Christian Forsich

Spectroscopic Ellipsometry as a Tool for On-Line Monitoring and Control of Surface Treatment Processes

Modern material technology relies increasingly on processes for surface modification and coating. Generally, we are lacking a possibility to monitor the progress of such processes. Thus the outcome can only be analyzed after the end of the whole process cycle. We are proposing to use spectroscopic ellipsometry (SE) as an on-line monitoring tool. SE, as an optical method, is not affected by high temperatures, process gases, plasmas, etc. It can be used as a monitoring tool or a sensor for closed loop control of processes. The main difficulty is the on-line interpretation of SE data. Depending on the nature of the process monitored or controlled, different models are used for the interpretation. These models predict the SE response depending on different parameters describing the surface under investigation. A fitting process is used to solve the inverse problem, i.e. extracting material data from the SE spectra. We expect increased process stability and shorter development time as a practical benefit from the use of SE.

Wear resistance of thick diamond like carbon coatings against polymeric materials used in single screw plasticizing technology

Wear on the screw and barrel surface accompany polymer single screw plasticizing technology from the beginning. In general, wear on screws can be reduced by using nitrided steel surfaces, fused armour alloys on the screw flights and coatings. However, DLC-coatings (Diamond Like Carbon) comprise a number of interesting properties such as a high hardness, a low coefficient of friction and an excellent corrosion resistance due to their amorphous structure. The wear resistance of about 50 µm thick DLC-coatings against polyamide 6.6, polybutylene terephthalate and polypropylene is investigated in this paper. The tribology in the solids conveying zone of a single screw extruder until the beginning of melting is evaluated using a pin on disc tribometer and a so called screw tribometer. The polymeric pins are pressed against coated metal samples using the pin on disc tribometer and the tests are carried out at a defined normal force and sliding velocity. The screw tribometer is used to perform tribological experi...

CCD camera-based analysis of thin film growth in industrial PACVD processes

In this paper we present a method for the characterization of (semi-transparent) thin film growth during PACVD processes (plasma assisted chemical vapour deposition), based on analysis of thermal radiation by means of nearinfrared imaging. Due to interference effects during thin film growth, characteristic emissivity signal variations can be observed which allow very detailed spatio-temporal analysis of growth characteristics (e.g. relative growth rates). We use a standard CCD camera with a near-infrared band-pass filter (center wavelength 1030 nm, FWHM 10nm) as a thermal imaging device. The spectral sensitivity of a Si-CCD sensor at 1μm is sufficient to allow the imaging of thermal radiation at temperatures above approx. 400°C, whereas light emissions from plasma discharges (which mainly occur in the visible range of the electromagnetic spectrum) barely affect the image formation.