Micro analytics

Scanning electron microscopy (SEM):

With scanning electron microscopy samples are scanned with a very fine electron beam. The resulting signal of the detector is recorded synchronously to the position. This creates images of samples with resolutions down to about 10 nm.

Typical properties:

• Lateral resolution: ~10 nm
• Topography and material contrast

Energy dispersive x-ray analysis (EDX):

When elements are irradiated by electrons, a characteristic X-radiation is emitted. The energy distribution is dependent on the respective element. This way material determination of microscopic samples can be carried out. Since this analysis can also be carried ot scanning, an imaging element analysis with microscopic resolution can be performed.

Typical properties:

• Element analysis from atomic number 7 (nitrogen)

Atomic force microscopy (AFM):

In atomic force microscopy a micro fabricated tip with a radius of a few nanometers is scanned over the sample. The elevation of the probe tip is recorded synchronously to the scanning position. The resulting images can have resolutions down to atomic level.

Typical properties:

• Lateral resolution: ~1 nm
• Only topographic contrast, no material contrast

Surface profiling:

A surface profiler either scans a sample optically with a focused beam of light or with a probe tip as in atomic force microscopy. The lateral resolution is significantly lower than in atomic force microscopy, therefor it can capture much greater measuring distances.

Spectral Reflectometry:

Spectral reflectometry is suitable for determining the thickness of optically transparent layers. At each interface between two materials with different refractive index a partial reflection of the incident optical wave takes place. On a substrate with a thin layer at least two reflections take place, one at the boundary air-layer and a another on at the interface layer-substrate. Depending on the refractive index and the thickness of the layer, the two reflections interfere constructively or destructively. With knowledge of the refractive index and the spectral reflectance the thickness of each layer can be determined.

Typical properties:

• range of measured thickness: a few 10nm - some 10µm

Measurable films:

Dielectric films and silicon layers up to several µm, metals up to a few 10 nm

Ellipsometry:

In contrast to spectral reflectometry ellipsometry uses, in addition to the reflected intensity, also the polarization of the reflected light. This additional information increases the measurement accuracy especially for very thin layers.

Typical properties:

• Thickness range: 1nm - some 10µm

Measurable films:

Dielectric films and silicon layers up to several µm, metals up to a few 10 nm