thus, the scanner position and the lift height of the MFM can be accurately and traceably determined with subnanometer accuracy, allowing accurate and traceable MFM measurements. The Met. LR-MFM has a measurement range of 25 mm × 25 mm × 5 mm, larger than conventional MFMs by almost three orders of magnitude. It is capable of measuring samples from the nanoscale to the macroscale, and thus, it has the potential to bridge different magnetic field measurement tools having different spatially resolved scales. Three different measurement strategies referred to as Topo&MFM, MFMXY, and MFMZ have been developed. The Topo&MFM is designed for measuring topography and MFM phase images, similar to conventional MFMs. The MFMXY differs from the Topo&MFM as it does not measure the topography profile of surfaces at the second and successive lines, thus reducing tip wear and saving measurement time. The MFMZ allows the imaging of the stray field in the xz- or yz-planes. A number of measurement examples on a multilayered thin film reference sample made of [Co(0.4 nm)/Pt(0.9 nm)]100 and on a patterned magnetic multilayer [Co(0.4 nm)/Pt(0.9 nm)]10 with stripes with a 9.9 μm line width and 20 μm periodicity are demonstrated, indicating excellent measurement performance

原子間力顕微鏡補助による走査トンネル顕微鏡を用いたMoS2ナノシートの局所状態密度観察

Tohoku University須藤彰三課

Scanning thermal microscopy using nanofabricated probes

Novel atomic force microscope (AFM) probes with integrated thin film thermal sensors are presented. Silicon micromachining and high resolution electron beam lithography (EBL) have been used to make batch fabricated, functionalised AFM probes. The AFM tips, situated at the ends of Si3N4 cantilevers, are shaped either as truncated pyramids or sharp triangular asperites. The former gives good thermalisation of the sensor to the specimen for flat specimens whereas the latter gives improved access to highly topographic specimens. Tip radii for the different probes are 1 m and 50 nm respectively. A variety of metal structures have been deposited on the tips using EBL and lift-off to form Au/Pd thermocouples and Pd resistance thermometer/heaters. Sensor dimensions down to 35 nm have been demonstrated. In the case of the sharp triangular tips, holes were etched into parts of the cantilever in order to provide self alignment of the sensor to the tip. On the pyramidal tips it has been shown that multiple sensors can be made on a single tip with good definition and matching between sensors. A conventional AFM was constructed in order to test the micromachined thermal probes. During scans of a photothermal test specimen using improved access thermocouple probes, 80 nm period metal gratings were thermally resolved. This is equivalent to a thermal lateral resolution of 40 nm. Pyramidal tips with a resistance thermometer/heater, which were made for the microscopy and analysis of polymers, have been showed by others to produce high resolution thermal conductivity images. The probes have also been shown to be capable of locally heating a polymer specimen and thermomechanically measuring phase changes in small volumes of material. Also presented here is a study of scanning thermal microscopy of semiconductor structures using a commercial AFM. Included are scans of several specimens using both commercial andthe new micromachined probes. Subsurface images of voids buried under a SiO2 passivation layer were taken. It is shown that contrast caused by thermal conductivity differences in the specimen may be detected at a depth of over 200 nm

Drift Correction for Scanning-Electron Microscopy by

Scanning electron micrographs at high magnification (100,000x and up) are distorted by motion of the sample during image acquisition, a phenomenon called drift. We propose a method for correcting drift distortion in images obtained on scanning electron and other scanned-beam microscopes by registering a series of images to create a drift-free composite. We develop a drift-distortion model for linear drift and use it as a basis for an affine correction between images in the sequence. The performance of our correction method is evaluated with simulated datasets and real datasets taken on both scanning electron and scanning helium-ion microscopes; we compare performance against translation only correction. In simulation, we exhibit a 12.5 dB improvement in SNR of our drift-corrected composite compared to a non-aligned composite, and a 3 dB improvement over translation correction. A more modest 0.

Development of a Traceable Atomic Force Microscope with Interferometer and Compensation Flexure Stage

