Scanning Microwave Impedance Microscopy (sMIM)

Complete Characterization of Complex Impedance for Nanoelectrical Devices

Scanning Microwave Impedance Microscopy (sMIM) uses a microwave signal that is reflected from the tip-sample interface to elucidate the electrodynamic properties of the sample surface underneath the tip apex. Detecting and processing the reflectance in real-time allows sMIM to directly access the permittivity and conductivity of the material. The near-field nature of sMIM, together with specialized AFM probes, delivers sub-aF sensitivity and allows routine electrical mapping with <30nm lateral resolution.

Bruker enhanced sMIM capabilities even further with the development of PeakForce sMIM and DataCube sMIM modes. These advanced sMIM modes provide simultaneous measurement of local variations in permittivity (ε) and conductivity (σ) for all types of materials relevant to nanoelectrical devices ⁠— including semiconductors, dielectrics, metals, metal oxides, buried structures, ferroelectrics, 1D and 2D materials, etc.

PeakForce sMIM unlocks challenging applications, such as delicate and rough samples, and allows direct correlation to nanomechanical properties;
DataCube sMIM enables hyperspectral mapping of sample impedance and ensures measurement repeatability; and
sMIM with ScanWave Pro Solutions allows quantification of both carrier type and carrier concentration for doped semiconductors.

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Diagram showing how scanning microwave impedance microscopy (sMIM) works. In addition to variations in permittivity and conductivity, applying a DC or AC bias to the AFM probe also enables measurement of the amplitude and phase of the dC/dV and dR/dV response. For doped semiconductors, these additional data channels provide valuable information on both the type of carrier and carrier concentration. Shown here are sMIM images of an iron oxide. Scale bar = 200nm.

PeakForce sMIM

PeakForce sMIM couples sMIM with Bruker’s PeakForce Tapping® technology to greatly expand its application to previously challenging samples (e.g., carbon nanotubes, nanoparticle oxide films, and semiconductor devices) and provides simultaneous mapping of correlated nanomechanical properties.

PeakForce sMIM mode:

Eliminates high-shear forces associated with contact-based electrical modes that can distort or dislocate delicate samples;
Allows high-resolution imaging of rough sample surfaces and delivers highly sensitive electrical measurements by removing convolution from topographical data; and
Enables multiparametric imaging with direct correlation to nanomechanical properties, such as modulus and adhesion.

PeakForce sMIM enables characterization of the nanoelectrical properties of fragile samples, such as carbon nanotubes (CNTs). High-resolution imaging of individual CNTs on the surface of an insulating glass substrate allows differentiation of CNTs with insulating, semiconducting, and metallic properties. The cross section (sMIM-C data channel) shows the sub-10nm resolution routinely achieved with PeakForce sMIM.

DataCube sMIM

Bruker’s DataCube Modes extend the capabilities of sMIM to acquire multidimensional datasets.

DataCube sMIM mode:

Enables voltage cycling at each pixel to provide a more comprehensive measurement of sample impedance in a single scan;
Allows measurement and subtraction of background capacitance contributions, improving data acquisition sensitivity;
Delivers correlated hyperspectral maps of nanoelectrical and nanomechanical properties; and
Provides increased tip and sample lifetime for enhanced measurement repeatability.

DataCube sMIM conducted on doped nanowires provides F-d, C-V, and dC/dV-V spectrum for every pixel. The hyperspectral nature of the data allows characterization of isolating material and doped semiconductor within the sample. (Sample courtesy of INPG Grenoble. Image scale bar = 600nm.)

ScanWave Pro Solutions

PrimeNano Inc. (the developer of sMIM) has now introduced ScanWave Pro Solutions for high-resolution quantitative carrier profiling of doped semiconductors, which

Enables automated quantification of dopant levels and identification of dopant type (n-type or p-type);
Provides highly repeatable measurements and highest sensitivity to dopant levels in the industry; and
Is only available on Bruker’s Dimension Icon® SPMs.

Integrated with Bruker’s Dimension Icon SPM, the new ScanWave Pro Solutions enables highly repeatable quantification of dopant levels and identification of the dopant type in semiconductors, as demonstrated on this n-type/p-type Silicon Staircase Doped Reference Sample. (Data courtesy of PrimeNano Inc.)