The Scanning Acoustic Microscope (SAM) uses the differences in acoustic impedance, absorption, and reflection of ultrasound waves in different materials to detect the internal structures, defects, and other features of semiconductor devices and various components. It performs qualitative analysis of components and materials and is currently an essential non-destructive testing method in nanotechnology research. Below is an explanation of commonly used professional terms in ultrasound scanning microscopy for your understanding:

Piezoelectric ceramics are polycrystalline materials with piezoelectric effects, named for their production process, which is similar to that of ceramics. They are made by mixing oxides (such as zirconium oxide, lead oxide, titanium oxide, etc.), followed by high-temperature sintering and solid-phase reactions to produce polycrystalline ferroelectric ceramics with piezoelectric properties. Piezoelectric ceramics have excellent mechanical properties and stable piezoelectric performance. As an important material sensitive to force, heat, electricity, and light, they are widely used in electronic components such as sensors, ultrasonic transducers, and micro-displacement devices.

Piezoelectric Effect: The piezoelectric effect refers to the phenomenon where certain materials generate an electric charge on their surface when subjected to mechanical stress, known as the direct piezoelectric effect. Conversely, when an electric field is applied, the material undergoes mechanical deformation, referred to as the inverse piezoelectric effect. The direct piezoelectric effect is essentially caused by mechanical stress leading to polarization of the material, while the inverse piezoelectric effect is caused by the electric field inducing polarization of the material.

Piezoelectric Materials: Materials that exhibit piezoelectric properties. Piezoelectric materials can be natural (e.g., quartz) or synthetic (e.g., piezoelectric ceramics).

Resonant Frequency: When an external voltage matches the inherent frequency of the piezoelectric ceramic, piezoelectric resonance occurs, causing a sudden increase in the amplitude of mechanical vibrations and optimizing the output of the sound wave signal. The frequency at which piezoelectric resonance occurs is called the resonant frequency.

Scanning Acoustic Microscope Probe (Probe) / Ultrasonic Transducer (Transducer): A single-crystal longitudinal wave probe, where a focusing lens is installed. Within the focusing range allowed by the given frequency and wafer size, spherical or cylindrical focusing is applied. This enhances the sensitivity and detection performance of the probe when inspecting specific areas of the workpiece, allowing for rapid scanning of the workpiece.

Longitudinal Wave: A wave where the particle vibration direction is the same as the wave propagation direction. The wavelength of a longitudinal wave is defined as the distance between two adjacent compressions or rarefactions. Scanning acoustic microscopes utilize longitudinal waves.

Shear Wave: Also known as a transverse wave (S-wave), it refers to a wave where the particle vibration direction is perpendicular to the wave propagation direction. In ultrasonic testing, shear waves can generally only be generated by an angled probe.