Entwicklung eines ruckfuhrbaren Rasterkraftmikroskops auf der Basis von Interferometern und einer geregelten Einkorperfuhrung Abstrakt Rastersondenmikroskope, zu denen unter anderem Rastertunnelmikroskope (STM) und Rasterkraftmikroskope (AFM) gezahlt werden, werden an vielen Stellen in der Material- und Oberflachenforschung, der Halbleitertechnologie sowie der Biotechnologie angewendet. Sie sind zudem denkbare Werkzeuge der Nanotechnologien, so beispielsweise der Nanolithographie. Zudem konnen sie der Manipulation von Atomen und zur Nanometrologie dienen. Kommerzielle AFM bestehen unter anderem aus einem Laser, Photoempfanger, Regler, Piezoantriebssystem sowie einem Tastsystem. Dabei kommt den Piezoelementen des Antriebssystems besondere Bedeutung zu. Die von Piezoelementen bekannten Nachteile, wie Nichtlinearitat, Hysterese, Alterung, thermische Drift, Kriechen und Ubersprechen, konnen durchaus 20% der Messabweichungen bei Vorwartssteuerung verursachen. Daher sollten AFM, Metrologiestandards entsprechend, zur Reduzierung der Mesunsicherheit regelmasig ruckfuhrbar kalibriert werden. Das Ziel der vorliegenden Arbeit bestand in der Entwicklung eines ruckfuhrbaren Rasterkraftmikroskops (Traceable Atomic Force Microscope, TAFM) zum Einsatz als staatliches Normal zur ruckfuhrbaren Vermessung von Normalen im Nanometer- Bereich fur die taiwanesische Industrie. Das TAFM wurde als Kombination eines kommerziellen AFM, zwei Laserinterferometern, einer aktiv geregelten dreiachsigen Prazisionsfuhrung, einem Metrologierahmen aus Super-Invar, einer Schwingungsdampfung sowie einer temperaturgeregelten Umhausung konzipiert und aufgebaut. Zur Reduzierung des Abbe-Offsets wurden die Interferometer derart angeordnet, dass sich ihre virtuell verlangerten Messstrahlen im Antastpunkt des Cantilevers und damit direkt auf der Probenoberflache im Messpunkt schneiden. Eine einwandfreie Referenzbewegung des Systems wurde durch die eingesetzten Prazisionsfuhrungen sichergestellt, wahrend die direkte Ruckfuhrbarkeit auf die Definition der Langeneinheit ?Meter" durch den Einsatz von zwei Laser- Interferometern erreicht wurde. Die ermittelte erweiterte Messunsicherheit des TAFM fur die laterale Messung einer Lange von 292 nm betrugt bei einer statistischen Sicherheit von 95% unter Berucksichtigung von 29 Freiheitsgraden 2,5 nm. Da die ermittelte erweiterte Messunsicherheit fur laterale Langenmessungen noch nicht zufriedenstellend und die Ruckfuhrbarkeit in Richtung der Z-Achse nicht gewahrleistet ist, soll das TAFM verbessert werden, um perspektivisch eine Messunsicherheit von 0,5 nm in allen drei Messachsen zu erreichen. Dieses Ziel kann zunachst durch den Einbau eines weiteren Laserinterferometers zur Kalibrierung des Messystems der Z-Achse erreicht werden. Zusatzlich sollte die Umhausung statt auf einem Tisch auf dem schwingungsarmeren Boden platziert werden, was das Rauschen der Interferometer auf weniger als 5 nm reduzieren sollte. Ein verstarkter Metrologierahmen, die Verlagerung der Referenzspiegel vom AFM auf die Prazisionsfuhrung und verkurzte Messkreise, die Konstruktion aller Teile aus dem gleichen Material, ein symmetrischer mechanischer Aufbau und der Einsatz einer aktiven Temperaturregelung mit einer Temperaturstabilitat von 20¡Ó0.1 ¢XC sind weitere wichtige Schritte.Scanning Probe Microscopes (SPMs), generally including such instruments as Scanning Tunneling Microscopes (STMs) and Atomic Force Microscopes (AFMs), have been widely applied to measure engineering surfaces in a variety of fields, such as material sciences, semiconductor industry, and biotechnology. SPMs will also be a potential tool in nanotechnology, for example nanolithography, atom manipulation, and nanometrology. Normally, a commercial AFM consists of a laser, a photo-detector, a controller, a piezo-scanner, and a cantilever tip. The piezo-scanner is critical to the performance of AFMs. The intrinsic properties of piezo-scanners, for instance non-linearity, hysteresis, aging, thermal drift, creep, and coupling effect will result in measurement errors that may reach up to 20 % of the reading. To reduce major measurement errors mentioned above, an AFM should be periodically calibrated with a traceable standard. The goal of my research study was to design a state-of-the-art Traceable Atomic Force Microscope (TAFM) to be used as a primary realization of nanometer scale standards for Taiwan industry. The TAFM was composed of a commercial AFM, two laser interferometers, a 3-axis active compensation flexure stage, a super-Invar metrology frame, a vibration isolator, and a temperature-controlled enclosed box with circulating water. To eliminate the Abbe-offset, the surface-plane of specimens was arranged on the same plane-level to the laser beams emitted by interferometers. The compensation flexure stage was aimed to provide a perfect reference motion mechanism. To achieve the direct traceability to the definition of meter, two interferometers were added to the flexure stage. The TAFM was evaluated to have an expanded uncertainty of 2.5 nm at a confidence level of 95 % and 29 degrees of freedom for a nominal pitch value of 292 nm. Since the expanded uncertainty of pitch measurement is not satisfactory and there is no traceability in the Z direction. The TAFM needs to be improved to meet the requirement of an expanded uncertainty of no more than 0.5 nm at 95 % confidence level at all three axes. The requirement can be achieved by the following improvements: A laser interferometer is added to the flexure stage for Z-height calibration. To reduce the noise of laser interferometer to about 5 nm, the support of the enclosed box is moved from tabletop to the floor. The metrology frame is improved by changing the reference mirrors from AFM to flexure stage, thickening the super-Invar frame, shortening the structure loop and metrology loop, using one material, and realizing a symmetrical mechanism design. The passive temperature control is changed to active temperature control, which will approach an anticipative temperature stability of (20¡Ó0.1) ¢XC in the measuring volume