PVA TePla AG

Usually, the contamination previously present in the removed material is not transferred to the gaseous phase and remains on the surface. In the subsequent step, a fluid is dripped over the surface, where it gathers up the remaining impurities. The content of the drops can be analyzed by an ICP-MS or a TXRF, for example.

Advantages:

• Modular design
• The modules can be used individually or in fully automatic combination in different-sized system housings
• Design as an analysis system with integrated ICP-MS

The effect of stress-induced birefringence is used here: Defects and material inhomogeneities are often accompanied by stress fields whose spatial expansion is several times greater than that of the cause itself. If a material is exposed to shear stresses, its refractive index becomes anisotropic and the material becomes birefringent. Incident linear polarized light (laser) is therefore depolarized by the sample in transmission or reflection. Consequently, the obtained depolarization maps of SIRD can be interpreted as shear stress distributions.

Intelligent software solutions help the SIRD system to convert the obtained maps into interpretable results efficiently.

The unique shaft configuration enables highest precision and therefore absolute linearity and reproducibility of the pulling speed. The CGS1218 features a multi-compartment chamber that allows for charging changes with reproducibility of thermal conditions in the process. The system is designed for hotzones from 32" - 36" and can be operated with single or dual camera systems via interactive software solutions.

Another advantage is the possibility of continuous doping from the gas phase, which enables a homogeneous resistivity distribution over the complete crystal length. As a result, the desired electrical properties can be achieved homogeneously over virtually the entire crystal. Due to the high charge carrier lifetimes and due to low degradation as a result of the extremely low oxygen content (crucible-free process), FZ crystals are also suitable for photovoltaics.

Compared to competing methods such as the Czochralski process, the FZ process offers the advantage of lower costs for consumables (no quartz crucibles to be used only once), lower energy costs, since only a small area of the crystal in the immediate vicinity of the induction coil has to be melted, and a significantly higher pulling speed. Furthermore, it is possible to increase the purity of crystals - both from silicon and from other suitable materials - significantly step by step through multiple processing.