Atomic force microscopy

What is AFM analysis used for?

AFM is a widely used characterization technique that provides high-resolution, three-dimensional mapping of the sample surface with a sub-nanometer resolution. This makes AFM ideal for analyzing nanoscale features such as surface roughness, topological features, and surface defects. In addition to topography, AFM can also map local mechanical and electromagnetic properties such as stiffness, adhesion, conductivity, surface potential, and magnetic domains through specialized modes.

AFM is suitable for a wide range of materials, including semiconductors, thin films, nanomaterials, metals, polymers, and biological samples. It is particularly valuable for characterizing thin films deposited by techniques such as Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD), Physical Vapor Deposition (PVD), and spin coating. Unlike many other surface analysis techniques, AFM does not require a vacuum or conductive samples. It can also operate in air, vacuum, or liquids, allowing for analysis of a wide range of materials.

As an example, AFM allows us to analyze the surface roughness of thin films processed at different temperatures. Quantitative data, such as root mean square (RMS) roughness or feature height distribution, can be extracted from the resulting 2D and 3D surface maps.

While AFM is a highly versatile and precise tool, its capabilities are limited by the imaging conditions. AFM can image features with a maximum height of 20 µm and areas up to 100 × 100 µm. For larger features or larger areas, we recommend using profilometry. AFM analysis is also most accurate on clean and flat surfaces, making very rough or oddly shaped surfaces difficult to analyze. However, when properly optimized, AFM provides invaluable data on surface properties essential in product development, quality control, and process optimization.

Measurlabs frequently provides AFM measurements for several large clients in the semiconductor industry. One of these is Okmetic, the world's seventh largest silicon wafer manufacturer. Read more about our cooperation here:

• Okmetic’s long-standing collaboration with Measurlabs drives smoother R&D projects.

How does atomic force microscopy work?

AFM operates by scanning a sharp tip mounted on a flexible cantilever across the sample’s surface. As the probe scans the sample surface, interactions between the tip and sample cause the cantilever to bend. A laser beam is reflected off the cantilever, tracking these deflections with high precision and recording changes in the tip's position. The recorded laser deflections are used to reconstruct a map of the sample surface.

AFM modes

AFM can operate in three different modes: Contact Mode, Tapping Mode, and Non-Contact Mode. Each mode offers its own advantages and is suited to different types of samples and measurements.

• Contact mode: the tip remains in continuous contact with the sample surface during scanning. Contact mode offers high resolution and fast imaging, but applies a constant force to the sample, which can damage the sample surface. It is best suited for hard, smooth surfaces such as wafers or thin films.

• Tapping mode: this is one of the most commonly used modes. In tapping mode, the cantilever oscillates so that the tip briefly touches the surface at each cycle. This reduces the pressure that can damage soft or loosely bound surfaces, while still maintaining high resolution. Tapping mode is ideal for a wide range of materials, including polymers, composites, and biological samples.

• Non-contact mode: the cantilever oscillates just above the sample surface without making physical contact. The tip senses long-range attractive forces (van der Waals), which slightly alter the oscillation amplitude and frequency. This mode is very gentle and is especially useful for soft, fragile, or contamination-sensitive surfaces. However, it typically provides lower resolution than tapping or contact mode and is more sensitive to environmental noise and contamination.

Need AFM analyses?

Measurlabs offers laboratory testing with AFM for thin films and other coatings. Our testing experts are happy to help select suitable methods and make sure you get insightful results - we offer a full set of advanced techniques for analyzing thin films and semiconductors so you can get the full scope easily from one partner. We can process even large sample batches efficiently and offer quick turnaround times to allow your projects to move forward with the pace you need. Contact us through the form below to get started!