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Bruker AFM Probes Announcements » SPM & AFM Modes

Scanning Capacitance Microscopy – SCM

SCM uses contact mode AFM and a conductive probe and applies to semiconductor samples with an AC bias (amplitude DV, ~90 kHz) with a DC offset. The capacitance of the metal-oxide-semiconductor (MOS) capacitor at tip-sample contact is a function of majority carrier concentration in the sample. SCM uses an ultra-high-frequency (1 GHz) detector to measure tip-sample capacitance variation, DC, at the bias frequency. Sensor Signal is DC/DV. In feedback mode, output signal is DV, adjusted to maintain a DC/DV Setpoint. SCM maps relative changes of majority carrier concentration in semiconductors.




Scanning Thermal Microscopy

In Scanning Thermal Microscopy (SThM) a heated tip is scanned across a sample. Changes in the tip’s resistivity reveal either thermal conductivity or thermal gradients on the sample. In Nanoscale Analysis (NA), a tip is heated in such a way that it induces a phase transition in the sample. That transition is monitored using the cantilever deflection and is material specific.



Piezoresponse Microscopy

Piezoresponse (Piezoforce) Microscopy (PFM) is a technique based on contact mode that maps out the inverse piezoelectric effect on a sample. The sample is electrically stimulated and the topographic response of the sample is monitored using lock-in techniques. Amplitude and phase information reveal information about the strength and direction of the polarization on the sample.



Critical Dimension Atomic Force Microscopy – CDAFM

Critical Dimension Atomic Force Microscopy (CDAFM) is a nondestructive, high-resolution technique that enables accurate measurement of three-dimensional (3D) features. CD-AFM is accurate as it provides highly linear measurement over a range of line-widths and is unaffected by feature type, density or material type. Additionally, the technique is able to measure undercut features and can be calibrated using NIST traceable calibration standards to ensure accuracy of measurements. CDAFM capabilities have enabled its use as a reference metrology tool.



Deep Trench Mode

Deep Trench (DT) Mode is an AFM mode developed specifically for the repeatable measurement of deep semiconductor trench structures for 90 nm and below. It is an adaptive scan method in which data is only collected when user-specified system state conditions are met. This means that the tip is “allowed” to move only in certain servo states. DT Mode “steps” the tip along the sample surface collecting data points only when “good” scan criteria are met. This permits feature-dependent scan optimization in which the concentration of data points is highest on the features of interest and low elsewhere, resulting in improved measurement precision.



Tapping Mode AFM

TappingMode™is a primary AFM mode. The probe is a microfabricated cantilever with a sharp tip. A drive signal, applied to the “tapping piezo,” mechanically oscillates the probe at or near its resonance frequency (usually the fundamental resonance). Detector signal is cantilever oscillation amplitude, or phase (relative to drive signal). In feedback mode, output signal usually adjusts the Z position of the scanner to maintain an (rms) amplitude setpoint. TappingMode enables numerous secondary modes, including PhaseImaging™, EFM, MFM, and Surface Potential imaging.





PeakForce Tapping

PeakForce Tapping™is an AC imaging technique, i.e., the cantilever is oscillated but well below resonance. This results in a continuous series of force-distance curves. As there is no tuning involved, the method is inherently stable.




ScanAsyst™ is an algorithm that self-optimizes an AFM operating in PeakForce Tapping™. Important scan parameters such as setpoint, feedback response, and scan rate are automatically selected and constantly adjusted. The technique works in air as well as in liquids.


SPM Operation

Scanning Probe Microscopy (SPM) is a technique to provide spatially localized three-dimensional information by raster scanning a sharp probe and a surface in close proximity relative to each other and monitoring probe-sample interactions. Depending on the interaction, a variety of surface properties can be measured in addition to topographic information, such as electrical, magnetic, and nanomechanical data. The main SPM scan modes are contact mode, TappingMode™,and PeakForce Tapping™ Mode, and these build the foundation of all advanced scanning techniques.



Electrostatic Force Microscopy – EFM

Electrostatic Force Microscopy (EFM) uses a combination of TappingMode™, LiftMode™and a conductive tip to gather information about the electric field above a sample. Each line of the sample is first scanned in TappingMode operation to obtain the sample topography. The topographic information is stored and retraced with a user- selectable height offset in LiftMode, during which the electrical data is collected. Typical lift heights in EFM range from 20-80 nm.