GHz half wavelength contact acoustic microscopy (HaWaCAM): a feasibility study

The semiconductor industry needs to fit ever more devices per unit area to improve their performance; hence a trend towards increasingly complex structures by varying material combinations and 3D geometries with increasing aspect ratios. The new materials used may be optically opaque, posing problems for traditional optical metrology methods....

Feasibility of 4 GHz half wavelength contact acoustic microscopy (HaWaCAM)

Several methods are being researched to detect and characterize buried nanoscale structures in hard solid samples. The most common acoustic method is acoustic microscopy. An acoustic microscope is based on a single element transducer operating in pulse-echo mode. The acoustic waves are coupled into a sample using a liquid couplant (eg water) and...

Scattering contrast in GHz frequency ultrasound subsurface atomic force microscopy for detection of deeply buried features

While Atomic Force Microscopy is mostly used to investigate surface properties, people have almost since its invention sought to apply its high resolution capability to image also structures buried within samples. One of the earliest techniques for this was based on using ultrasound excitations to visualize local differences in effective tip...

High resolution acoustic metrology by combining high GHZ frequency ultrasound and scanning probe microscopy

In order to extract ever more performance from semiconductor devices on the same device area, the semiconductor industry is moving towards device structures with increasingly complex material combinations and 3D geometries. To ensure cost effective fabrication of next generation devices, metrology solutions are needed that tackle the specific...

Suitability of AFM cantilevers as wideband acoustic point receivers for the characterization of acoustic sources

In Subsurface Scanning Probe Microscopy (SSPM), Atomic Force Microscopy (AFM) is combined with ultrasound. The AFM cantilever is used as a receiver. At low frequencies (O(MHz)) the method can be used to measure the stiffness contrast in a sample and at high frequencies (O(GHz)) to measure scattering based contrast. Both variants use modulated...

High resolution acoustic metrology by combining high GHZ frequency ultrasound and scanning probe microscopy

In order to extract ever more performance from semiconductor devices on the same device area, the semiconductor industry is moving towards device structures with increasingly complex material combinations and 3D geometries. To ensure cost effective fabrication of next generation devices, metrology solutions are needed that tackle the specific...

Optimization of acoustic coupling for bottom actuated scattering based subsurface scanning probe microscopy

The characterization of buried nanoscale structures nondestructively is an important challenge in a number of applications, such as defect detection and metrology in the semiconductor industry. A promising technique is Subsurface Scanning Probe Microscopy (SSPM), which combines ultrasound with Atomic Force Microscopy (AFM). Initially, SSPM was...

Development of a sample clamp for GHZ subsurface probe microscopy

Advanced excitation waveforms in ultrasound sub-surface atomic force microscopy

This technique uses an Atomic force microscope (AFM) to map the elastic properties of buried materials with high spatial resolution. Ultrasound excitation is applied to the tip-sample interface in the AFM, while the probe’s dynamic response is monitored. The excitation is a carrier of high frequency fc, that is amplitude-modulated at a lower...

Efficient and Stable Acoustical Coupling for GHz Subsurface Probe Microscopy

Many techniques are under development for the detection of subsurface defects or cracks. One such method is GHz subsurface probe microscopy (GHz SSPM). Here, modulated GHz elastic waves are transmitted through the bottom of a sample. The waves are scattered by buried features and detected using the probe of an atomic force microscope (AFM),...