Dr. Ahmad Echresh

Cleanroom Manager
Postdoctoral researcher
Nanofabrication and Analysis
Phone: +49 351 260 3893

Dr. Ciaran Fowley

Head Nanofabrication and Analysis
Phone: +49 351 260 3253

Measuring techniques

Optical thin layer thickness measurements

Optical measuring techniques are applied to thickness measurements of thin transparent or semi-transparent layers. The SiO2 layer thickness measurements are necessary for process control of thermal oxidation and SiO2 layer thinning using wet chemical etching. Ellipsometry is preferentially applied to the thickness determination of ultra-thin layers (d = 1-50 nm) and to the determination of the refractive and extinction coefficients of a wide variety of thin film systems.

For this purposes the following equipment is available:

  • Spectroscopic reflectometer NanoCalc-2000-UV/VIS (Micropack GmbH)
    • Layer thickness range: 10 nm - 20 µm
    • Wavelength region: 250-850 nm
  • Variable angel spectroscopic ellipsometer WVASE 32 (J.A.Woolam Inc.)
    • Layer thickness range: 1 nm – 1 µm
    • Wavelength region: 400-1100 nm

Optical Microscopy

Different optical microscopes with a max. magnification up to 500x and equipped with bright- and dark-field imaging are used for inspection of wafer and sample surfaces after different processing steps. Some microscopes are additionally equipped with a CCD camera and digital image processing allowing the measurement and control of lateral dimensions in the µm-range, especially after photolithographic patterning.

  • Microscopes: 
    • 3 x JENTECH Inspection (Carl Zeiss Jena)
    • 2 x OLYMPUS BX51 (Olympus Deutschland GmbH)
    • 2 x Stereo-microscope SMC4 (Acamia Werke rathenow GmbH)
    • 1 x Stereo-microscope (Vision Engineering Ltd.)
  • Optical dimension measurement:
    • TSO-VID-MES-RY measuring system (Thalheim Spezialoptik Pulsnitz)
    • MFK II measuring system (Carl Zeiss Jena)

Surface profiling and roughness measurement

Stylus profilers are precise tools for step high measurement on both patterned thin and thick films and on patterned and etched semiconductor substrates in the range between 5 nm and 65 µm. Due to the variable scan length between 50 µm and 50 mm surface planarity, wafer flatness and film stress can be measured. Furthermore, the application of the surface profiler includes the measurement of the roughness of thin layers and of etched wafer surfaces.

Dektak 3 Surface Profiler (VEECO Instruments GmbH)

Specification Dektak 3
Stylus force range 10 – 50 mg

Stylus force adjustment


Stylus Tip radius

12.5 µm
Max. data points per scan 2000
Max. Vertical range 65 µm
Vertical data resolution 0.5 nm

Step high repeatability (1σ)

1.0 nm

Atomic Force Microskopy (AFM)

The combination of a high resolution optical microscope (Olympus BX 51) with an AFM (ULTRAObjective, Fa. SIS, Germany) enables the application of the AFM for investigations of surface micro- and nano-patterns. The advantage of this AFM is a relatively easy optical alignment of the surface area to be investigated with an accuracy below 1 µm. The AFM can be used in the contact- as well as in the non-contact-mode (Tapping mode).

Specification ULTRAObjective
Raster width 25 x 25 x 3 µm
Noise level 0.1 nm rms vertical
Laterale resolution < 2 nm
Raster speed typ. 1 to 10 Hz
Tip change without adjustment
Digital I/O resolution 16 bit
Image size 128 to 1024 pixels
Interface USB
Operating system MS Windows

Electrical measurements (I/U-, MOS-C/V-measurements)

The electrical characteristics  of  semiconductor diodes, MOS capacitors and transistors are investigated by current-voltage (IU) and capacitance-voltage (CV) measurements on corresponding test and device structures. From these measurements conclusions can be done concerning the optimization of process developments including ion implantation and ion beam synthesis for the fabrication of new electronic and opto-electronic semiconductor devices.

For these purposes two measuring facilities are available:

  • Manual prober, type MP5 (SÜSS MicroTech GmbH, Sacka)
    • Wafer diameter. up to 150 mm
    • Temperature: room temperature
    • 4 prober heads with test needles
    • Data collection and processing:
      •  PC-controlled configuration of the following devives (Keithley Instruments):
      • 237 High Voltage Source Measure Unit (SMU) for I/U-measurements
      • 590 CV Analyzer for 100 kHz HF-CV-measurements
      • Model 82-DOS Simultaneous CV for HF- and quasi-static C/V-measurements
      • Precision LCR-Meter HP 4284A (Hewlett Packard) for CV-measurements in the frequency range from 20 Hz up to 1 MHz
  • Semi-automatic Prober, Typ PA200 (SÜSS MicroTech Test Systems GmbH, Sacka)
    • Wafer diameter: up to 200 mm
    • Temperature: -60 bis +300 °C (ATT Chuck System)
    • 6 prober heads test needles
    • Data collection and processing:
      • Semiconductor measuring system, Model 4200-SCS (Keithley Instruments) with following components:
        • 4 x SMU (including 2 x High Power SMU)
        • Ultra-Low-Current Switch Matrix 8x12
        • Dual-channel digital oscilloscope
        • Dual-channel pulse generator